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Organometallic nitrosyl hydrides of tungsten 1987

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ORGANOMETALLIC NITROSYL HYDRIDES OF TUNGSTEN By JEFFREY THOMAS MARTIN B.Sc. (Hons, Eng. Chem.), Queen's U n i v e r s i t y at. Kingston, 1978 M.Sc, Queen's U n i v e r s i t y a t Kingston, 1983 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n THE FACULTY OF GRADUATE STUDIES (Department of Chemistry) We accept t h i s t h e s i s as conforming t o the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA September 1987 © J e f f r e y Thomas Mar t i n , 1987 4 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of Chemistry The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date 17 September, 1987 DE-6(3/81) A b s t r a c t Although h y d r i d e s o f metal c a r b o n y l s are widely known, the number o f hydri d e s i n the r e l a t e d f a m i l y o f metal n i t r o s y l s i s extremely s m a l l . The p r e p a r a t i o n o f a s e r i e s o f n l t r o s y l h y d r i d e s from the treatment o f [CpW(NO)1„]_ (Cp=n 5-C CH C) with Na[H 2Al(OCH 2CH 2OCH 3) 2] i s d e s c r i b e d . The a d d i t i o n o f one or two e q u i v a l e n t s o f the aluminum reagent r e s u l t s i n the for m a t i o n of [CpW(NO)IH] 2 or [CpW(NO)H 2 3 2 r e s p e c t i v e l y . The r e a c t i o n o f [CpW(NO)IH] 2 with a Lewis base (L=P(OPh> 3, P(OMe) 3, PPh 3 or PMe 3) gi v e s the monometallic CpW(NO)IHL, while [CpW(NO)H 2 3 2 r e a c t s with P(OPh) 3 or P(OMe) 3 t o y i e l d [CpW(NO)HL] 2 which undergoes f u r t h e r r e a c t i o n t o g i v e CpW(NO)H 2L. Proton NMR spectroscopy shows t h a t a l l b i m e t a l l i c s p e c i e s c o n t a i n b r i d g i n g h y d r i d e l i g a n d s and are t h e r e f o r e best, formulated as [CpW(NO)1] 2(u-H) 2, [CpW(NO)H] 2(u-H) 2 and [CpW(NO)L] 2(u-H) 2- The JH NMR spectrum o f [CpW(NO)H] 2(u-H) 2 shows t h a t t h e r e i s no h y d r i d e l i g a n d exchange on the NMR time s c a l e and t h a t 1 1 2 J U , , . , «,, * J I J « v _ ; : M n \ 11 > From t h i s f i n d i n g , i t i s H(terminal)W H(bndging)W HW a ' p o s s i b l e t o develop new c r i t e r i a f o r a s s e s s i n g the s t a t i c or f l u x l o n a l nature o f hy d r i d e l i g a n d s f o r s e v e r a l f a m i l i e s o f organotungsten h y d r i d e s (Cp2W, CpW(CO) 3, W(CO>5 and CpW(NO) x (x=l or 2)). Within each f a m i l y , the magnitude o f * J H W s t r o n g l y r e f l e c t s the type o f metal h y d r i d e bonding, i . e . H H H H W = * = M > W=Jp=M > w^k.M * W — j — M « W — H 1 1 and suggests t h a t b r i d g e bonding i n v o l v e s a l l the atoms in the b r i d g e and t h e r e f o r e the " f u s e d " n o t a t i o n i s introduced. Treatment o f CpW(NO)(CH 2SiMe 3) 2 with low p r e s s u r e s o f H 2 (60-80 p s i g ) in the presence of Lewis bases (L=P(0Ph) 3, PMePh 2) gi v e s the u n u s u a l l y s t a b l e a l k y l hydride compounds CpW(NO)(H)(CH 2SiMe 3)L. T h i s chemistry i s then extended t o the 5 Cp* (Cp*=n -C^Me^) analogues, i n c l u d i n g the p r e p a r a t i o n o f the a p p r o p r i a t e s t a r t i n g m a t e r i a l s . Upon t h e r m o l y s i s o f Cp*W(NO)(H)(CH 2SiMe 3)(PMe 3) in C &H 6, the intermo1 ecu 1ar C-H a c t i v a t i o n product Cp*W(N0)(H)(C^H^)(PMe 3) i s c l e a n l y formed. However, i ntermol ecu 1 ar a c t i v a t i o n of CH „, C^-H,„ or n-C-H,., does 4 6 12 6 14 not occur under s i m i l a r experimental c o n d i t i o n s . Hydrogenolysis o f Cp*W(NO)(CH 2SiMe 3) 2 a t high p r e s s u r e s (*920 ps i g ) with no Lewis base present r e s u l t s i n the formation o f i s o l a b l e [Cp*W(NO)H] 2(u-H) 2 and [Cp*W(N0)H](p-H) 2[Cp*W(N0)(CH 2SiMe 3)]. The l a t t e r i s a new example o f the r a r e c l a s s o f d i n u c l e a r a l k y l h ydride complexes. Proton NMR s p i n t i c k l i n g experiments on t h i s compound a l l o w the complete assignment o f a l l c o u p l i n g s i n the spectrum and show t h a t l j H ( t e r m i n a l ) W 1 J H ( b r i d g i ng) W a n d 2jHW h a v e t h e s a m e s ,'9 n" i i i Tab 1e o f Contents Page A b s t r a c t i i Table o f Contents iv L i s t o f Tables v i i i L i s t o f F i g u r e s x L i s t o f Schemes x i v L i s t o f A b b r e v i a t i o n s xv Acknowledgements x v i i Chapter 1 - I n t r o d u c t i o n 1 A. H i s t o r i c a l Background 1 B. S t r u c t u r e and Bonding 3 C. C h a r a c t e r i z a t i o n o f Metal Hydrides 7 D. P r e p a r a t i o n 10 E. N i t r o s y l Hydrides 12 F. Scope o f the Present Work 13 G. References and Notes 15 Chapter 2 - New Organometa11ic Hydrido N i t r o s y l Complexes o f Tungsten 20 Experimental S e c t i o n 20 i v R e s u l t s and D i s c u s s i o n 35 A. P r e p a r a t i o n of [Cpw(NO)IH] 2 35 B. S p e c t r o s c o p i c P r o p e r t i e s o f [CpW(NO)IH] 2 38 C. The Complexes o f CpW(N0)lHL (L=Phosphine or Phosphite) 42 D. S y n t h e s i s and P r o p e r t i e s o f [CpW(N0)H 2] 2 48 E. Molecular S t r u c t u r e s o f [Cpw(NO)H] 2(u-H) 2 and [CpW(NO)1J 2(u-H) 2 52 F. Reactions of [CpW(NO)H] 2(u-H) 2 with PR 3 (P=OPh or OMe) 56 G. P r e p a r a t i o n and P r o p e r t i e s of [CpW(NO)Br 2] 2 62 H. P r e p a r a t i o n and P r o p e r t i e s of CpW(NO)BrH[P(OPh) ] 69 I. The C y c l i c Voltammogram o f [CpW(NO)I 2] 2 72 J . References and Notes 75 Chapter 3 - On the *H Nuclear Magnetic Resonance Spe c t r a o f Organometa11ic Tungsten Hydrides 79 R e s u l t s and D i s c u s s i o n 81 A. C r y s t a l and Molecular S t r u c t u r e s o f [CpW(NO)H] 2(u-H) 2 81 B. Bonding i n the W 2(u-H) 2 U n i t o f [CpW(NO)H] 2(u-H) 2 86 C. The lh NMR Spectrum of [CpW(NO)H] 2( M-H) 2 87 v D. H NMR S p e c t r o s c o p i c C r i t e r i a f o r E l u c i d a t i n g the S t r u c t u r e s o f B i m e t a l l i c Organotungsten Hydrides in S o l u t i o n 88 E. Cp2W D e r i v a t i v e s 92 F. CpW(CO) 3 D e r i v a t i v e s 97 G. W(CO) c D e r i v a t i v e s 101 H. CpW(NO) x (x = 2 or 1) D e r i v a t i v e s 104 I. J u s t i f i c a t i o n f o r Using "Fused" Bonding Representations 110 J . Summary 1 13 K. References and Notes 116 Chapter 4 - S t a b l e A l k y l Hydride Complexes o f Tungsten 124 Experimental S e c t i o n 125 R e s u l t s and D i s c u s s i o n 147 A. CpW(NO)(H)(CH 2SiMe 3)L (L=P(0Ph> 3, PMePh2> 147 B. Thermolysis o f CpW(NO)(H)(CH 2Si Me 3)[P(OPh) 3] 158 C. Reactions o f CpW(NO)(CH 2SiMe 3) 2, H £ and L i n NMR Tubes 161 D. The E q u i l i b r i u m Between CpW(NO)(CH 2SiMe 3) 2 and PMePh 2 167 E. Cp*W(NO)I 2 172 F. Cp*W(N0)(CH 2SiMe 3) 2 176 G. Cp*W(NO)(H)(CH 2SiMe 3)(PMe 3) 179 v i H. Thermal C-H A c t i v a t i o n I n v o l v i n g Cp*W(NO)(H)(CH 2SiMe 3)(PMe 3) 186 I. The Redox Chemistry o f Cp»W(NO)(H)(CH 2SiMe 3)(PMe 3) 189 J . Hydrogenolysis of Cp*W(NO)(CH 2SiMe 3> 2 With No L Present 193 K. [Cp*W(NO)H] 2(y-H) 2 195 L. [Cp*W(NO)H] (y-H)2[Cp',W(NO) (CH 2SiMe 3) ] 201 M. The *H NMR Spectrum of [Cp*W(NO)H] (ii-H) 2[Cp*W(N0) (CH 2SiMe 3) ] 205 N. The Pathway f o r the Formation o f [Cp*W(NO)H] 2( u-H) 2 and [Cp*W(N0)H](y-H) 2[Cp*W(NO)(CH 2SiMe 3>] 218 O. References and Notes 223 S p e c t r a l Appendix 232 vi i L i s t o f Tables Table 2-1 A n a l y t i c a l and I n f r a r e d Data f o r the Complexes 2-1 I NMR Data f o r the Complexes 2- 11 I Comparative S p e c t r o s c o p i c Data f o r the CpW(NO)XH[P(OPh) 33 Complexes 3- 1 Atomic Coordinates f o r [CpW(NO)H] (y-H) 3-1 I Important Interatomic Distances (A) and Angles (deg) f o r [CpW(NO)H] ( y - H ) 2 1 183 3-1 I I Approximate H- W Coupling Constants Expected f o r Stereochemica11y R i g i d Organotungsten Hydrides 3-IV Tungsten Hydride *H NMR Parameters f o r Cp2W D e r i v a t i v e s 3-V Tungsten Hydride lH NMR Parameters f o r CpW(CO) 3 D e r i v a t i v e s 3-VI Tungsten Hydride lH NMR Parameters f o r W(CO)^ D e r i v a t i v e s 3- VI I Tungsten Hydride lH NMR Parameters f o r CpW(NO) x (x = 2 or 1) D e r i v a t i v e s 4 - 1 A n a l y t i c a l , I n f r a r e d and Mass S p e c t r a l Data f o r the Complexes vi i i 4-1 I NMR Data f o r the Complexes 139 4-1 I I Important Interatomic Distances (A) and Angles (deg) f o r CpW(NO)(H)(CH 2SiMe 3)(PMePh 2> 152 4-IV Important Interatomic Distances (A) and Angles (deg) f o r CpW(NO)(H)[P(OPh) 2(OCgH^)] 159 4-V The E q u i l i b r i u m Data f o r the Reaction Between CpW(NO)(CH 2SiMe 3) 2 and PMePh 2 in toluene-dg 168 4-VI Important Interatomic Distances (A) and Angles (deg) f o r Cp*W(NO)(H)(CH 2S i Me 3)(PMe 3) 183 4-VI I Important Interatomic Distances (A), Angles (deg) and T o r s i o n Angles (deg) f o r [Cp*W(NO)H](u-H) 2[Cp*W(NO)(CH 2SiMe 3)] 202 i x L i s t o f F i gures F i gure Page 2-1 The 270-MHz lh NMR spectrum of [CpW(NO)I]2(u-H)^ in CDC1 3 39 2-2 T experiment on [CpW(NO)I] (y-H) 2 41 2-3 The 400-MHz lH NMR spectrum of [CpW(NO)H] 2(y-H) 2 in C & D 6 51 2-4 Probable molecular s t r u c t u r e s o f [CpW(NO)H] 2(y-H) 2 and [CpW(NO)I] 2(u-H) 2 55 2-5 The hydride r e g i o n s o f the 400-MHz a) !H, and b) lh{3lP} NMR s p e c t r a of [CpW(NO){P(OPh) 3}] 2(y-H) 2 in C 6 D 6 58 2-6 Proposed s t r u c t u r e o f [CpW(NO){P(OPh) } ] 2 ( y - H ) 2 59 2-7 The 80-MHz lH NMR spectrum of CpW(N0)Br 2 in CDC1 3 65 2-8 U V - v i s i b l e s p e c t r a o f CpW(NO)Br 2 and CpW(NO)I £ in CH 2C1 2 67 2-9 The ( r e d u c t i v e ) c y c l i c voltammogram o f CpW(NO)I„ i n C H „ C 1 0 73 3-1 View o f the molecular s t r u c t u r e o f [CpW(NO)H] 2(y-H) 2 82 3-2 End view o f [CpW(NO)H] (y-H) down the W-W a x i s 82 x E x p e c t e d H NMR p a t t e r n f o r s t a t i c a n d f l u x i o n a l W-H-W s y s t e m s The 8 0 - M H z *H NMR s p e c t r u m o f C p W ( N O ) 2 H i n C 6 D 6 A s e c t i o n o f t h e 4 0 0 - M H z *H NMR s p e c t r u m o f C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e P h 2 ) SNOOP I d i a g r a m s o f t h e m o l e c u l a r s t r u c t u r e o f C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e P h 2 ) S t i c k d i a g r a m o f t h e s t r u c t u r e o f C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e P h 2 ) a s v i e w e d f r o m d i r e c t l y a b o v e t h e Cp r i n g SNOOPI d i a g r a m s o f t h e m o l e c u l a r s t r u c t u r e o f C p W ( N O ) ( H ) [ P ( O P h ) 2 ( O C 6 H 4 ) ] S t i c k d i a g r a m o f t h e s t r u c t u r e o f C p W ( N O ) ( H ) [ P ( O P h ) 2 ( O C 6 H 4 ) ] a s v i e w e d f r o m d i r e c t l y a b o v e t h e Cp r i n g The 3 0 0 - M H z *H NMR s p e c t r u m o f t h e r e a c t i o n b e t w e e n C p W ( N O ) ( C H 2 S i M e 3 ) 2 , P ( O P h ) 3 a n d H 2 T h e 1 2 1 . 4 2 1 - M H z 3 1 P { 1 H > NMR s p e c t r u m o f t h e r e a c t i o n b e t w e e n C p W ( N O ) ( C H 2 S i M e 3 ) 2 , P ( O P h ) 3 a n d H 2 V a r i a b l e t e m p e r a t u r e lH a n d 3 1 P { 1 H } NMR s p e c t r a ( t o l u e n e - d g ) s h o w i n g t h e e q u i l i b r i u m b e t w e e n C p W ( N O ) ( C H 2 S i M e 3 ) 2 a n d P M e P h 2 x i 4-9 V a r i a b l e temperature U V - v i s i b l e spectrum of Cp*W(NO)I 2 i n CH 2C1 2 175 4-10 The 80-MHz *H NMR spectrum of Cp*W(N0)(CH 2SiMe 3) 2 in CgDg 178 4-11 NOE d i f f e r e n c e experiment on Cp*W(N0)(H)(CH 2SiMe 3)(PMe 3) 182 4-12 SNOOPI diagram o f the molecular s t r u c t u r e o f Cp*W(N0)(H)(CH 2SiMe 3)(PMe 3) 184 4-13 S t i c k diagram o f the s t r u c t u r e o f Cp*W(N0)(H)(CH 2SiMe 3)(PMe 3) as viewed from d i r e c t l y above the Cp* r i n g 184 4-14 Side view o f the s t r u c t u r e o f Cp»W(NO)(H)(CH 2SiMe 3)(PMe 3) 185 4-15 The 300-MHz *H NMR spectrum o f Cp*W(NO)(H)(C H)(PMe,) in C,D, 187 D D J D O 4-16 C y c l i c voltammograms of the o x i d a t i o n o f Cp*W(NO)(H)(CH 2SiMe 3)(PMe 3) 191 4-17 P l o t o f 1 / i as a f u n c t i o n o f the scan r a t e pc pa f o r the o x i d a t i o n o f Cp*W(N0)(H)(CH 2SiMe 3)(PMe 3) 193 4-18 The 400-MHz *H NMR spectrum o f [Cp*W(N0)H] 2(u-H) 2 in C&D6 198 4-19 SNOOPI diagrams o f the molecular s t r u c t u r e o f [Cp*W(N0)H](u-H) 2[Cp*W(N0)(CH 2SiMe 3)] 204 xi i 4-20 The 400-MHz *H NMR spectrum o f [Cp*W(N0)H](u-H) 2[Cp*W(N0)(CH 2SiMe 3)] in CD 3N0 2 206 4-21 Expansions o f the experimental and simulated peaks o f the hydride r e g i o n s o f the 400-MHz *H NMR spectrum o f [Cp*W(N0)Hj(y-H) 2[Cp*W(N0)(CH 2SiMe 3>] 208 4-22 A s i m p l i f i e d s p l i t t i n g diagram f o r c o u p l i n g s e x h i b i t e d by [Cp*W(N0)H](u-H) 2[Cp*W(N0)(CH 2SiMe 3)] 212 4-23 Spin t i c k l i n g experiment on [Cp*W(NO)H](u-H) [Cp*W(N0)(CH Si Me )] 213- 215 xi i i L i s t o f S c h e m e s S c h e m e 2 - 1 2 - 1 I 4 - 1 4 - 1 I 4 - 1 I I 4 - 1 V 4 - V P a g e 3 6 63 148 165 167 190 2 2 0 x i v L i s t o f Abbrev i a t i ons 5 Cp - n -eye 1opentadieny1 5 Cp* - n -pentamethyleye 1opentadieny1 CP - c e n t r o i d o f a Cp or Cp* r i n g Me - CH 3, methyl Et - CH 2CH 3, et h y l Ph - C 6H 5, phenyl E t 2 0 - (CH 3CH 2) 20, d i e t h y l ether THF - C 4HgO, t e t r a h y d r o f u r a n TMS - Me^Si, tetramethy1si1ane C 6 D & - benzene-d 6 CDC1 3 - ch l o r o f o r m - d j CD 2C1 2 - dich1oromethane-d 2 CD 3N0 2 - nitromethane-d 3 (CD 3) 2CO - a c e t o n e - d 6 IR - i n f r a r e d NMR - nu c l e a r magnetic resonance MS - mass spectrum P + - molecular ion ( i n the mass spectrum) GC-MS - gas chromatography-mass spectrum EI - e l e c t r o n impact CV - eye l i e vo1tammogram SCE - standard calomel e l e c t r o d e lH{ 3 1P} - phosphorus-31 decoupled proton P{ H) - proton decoupled phosphorus-31 xv JC{ H) - proton decoupled carbon-13 NOE - n u c l e a r Overhauser e f f e c t p s l g - pounds per square inch gauge (14.7 p s i g = 1 atm above atmospheric pressure) m/z - mass-to-charge r a t i o i n the mass spectrum dppm - bis(diphenylphosphino)methane dppe - b i s ( d i p h e n y l p h o s p h i n o ) e t h a n e xv i Acknow)edgements I would f i r s t l i k e t o thank the boss. P r o f e s s o r Peter Legzdins, f o r p r o v i d i n g much u s e f u l a d v i c e and l o t s o f encouragement d u r i n g the l a s t f i v e years. 1 a l s o want t o thank a l l the denizens o f 325/319, both past and present, f o r t h e i r f r i e n d s h i p and o c c a s i o n a l abuse. In p a r t i c u l a r , my thanks go t o George Richter-Addo and L u i s Sanchez, not o n l y f o r t h e i r t e c h n i c a l help, but a l s o f o r d i s c u s s i o n s too numerous t o mention. My thanks a l s o go t o J u l i u s Balatom" f o r some Tj measurements and t o N e i l Oryden f o r some computing a s s i s t a n c e . I would a l s o l i k e t o express my a p p r e c i a t i o n t o Rich a r d Jones, Tony W i l l i s and Fred E i n s t e i n a t Simon F r a s e r f o r s o l v i n g the X-ray s t r u c t u r e s . This work was a i d e d enormously by the e x c e l l e n t t e c h n i c a l s t a f f i n the department and 1 would p a r t i c u l a r l y l i k e t o thank Steve and Steve in the g l a s s shop, M a r i e t t a and Liane in the NMR lab and Peter Borda in the m i c r o a n a l y s i s lab. My thanks a l s o goes t o numerous other members of the department f o r a l o t of us e f u l a d v i c e and many p r o f i t a b l e d i s c u s s i o n s . I would l i k e t o acknowledge a l s o the f i n a n c i a l support o f the H.R. MacMillan Foundation f o r the r e c e i p t o f a Family Fe11owshi p. The support, encouragement and enthusiasm o f my f a m i l y has made a l l t h i s p o s s i b l e and I want t o express my deepest thanks t o them f o r p u t t i n g up with me a l l t h i s time. F i n a l l y , v i l l j a g xv i i ocksa tacka Anna-Tora f o r hennes k a r l e k och talamod under dessa fern 1anga a r . xv i i i " I f the Lord Almighty had c o n s u l t e d me bef o r e embarking upon C r e a t i o n , I would have recommended something s i m p l e r " A l f o n s o X (the Wise, King o f C a s t i l i e ) 1226-1284 xix Chapter 1 Introduct i on A. H i s t o r i c a l Background The f i r s t organometa1 I i c (or organometal1ic-1ike) t r a n s i t i o n - m e t a l h ydride complexes i d e n t i f i e d were H^Fe(CO)^^ and H C o ( C O ) 4 ( 2 ) by Hieber's group i n 1931 and 1935 r e s p e c t i v e l y . These remained the o n l y such hydride complexes known u n t i l the mid-1950's when the foundations o f modern organometal1ic (3) chemistry were being l a i d and Cp 2ReH and CpM(CO) 3H (M=Cr,Mo,w)v ' were i s o l a t e d . Although the t r u e nature o f the metal-H l i n k was not p r o p e r l y understood then, i t was r e c o g n i z e d t h a t t h e r e was a d i r e c t metal-H i n t e r a c t i o n and t h i s caused an e x p l o s i o n o f i n t e r e s t in these types o f compounds, with many more being prepared i n the succeeding y e a r s . T h i s e x p l o s i o n o f i n t e r e s t was f u r t h e r f u e l l e d because i t was r e a l i z e d from e a r l y on t h a t t r a n s i t i o n - m e t a l h y d r i d e compounds were important i n a number o f h i g h l y d e s i r a b l e , c a t a l y t i c r e a c t i o n s . Even i n the 1940's, HCo(C0) 4 was r e c o g n i z e d as a key element i n the newly developed hydroformy1 a t i o n (C n (5) o l e f i n -»• C n + 1 aldehyde) and a l c o h o l homologation r e a c t i o n s ( C n a l c o h o l •* C n + 1 a l c o h o l ) . ( 6 ) In the e a r l y 1960's, C l R h ( P P h 3 ) 3 v i a a hydride intermediate was d i s c o v e r e d t o be a r a p i d and e f f i c i e n t homogeneous c a t a l y s t f o r o l e f i n hydrogenation under e x c e p t i o n a l l y m i l d c o n d i t i o n s . S t i l l today, much o f the 1 i n t e r e s t i n t h i s g e n e r a l c l a s s o f compounds stems f r o m t h e i r u t i l i t y i n c a t a l y t i c s y s t e m s . The f i r s t two h y d r i d e s were i d e n t i f i e d a s h a v i n g H atoms i n t h e m o l e c u l e s i n c e H 2 was p r o d u c e d upon t h e i r h y d r o l y s i s . E a r l y e l e c t r o n - d i f f r a c t i o n measurements s u g g e s t e d a t e t r a h e d r a l a r r a n g e m e n t o f C atoms a b o u t t h e m e t a l - c e n t r e a n d t h e f o r m u l a t i o n s C o ( C O ) 3 ( C O H ) and F e ( C O ) 2 ( C O H ) 2 were s u g g e s t e d . ( 8 ) L a t e r , H i e b e r had c h e m i c a l e v i d e n c e f o r a d i r e c t M-H l i n k and so i t was s u g g e s t e d t h a t t h e H a t o m ( s ) was b u r i e d i n t h e o r b i t a l s o f (9) t h e m e t a l . T h i s e x p l a n a t i o n was u s e d f o r a number o f y e a r s t o e x p l a i n t h e r e s u l t s o f numerous IR, NMR, b r o a d - 1 i n e NMR a n d e l e c t r o n d i f f r a c t i o n e x p e r i m e n t s c a r r i e d o u t o v e r t h e p e r i o d 1939-59. In p a r t i c u l a r , i t was u s e d t o e x p l a i n t h e u n u s u a l h i g h - f i e l d c h e m i c a l s h i f t s t h a t t h e h y d r i d e H's e x h i b i t e d i n t h e i r h i g h - r e s o l u t i o n NMR s p e c t r a t h a t g r e a t l y a i d e d W i l k i n s o n and B i r m i n g h a m i n t h e i r i n i t i a l s t u d i e s on Cp 2ReH and i t s (3) r e 1 a t i v e s . However, t h e p r e s e n t l y a c c e p t e d n a t u r e o f h y d r i d e l i g a n d s , t h a t t h e y o c c u p y normal c o o r d i n a t i o n p o s i t i o n s w i t h normal c o v a l e n t b onds, was r e c o g n i z e d In t h e e a r l y s i x t i e s when X - r a y d i f f r a c t i o n s t u d i e s on s u c h compounds a s t r a n s - H P t B r ( P E t ^ ) 2 ^ ^ ^ and H R h ( C O ) ( P P h 3 > 3 ^ 1 1 ^ were done. The f i r s t n e u t r o n d i f f r a c t i o n 2— s t u d y c o n f i r m e d t h i s n a t u r e , a s R e H g was f o u n d t o be a (12) t r i c a p p e d t r i g o n a l p r i s m w i t h Re-H d i s t a n c e s o f 1.68A. 2 B . S t r u c t u r e a n d B o n d i n g T h e m o s t c o m m o n t y p e o f h y d r i d e c o m p l e x e s a r e t h o s e c o n t a i n i n g s i m p l e , t w o e l e c t r o n c o v a l e n t b o n d s b e t w e e n t h e m e t a l a n d t e r m i n a l h y d r i d e l i g a n d s . T h e s e c o m p l e x e s m a y h a v e a n y w h e r e f r o m o n e t o n i n e h y d r i d e l i g a n d s ( e . g . H C o ( C O ) 4 , H 2 F e ( C 0 ) 4 , 2 - R e H g ) . A l s o c o m m o n a r e h y d r i d e s t h a t b r i d g e t w o o r m o r e m e t a l c e n t r e s . S i n c e t h i s t h e s i s i s o n l y c o n c e r n e d w i t h m o n o a n d d i n u c l e a r c o m p o u n d s , h y d r i d e b o n d i n g i n h i g h e r o r d e r c l u s t e r s w i l l n o t b e d i s c u s s e d h e r e . When o n e h y d r i d e b r i d g e s t w o a t o m s , i t s b o n d i n g i s g e n e r a l l y d i s c u s s e d i n t e r m s o f " o p e n " o r " c l o s e d " c e n t r e b o n d i n g , a f t e r t h e c l a s s i c b o n d i n g d e s c r i p t i o n s d e v e l o p e d i n b o r a n e ( 1 3 ) c h e m i s t r y . T h e f i r s t t w o s u c h m o l e c u l e s t o b e t h o r o u g h l y s t u d i e d w e r e H W 2 ( C O ) 9 ( N O ) a n d H W 2 ( C O ) Q ( N O ) [ P ( O M e ) 3 ] , 1 4 w h e r e i t w a s f o u n d t h a t t h e W - H - W l i n k a g e s a r e d i s t i n c t l y b e n t , w i t h t h e H a t o m d i s p l a c e d a w a y f r o m i t s e x p e c t e d p o s i t i o n b a s e d o n a s t r i c t l y o c t a h e d r a l m o d e l : T h i s b o n d i n g h a s a l w a y s b e e n d e s c r i b e d a s a " c l o s e d " , 3 - c e n t r e , 2 e l e c t r o n s y s t e m , w i t h o v e r l a p o f o r b l t a l s f r o m a l l t h r e e a t o m s 3 i n v o l v e d a nd a d i r e c t meta1-meta1 i n t e r a c t i o n . ^ T h i s i s t h e commonly a c c e p t e d b o n d i n g r a t i o n a l e f o r most u n s u p p o r t e d M-H-h" b r i d g e bonds i n t r a n s i t i o n - m e t a l c o m p l e x e s . However, some c a l c u l a t i o n s s u g g e s t t h a t t h e r e i s l i t t l e o r no d i r e c t b o n d i n g between t h e metal atoms, and t h a t t h e b o n d i n g t a k e s p l a c e a l m o s t e x c l u s i v e l y t h r o u g h t h e h y d r o g e n b r i d g e i n an open f a s h i o n , t h e (15b c) same a s t h a t commonly a c c e p t e d f o r b o r a n e s ( e . g . B H,). ' Z o I t i s a p p a r e n t t h a t t h i s p o i n t s t i l l needs c l a r i f i c a t i o n . T h e r e a r e a l s o a number o f compounds t h a t have two H atoms b r i d g i n g two metal c e n t r e s , s u c h a s i n [H 2W 2 ( C O ) Q] 2~.* 1 5 ^ In t h e s e c a s e s , t h e H atoms a r e a l m o s t a l w a y s f o u n d i n s i d e t h e p o s i t i o n s e x p e c t e d b a s e d on an o c t a h e d r a l m o d e l . A l t h o u g h t h e r e i s u n q u e s t i o n a b l y a d i r e c t m e t a l - m e t a l i n t e r a c t i o n ( e . g . W-W = 3.0162 A i n [H 2W 2 ( C O ) Q ] 2 ~ ) t h e r e i s c o n s i d e r a b l e d e b a t e a s t o W W - vv w what t h e b e s t d e s c r i p t i o n o f t h e b o n d i n g i s i n t h e s e c o m p l e x e s and t h i s w i l l be d e a l t w i t h i n more d e t a i l i n c h a p t e r 3. E a r l i e r t r a n s i t i o n - m e t a l a nd a c t i n i d e h y d r i d e s a l s o e x h i b i t M(ii-H) 2M s y s t e m s , b u t t h e s e d i f f e r somewhat i n c h a r a c t e r . In [ C p » T h H ] 2 ( y - H ) 2 ( 1 6 ) a n d t n 5 - C 5 H 4 M e ) 2 Z r H ] 2 ( y - H ) 2 , ( 1 7 ) t h e m e t a l - T h i s t h e r e f o r e seems t o be a n a l o g o u s t o t h e open c e n t r e b o n d i n g u s e d t o d e s c r i b e t h e B-H-B b r i d g i n g s y s t e m . T h e r e a r e a few examples o f t h r e e o r f o u r h y d r i d e l i g a n d s b r i d g i n g two m e t a l c e n t r e s . T h e s e I n c l u d e The l a t t e r i s an example o f a complex t h a t c o n t a i n s b o t h b r i d g i n g a n d t e r m i n a l h y d r i d e l i g a n d s — a s i s common w i t h compounds o f t h i s t y p e , i t i s h i g h l y f l u x i o n a l and a l l e i g h t H atoms a r e e q u i v a l e n t on t h e NMR t i m e s c a l e ( s e e c h a p t e r 3 ) . More r e c e n t l y , two new t y p e s o f h y d r o g e n s bonded d i r e c t l y t o t r a n s i t i o n m e t a l s have been r e c o g n i z e d . The f i r s t o f t h e s e , dubbed " a g o s t i c " , i s o b s e r v e d a s a n H atom b r i d g i n g a metal a n d a c a r b o n o f an a l k y ) g r o u p , u s u a l l y i t s e l f b onded t o t h e m e t a l . { ( v - H ) 3 F e 2 [ ( P h 2 P C H 2 ) 3 C M e j 2 ) + ( 1 8 ) a n d H 4 ( u - H ) 4 R e 2 ( P E t 2 P h ) ( 1 9 ) • 2 5 This may be described as an arrested elimination (e.g. a-elimination in 1) or oxidative addition (e.g. 2 ) reaction. This type of interaction is generally the re s u l t of an electron d e f i c i e n t metal centre attempting to r e l i e v e t h i s deficiency by accepting some electron density from the C-H bond. It is usually i d e n t i f i e d by the observation of unusual chemical s h i f t s and/or one-bond carbon-H coupling constants for the alkyl H's involved in the interaction. The second, new type of "hydride" is the interesting s i t u a t i o n of dihydrogen bonded in a dihapto fashion to the metal. ( i -Pr) , cr P ( i -Pr) 0 c Fe p H - H p 1 (ref. 2 1 ) (ref. 2 2 ) This may be described as an arrested oxidative addition of to the metal centre. It i s interesting to note that both c l a s s i c a l 2 ( 2 2 ) hydride and n -H^ ligands may be present on the same metal. The compounds are generally Identified by the large magnitude of the H-D J coupling observed in the 1 H NMR spectrum of the HD (vs. ( 2 1 > H ?) analogue, or by the observation of very short T, 2 (23 1 r e l a x a t i o n t i m e s f o r t h e c o o r d i n a t e d n -H , v ' a s w e l l a s by t h e u s u a l d i f f r a c t i o n t e c h n i q u e s . C. C h a r a c t e r i z a t i o n o f M e t a l H y d r i d e s T h e r e a r e e s s e n t i a l l y t h r e e t e c h n i q u e s u s e d t o c h a r a c t e r i z e a n d i d e n t i f y t r a n s i t i o n m e t a l h y d r i d e s : IR a n d NMR s p e c t r o s c o p y , and d i f f r a c t i o n methods. T e r m i n a l m e t a l h y d r i d e s u s u a l l y e x h i b i t IR s t r e t c h i n g f r e q u e n c i e s ( v ^ ) i n t h e r e g i o n 1650-2250 c m - 1 . ( 2 4 ^ T h e s e bands MH a r e g e n e r a l l y q u i t e weak i n i n t e n s i t y making them d i f f i c u l t t o i d e n t i f y , p a r t i c u l a r l y i n c a r b o n y l , c y a n o an d n i t r o s y l c o m p l e x e s where t h e y a r e o f t e n d e g e n e r a t e w i t h t h e V Q Q » V ^ n a n d V ^ Q b a n d s . C o m p a r i s o n s o f t h e s p e c t r a o f t h e compounds w i t h t h o s e o f t h e i r d e u t e r i o a n a l o g u e a r e f r e q u e n t l y done, a s t h e v M H / V H Q r a t i o i s u s u a l l y t h e e x p e c t e d 1 . 4 . E v e n s o , i t i s n o t a l w a y s p o s s i b l e t o f i n d t h e s e b a n d s . H y d r i d e 1 i g a n d s b r i d g i n g two m e t a l c e n t r e s g e n e r a l l y e x n i b i t IR f r e q u e n c i e s a t much lower e n e r g i e s , t y p i c a l l y 1000-1700 cm ^ . ^ S ) j n e y a r e u s u a l l y e v e n weaker i n i n t e n s i t y t h a n t h e t e r m i n a l M-H b a n d s , an d v e r y b r o a d , a n d a r e t h e r e f o r e o f t e n I m p o s s i b l e t o d e t e c t i n r o u t i n e IR s p e c t r a . Raman and l o w - t e m p e r a t u r e ( 4 K ) IR s t u d i e s c a n sometimes be u s e d t o f i n d t h e s e b a n d s . Not s u r p r i s i n g l y , *H NMR s p e c t r o s c o p y i s a n e x t r e m e l y u s e f u l t o o l i n d e t e c t i n g t h e p r e s e n c e o f h y d r i d e l i g a n d s . U s u a l l y , p a r t i c u l a r l y f o r t h e l a t e r t r a n s i t i o n m e t a l s , h y d r i d e l i g a n d s e x h i b i t c h a r a c t e r i s t i c h i g h - f i e l d c h e m i c a l s h i f t s , w i t h ( 2 6 ) r e s o n a n c e s g e n e r a l l y i n t h e r e g i o n 6 = -5 t o -50 ppm. E a r l i e r t r a n s i t i o n m e t a l , and l a n t h a n i d e and a c t f n i d e h y d r i d e s commonly e x h i b i t h y d r i d e r e s o n a n c e s i n t h e more u s u a l " o r g a n i c " r e g i o n o f t h e s p e c t r u m and a r e c o n s e q u e n t l y more d i f f i c u l t t o (21) i d e n t i f y . ' The o b s e r v a t i o n o f s p i n - s p i n c o u p l i n g s o f t h e h y d r i d e 1 i g a n d t o o t h e r NMR a c t i v e n u c l e i i n t h e m o l e c u l e i s o f t e n an e x t r e m e l y u s e f u l way o f d e t e r m i n i n g s t r u c t u r e a n d / o r number o f h y d r i d e h y d r o g e n s . T h i s may t a k e t h e f o r m o f c o u p l i n g Q Q I Q 2 I (I'D d i r e c t l y t o an NMR a c t i v e m e t a l c e n t r e ( e . g . o : ? Y , 1 0 3 W , l u J R h , 195 3 1 P t ) o r t o n u c l e i o f o t h e r l i g a n d s , p a r t i c u l a r l y P i n p h o s p h i n e o r p h o s p h i n e - 1 i k e l i g a n d s . Of c o u r s e , t h e most d e f i n i t i v e ways o f e s t a b l i s h i n g t h e s t r u c t u r e s o f compounds ( i n t h e s o l i d s t a t e ) a r e s i n g l e - c r y s t a l d i f f r a c t i o n t e c h n i q u e s . As m e n t i o n e d e a r l i e r , i t was t h r o u g h t h e u s e o f t h e s e t e c h n i q u e s t h a t t h e t r u e n a t u r e o f t h e h y d r i d e 1 i g a n d was d i s c o v e r e d . U n f o r t u n a t e l y , s i n c e X - r a y d i f f r a c t i o n d e p e nds upon e l e c t r o n d e n s i t y and h y d r o g e n atoms have few e l e c t r o n s a s s o c i a t e d w i t h them, i t i s o f t e n d i f f i c u l t t o f i n d h y d r i d e h y d r o g e n s , p a r t i c u l a r l y when t h e y a r e c l o s e t o h e a v y m e t a l c e n t r e s s u c h a s W o r P t . F r e q u e n t l y , t h e r e f o r e , t h e l o c a t i o n o f a h y d r i d e h y d r o g e n i s i n f e r r e d f r o m t h e o b s e r v a t i o n o f a " h o l e " i n t h e c o o r d i n a t i o n s p h e r e o f t h e m e t a l . F o r example, t h e f i r s t s i n g l e - c r y s t a l X - r a y s t r u c t u r e o f a h y d r i d e complex was done on t r a n s - H P t B r ( P E t 3 ) 2 and t h e B r a n d P E t 3 8 1igands were found t o form a T-shape about the metal. The h y d r i d e was assumed t o occupy the f o u r t h p o s i t i o n i n a normal square-planar compound.^^^ T h i s s i t u a t i o n i s c o mplicated by the f a c t t h a t the h y d r i d e 1igand i s not very stereochemica11y demanding and so i t i s not always p o s s i b l e t o f i n d an obvious (15) " h o l e " where the h y d r i d e may be l o c a t e d . ' Under the best c o n d i t i o n s , the h y d r i d e 1igand may be found by X-ray d i f f r a c t i o n such as f o r H R h ( C O ) ( P P h 3 > 3 . ( 1 1 * Neutron d i f f r a c t i o n remains the most d e f i n i t i v e way t o f u l l y s o l v e a hydride compound's s t r u c t u r e , s i n c e the neutron s c a t t e r i n g f a c t o r s f o r most elements are o f the same order o f magnitude and so h y d r i d e s are not "swamped out" by h e a v i e r atoms. T h i s allowed the proper 2- (12) i d e n t i f i c a t i o n o f ReH^ i n the n o w - c l a s s i c case. Neutron d i f f r a c t i o n i s , however, very expensive t o do and demands c r y s t a l s 100 t o 1000 times l a r g e r than those needed f o r X-ray d i f f r a c t i o n and consequently the number o f h y d r i d e compounds t h a t have been a n a l y z e d u s i n g t h i s technique i s s m a l l e r than might be ( 1 5) d e s i r e d . X-ray and neutron s t u d i e s have been s u c c e s s f u l l y combined on o c c a s i o n t o y i e l d very u s e f u l r e s u l t s — f o r example in the s o l u t i o n o f the s t r u c t u r e o f H ^ O S ^ C C O J Q . The two t e c h n i q u e s g e n e r a l l y g i v e s l i g h t l y d i f f e r e n t bond lengths f o r the metal-H d i s t a n c e . T h i s i s because in a metal-H l i n k , the e l e c t r o n d e n s i t y i s skewed toward the heavy atom and so X-ray data tend t o g i v e unreasonably s h o r t M-H d i s t a n c e s . Neutron d i f f r a c t i o n , on the other hand, depends on the p r o p e r t i e s o f the atomic n u c l e i and so M-H i n t e r a t o m i c d i s t a n c e s from t h i s technique a r e much more r e l i a b l e . D. P r e p a r a t i o n Metal h y d r i d e complexes can be made in a number o f d i f f e r e n t ways but the p r e p a r a t i o n s may g e n e r a l l y be d i v i d e d i n t o f i v e (29) c a t e g o r 1 e s . 1. Ox i dat i ve Add i t i on a) o x i d a t i v e a d d i t i o n o f H 2 t r a n s [ I r C l ( C O ) ( P P h 3 ) 2 ] H 2 I r C l ( C O ) ( P P h g ) 2 ( 3 0 ) PhMe b) h y d r o g e n o l y s i s o f a l k y l groups 2 ( n 5 - C 5 H 4 M e ) 2 Z r M e 2 - [ ( n 5 - C 5 H 4 M e ) 2 Z r H ] 2 ( u - H ) 2 ( 3 1 ) +4 CH A PhH * c) o x i d a t i v e a d d i t i o n o f HX (X = h a l l d e , c a r b y l ) HC1(aq) I r C l ( C O ) ( P E t 2 P h ) 2 - H l r C l 2 ( C O ) ( P E t 2 P h ) 2 ( 3 2 ) EtOH C 6 H 1 2 Cp«»(PMe 3) l r H 2 • Cp»(PMe 3) Ir(H) (CgHj j ) hv,-H 2 ( 3 3 ) 10 2. Reduction o f Metal H a l i d e s (metatnesis) L i A l H „ 4 ReC I 3 (PEt 2Ph) 3 - ReH 5 (PEt 2Ph) 3 THF 3 . Hydride T r a n s f e r a) base c a t a l y z e d r e d u c t i o n s u s i n g a l c o h o l s 0h~ I rC) 3 (PEt 2Ph) 3 «• H1 rC ) 2 (PEt 2Ph) 3 EtOH D) hydride a b s t r a c t i o n from s o l v e n t s THF, N 2 P P h ( t - B u ) 2 RhCl_ + 2 PPh(t-Bu)„ *• H-Rh-N=N 3 ' I Na/Hg PPh(t-Bu) THF (34) (35) (36) 4. P r o t o n a t i o n of Complex Metal Anions Na/Hg 1/2 Co 2(CO) 6CPMePn 23 2 • Na[Co(CO) 3(PMePh 2)] ( 6 ) H 3 P 0 4 HCo(CO) 3(PMePh 2) 5 . P r o t o n a t i o n o f Neutral Complexes HSO 3F ( n 4 - C 7 H 8 ) ( C O ) 3 F e • [ ( n 4 - C ? H 8 ) ( C O ) 3 F e ( H ) ] + ( 3 7 ) 1i q S 0 2 1 1 Methods #1, 2 and 4 a r e t h e most common b u t t h e c h o i c e o f method i s p r i m a r i l y g o v e r n e d by t h e a v a i l a b i l i t y o f a p p r o p r i a t e s t a r t i n g m a t e r i a l s . H y d r i d e c o m p l e x e s can a l s o r e s u l t f r o m more i n d i r e c t r o u t e s , s u c h a s d e c o m p o s i t i o n o f e x i s t i n g compounds ( e . g . B - e l i m i n a t i o n o f m e t a l a Iky I c o m p l e x e s ) . E. N i t r o s y l H y d r i d e s A l t h o u g h h y d r i d e s o f m e t a l c a r b o n y l s a r e w i d e l y known and examples e x i s t f o r a l m o s t e v e r y t r a n s i t i o n m e t a l , t h e number o f h y d r i d e s o f t h e r e l a t e d f a m i l y o f m e t a l n i t r o s y l s i s e x t r e m e l y s m a l l . When work began on t h e p r o j e c t d e s c r i b e d i n t h i s t h e s i s , o n l y a n a n d f u l o f n i t r o s y l h y d r i d e c o m p l e x e s had been i d e n t i f i e d . The f i r s t o f t h i s c l a s s o f compound p r e p a r e d was H M n ( N O ) 2 ( P P h 3 ) 2 (38) i n 1962. The n e x t r e p o r t d i d n o t a p p e a r u n t i 1 1972 when CpRe(CO)(NO)H was communicated by Graham and S w e e t . * 3 9 * S i n c e t h a t t i m e , o t h e r t h a n work done i n o u r l a b o r a t o r y , o n l y H W 2 ( C 0 ) 8 ( N 0 ) L (L=C0, P ( O M e ) 3 ) , ( 1 4 } H R e ( N O ) 2 ( P P h 3 ) 2 , ( 4 0 } H 2 R e ( N O ) ( P P h 3 ) 3 , ( 4 1 } H M 3 ( C O ) 1 Q ( N 0 ) (M=Ru, 0 s ) , ( 4 2 ) H F e ( C O ) 2 ( P P h 3 ) 2 ( N O ) ( 4 3 ) a n d H W ( C O ) 2 [ P ( 0 - i - P r ) 3 ] 2 ( N O ) ( 4 4 ) have been d e s c r i b e d ( a s w e l l a s a few p h o s p h i n e s u b s t i t u t i o n p r o d u c t s o f t h e s e compounds). H y d r i d e p r e p a r a t i o n i n o u r l a b o r a t o r y s t a r t e d i n 1979 when CpW(NO) 2H was s y n t h e s i z e d f r o m CpW(NO) 2Cl and N a [ H 2 A l ( O C H 2 C H 2 O C H 3 ) 2 3 . ( 4 5 ) T h i s compound i s p a r t i c u l a r l y I n t e r e s t i n g i n t h a t i t a c t s a s a m i l d s o u r c e o f H~, a s o p p o s e d t o 12 t h e r e l a t e d c a r b o n y l a n a l o g u e CpW(CO> 3H, w h i c h i s a m o d e r a t e l y + (A) s t r o n g a c i d (H ). M o l e c u l a r o r b i t a l c a l c u l a t i o n s have a t t r i b u t e d t h i s t o t h e t h r e e - l e g g e d p i a n o - s t o o l s t r u c t u r e o f CpW(NO> 2H, a s compared t o t h e f o u i — l e g g e d c o n f i g u r a t i o n o f t h e c a r b o n y l h y d r i d e . ^ 4 6 * In a d d i t i o n , p a r t i a l h y d r i d e a b s t r a c t i o n by P h 3 C + o f Cpw(NO) 2H l e a d s t o t h e f o r m a t i o n o f t h e d i n u c l e a r h y d r i d e [CpW(NO) ] ( y - H ) + (and ana 1 o g u e s ) . ( 4 7 * B e c a u s e o f t h e c h e m i s t r y o b s e r v e d f o r CpW(NO) 2H, i t was o f i n t e r e s t t o p r e p a r e o t h e r n i t r o s y l h y d r i d e s a n d i n v e s t i g a t e t h e i r p r o p e r t i e s . F. Scope o f t h e P r e s e n t Work The work d e s c r i b e d i n t h i s t h e s i s i s a d i r e c t c o n t i n u a t i o n o f t h e work s t a r t e d by J.C. 0 x l e y . ( 4 8 ) C h a p t e r 2 d e s c r i b e s t h e p r e p a r a t i o n o f a s e r i e s o f n i t r o s y l (49) h y d r i d e s d e r i v e d f r o m [ C p W ( N O ) I 2 J 2 a n d i n p a r t i c u l a r t h e p r o p e r t i e s o f t h r e e d i m e r i c compounds. As a r e s u l t o f c h a r a c t e r i z i n g t h e compounds d e s c r i b e d i n c h a p t e r 2 and t h e a s s o c i a t e d s u r v e y o f t h e l i t e r a t u r e , some i n t e r e s t i n g a nd s i g n i f i c a n t NMR p r o p e r t i e s o f t u n g s t e n h y d r i d e s were d i s c o v e r e d — t h e s e a r e d i s c u s s e d In c h a p t e r 3. W h i l e t h e work d e s c r i b e d i n c h a p t e r s 2 a n d 3 was i n p r o g r e s s , t h e n o v e l , s t a b l e 16 e l e c t r o n compounds CpM(NO)R 2 (M=Mo, W; R=bulky a l k y l ) were p r e p a r e d i n o u r 50 l a b o r a t o r y by t h e r e a c t i o n 13 1. RMgX [CpM(NO)I 2] 2 - 2 CpM(NO)R 2 2. H 20 These compounds were found t o undergo unique r e a c t i v i t y with S o t ( 5 1 ) 0 „ ( 5 2 ) and NO. ( 5 3 ) Because the y i e l d s o f the i n t e r e s t i n g compounds d e s c r i b e d i n chapter 2 were too low t o a l l o w much d e r i v a t i v e chemistry t o be done, i t was decided t o t r y and o b t a i n n i t r o s y l h y d r i d e s from the hydrogenation o f CpW(NO)(CH 2SiMe 3) 2. T h i s work i s d e t a i l e d in chapter 4, along with i t s e x t e n s i o n t o the Cp* analogues. 14 G. References and Notes 1. Hieber, W. ; L e u t e r t , F. Zj_ Anorg. Al 1 g. Chem. 1932, 204, 145-164. 2. Hieber, W. Elektrochem. 1934, 40, 158-159. 3. W i l k i n s o n , G.; Birmingham, J.M. J ^ Am. Chem. Soc. 1955, 77, 3421-3422. 4. F i s h e r , E.O.; Hafner, W. ; S t a h l , H.O. Zj_ Anorg. Al l g . Chem. 1955, 282, 47-62. 5. P a r s h a l 1 , G.W. "Homogeneous C a t a l y s i s " , W i l e y - I n t e r s c i e n c e : Toronto, 1980 and r e f e r e n c e s t h e r e i n . 6. Mar t i n , J.T.; B a i r d , M.C. Organometal1ics 1983, 2, 1073- 1078. 7. 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Ox l e y , J . C . Ph.D. D i s s e r t a t i o n , The U n i v e r s i t y of" B r i t i s h C o l u m b i a , 1983. 49. L e g z d i n s , P.; M a r t i n , D.T.; N u r s e , C.R. I n o r g . Chem. 1980, 19, 1560-1564. 50. L e g z d i n s , P.; R e t t i g , S . J . ; S a n c h e z , L.; B u r s t e n , B.E.; G a t t e r , M.G. J . Am. Chem. S o c . 1985, 107, 1411-1413. 51. L e g z d i n s , P.; S a n c h e z , L. J ^ Am. Chem. S o c . 1985, 107, 5525-5526. 52. L e g z d i n s , P.; R e t t i g , S . J . S a n c h e z , L. O r g a n o m e t a l 1 i c s 1985, 4, 1470-1471. 53. E v a n s , S.V.; L e g z d i n s , P.; R e t t i g , S . J . ; S a n c h e z , L.; T r o t t e r , J . p e r s o n a l c o m m u n i c a t i o n . 19 C h a p t e r 2 New Organometa1 1 i c Hydr i do N i t r o s y 1 Complexes o f T u n g s t e n V e r y few o r g a n o m e t a 1 1 i c n i t r o s y l h y d r i d e c o m p l e x e s a r e known. As d i s c u s s e d i n t h e p r e v i o u s c h a p t e r , when work i n t h i s a r e a was s t a r t e d i n o u r l a b o r a t o r y , o n l y CpRe(CO)(NO)H was known and t h e u n u s u a l p r o p e r t i e s o f CpW(NO) 2H s u b s e q u e n t l y f o u n d s p u r r e d o u r i n t e r e s t i n t h e t o p i c . In 1980, [CpW(NO)I 1 * was p r e p a r e d i n o u r l a b o r a t o r y and i t was hoped t h a t h y d r i d e c o m p l e x e s c o u l d be made f r o m i t by ha 1 i d e / h y d r i d e m e t a t h e s i s ( p r e p a r a t i o n method #2 - c h a p t e r 1 ) . T h i s work was s t a r t e d by (2) J . C . Ox l e y , who p r e p a r e d t h e s e r i e s o f compounds CpW(NO)IHI_ ( L = P ( 0 P h ) 3 , P ( 0 M e ) 3 , P P h 3 ) and C p W ( N O ) H 2 [ P ( O P h ) 3 ] , a s w e l l a s t h e compounds [ C p W ( N O ) I H ] 2 , [ C p W ( N 0 ) H 2 ] 2 and [ C p W ( N O ) H { P ( 0 P h ) 3 } ] 2 . However, t h e s e t h r e e d i m e r i c s p e c i e s were n o t c o r r e c t l y c h a r a c t e r i z e d a n d t h e work d e s c r i b e d i n t h i s c h a p t e r m a i n l y i n v o l v e d t h e s y n t h e s i s and c o m p l e t e c h a r a c t e r i z a t i o n o f t h e s e t h r e e c o m p l e x e s , a s w e l l a s a f u l l d e s c r i p t i o n o f t h e p r o p e r t i e s o f t h e CpW(N0)XX'L (X=I o r H; L = P ( O P h ) 3 , P ( 0 M e ) 3 , P P h 3 a n d / o r PMe 3) s e r i e s o f compounds. E x p e r i menta1 S e c t i on A l l m a n i p u l a t i o n s were p e r f o r m e d so a s t o m a i n t a i n a l l c h e m i c a l s u n d e r an a t m o s p h e r e o f p r e p u r i f i e d d i n i t r o g e n e i t h e r on (3 ) t h e b e nch u s i n g c o n v e n t i o n a l S c h l e n k t e c h n i q u e s * ' o r i n a Vacuum 20 A t m o s p h e r e s C o r p . D r i - L a b Model HE-43-2 d r y b o x . A l l c h e m i c a l s u s e d were o f r e a g e n t g r a d e o r c o m p a r a b l e p u r i t y . A l l r e a g e n t s were e i t h e r p u r c h a s e d f r o m c o m m e r c i a l s u p p l i e r s o r p r e p a r e d a c c o r d i n g t o p u b l i s h e d p r o c e d u r e s , and t h e i r p u r i t y was c h e c k e d by e l e m e n t a l a n a l y s e s a n d / o r o t h e r s u i t a b l e methods. M e l t i n g p o i n t s were t a k e n i n c a p i l l a r i e s u n d e r n i t r o g e n u s i n g a G a l l e n k a m p M e l t i n g P o i n t a p p a r a t u s and a r e u n c o r r e c t e d . Hexanes and b e n z e n e were d r i e d w i t h CaH^, t o l u e n e , d i e t h y l e t h e r and THF were d r i e d w i t h Na/benzophenone k e t y l and C H ^ C ^ was d r i e d w i t h P 2 0 5 . A l l s o l v e n t s were d i s t i l l e d o f f t h e i r r e s p e c t i v e d r y i n g a g e n t s and p u r g e d w i t h N 2 j u s t p r i o r t o u s e . U n l e s s o t h e r w i s e s p e c i f i e d , t h e r e a c t i o n s d e s c r i b e d below were done a t a m b i e n t t e m p e r a t u r e s . I n f r a r e d s p e c t r a were r e c o r d e d on a N i c o l e t 5DX FT-IR i n s t r u m e n t . P r o t o n m a g n e t i c r e s o n a n c e s p e c t r a were o b t a i n e d on a B r u k e r WP-80, WH-400, HXS-270, N i c o 1 e t - O x f o r d H-270 o r V a r i a n XL- 300 s p e c t r o m e t e r w i t h r e f e r e n c e t o t h e r e s i d u a l p r o t o n s i g n a l o f (A) t h e d e u t e r i a t e d s o l v e n t employed, and a r e r e p o r t e d i n ppm 3 1 d o w n f i e l d f r o m M e „ S i . P NMR s p e c t r a were r e c o r d e d a t 121.4-MHz 4 on a V a r i a n XL-300, 40.5-MHz on a V a r i a n XL-100, o r a t 32.38-MHz 2 on a B r u k e r WP-80 s p e c t r o m e t e r u s i n g H a s t h e i n t e r n a l l o c k . The o b s e r v e d r e s o n a n c e s were r e f e r e n c e d t o e x t e r n a l P ( 0 M e ) 3 w h i c h was c o n s i d e r e d t o have a c h e m i c a l s h i f t o f +141 ppm d o w n f i e l d f r o m 85% H 3 P 0 4 . ( 5 ) Mrs. M.T. A u s t r i a , Ms. M.A. Heldman, Ms. L.K. Darge and Dr. S.O. Chan a s s i s t e d i n o b t a i n i n g t h e NMR d a t a . 21 E l e c t r o n impact mass s p e c t r a were r e c o r d e d a t 70 eV on an A t l a s CH4B o r a K r a t o s MS50 s p e c t r o m e t e r u s i n g t h e d i r e c t - i n s e r t i o n method w i t h t h e a s s i s t a n c e o f Mr. M.A. Lapawa, Mr. J.W. N i p a n d Dr. G.K. E i g e n d o r f . The GC-MS sa m p l e s were r u n on a V a r i a n V i s t a 6000 gas c h r o m a t o g r a p h i n t e r f a c e d w i t h a Nermag RIO-10 q u a d r u p o l e mass s p e c t r o m e t e r o r a C a r l o E r b a GC i n t e r f a c e d w i t h a K r a t o s MS-80 RFA s p e c t r o m e t e r u s i n g t h e c o n d i t i o n s s p e c i f i e d b elow w i t h t h e a s s i s t a n c e o f Ms. C. Moxham. Gas c h r o m a t o g r a p h i c a n a l y s e s were c a r r i e d o u t on a P e r k i n E l m e r Sigma 4B i n s t r u m e n t u s i n g a 30' x 1/8" 237. SP-1700 on 80/100 Ch r o m o s o r b P AW column a t 70°C w i t h 25 ml./min He c a r r i e r g a s . E l e m e n t a l a n a l y s e s were p e r f o r m e d by Mr. P. B o r d a . P r e p a r a t i o n o f C p W ( N 0 ) I 2 L (L = P ( 0 M e ) 3 o r PMe 3>. T h e s e compounds were p r e p a r e d by t r e a t i n g [ C p W ( N 0 ) I 2 ] 2 i n C H 2 C 1 2 w i t h 2 e q u i v a l e n t s o f L i n t h e manner d e s c r i b e d p r e v i o u s l y * 1 * f o r L=P(OPh> 3 o r P P h 3 « B o t h c o m p l e x e s were i s o l a t e d a s brown c r y s t a l s i n y i e l d s o f 877.. The a n a l y t i c a l , IR and NMR d a t a f o r t h e s e and t h e o t h e r compounds s y n t h e s i z e d i n (2) t h i s work, a s w e l l a s r e l a t e d s p e c i e s f r o m p r e l i m i n a r y work a r e c o l l e c t e d i n T a b l e s 2-1 a n d 2-1 I. P r e p a r a t i on o f [CpW(NO)IH] . A v i g o u r o u s l y s t i r r e d m i x t u r e o f [ C p W ( N O ) I 2 ] 2 * 1 * (3.00 g, 2.82 mmol), CH C L (25 mL) a n d benzene (150 mL) was h e a t e d g e n t l y 22 t o s o l u b i l i z e t h e o r g a n o m e t a 1 1 i c s t a r t i n g m a t e r i a l . Once a c l e a r , y e l l o w - b r o w n s o l u t i o n was o b t a i n e d , t h e m i x t u r e was c o o l e d t o room t e m p e r a t u r e w i t h a w a t e r b a t h . Then, b e f o r e p r e c i p i t a t i o n o f [ C p W ( N O ) l 2 ] 2 c o u l d o c c u r , 0.85 mL (2.9 mmol) o f a 3.4 M s o l u t i o n o f N a [ H 2 A l ( 0 C H 2 C H 2 0 C H 3 ) 2 J i n t o l u e n e ( 6 ) was r a p i d l y a d d e d d r o p w i s e . The r e a c t i o n m i x t u r e i m m e d i a t e l y t u r n e d an i n t e n s e , d a r k g r e e n c o l o u r w i t h t h e s i m u l t a n e o u s f o r m a t i o n o f a l a r g e amount o f v e r y f i n e , brown, i n t r a c t a b l e p r e c i p i t a t e . The m i x t u r e was t h e n f i l t e r e d a s r a p i d l y a s p o s s i b l e t h r o u g h a 3 x 4 cm column o f C e l i t e s u p p o r t e d on a medium p o r o s i t y g l a s s f r i t , w h i c h was s u b s e q u e n t l y washed w i t h 2 x 15 mL p o r t i o n s o f b e n z e n e . The f i l t r a t e was c o n c e n t r a t e d u n d e r vacuum t o 10-15 mL w h i c h i n d u c e d t h e f o r m a t i o n o f v e r y i n t e n s e l y c o l o u r e d d a r k g r e e n m i c r o c r y s t a l s . T h i s m a t e r i a l was c o l l e c t e d by f i l t r a t i o n , washed w i t h b e n z e n e (3 x 5 mL) and d r i e d u n d e r vacuum (0.005 mm Hg) t o g i v e 0.80 g ( 3 5 % y i e l d ) o f a n a l y t i c a l l y p u r e [ C p W ( N O ) I H ] 2 > P r e p a r a t i o n o f C p W ( N O ) l H ( P M e 3 ) . A d d i t i o n o f n e a t Ph*e 3 (0.40 mL, 0.30 g, 4.0 mmol) t o t h e d a r k g r e e n f i l t r a t e c o n t a i n i n g [ C p W ( N 0 ) I H ] 2 ( d e s c r i b e d a b o v e ) c a u s e d an immediate c o l o u r c hange t o o r a n g e a n d t h e p r e c i p i t a t i o n o f a brown i n t r a c t a b l e s o l i d . The s u p e r n a t a n t s o l u t i o n was f i l t e r c a n n u l a t e d away f r o m t h e p r e c i p i t a t e a n d i t s volume d e c r e a s e d t o 50 mL u n d e r r e d u c e d p r e s s u r e . Hexanes (60 mL) were a d d e d , and t h e r e s u l t i n g s o l u t i o n was f u r t h e r c o n c e n t r a t e d t o 40 23 mL and l e t s t a n d o v e r n i g h t . T h i s r e s u l t e d i n t h e f o r m a t i o n o f a l i g h t brown, m i c r o c y r s t a 1 1 i n e p r e c i p i t a t e w h i c h was c o l l e c t e d by f i l t r a t i o n a nd washed w i t h h e x a nes (5 x 10 mL) t o o b t a i n 0.98 g (367. y i e l d b a s e d on [ C p W ( N O ) I 2 ] 2 ) of a s o l i d w h i c h a n a l y z e d as CpW(NO)IH(PMe 3) ( s e e r e s u l t s and d i s c u s s i o n ) . P r e p a r a t i o n o f [ C p W ( N O ) H 2 ] 2 . The s t i r r e d d a r k g r e e n f i l t r a t e c o n t a i n i n g [ C p w ( N O ) I H ] 2 ( g e n e r a t e d a s a b o v e ) was t r e a t e d d r o p w i s e w i t h a 3.4 M t o l u e n e s o l u t i o n o f N a [ H 2 A l ( O C H 2 C H 2 O C H 3 ) 2 ] u n t i l t h e g r e e n c o l o u r j u s t d i s a p p e a r e d (~0.7 mL, * 2.4 mmol). The f i n a l r e a c t i o n m i x t u r e c o n s i s t e d o f a l a r g e amount o f t h e u s u a l f i n e , brown p r e c i p i t a t e a n d a d a r k r e d - b r o w n s o l u t i o n . The m i x t u r e was t h e n f i l t e r e d a s r a p i d l y a s p o s s i b l e t h r o u g h a 3 x 4 cm column o f C e l i t e s u p p o r t e d on a medium p o r o s i t y g l a s s f r i t a nd t h e column washed w i t h b e n z e n e (2 x 15 mL). The r e s u l t i n g r e d - b rown f i l t r a t e was t h e n c o n c e n t r a t e d u n d e r vacuum t o ~10 mL, l e t s t a n d f o r s e v e r a l h o u r s , a n d t h e r e s u l t i n g o r a n g e powder c o l l e c t e d by f i l t r a t i o n . I t was t h e n washed w i t h b e n z e n e (3 x 5 mL) and d r i e d u n d e r vacuum (0.005 mm Hg) t o g i v e 0.16 g ( 1 0 % y i e l d b a s e d on o r i g i n a l [ C p W ( N O ) I 2 ] 2 ) o f a n a l y t i c a l l y p u r e [ C p W ( N O ) H 2 ] 2 . T h i s powder c o u l d be c o n v e r t e d t o s m a l l , w e l l - f o r m e d c r y s t a l s o f [ C p W ( N O ) H 2 3 2 i n v e r y low y i e l d i n t h e f o l l o w i n g manner. The powder was s t i r r e d w i t h t o l u e n e (50 mL) and warmed s l i g h t l y (~50°C) t o promote s o l u b i l i z a t i o n . The o r a n g e s o l u t i o n was t h e n f i l t e r c a n n u l a t e d 24 i n t o a n o t h e r f l a s k a n a volume r e d u c e d under vacuum u n t i l p r e c i p i t a t i o n s t a r t e d t o o c c u r (-15 mL). The s o l u t i o n was t h e n f i l t e r c a n n u l a t e d i n t o a l o n g , n a r r o w S c h l e n k t u b e , e n s u r i n g t h a t no p r e c i p i t a t e came o v e r an d t h e s o l u t i o n was comp1ete1y c l e a r . The S c h l e n k t u b e was t h e n s t o r e d a t - 2 5 ° C o v e r n i g h t , i n d u c i n g f o r m a t i o n o f t h e c r y s t a l s . The mother l i q u o r was t h e n c a n n u l a t e d o f f a n d t h e c r y s t a l s washed w i t h 3 x 10 mL o f d i e t h y l e t h e r , and d r i e d u nder vacuum (0.005 mm Hg) t o y i e l d ~20 mg o f c r y s t a l l i n e [ C p W ( N O ) H 2 ] 2 . P r e p a r a t i o n o f [ C p W ( N O ) H { P ( 0 P h ) 3 } ] 2 and CpW(NO)H 2[P(0Ph) ] . A m i x t u r e o f [ C p W ( N O ) H 2 ] 2 (0.10 g, 0.18 mmol) and b e n z e n e (30 mL) was s t i r r e d and warmed w i t h a w a t e r b a t h (~50°C) u n t i l a c l e a r , o r a n g e s o l u t i o n r e s u l t e d (~10 m i n ) . To t h i s was a d d e d n e a t P ( 0 P h ) 3 (93 yL, 0.35 mmol) and t h e s o l u t i o n s t i r r e d f o r 6 h a s i t t u r n e d a v e r y i n t e n s e p u r p l e c o l o u r . The s o l v e n t was t h e n removed u n d e r vacuum and t h e p u r p l e , o i l y r e s i d u e t a k e n up i n 15 mL b e n z e n e , f i l t e r e d , and 25 mL o f h e x a nes were a d d e d t o p r e c i p i t a t e t h e p r o d u c t . The v e r y i n t e n s e l y c o l o u r e d , p u r p l e , m i c r o c r y s t a l 1 i n e m a t e r i a l was c o l l e c t e d by f i l t r a t i o n , washed w i t h h e x a n e s and d r i e d u n d e r vacuum t o g i v e 0.086 g ( 4 1 % y i e l d ) o f [ C p W ( N O ) H { P ( O P h ) 3 } ] 2 . A s m a l l amount o f t h e p u r p l e c r y s t a l s was d i s s o l v e d i n C H 2 C 1 2 (10 mL) a n d t h e r e s u l t i n g s o l u t i o n was s t i r r e d f o r 3 h whereupon i t became o r a n g e . A d d i t i o n o f h e x a n e s t o t h i s s o l u t i o n 25 o f a n a l y t i c a l l y p u r e was c o l l e c t e d by P r e p a r a t i o n o f [ C p W ( N O ) B r 2 ] 2 . A s o l u t i o n o f CpW(CO> 2(NO) (5.00 g, 15.0 mmol) i n 40 mL C H 2 C 1 2 was s t i r r e d a n d c o o l e d t o - 4 0 ° C whereupon a s o l u t i o n o f B r 2 (0.77 mL, 15.0 mmol) i n 10 mL C H 2 C 1 2 was s l o w l y a d d e d d r o p w i s e . The m i x t u r e i m m e d i a t e l y t u r n e d d a r k r e d - b r o w n a n d v i g o r o u s gas e v o l u t i o n o c c u r r e d w h i l e a d a r k brown p r e c i p i t a t e began t o f o r m . A f t e r s t i r r i n g f o r ~5 min, t h e c o l d b a t h was removed and t h e r e a c t i o n m i x t u r e g r a d u a l l y a l l o w e d t o warm t o n e a r room t e m p e r a t u r e . The s o l v e n t was removed under vacuum u n t i l ~20 mL r e m a i n e d , g i v i n g a d e e p g r e e n s o l u t i o n a b o v e a d a r k brown p r e c i p i t a t e . An IR s p e c t r u m o f t h e s o l u t i o n showed bands a t 2 0 9 9 ( s ) , 2 0 1 0 ( s ) , 1 9 2 7 ( s ) , 1693(s) and 1655 c m - 1 . Hexanes (25 mL) were a d d e d and t h e volume o f t h e s o l u t i o n f u r t h e r d e c r e a s e d u n d e r vacuum u n t i l ~10 mL o f a v e r y p a l e g r e e n s o l u t i o n was l e f t o v e r a d a r k brown p r e c i p i t a t e . T h i s p r e c i p i t a t e was t h e n f i l t e r e d , washed w i t h 3 x 20 mL h e x a n e s a n d d r i e d i n vacuum (0.005 mm Hg) o v e r n i g h t t o g i v e 5.20 g ( 7 9 . 2 % y i e l d ) o f d a r k brown m i c r o c r y s t a 1 1 i n e [CpW(N0)Br i n d u c e d t h e p r e c i p i t a t i o n o f a s m a l l amount C p W ( N 0 ) H 2 P ( 0 P h ) 3 a s an o r a n g e powder, w h i c h f i l t r a t i o n a s a b o v e . 26 P r e p a r a t i o n o f C p W ( N O ) B r H [ P ( O P h ) 3 ] . To a d a r k g r e e n s o l u t i o n o f [ C p w ( N O ) B r 2 ] 2 (1.00 g, 1.14 mmol) i n 10 mL C H 2 C 1 2 a n d 50 mL be n z e n e was add e d r a p i d l y d r o p w i s e 0.34 mL (1.1 mmol) o f a 3.4 M s o l u t i o n o f N a [ H 2 A l ( O C H 2 C H 2 O C H 3 ) 2 3 i n t o l u e n e . The s o l u t i o n i n s t a n t l y t u r n e d o r a n g e and a l a r g e amount o f brown p r e c i p i t a t e f o r m e d . The m i x t u r e was r a p i d l y f i l t e r e d t h r o u g h a 3 x 4 cm column o f C e l i t e s u p p o r t e d on a medium p o r o s i t y g l a s s f r i t w h i c h was t h e n washed w i t h 2 x 15 mL p o r t i o n s o f b e n z e n e . T r i p h e n y l p h o s p h i t e ( P ( 0 P h ) 3 > 0.60 mL, 2.28 mmol) was t h e n a d d e d t o t h e f i l t r a t e a nd no s i g n i f i c a n t c o l o u r change was o b s e r v e d . The volume o f t h e s o l u t i o n was r e d u c e d t o ~10 mL un d e r vacuum and c h r o m a t o g r a p h e d on F l o r i s i l (2 x 10 cm) u s i n g b e n z e n e a s e l u e n t t o g i v e o n l y one o r a n g e band. T h i s band was c o l l e c t e d , t h e s o l v e n t removed under vacuum, a n d t h e r e s u l t i n g o i l r e c r y s t a 1 1 i z e d f r o m C H 2 C 1 2 / h e x a n e s t o g i v e 0.20 g (137. y i e l d ) o f l a r g e , r e d - b r o w n c r y s t a l s o f CpW(NO)BrH[P(OPh) ] . 27 Table 2-1. Analytical and Infrared Data for the Complexes an a l y t i c a l data C H N other IR data (CH.Ct,) complex •P, °c (dec) calcd found calcd found calcd found calcd found -1 CI CpM(H0)l 2[P(0Ph) 3] ( 1 1 1663 CpH(NO)I 2(P(0(le> 3] 178 14.63 14.58 2.15 2.18 2.13 2.12 1 38.64 38.49 1653 CpM(MO)I 2(PPn 3) U ) 1646 Cp«(«0)l 2(P«e 3) 160 15.78 15.70 2.32 2.28 2.30 2.28 1 41.69 41.55 1638 CpH(N0)IH[P(0Ph) 3] 112 38.52 38.46 2.95 3.10 1.95 1.89 1643 1883 CpH(N0)IH[P(0lle) 3] 103 18.08 17.96 2.82 2.84 2.64 2.65 1629 1923 CpH(NO)IH(PPh 3) ( 2' 1615 ? a CpH(NO)IH(Plte3) t C p « ( N 0 ) l 2 ] 2 ( n 101 19.90 19.90 19.80 19.86 3.13 3.13 3.24 3.00 2.90 2.90 2.85 2.85 I 26.28 26.40 1613 (isoaer A) 1609 (A + B) 1655 1931 1929, 189! [Cp«(N0)IH) 2 174 14.74 14.75 1.47 1.50 3.44 3.49 1646 n.o. (Cp«(N0)H 2] 2 130 21.37 21.44 2.51 2.46 4.99 4.93 0 5.69 6.00 1599 1906 lCp«(KO)H{P(OPh) 3}] 2 85 46.80' 46.64 3.59 3.63 2.37 2.36 1578 n.o. CpH(N0)H 2(P(0Ph) 3J , 2 ) 1607 1863 [CpH(N0)Br 2] 2 13.69 13.57 1.15 1.16 3.19 3.15 Br 36.42 36.28 1655 Cp«(N0)BrH[P(0Ph) 3) 102 41.22 41.40 3.16 3.29 2.09 2.05 Br 11.96 12.11 1636 1869 a The for CpK(NO)lH(PPhJ cannot be unequivocally assigned as there are several bands in the appropriate spectral regions. 28 T a b l e 2-11. NRR Data f o r t h e Complexes Coap1 ex n u c l e u s s o l v I s o n r a s s g ' t i ( J , Hz) C p K ( N O ) l 2 ( P ( O P h ) 3 ] ' H C D C I 3 CP 5.90 ( d , 5, 3 J H p = 3) P ( 0 P h ) 3 7.2 ( b r , 15) C6°6 CP 5.43 ( d , 5, 3 J H P = 3) P ( 0 P h ) 3 7.1 ( b r , 15) C p M ( H 0 ) I 2 [ P ( 0 H e ) 3 ] ' H C D C I 3 CP 5.98 ( d , 5, 3 J H P 2) P ( 0 H e ) 3 3.83 ( d , 9, 3 J H p = 1 1 ) C6°6 CP 5.43 ( d , 5, 3 J H P = 3) P(0«e) 3 3.45 ( d , 9, 3 J H p = I I ) C p H ( N O ) I 2 ( P P h 3 ) ' H coci3 CP 5.91 ( d , 5, 3 J H P = 1.2) P P h 3 7.5 ( b r , 15) C6°6 CP 5.26 ( d , 5, 3 J H P = 2) PPh,3 7.1 ( b r , 15) C p H ( w O ) l 2 ( P n e 3 ) a coci3 A CP 5.94 (d, 5, 3 J H p = 2.8) p5i 3 1.90 ( d , 9, 3 J H p = 10.2) C 6 ° 6 A CP 5.06 ( d , 5, 3 J H P = 2.8) P 5 i 3 1.08 ( d , 9, 3 J H R = 10.2) 6 CP 5.20 ( s , 5) P"e 3 1.54 ( d , 9, 3 J H p = 10) 29 Table 2-11 (Cont'd) CpH(H0)lH[P(OPh)3J ' H C0CI3 C6D6 3 1 P { ' H ) C 6 O 6 Cp P(OPh) U-H Cp P(OPh) Hi 3 3 5.25 (s, 5) 7.2 (br, 15) -2.04 (d, I, Z J H p = 112. 'j H | ( = 54) 4.85 (s, 5) 7.1 (br, 15) -2.06 (d, I, 2 J H p = 112, ' j H l j = 54) 115.5 (s, l J p ) ( 363) Cp«(HO)lH[P(OBe)3] *H CDCIJ Vs 3 1 P('H) cfio6 CP P«OBe)3 U-H Cp P(OHe) 3 M-H 5.81 (s, 5) 3.73 (d, 9, J J H R * 12) -1.44 (d, 1, 2 J H p = 101, 'J H ( ( = 57) 5.12 (s, 5) 3.36 (d, 9, J H p = 12) - i . 4 i (d, i, 2aHp * 101, 'J H B = 57) 131 (s) Cp¥(NO)lH(PPh.) H CDC) 3 C6D6 3 1 P { ' H) C CP ppn_3 U-H CP PPh3 K-H 6"6 5.63 (s, 5) 7.4 (br, 15) 0.31 (d, 1, 2 J H p = 85, ' J H | ( = 58) 5.10 (s, 5) 7.4 (br, 15) 0.10 (d, 1, 2 J H p r 85, ' J H | ( = 58) 14.1 (s) 30 Table 2-11 (Cont'd) CpH(NO)lH(PKe3) CDC I. C6°6 C P Pne3 » - H C P p5ij K-H C P Pfte3 Hi C P PBe3 U-H 5.60 (d, 5, J J H p < I) 1.87 (d, 9, 3 J H p = 9.5) -0.65 (d, 1, 2 J M p r 84, 'JH | ( * 66) 5.73 (dd, 5, 3 J H p , 3 J H M = 1.5, < I) 1.80 (d, 9, 3 J H p = 9.7) HO6 5.11 U, 5) 1.39 (d, 9, J J H p = 9) -1.13 (d, I, 2J HP 84, ' J H y = 66) 4.80 (d, 5, J : 1.8) 1.20 (d, 9, 3 J H p * 9.5) H0D CpH(H0)H2(P(OPn)3] ' H COCI^ C6°6 3 , P { I H ) C 6 O 6 C P P(OPh)3 U-H C P P(OPh)3 U-H 5.10 (S, 5) 7.3 (br, 15) -1.82 9d, 2, 2 J H p = 86, ' j ^ = 88) 4.69 (s, 5) 7.2 (br, 15) -1.58 (d, 2, 2 J H p = 87, 'j H | j = 87) 137 (s) Cp«(KO)H2(P(OHe)3] ' H Cfi06 C P 5.17 (s, 5) P(0*e)3 K-H 3.47 (d, 9, J J H p = 12) -1.74 (d, 2, 2 J H p =  81, ' j ^ = 87) 31 Table 2-11 (Cont'd) [ C p W ( N 0 ) l 2 ] 2 CDC I C 6 ° 6 CP CP 6.30 ( s , ' 1.8) 5.00 (s) [ C p K ( N 0 ) l ] 2 ( | H f ) 2 l H CDC I 3 C 6 ° 6 CP H - H - K CP U - H 6.21 ( s , 10) -1.21 ( s , 2, 'j H ( ), = 3.7, ' J H ( ) = 88.3, Vi. " 7(,•8, 5.31 (3, 10) -1.21 ( s , 2 ) d ( C P « ( H 0 ) H ] 2 ( U - H ) 2 C L H C D C I 3 A CP CP W - * A ""V Cp CP 5.95 ( s , 10) 3 2 6.99 (•• 2, J H ( A ) H ( A , , • I . J H ( A ) H ( X ) " 2 J H ( A ) H ( X ' ) * 4 - 5 , \ * = 9 5 , 2 J H I . ' , 3 ) -2.05 (., 2. \ { m { r ) - 4. UU\m J H ( X ' ) « 1 = 9 3 ) 5.93 ( s , 10) 6.55 (dd, 2, 2 J H ( A ) H ( B ) -- 3.0, 2 J H ( A ) H ( X ) 8.5, \ m - 99) , < 3 9 L J H ( ( l ) H ( X ) = 2 < 5 , ,JH(I1)« = -5.94 ( t d , I . \ M - % ) 5.23 ( s , 10) 7.01 (•, 2) -1.90 (•, 2) 5.26 ( s , 10) 32 Table 2-11 (Cont'd) 6.64 ( d d , 2) 1.66 H , I) - 5 . 9 9 ( t d , 1) ( C p « ( H O ) ( P ( O P h ) 3 ) ] 2 ( M - H ) 2 C ' H C 0 C l 3 f 31 C6°6 P('H) cfio6 Cp P ( 0 P h ) 3 U-H-U CP P(0Ph) 3 U-H-U 4.97 (5, 10) 7.4 ( b r , 30) 1.10 (• , 2) 5.17 ( d , 10, J J H p * I) 7.0 ( b r , 30) 1.32 ( t , 2 , 2 J H p = 24, ' j 151 ( s , ' j p t ( * 595) [CpU(NO(P(One) 3 )l 2 (B-H) 2 *H C f i D 6 CP P ( 0 B e ) 3 U-H-U CP P ( 0 $ e ) 3 U-H-U 5.23 ( s , 10) 3.67 ( d , 18, J H p = 12) 0.82 ( t , 2 , 2 J H p = 24, * J 5.60 ( s , 10, 3 J H p = 1) 3.55 ( d , 18, 3 J H f > = 12) 0.84 ( t , 2 , 2 J H p = 26, ' j [CoM{NO)Br2!2 *H COCI C 6 D 6 Cp CP 6.35 ( s , J H ) ( = 1.8) 5.08 (s) 33 Table 2-11 (Cont'd) CpK(N0)BrH[P(0Ph)3) H COCIj C6°6 3 1 P { ' H ) C 6 D 6 CP 5.29 (d, 5, J J H H = 0.7) PlOfnJj K-H 7.3 (br, 15) 0.21 (d sex, I, a J H H = 0.7, CP P(OPh)3 K-H 4.84 (d, 5, 3 J H f ) = 0.7) 6.8-7.5 (br, 15) 0.20 (d sex, 1, 3 J H H = 0.7, 120.2 ( ' J w = 360) a In COCIj, CpM(NO)l2<P'le3) exists exclusively as isoier A. b NO = not observed. c See text for a coapiete discussion of the ' H IMP. spectrut of this coiplex. 183 d (CpH(NO)l],(ii-H), is not sufficiently soluble in C,0, to periit resolution of the « satell ites. 2 i b o e Couplings not as well resolved as in CDC 13. f Couplings not resolved in CDC I ~ 34 R e s u 1 t s an d D i s c u s s i o n The i n t e r r e l a t i o n s h i p s between t h e compounds s t u d i e d i n t h i s i n v e s t i g a t i o n a r e summarized i n Scheme 2-1. The p r e p a r a t i o n and c h a r a c t e r i z a t i o n o f e a c h o f t h e s e c o m p l e x e s w i l l now be c o n s i d e r e d i n t u r n . A. P r e p a r a t i o n o f [ C p W ( N O ) I H ] 2 . (2) As has been p r e v i o u s l y r e p o r t e d , [ C p W ( N O ) I H ] 2 may be p r e p a r e d a s an a n a l y t i c a l l y p u r e compound v i a s t e p a i n Scheme 2-1 ( e q . 2-1) by t h e t r e a t m e n t o f [ C p w ( N O ) I 2 ] 2 w i t h an e q u i m o l a r N a [ H 2 A l ( O C H 2 C H 2 O C H 3 ) 2 ] [ C p W ( N O ) I 2 ] 2 - [ C p W ( N O ) I H ] 2 (2-1) C H 2 C 1 2 / P h H amount o f N a [ H 2 A 1 ( O C H 2 C H 2 O C H 3 ) 2 ] i n a m i x e d s o l v e n t s y s t e m o f C H 2 C l 2 / P h H . However, t h e r e a r e a number o f i m p o r t a n t f a c t o r s i n t h i s p r e p a r a t i o n w h i c h have n o t p r e v i o u s l y been d e t a i l e d t h a t must be c o n t r o l l e d i n o r d e r t o o b t a i n u n c o n t a m i n a t e d [ C p W ( N O ) I H ] 2 . F i r s t l y , t h e r e a c t i o n must be done a s q u i c k l y a s p o s s i b l e s i n c e t h e p r e p a r a t i o n o f [ C p w ( N O ) I H ] 2 i s a c c o m p a n i e d by t h e f o r m a t i o n o f some brown, i n s o l u b l e b y p r o d u c t s w h i c h a p p e a r t o c a t a l y z e t h e d e c o m p o s i t i o n o f t h e d e s i r e d s p e c i e s a n d s o t h i s m a t e r i a l must be r a p i d l y f i l t e r e d away. S e c o n d l y , t h e s t o i c h i o m e t r y o f t h e N a [ H 2 A l ( O C H 2 C H 2 O C H 3 ) 2 3 a d d i t i o n i s i m p o r t a n t b e c a u s e i t r e a c t s f u r t h e r w i t h [ C p W ( N O ) I H ] „ ( s e e b e l o w ) . 35 Scheme 2-1 [CpW(N0)I2]2 a 2PR 3,CH 2CI 2 f 2CpW(N0)I2(PR3) g 2H" CHgClg, PhH [CpW(N0)IH]2 zPRyCHgP^-P^. 2CpW(N0)IH(PR3) 2H _ PhH 2H" wCH 2CI 2, PhH [CpW(NO)H2]; 2 PR: PhH ' [CpW(N0)H(PR3)]s where R= Me, Ph, OMe, or OPh h X 2H" PhH CpW(N0)H2(PR3) PhH or CH£\2 T h i r d l y , t h e s p e c i f i e d m i x e d s o l v e n t s y s t e m i s n e c e s s a r y . The p r e s e n c e o f C H ^ C l 2 i s needed t o s o l u b i l i z e t h e [ C p W ( N O ) I 2 ] 2 s t a r t i n g m a t e r i a l , b u t u s i n g t h i s e x c l u s i v e l y a s a s o l v e n t r e s u l t s i n t h e f i n a l p r o d u c t b e i n g c o n t a m i n a t e d w i t h N a l . * 7 ^ (Nal i s i n s o l u b l e i n t h e p r e s c r i b e d s o l v e n t s y s t e m ) . I f benzene a l o n e i s u s e d a s t h e s o l v e n t , a l a r g e amount i s n e e d e d t o s o l u b i l i z e t h e s t a r t i n g m a t e r i a l a n d i s o l a t e d y i e l d s a r e g e n e r a l l y r e d u c e d . I n t e r e s t i n g l y enough, [ C p w ( N O ) I 2 ] 2 i s s u f f i c i e n t l y l e s s s o l u b l e i n t o l u e n e t h a n i n b e n z e n e so a s t o make t h e f o r m e r s o l v e n t i n a p p r o p r i a t e f o r t h i s r e a c t i o n . F i n a l l y , i f [ C p W ( N O ) I H ] 2 i s o b t a i n e d i n an impure f o r m , i t i s 36 p r o n e t o u n d e r g o r a p i d d e c o m p o s i t i o n b o t h i n s o l u t i o n and i n t h e s o l i d s t a t e t o a brown, i n t r a c t a b l e s o l i d . P u r e [ C p W ( N O ) I H ] 2 i s a d e e p l y c o l o u r e d , d a r k g r e e n s o l i d w h i c h i s t h e r m a l l y s t a b l e a t room t e m p e r a t u r e i n t h e s o l i d s t a t e u n d e r N 2 f o r s e v e r a l months. As a s o l i d , i t i s a i r - s t a b l e f o r s h o r t p e r i o d s o f t i m e , a l t h o u g h s o l u t i o n s a r e somewhat more a i r - s e n s i t i v e . The complex i s o n l y s l i g h t l y s o l u b l e i n n ondonor o r w e a k l y d o n a t i n g s o l v e n t s , w i t h t h e s o l u b i l i t y i n c r e a s i n g i n t h e o r d e r h e x a n e s , Et2<D ( i n s o l u b l e ) < t o l u e n e < b e n z e n e < C H 2 C 1 2 . The r e s u l t i n g s o l u t i o n s a r e i n t e n s e l y g r e e n i n c o l o u r and a p p e a r r e d t o t r a n s m i t t e d l i g h t . Donor s o l v e n t s , however, a p p e a r t o c l e a v e t h e d i m e r a f t e r f n i t i t a l s o l u b i l i z a t i o n ( c f . s t e p b o f Scheme 2-1) w i t h "t 2 -20 min i n THF ( e q 2 - 2 ) . In s o l v e n t s i n [CpW(NO) I H ] 2 + 2 THF - 2 CpW (NO) I H (THF ) (2-2) g r e e n , i n i t i a l V N Q o r a n g e , f i n a l V N Q • 1650 c m - 1 = 1632 c m - 1 w h i c h i t r e t a i n s i t s d i m e r i c f o r m , [ C p W ( N 0 ) I H ] 2 i s much l e s s s t a b l e t h a n a s a s o l i d , t h e r e b y p r e c l u d i n g r e c r y s t a l 1 i z a t i o n . F o r example, o v e r t h e c o u r s e o f 3 d a y s i n C^Dg (more q u i c k l y i n C DC1 3) a t room t e m p e r a t u r e , a g r e e n s o l u t i o n o f [ C p W ( N 0 ) I H ] 2 s l o w l y d e p o s i t s t h e u b i q u i t o u s brown s o l i d , a n d a s h a r p s i n g l e t a t 6 = 1.50 a p p e a r s i n t h e *H NMR o f t h e c o l o u r l e s s s u p e r n a t a n t , a l o n g w i t h a t t e n d a n t l o s s o f a l l s i g n a l s due t o [ C p W ( N O ) I H ] 2 . (8) A n a l y s i s by gas c h r o m a t o g r a p h y an d GC-MS o f t h e s o l v e n t a f t e r 37 d i s t i l l a t i o n showed t h e p r o d u c t o f t h i s d e c o m p o s i t i o n t o be u n d e u t e r i a t e d eye 1opentane, C ^ g , i n ~60-70% y i e l d b a s e d on a v a i l a b l e h y d r i d e H atoms. T h i s must r e s u l t f r o m t h e a u t o - h y d r o g e n a t i o n by t h e compound o f i t s eye 1 o p e n t a d i e n y 1 l i g a n d s . T h i s mode o f d e c o m p o s i t i o n i s i n marked c o n t r a s t t o t h a t o b s e r v e d f o r t h e u n s t a b l e molybdenum a n a l o g u e , w h i c h a p p a r e n t l y r a p i d l y l o s e s H 2 i n s o l u t i o n and c o n v e r t s t o t h e w e l l - k n o w n ( 1 9) [ C p M o ( N O ) I ] ^ . ' The t u n g s t e n c o n g e n e r o f t h i s l a t t e r complex i s , a s y e t , unknown. B. S p e c t r o s c o p i c P r o p e r t i e s o f [ C p W ( N O ) I H ] 2 . The d i m e r i c n a t u r e o f t h e complex i s s u g g e s t e d by t h e o b s e r v a t i o n o f a p a r e n t i o n ( m i x t u r e o f P + , ( P + 2 H ) + ; m/z = 816) i n t h e l o w - r e s o l u t i o n mass s p e c t r u m . U n f o r t u n a t e l y , o v e r l a p p i n g o f some medium and s t r o n g i n t e n s i t y p e a k s i n t h e lower mass r a n g e makes any f u r t h e r unambiguous a s s i g n m e n t s e x t r e m e l y d i f f i c u l t . I n f r a r e d s p e c t r a o f [CpW(NO) I H ] 2 , e i t h e r a s a c o n c e n t r a t e d N u j o l m u l l o r a s a C H 2 C 1 2 s o l u t i o n , show s t r o n g a b s o r p t i o n s a t t r i b u t a b l e t o t e r m i n a l NO g r o u p s ( e g . 1646 c m - 1 i n C H 2 C 1 2 ) , b u t a p p e a r t o l a c k any bands a t t r i b u t a b l e t o t e r m i n a l W-H 1 i n k a g e s ; ^ ; a b s o r p t i o n s a t t r i b u t a b l e t o W-H-W b r i d g e s a r e n o t v i s i b l e e i t h e r , b u t , a s n o t e d i n c h a p t e r 1, t h e s e a r e e x p e c t e d t o be e x t r e m e l y weak and d i f f i c u l t t o i d e n t i f y . * 1 1 ^ The iH NMR s p e c t r u m o f t h e complex i n CDC 1 ( s e e T a b l e 2-1 I, F i g . 2-1) i s p a r t i c u l a r l y i n t e r e s t i n g . The h y d r i d e r e g i o n 38 LO 1 JL 3 8(ppm) 2 1 0 "1 "2 F i g . 2-1. The 270-MHz ' H NMR s p e c t r u m o f [CpW(NO) I ] 2 (M—H) 2 In CDCIg. c o n s i s t s o f a s i n g l e t , s u r r o u n d e d by two AA'X q u a r t e t s due t o 183 c o u p l i n g t o W (I = 1/2, n a t u r a l a b u n d a n c e = 1 4 . 4 % ) whose combi n e d a r e a i n t e g r a t e s t o ~257. o f t h e t o t a l h y d r i d e r e s o n a n c e ( t h e c o u p l i n g c o n s t a n t s g i v e n i n T a b l e 2-1 I were c a l c u l a t e d f r o m c o n v e n t i o n a l a l g e b r a i c e q u a t i o n s ) . * 1 2 * F u r t h e r m o r e , i f t h e *H NMR s p e c t r u m i s r e c o r d e d u n d e r o u r u s u a l F o u r i e r t r a n s f o r m c o n d i t i o n s o f a 4 5 ° f l i p a n g l e a n d ~ 2 . 5 s between p u l s e s , t h e r e l a t i v e i n t e g r a t i o n s o f t h e C_H C:W-H r e s o n a n c e s a r e ~ 3 . 5 : 1 i n s t e a d o f t h e e x p e c t e d 5 : 1 . T h i s was c u r i o u s , a s metal h y d r i d e s ( 1 3 ) a r e known f o r o f t e n h a v i n g l e n g t h y r e l a x a t i o n t i m e s . C o n s e q u e n t l y , a T j e x p e r i m e n t was p e r f o r m e d w i t h t h e r e s u l t t h a t t h e T f o r t h e C 5 H 5 peak was f o u n d t o be 15.3 s, w h i l e t h a t f o r t h e h y d r i d e r e s o n a n c e was 2.74 s ( s e e F i g . 2 - 2 ) . * 1 4 * R e p o r t s o f s u c h a l o n g r e l a x a t i o n t i m e f o r eye I o p e n t a d i e n y 1 p r o t o n s a r e r a r e , o n l y one h a v i n g p r e v i o u s l y a p p e a r e d . T h i s phenomenon has been a t t r i b u t e d t o r a p i d r o t a t i o n o f t h e Cp 1 i g a n d a b o u t t h e meta1-Cp c e n t r o i d a x i s . We have a l s o f o u n d a n a l o g o u s l y low i n t e g r a t i o n s f o r C^H^ r e s o n a n c e s i n t h e NMR s p e c t r a o f most o f t h e c o m p l e x e s i n v e s t i g a t e d i n t h i s s t u d y when a s u i t a b l e d e l a y between p u l s e s was n o t e m p l o y e d . T^ v a l u e s were n o t m easured f o r a n y o f t h e o t h e r compounds. W i t h t h e IR s p e c t r u m o f t h e compound s h o w i n g no bands a t t r i b u t a b l e t o t e r m i n a l W-H l i g a n d s and t h e h y d r i d e r e g i o n o f I 18 3 t h e lH NMR s p e c t r u m s h o w i n g W s a t e l l i t e s i n t e g r a t i n g t o 2 5 % o f t h e a r e a ( s e e b e l o w ) , t h e p o s s i b i l i t y o f [CpW(N0)lH]2 c o n t a i n i n g 40 1 ' 3= ^ 1 » 1 1 . . I s 3Z 40 s 50 s 60s •75 s -90s 1s 600 ms 2s 3s 5s •10 s 15 s -20 s 300 ms 1 100 ms -| ' 20 ms F l a . 2=2. S t a c k e d p l o t s o f t h e r e s u l t s o f t h e 270-MHz H NMR T j e x p e r i m e n t on [CpW(NO)I] ( u - H ) 2 i n CgDg u s i n g a 1 8 0 ° - T - 9 0 ( p u l s e s e q u e n c e . The i f o r e a c h s u b - e x p e r i m e n t i s g i v e n b e s i d e each p l o t . T ^ s : Cp = 15.3 s, W 2 ( u - H ) 2 = 2.7 s. b r i d g i n g H l i g a n d s i s s u g g e s t e d . However, f u r t h e r d i s c u s s i o n on t h e s t r u c t u r e o f t h i s compound w i l l be d e f e r r e d u n t i l t h e p r o p e r t i e s o f s e v e r a l r e l a t e d compounds a r e d i s c u s s e d . C. The Complexes CpW(NO)IHL ( L = P h o s p h i n e o r P h o s p h i t e ) . The o r a n g e compounds CpW(NO)IHL ( L = P ( O P h ) 3 , P ( O M e ) 3 and P P h 3 ) have been d e s c r i b e d p r e v i o u s l y * ' and t h e i r IR and NMR d a t a have been i n c l u d e d i n T a b l e s 2-1 and 2-1 I f o r t h e s a k e o f c o m p l e t e n e s s . B r i e f l y , t h e y a r e p r e p a r e d i n ~407. y i e l d ( b a s e d on [ CpW (NO) 1 ,_,].-> by a d d i t i o n o f a s t o i c h i o m e t r i c q u a n t i t y o f t h e L e w i s b a s e t o a d a r k g r e e n s o l u t i o n o f [ C p W ( N O ) I H ] 2 , f o l l o w e d by c h r o m a t o g r a p h y on F l o r i s i l and c r y s t a l l i z a t i o n f r o m C H 2 C 1 2 / h e x a n e s ( s t e p s a and b i n Scheme 2-1, e q . 2 - 3 ) . The [CpW(NO) I H ] 2 + 2 L -2 CpW(NO)IHL (2-3) C H 2 C l 2 / P h H y i e l d s o f monomers a r e e s s e n t i a l l y q u a n t i t a t i v e f r o m t h e [ C p W ( N O ) I H ] 2 d i m e r and a r e marked improvements on t h e i r (2) p r e p a r a t i o n s v i a s t e p s f a n d g i n Scheme 2-1. The p h y s i c a l a n d s p e c t r a l p r o p e r t i e s o f t h e s e t h r e e compounds, a s w e l l a s i s o m e r A o f CpW(NO)IH(PMe 3) ( s e e b e l o w ) , s u g g e s t t h e y a r e a l l monomers and a r e i s o s t r u c t u r a 1 . They a r e a l l o r a n g e , d i a m a g n e t i c compounds t h a t a r e s t a b l e i n a i r f o r a t l e a s t s e v e r a l h o u r s w i t h no n o t i c a b l e d e c o m p o s i t i o n o c c u r r i n g . T h e y a r e q u i t e s o l u b l e i n p o l a r o r g a n i c s o l v e n t s ( e . g . C H „ C 1 ~ ) , 42 b u t o n l y s p a r i n g l y s o l u b l e i n n o n - p o l a r o n e s , t o g i v e m i l d l y a i r - s e n s i t i v e s o l u t i o n s . T h e i r l o w - r e s o l u t i o n mass s p e c t r a d i s p l a y p e a k s c o r r e s p o n d i n g t o P + , ( P - I ) + and ( P - L ) + , where P = monomeric p a r e n t f r a g m e n t . T h e i r IR s p e c t r a d i s p l a y v N Q ' s i n t h e r e g i o n 1643-1613 cm 1 ( T a b l e 2 - 1 ) , s u g g e s t i n g t e r m i n a l NO l i g a n d s . T h e s e f r e q u e n c i e s d e c r e a s e , a s e x p e c t e d , a s t h e e l e c t r o n - d o n a t i n g a b i l i t i e s o f L i n c r e a s e * 1 6 * i n t h e o r d e r L = P ( O P h ) 3 < P ( O M e ) 3 < P P h 3 < P M e 3 « In a d d i t i o n , weak a b s o r p t i o n s a t t r i b u t a b l e t o t e r m i n a l W-H s t r e t c h i n g v i b r a t i o n s (v.,,,)* 1*** a r e o b s e r v a b l e a t W n ~1900 c m - 1 i n t h e s e s p e c t r a . T h e s e l a t t e r v i b r a t i o n s i n c r e a s e i n f r e q u e n c y w i t h t h e e l e c t r o n d o n a t i n g a b i l i t i e s o f L , * 1 6 * t h e r e b y p r e s u m a b l y i n d i c a t i n g a c o r r e s p o n d i n g i n c r e a s e i n t h e W-H bond s t r e n g t h . By a n a l o g y w i t h t h e b e t t e r known CpM(CO) ...HL (M=Cr, Mo o r W; L=CO o r p h o s p h i n e ) , t h e s e compounds p r o b a b l y p o s s e s s a c o n v e n t i o n a l " f o u i — l e g g e d p i a n o - s t o o l " m o l e c u l a r s t r u c t u r e . * 1 7 * . In o u r c a s e , w i t h f o u r u n i q u e 1 i g a n d s i n a d d i t i o n t o t h e Cp g r o u p , t h e r e a r e a number o f p o s s i b l e a r r a n g e m e n t s o f t h e s e 1 i g a n d s i n t h e b a s a l p l a n e . B e c a u s e t h e W atom i n t h e s e m o l e c u l e s i s a c h i r a l c e n t r e , t h e s e i s o m e r s c o n s i s t o f t h r e e s e t s o f e n a n t i o m e r i c p a i r s . The *H NMR s p e c t r a o f t h e s e c o m p l e x e s i n C D C l ^ o r C,D, O D O ( T a b l e 2-1 I) s u g g e s t t h e p r e s e n c e o f o n l y one i s o m e r (as w e l l , o f c o u r s e , a s i t s e n a n t i o m e r ) i n s o l u t i o n . The o b s e r v a t i o n o f a 2 s i n g l e t C^H 5 r e s o n a n c e and ( l a r g e ) J ^ p v a l u e s i n t h e r a n g e o f 84 (18) t o 112 HZ i s i n d i c a t i v e o f a c i s o r i e n t a t i o n ^ ' o f t h e L and H 43 l i g a n d s (I and I I ) ( J H P ' s o f -20 Hz would be e x p e c t e d f o r a (18) 31 t r a n s c o n f i g u r a t i o n ) . In a d d i t i o n t o c o u p l i n g t o P, t h e I 1 I 183 h y d r i d e r e s o n a n c e s e x h i b i t c o u p l i n g t o W, w i t h t h e s e s a t e l l i t e s i n t e g r a t i n g t o t h e e x p e c t e d 157. o f t h e t o t a l h y d r i d e i n t e g r a t i o n . U n l i k e t h e p o s i t i o n s o f t h e v N Q a n d v W H f r e q u e n c i e s i n t h e IR s p e c t r a , no t r e n d s a r e e v i d e n t i n t h e p o s i t i o n s o f t h e eye 1 o p e n t a d i e n y 1 o r h y d r i d e r e s o n a n c e s i n t h e NMR s p e c t r a w i t h r e s p e c t t o t h e e l e c t r o n d o n a t i n g a b i l i t i e s o r s t e r i c b u l k s o f ^ (16) j h i s i S j n a g r e e m e n t w i t h D a r e n s b o u r g a n d c o - w o r k e r s ' - (19) o b s e r v a t i o n s on t h e [ H W ( C 0 ) 4 L ] s y s t e m . ' However, a s summarized i n T a b l e 2-1 I, t h e v a l u e s o f ^J,.,, do i n c r e a s e and n W 2 t h o s e o f J H p do d e c r e a s e a s t h e e l e c t r o n - d o n a t i n g a b i l i t y o f L i n c r e a s e s . T h i s i s i n c o n t r a s t w i t h t h e c a r b o n y l r e s u l t s , where 2 t h e J H p v a l u e s were o b s e r v e d t o c o r r e l a t e w i t h t h e s t e r i c , r a t h e r t h a n e l e c t r o n i c , p r o p e r t i e s o f L, a n d no t r e n d was o b s e r v a b l e w i t h r e s p e c t t o i J H W . ^ 1 9 ^ The m a t t e r o f t h e m a g n i t u d e 44 o f J|_j^ i n t h e s e and o t h e r c o m p l e x e s w i l l be d e a l t w i t h i n much more d e t a i l i n c h a p t e r 3. On t h e b a s i s o f a l 1 t h e s e d a t a , i t i s n o t p o s s i b l e t o d e t e r m i n e w h e t h e r t h e NO 1 i g a n d i s t r a n s t o L ( s t r u c t u r e I) o r t r a n s t o H ( s t r u c t u r e I I ) . Our p r e f e r e n c e i s f o r s t r u c t u r e I, w i t h t h e s t r o n g l y e l e c t r o n w i t h d r a w i n g NO t r a n s t o t h e L don o r 1 i g a n d , and t h e two, o n e - e l e c t r o n l i g a n d s m u t u a l l y t r a n s , b u t s u c h an i d e n t i f i c a t i o n must a w a i t a s i n g l e - c r y s t a l X- r a y a n a l y s i s o f one o f t h e s e compounds. When L i n r e a c t i o n 2-3 i s PMe 3, t h e s i t u a t i o n i s s l i g h t l y more c o m p l i c a t e d t h a n w i t h t h e o t h e r L ' s j u s t c o n s i d e r e d . The CpW(NO)IHKPMe^) p r o d u c t i s f o r m e d a s a m i x t u r e o f two i s o m e r s ( d e s i g n a t e d A and B i n T a b l e s 2-1 and 2-1 I ) . One o f t h e i s o m e r s (A) i s i s o l a b l e i n 117. y i e l d by u s i n g t h e c h r o m a t o g r a p h i c p r o c e d u r e employed f o r t h e o t h e r CpW(NO)IHI_ compounds. However, f r a c t i o n a l c r y s t a l l i z a t i o n o f t h e r e a c t i o n m i x t u r e b e f o r e c h r o m a t o g r a p h y g i v e s an a n a l y t i c a l l y p u r e l i g h t brown m i x t u r e o f t h e two i s o m e r s i n 367. y i e l d . As d i s c u s s e d a b o v e , t h e s p e c t r o s c o p i c p r o p e r t i e s o f i s o m e r A s u g g e s t i t i s i s o s t r u c t u r a 1 w i t h t h e o t h e r CpW(NO)IHL compounds. C o m p a r i s o n o f t h e IR s p e c t r u m ( C H ^ C ^ ) o f t h e i s o m e r i c m i x t u r e w i t h t h a t o f A a l o n e shows b o t h a b r o a d e n i n g o f t h e NO s t r e t c h i n g band and t h e a p p e a r a n c e o f a new v W H a t 1898 c m - 1 . The *H NMR s p e c t r u m o f t h e m i x t u r e i n C^D 0 shows t h a t t h e y e x i s t i n an a p p r o x i m a t e 5:1 r a t i o (A:B) i n i t i a l l y . The s p e c t r u m i n C D C ) 3 , w h i c h has b e t t e r r e s o l u t i o n , shows t h e Cp r e s o n a n c e f o r isom e r B t o be r e s o l v e d 45 i n t o a d o u b l e t o f d o u b l e t s , p r e s u m a b l y due t o c o u p l i n g t o b o t h (18) t h e P and h y d r i d e atoms. T h i s s u g g e s t s t h a t i s o m e r B p r o b a b l y has t h e s t r u c t u r e o f t h e t h i r d p a i r o f e n a n t i o m e r s r e f e r r e d t o a b o v e , namely w i t h t h e H and PMe^ l i g a n d s m u t u a l l y t r a n s , i . e . C u r i o u s l y , no d i s t i n c t r e s o n a n c e due t o t h e h y d r i d e atom o f isomer B c o u l d be f o u n d i n t h e *H NMR s p e c t r u m o f t h e m i x t u r e . Now h a v i n g t h e CpW(NO)IHL compounds, i t i s i n t e r e s t i n g t o (18) compare t h e i r p r o p e r t i e s w i t h t h o s e o f t h e CpW(CO)^HL v 7 a n d C p W ( N O ) 1 2 L * 1 * s e r i e s . The most s t r i k i n g d i f f e r e n c e between t h e CpW(NO)IHL a n d CpW(CO) 2HL c o m p l e x e s i s t h a t t h e l a t t e r u n d e r g o r a p i d c i s / t r a n s i s o m e r i z a t i o n i n s o l u t i o n u n d e r a m b i e n t (18 c o n d i t i o n s a n d t h e i s o m e r s c a n n o t be i s o l a t e d i n d e p e n d e n t l y . The CpW(NO)lHL compounds, on t h e o t h e r hand, g e n e r a l l y e x i s t a s 46 o n l y one i s o m e r (H a n d L c i s ) a n d no i s o m e n ' z a t i o n a p p e a r s t o o c c u r . In t h e one c a s e where m i x t u r e s o f i s o m e r s c a n be p r e p a r e d ( L=PMe 3), t h e i s o m e r w i t h H and L t r a n s u n d e r g o e s s p o n t a n e o u s i somen" z a t i o n t o t h e o t h e r i s o m e r i n C D C l ^ s o l u t i o n o v e r t h e c o u r s e o f one week a t 20° C . S i m i l a r l y , p r e p a r a t i o n o f t h e CpW(NO)I 2L c o m p l e x e s a c c o r d i n g t o s t e p f i n Scheme 2-1 ( e q . 2-4) r e s u l t s i n o n l y one isom e r when L = P ( O P h ) 3 , P ( O M e ) 3 o r PPhg. A g a i n , when L=PMe 3, two i s o m e r s (A a n d B i n T a b l e 2-11) a r e f o r m e d i n t h e r a t i o o f ~5:1. In t h i s c a s e , i s o m e r B i s even C H 2 C 1 2 [CpW(NO) I 2 ] 2 + 2 L - 2 CpW(NO)I 2L (2-4) l e s s k i n e t i c a l l y s t a b l e t h a n i n t h e c a s e o f CpW(NO)IHL, a s i t i s c o n v e r t e d i n t o i s o m e r A i m m e d i a t e l y upon d i s s o l u t i o n i n CDC1 3 a n d somewhat more s l o w l y i n C^O,.. b b The s e c o n d d i f f e r e n c e between t h e c a r b o n y l a n d n i t r o s y l c o m p l e x e s i s t h a t t h e h y d r i d e r e s o n a n c e s i n t h e *H NMR s p e c t r a o f t h e CpW(NO)lHL c o m p l e x e s a p p e a r a t much lower f i e l d (by 6-8 ppm) t h a n do t h e c o r r e s p o n d i n g s i g n a l s f o r t h e CpW(CO) 2HL compounds. In f a c t , t h e h y d r i d e r e s o n a n c e s f o r a l l t h e h y d r i d o n i t r o s y l c o m p l e x e s i n v e s t i g a t e d d u r i n g t h i s s t u d y a r e much l e s s s h i e l d e d t h a n i s c u s t o m a r y f o r m i d d l e and l a t e t r a n s i t i o n - m e t a l h y d r i d e s ( s e e c h a p t e r 1 ) . T h i s p o i n t w i l l be d i s c u s s e d f u r t h e r i n c h a p t e r 3. F i n a l l y , a c o m p a r i s o n o f IR d a t a shows a n o t h e r i n t e r e s t i n g 47 t r e n d ( T a b l e 2 - 1 ) . When one o f t h e I atoms o f C p W ( N 0 ) I 2 L i s r e p l a c e d by an H atom, t h e v N Q d i m i n i s h e s by 20-25 cm T h i s i s p r o b a b l y a r e f l e c t i o n o f t h e lower e l e c t r o n e g a t i v i t y o f t h e H atom v e r s u s an I atom and t h e c o r r e s p o n d i n g l y g r e a t e r e l e c t r o n d e n s i t y on t h e m e t a l c e n t r e o f t h e h y d r i d e complex a v a i l a b l e f o r b a c k - d o n a t i o n t o t h e NO 1igand. However, no t r e n d i n t h e c h e m i c a l s h i f t s o f t h e *H NMR s i g n a l s o f t h e eye 1opentadieny1 l i g a n d s i s e v i d e n t when t h e r e p l a c e m e n t o c c u r s ( T a b l e 2 - 1 I ) . D. S y n t h e s i s a n d P r o p e r t i e s o f [ C p W ( N 0 ) H 2 ] 2 . As i s shown i n s t e p c o f Scheme 2 - 1 , f u r t h e r a d d i t i o n o f N a [ H 2 A l ( O C H 2 C H 2 O C H 3 ) 2 3 t o t h e g r e e n f i l t r a t e c o n t a i n i n g [ C p W ( N 0 ) I H ] 2 g i v e s , a f t e r workup, low y i e l d s o f o r a n g e [ C p W ( N O ) H 2 ] 2 ( e q . 2 - 5 ) . U n f o r t u n a t e l y , t h i s a d d i t i o n i s v e r y N a [ H 2 A l ( O C H 2 C H 2 O C H 3 ) 2 ] [CpW(NO) I H ] 2 - [ C p W ( N O ) H 2 ] 2 (2-5) CH 2C1 2/PhH d i f f i c u l t t o m o n i t o r b e c a u s e t h e q u a n t i t y o f [ C p W ( N 0 ) I H ] 2 c o n t a i n e d i n t h e f i l t r a t e i s n o t p r e c i s e l y known. I t has p r o v e n i m p o s s i b l e t o f o l l o w t h e r e a c t i o n by IR s p e c t r o s c o p y , a s t h e NO band o f t h e [ C p W ( N O ) I H ] 2 s t a r t i n g m a t e r i a l i s v e r y weak i n t h i s s y s t e m and i t i s d i f f i c u l t t o t e l l when i t has j u s t d i s a p p e a r e d . F u r t h e r m o r e , t h e b e n z e n e s o l v e n t has a band t h a t d i r e c t l y o v e r l a p s t h e v M n o f t h e p r o d u c t . A t t e m p t s t o f o l l o w t h e r e a c t i o n 48 by FT-IR s p e c t r o s c o p y and e m p l o y i n g computer s u b t r a c t i o n o f s o l v e n t p e a k s were u n s u c c e s s f u l b e c a u s e t h e r e a c t i o n must be done r a p i d l y f o r t h e same r e a s o n s a s d i s c u s s e d above f o r t h e p r e p a r a t i o n o f [CpW(NO)IH]^. C o n s e q u e n t l y , t h e a d d i t i o n o f t h e aluminum r e a g e n t must be m o n i t o r e d v i s u a l l y , w i t h a d d i t i o n c e a s i n g when t h e r e a c t i o n m i x t u r e i s no l o n g e r g r e e n , b u t r a t h e r a d a r k , o r a n g e - b r o w n c o l o u r . A g a i n , t h i s i s d i f f i c u l t t o do b e c a u s e t h e s o l u t i o n s a r e e x t r e m e l y i n t e n s e l y c o l o u r e d , b u t i t has p r o v e n t o be t h e o n l y s u c c e s s f u l method. I n d e p e n d e n t e x p e r i m e n t s i n v o l v i n g a d d i t i o n o f t h e aluminum h y d r i d e t o a s o l u t i o n made f r o m a known amount o f i s o l a t e d [CpW(NO) IH],, e s t a b l i s h e d t h a t t h e s t o i c h i o m e t r y i s 1:1, however, i s o l a t i o n o f t h e p r o d u c t [ C p W ( N O ) H 2 ] 2 f r o m t h i s p r o c e d u r e l e d t o a lower o v e r a l l y i e l d ( b a s e d on [CpW(NO)1 J 2 ) t h a n t h a t a b o v e . A d d i t i o n o f e x c e s s N a [ H 2 A l ( O C H 2 C H 2 O C H 3 ) 2 ] r e s u l t s i n f u r t h e r r e a c t i o n t o g i v e , a s y e t , u n i d e n t i f i e d h y d r i d e - c o n t a i n i n g p r o d u c t s ( a s j u d g e d by *H NMR s p e c t r o s c o p y ) . The [CpW(NO)H 2 3 2 i s o l a t e d f r o m t h e r e a c t i o n m i x t u r e i s an o r a n g e powder an d may be c r y s t a l l i z e d t o g i v e s m a l l , r e d - o r a n g e c r y s t a l s i n low y i e l d a s d e s c r i b e d i n t h e E x p e r i m e n t a l S e c t i o n . The p u r e compound i s a d i a m a g n e t i c s o l i d w h i c h p e r s i s t s i n a i r f o r s h o r t p e r i o d s o f t i m e a n d i s r e m a r k a b l y t h e r m a l l y s t a b l e , b e i n g l e f t u n changed when h e a t e d a t 100°C o v e r n i g h t u n d e r N 2 . I t s s o l u b i l i t y p r o p e r t i e s a r e v e r y s i m i l a r t o t h o s e o f [ C p W ( N O ) I H ] „ . L i k e t h e l a t t e r c omplex, t h e d i h y d r i d e d i m e r 49 u n d e r g o e s d e c o m p o s i t i o n d u r i n g 1 week i n C D C l ^ a t room t e m p e r a t u r e w i t h t h e r e s u l t i n g f o r m a t i o n o f eye 1opentane. However, C^D^ s o l u t i o n s o f t h i s compound show no e v i d e n c e o f d e c o m p o s i t i o n e v e n a f t e r s e v e r a l weeks u n d e r t h e same c o n d i t i o n s . The IR s p e c t r u m o f [ C p W ( N O ) H 2 ] 2 i n C H 2 C l 2 shows a s t r o n g v N g a t 1599 cm * a n d a much weaker, t e r m i n a l v a t 1906 cm" 1, t h e l a t t e r c o n t r a s t i n g t o t h e s p e c t r u m o f [ C p w ( N O ) I H ] 2 , w h i c h has no s u c h band. The l o w - r e s o l u t i o n mass s p e c t r u m ( p r o b e t e m p e r a t u r e 120°C) o f [ C p W ( N 0 ) H 2 ] 2 s u g g e s t s t h e e x p e c t e d d i m e r i c s t r u c t u r e , w i t h a h i g h e s t - m a s s peak a t m/z = 560, c o r r e s p o n d i n g t o + (2) (P-2H) . ' I t i s t h e *H NMR s p e c t r u m , however, p a r t i c u l a r l y i n CDC 1 , t h a t p r o v i d e s t h e most i n f o r m a t i o n a b o u t t h e s t r u c t u r e o f t h e compound ( F i g . 2 - 3 ) . T h i s s p e c t r u m shows t h a t two i s o m e r s (A a n d B i n F i g . 2-3) a r e p r e s e n t i n s o l u t i o n , i n an a p p r o x i m a t e 1.3:1 r a t i o , w i t h t h i s c o n s t a n t i n C DC1 3 a n d C^Dg. The a s s i g n m e n t s o f t h e o b s e r v e d r e s o n a n c e s t o i n d i v i d u a l i s o m e r s were made on t h e (2) b a s i s o f h o m o n u c l e a r d e c o u p l i n g e x p e r i m e n t s . E x c l u s i v e o f 1 ft -i W s a t e l l i t e s , i s o m e r s A and B e x h i b i t AA'XX' and A 2MX p a t t e r n s , r e s p e c t i v e l y , f o r t h e i r h y d r i d e l i g a n d s . The c o u p l i n g c o n s t a n t s f o r i s o m e r B a r e , o f c o u r s e , e a s i l y c a l c u l a t e d s i n c e i t i s a f i r s t - o r d e r s p e c t r u m . However, p r e c i s e c a l c u l a t i o n o f s u c h c o n s t a n t s * * ^ i s n o t p o s s i b l e f o r t h e AA'XX' s y s t e m o f i s o m e r A ( 1 2 ) b e c a u s e t h e s p e c t r u m i s n o t s u f f i c i e n t l y w e l l r e s o l v e d . ' N e v e r t h e l e s s , t h e s e numbers may be r e a s o n a b l y e s t i m a t e d by 50 8 ' 6 4 2 0 -2 -4 -6 • 8 (ppm) F i g . 2-3. The 400-MHz lH NMR s p e c t r u m o f [ C p W ( N 0 ) H ] 2 ( u - H ) 2 i n C D C l g . " A " and " B " r e f e r t o t h e h y d r i d e r e s o n a n c e s a s s i g n a b l e t o i s o m e r s A and B. i t e r a t i v e s i m u l a t i o n and t h e y a r e i n c l u d e d i n T a b l e 2-1 I. The a s s i g n m e n t o f c i s and t r a n s ^ - ' H c o u p l i n g s a c r o s s t h e m e t a l c e n t r e s ( s e e below and F i g . 2-4) a r e b a s e d on r e l a t e d a s s i g n m e n t s d i s c u s s e d i n c h a p t e r 4. E. M o l e c u l a r S t r u c t u r e s o f [ C p W ( N O ) H ] 2 ( y - H ) 2 a n d [ C p W ( N O ) I ] 2 ( y - H ) 2 . Numerous p o s s i b l e s t r u c t u r e s o f [CpW(NO)H„]„ h a v i n g d i f f e r e n t c o n f i g u r a t i o n s o f b r i d g i n g and t e r m i n a l h y d r i d e l i g a n d s c a n be e n v i s a g e d . The *H NMR s p e c t r u m o f t h i s c omplex, however, c l e a r l y shows t h a t e a c h o f t h e two i s o m e r s A and B have two b r i d g i n g and two t e r m i n a l h y d r i d e l i g a n d s . G e n e r a l l y s p e a k i n g , i n m o l e c u l e s o f t h i s k i n d , t h e r e s o n a n c e s f o r b r i d g i n g h y d r i d e s o c c u r a t h i g h e r f i e l d t h a n t h o s e f o r t e r m i n a l h y d r i d e s . ' On t h i s b a s i s , t h e low f i e l d s i g n a l s f o r e a c h i s o m e r ( w h i c h have a r e l a t i v e i n t e n s i t y o f 2) may be t e n t a t i v e l y a s s i g n e d t o t e r m i n a l W-H g r o u p s w i t h t h e r e m a i n i n g s i g n a l s a t t r i b u t a b l e t o W-H-W b r i d g i n g l i n k a g e s . More d e f i n i t i v e , however, a r e t h e 183 i n t e g r a t i o n s o f t h e W s a t e l l i t e s a s s o c i a t e d w i t h e a c h h y d r i d e s i g n a l . The two d o w n f i e l d s i g n a l s (<5 = 6.99 a n d 6.55) have s a t e l l i t e s t h a t i n t e g r a t e t o ~167. o f t h e t o t a l a r e a f o r e a c h s i g n a l , w h i l e t h e t h e t h r e e u p f i e l d s i g n a l s (<5 = 1 .39, -2.05 and -5.94) have s a t e l l i t e s i n t e g r a t i n g t o ~287.. In a b i n u c l e a r s y s t e m , t h e r e l a t i v e p r o p o r t i o n s o f i s o t o p o m e r s c o n t a i n i n g z e r o , 183 one a n d two W n u c l e i (14.47. n a t u r a l a b undance) a r e 52 (22) 73.3:24.7:2.1. T h e r e f o r e , t h e t h r e e h i g h e r f i e l d r e s o n a n c e s a r e due t o H atoms t h a t show a l m o s t e q u a l (and l a r g e ) c o u p l i n g t o 1 Q O a W n u c l e u s when i t i s a t e i t h e r m e tal c e n t r e . On t h e o t h e r 183 hand, t h e two lower f i e l d h y d r i d e p eaks show c o u p l i n g t o a W n u c l e u s ( w i t h l a r g e , one-bond c o u p l i n g o f 90-100 Hz) when i t i s a t o n l y one o f t h e two m e tal c e n t r e s . Hence, t h e t h r e e u p f i e l d r e s o n a n c e s a r e due t o b r i d g i n g h y d r i d e s and t h e two d o w n f i e l d due t o t e r m i n a l h y d r i d e s . Oeubzer and K a e s z have f o u n d t h a t f o r Cp oH„W->W(C0) c , 2 J 1 _ 1 1 . = 19.2 H z ( 2 3 ) — w i t h t h i s i n mind, s h o u l d e r s c c. D HW on t h e two d o w n f i e l d p e a k s may be a t t r i b u t e d t o two-bond, 183 2 t u n g s t e n - h y d r o g e n c o u p l i n g a c r o s s t h e H-W- W s y s t e m , w i t h J ^ w -13 and =l5 Hz f o r i s o m e r s A and 8, r e s p e c t i v e l y . T h i s a t t r i b u t i o n i s a l s o c o n s i s t e n t w i t h t h e a b s e n c e o f t h e s e s h o u l d e r s on t h e r e s o n a n c e s due t o t h e b r i d g i n g h y d r i d e s , f o r w h i c h s u c h two-bond c o u p l i n g i s n o t p o s s i b l e . On t h e b a s i s o f t h i s e v i d e n c e , [ C p W ( N O ) H 2 ] 2 c a n t h e r e f o r e be more p r o p e r l y f o r m u l a t e d a s [ CpW(NO)H] 2(w-H) 2. A l a r g e number o f s t r u c t u r e s c o n s i s t e n t w i t h t h e s p e c t r o s c o p i c e v i d e n c e a r e s t i l l p o s s i b l e . A f t e r most o f t h e work d e s c r i b e d i n t h i s c h a p t e r had (27) been p u b l i s h e d , we were f o r t u n a t e t o o b t a i n a s i n g l e c r y s t a l o f t h i s compound s u i t a b l e f o r X - r a y a n a l y s i s . T h i s s t r u c t u r e w i l l be d i s c u s s e d i n d e t a i l i n c h a p t e r 3 i n a b o n d i n g c o n t e x t , b u t i n s p e c t i o n o f t h e s t r u c t u r e o b t a i n e d ( F i g . 3-1 and 3-2) shows t h a t i t s h y d r i d e l i g a n d s would e x h i b i t an AA'XX' p a t t e r n i n t h e *H NMR s p e c t r u m and t h e s t r u c t u r e i s t h e r e f o r e t h a t o f i s o m e r A. 53 A d r a w i n g o f t h i s s t r u c t u r e i s shown i n F i g . 2-4. . The t u n g s t e n c e n t r e s i n t h i s compound may be s i m p 1 i s t i c a 1 1 y t h o u g h t o f a s f o u r - c o o r d i n a t e and c h i r a l due t o h a v i n g f o u r d i f f e r e n t s u b s t i t u e n t s (H, NO, Cp and CpW(N0)H 2). F u r t h e r e x a m i n a t i o n o f i s o m e r A shows, i n f a c t , t h a t i t i s a meso s t r u c t u r e . I t i s p r o b a b l e , t h e r e f o r e , t h a t i s o m e r B i s a m i x t u r e o f two e n a n t i o m e r s o f a d i a s t e r e o m e r o f A. However, u n l i k e a t a n a l o g o u s c h i r a l C c e n t r e s where t h e r e i s f r e e r o t a t i o n a b o u t a l l C-X a x e s (X=any s u b s t i t u e n t ) , t h e r e i s no f r e e r o t a t i o n a b o u t t h e W-W a x i s i n [ C p W ( N 0 ) H ] 2 ( y - H ) 2 ( s e e c h a p t e r 3 ) . T h i s means any r e o r i e n t a t i o n o f t h e W 2 ( y - H ) 2 p l a n e w i t h r e s p e c t t o a f i x e d o r i e n t a t i o n o f t h e two CpW(NO)H end u n i t s w o u l d r e s u l t i n a d i f f e r e n t m o l e c u l e a n d a d i f f e r e n t h y d r i d e p a t t e r n i n i t s *H NMR s p e c t r u m . C o n s e q u e n t l y , t h e r e a r e a number o f p o s s i b l e s t r u c t u r e s o f i s o m e r B t h a t c a n be e n v i s a g e d — o n e o f t h e s e i s d e p i c t e d i n F i g . 2-4. T h i s was c h o s e n s i m p l y on t h e b a s i s t h a t i t c a n be d e r i v e d f r o m t h e s t r u c t u r e o f A by t h e minimum number o f 1 i g a n d e x c h a n g e s and s t i l l y i e l d an A 2MX p a t t e r n f o r t h e *H NMR s p e c t r u m o f t h e h y d r i d e l i g a n d s . The W 2 ( u - H ) 2 l i n k a g e o f t h e d i h y d r i d e d i m e r i s n o t w i t h o u t p r e c e d e n c e i n t h e l i t e r a t u r e , h a v i n g been d e m o n s t r a t e d c r y s t a l l o g r a p h i c a l l y by C h u r c h i l l a n d Chang, a n d Bau and c o - w o r k e r s 1 ' f o r [ ( U - H ) 2 W 2 ( C O ) Q ] a n d h a v i n g been p r o p o s e d by A l t and c o - w o r k e r s ( 2 6 ) f o r [ C p W ( C O ) 2 ] 2 ( y - H ) 2 . In t h e l a t t e r c a s e , t h e s t r u c t u r a l p r o p o s a l was b a s e d p r i m a r i l y on t h e *H NMR 54 1 8 3 s p e c t r u m e x h i b i t i n g W s a t e l l i t e s w h i c h were 247, o f t h e t o t a l h y d r i d e s i g n a l i n t e n s i t y . Our o b s e r v a t i o n s on t h e v a l e n c e i s o e l e c t r o n i c [CpW(NO) H ] 2 (u-H)^ s u p p o r t t h i s p r o p o s a l . C p v H x HA C p v H x ^ Cp ON—W =j=W^NO ON—W =|=W^NO H A < '"Cp \\f H M * " H A Isomer A Isomer B (AA'XX1) (A2MX) C p v H I ON—W=+=Wr-,NO r H cp F i a . 2-4. P r o b a b l e m o l e c u l a r s t r u c t u r e s o f [ C p W ( N O ) H ] 2 ( u - H ) 2 a n d ( 2 4 ) [ C p W ( N O ) I ] 2 ( u - H ) 2 . ' The s t r u c t u r e o f isom e r A o f [ C p W ( N O ) H ] 2 ( u - H ) 2 has been v e r i f i e d by a s i n g l e c r y s t a l X - r a y a n a l y s i s ( s e e c h a p t e r 3 ) . B e a r i n g i n mind t h e s p e c t r a l p r o p e r t i e s o f [ C p W ( N O ) H ] 2 ( u - H ) 2 » we c a n now c o n s i d e r t h e s t r u c t u r e o f [ C p W ( N O ) I H ] 2 . J . C . Ox l e y o r i g i n a l l y f o r m u l a t e d t h i s (2) compound a s 5 „ 5 v -C5H5 j -n -C5H5 O N — ^ W — N O H ^ 1 55 on t h e b a s i s o f t h e 1 8 - e l e c t r o n r u l e and i n c o m p l e t e a n a l y s i s o f 1 183 t h e H NMR s p e c t r u m . The o b s e r v a t i o n o f W s a t e l 1 i t e s I n t e g r a t i n g t o 257. o f t h e t o t a l a r e a o f t h e h y d r i d e s i g n a l r u l e s o u t t h i s p o s s i b i l i t y a s a s t a t i c ( n o n - f 1 u x i o n a l ) s t r u c t u r e . In 183 1 a d d i t i o n , t h e AA'X p a t t e r n o f t h e W s a t e l l i t e s w i t h s t r o n g H- 1 8 3W c o u p l i n g ( ! < J H W = 88.3 and l ^ h > w = 70.8 Hz) l e a d s us t o r e f o r m u l a t e t h i s compound a s [ C p W ( N O ) I 3 2 ( y - H ) 2 ( F i g . 2 - 4 ) . (We have p r e v i o u s l y s u g g e s t e d t h e f o r m u l a t i o n o f [ C p W ( N O ) ] 2 ( u - H ) 2 ( u - I ) 2 , ( 2 7 ) b u t now b e l i e v e t h e s t r u c t u r e w i t h b r i d g i n g h y d r i d e s and t e r m i n a l ha 1 i d e s t o be t h e c o r r e c t one b a s e d on a r g u m e n t s p r e s e n t e d i n c h a p t e r 3 ) . S uch a b r i d g i n g h y d r i d e f o r m u l a t i o n a l s o a c c o u n t s f o r t h e l a c k o f a b s o r p t i o n a t t r i b u t a b l e t o t e r m i n a l W-H g r o u p s i n i t s IR s p e c t r u m . U n f o r t u n a t e l y , i t has n o t y e t p r o v e n p o s s i b l e t o grow s i n g l e c r y s t a l s o f [CpW(NO) I 3 2(y-H) 2 s u i t a b l e f o r X - r a y a n a l y s i s due t o i t s i n s t a b i l i t y i n s o l u t i o n . F. R e a c t i o n s o f [ C p W ( N 0 ) H ] 2 ( y - H ) 2 w i t h P R 3 (R=0Ph o r OMe). Upon t h e a d d i t i o n o f 2 e q u i v a l e n t s o f P ( 0 P h ) 3 t o a b e n z e n e s o l u t i o n o f [ C p W ( N O ) H ] 2 ( y - H ) 2 a t room t e m p e r a t u r e , t h e r e a c t i o n g r a d u a l l y c h a n g e s f r o m o r a n g e t o i n t e n s e p u r p l e i n c o l o u r a s r e a c t i o n 2-6 o c c u r s ( s t e p d o f Scheme 2 - 1 ) . The o r g a n o m e t a 1 1 i c [ C p W ( N 0 ) H 2 ] 2 + 2 P ( 0 P h ) 3 • [ C p W ( N O ) H { P ( O P h ) 3 } ] 2 + H 2 (2-6) PhH 56 p r o d u c t may be i s o l a t e d a s a p u r p l e mi c r o c r y s t a 1 1 i ne s o l i d i n 417, (28) y i e l d , w h i l e t h e p r o d u c t was i d e n t i f i e d by GC-MS V . The s o l i d may be h a n d l e d i n a i r f o r s h o r t p e r i o d s o f t i m e and i s m o d e r a t e l y s o l u b l e i n n o n - a l i p h a t i c o r g a n i c s o l v e n t s t o p r o d u c e i n t e n s e p u r p l e , a i r - s e n s i t i v e s o l u t i o n s . The IR s p e c t r u m o f [ C p W ( N O ) H { P ( O P h ) 3 ) ] 2 i n C H 2 C 1 2 shows a s t r o n g v,,„ a t 1591 c m - 1 ( w h i c h i s v e r y s i m i l a r t o t h a t o f t h e NO d i h y d r i d e d i m e r a t 1599 c m - 1 ) b u t no a b s o r p t i o n a t t r i b u t a b l e t o a t e r m i n a l v. I L J. The NMR s p e c t r u m o f t h e complex i n C.D, Wn 6 D c o n t a i n s t h e e x p e c t e d s i g n a l s due t o t h e p h o s p h i t e and eye 1 o p e n t a d i e n y 1 l i g a n d s a n d , more i m p o r t a n t l y , o n l y one complex m u l t i p l e t t h a t may be a t t r i b u t e d t o h y d r i d e h y d r o g e n s ( F i g . 2- 5 a ) . C a r e f u l i n t e g r a t i o n o f t h e s p e c t r u m , r u n w i t h a s u f f i c i e n t d e l a y (45° p u l s e a n g l e , -10 s d e l a y ) between p u l s e s t o a l l o w t h e eye 1 o p e n t a d i e n y 1 p e a k s t o r e l a x p r o p e r l y , shows t h a t t h e r a t i o o f (29) 1 Cp t o h y d r i d e h y d r o g e n s i s 5 : 1 v '. In a d d i t i o n , t h e H s p e c t r u m r u n w i t h 3 1 P d e c o u p l i n g ( F i g . 2-5b) shows i ^ H V ) = 55 Hz. T h i s f a c t p e r m i t s t h e a s s i g n m e n t o f t h e complex m u l t i p l e t shown i n F i g . 2-5a a s t h e s u p e r i m p o s i t i o n o f a 1:2:1 t r i p l e t (due t o 1 H - 3 1 P c o u p l i n g , 2 J H p = 24 Hz) on t o p o f a d o u b l e t (due t o 1 183 H- W c o u p l i n g ) o f 1:2:1 t r i p l e t s . I n t e g r a t i o n o f e i t h e r o f 183 t h e h y d r i d e s i g n a l s i n F i g u r e 5 shows t h e W s a t e l l i t e s t o 31 c o n s t i t u t e ~257. o f t h e t o t a l s i g n a l i n t e n s i t y . F i n a l l y , t h e P NMR s p e c t r u m , r e c o r d e d w i t h o n l y t h e p h o s p h i t e p r o t o n s d e c o u p l e d , JPH 2 c o n s i s t s o f a 1:2:1 t r i p l e t w i t h j = 24 Hz, i n ag r e e m e n t w i t h 57 t h e *H s p e c t r u m . * 2 * T h i s r e l a t i v e l y s m a l l *H- 3 1P c o u p l i n g i s o f t h e m a g n i t u d e e x p e c t e d f o r a t r a n s H-L c o n f i g u r a t i o n by a n a l o g y t o t h o s e o b s e r v e d f o r t h e CpM(CO) 2HL ( L = t e r t i a r y p h o s p h i n e ) s e r i e s o f compounds. (18) a) 1.40 1.30 8(ppm) 120 b) 1.40 1.30 8(ppm) F i a . 2-5. The h y d r i d e r e g i o n s o f t h e 400-MHz a) H, a n d b) ! H { 3 1 P } NMR s p e c t r a o f [ C p W ( N O ) { P ( 0 P h ) 3 > ] 2 ( u - H ) 2 i n C 6 D 6 - T a k e n t o g e t h e r , t h e s p e c t r o s c o p i c p r o p e r t i e s o f t C p W ( N O ) H { P ( O P h ) 3 ) 2 ] s u g g e s t i t s d i m e r l c f o r m u l a t i o n a n d i t Is t h e r e f o r e , p e r h a p s , b e s t f o r m u l a t e d a s [ C p W ( N O ) { P ( 0 P h ) 3 > ] 2 ( p - H ) 2 (24) w i t h a s t r u c t u r e a s d e p i c t e d i n F i g . 2-6. The two p h o s p h i t e 58 l i g a n d s a r e shown a s b e i n g t r a n s t o e a c h o t h e r s i n c e m o l e c u l a r m o d e l s s u g g e s t t h a t a c i s c o n f i g u r a t i o n w o u l d be v e r y u n f a v o u r a b l e on s t e r i c g r o u n d s . The h y d r i d e l i g a n d s must be e x c h a n g i n g r a p i d l y on t h e NMR t i m e s c a l e i n o r d e r t o m a i n t a i n , on t h e a v e r a g e , s o m e t h i n g a k i n t o a t r a n s o r i e n t a t i o n w i t h r e s p e c t t o t h e two p h o s p h i t e l i g a n d s . T h i s w i l l be d e a l t w i t h f u r t h e r i n c h a p t e r 3. The W 2 ( u - H ) 2 l i n k a g e i n t h i s s y s t e m must be weaker t h a n t h o s e i n [ C p W ( N O ) 1 ] 2 ( u - H ) 2 a n d [ C p W ( N O ) H ] 2 ( u - H ) 2 s i n c e t h e l o w - r e s o l u t i o n mass s p e c t r u m o f [CpW(NO){P(OPh) } ] 2 ( u - H ) 2 ( p r o b e t e m p e r a t u r e = 120°C) shows h i g h e s t - m a s s p e a k s a t t r i b u t a b l e o n l y t o a m i x t u r e o f [ C p W ( N O ) H { P ( O P h ) 3 } ] + and [ C p W ( N O ) { P ( O P h ) 3 ) ] + (m/z = 5 9 0 , 1 8 4 W ) . ( 2 ) (OPh)3P ..P(OPh), F i g . ? - f i . P r o p o s e d s t r u c t u r e o f [CpW(NO){P(OPh) }] ( u - H ) 2 . (24) The weakness o f t h i s W 2 ( u - H ) 2 i n t e r a c t i o n i s r e f l e c t e d i n t h e i n s t a b i l i t y o f t h e compound. As summarized i n s t e p e o f Scheme 2-1, when a p u r p l e s o l u t i o n o f [CpW(NO){P(OPh) }] ( u ~ H ) 2 59 i s s t i r r e d a t room t e m p e r a t u r e ( f o r a few d a y s i n be n z e n e o r a few h o u r s i n C H ^ C l ^ ) i t g r a d u a l l y becomes o r a n g e . A d d i t i o n o f he x a n e s t o t h e f i n a l s o l u t i o n i n d u c e s t h e p r e c i p i t a t i o n o f a s m a l l amount o f CpW(NO)H 2[P(OPh ) 3 3 a s an a n a l y t i c a l l y p u r e o r a n g e powder. T h i s complex e v i d e n t l y r e s u l t s f r o m a d i s p r o p o r t i o n a t i o n r e a c t i o n o f t h e s t a r t i n g d i m e r ( e q . 2 - 7 ) , b u t t h e n a t u r e o f t h e o t h e r o r g a n o m e t a 1 1 i c p r o d u c t s i s n o t c l e a r . A number o f new, C H 2 C 1 2 o r PhH [ C p w ( N O ) { P ( O P h ) 3 } ] 2 ( y - H ) 2 ^ C p W ( N O ) H 2 [ P ( O P h ) 3 ] (2-7) - " C p W ( N O ) [ P ( O P h ) 3 ] " e y e l o p e n t a d i e n y 1 - t y p e r e s o n a n c e s a r e o b s e r v e d when t h i s r e a c t i o n i s f o l l o w e d by *H NMR s p e c t r o s c o p y . In any e v e n t , t h e o c c u r r e n c e o f t h e i n d i v i d u a l r e a c t i o n s 2-6 a n d 2-7 ( s t e p s d a n d e o f Scheme 2-1) c l e a r l y shows t h a t t h e r e a c t i o n o f [ C p W ( N O ) H ] 2 ( y - H ) 2 w i t h L e w i s b a s e d o e s n o t p r o c e e d s i m p l y i n a manner a n a l o g o u s t o t h a t o f s t e p s b and f ( e q . 2-3 a n d 2 - 4 ) , a s i n e q . 2-8. S u r p r i s i n g l y , C p W ( N O ) H 2 [ P ( O P h ) 3 ] d o e s n o t a p p e a r t o be a c c e s s i b l e v i a s t e p h (Scheme 2-1) — i . e . m e t a t h e s i s o f an i o d o 1 i g a n d w i t h N a [ H 2 A l ( O C H 2 C H 2 O C H 3 ) 2 ] . S t i r r i n g o f C p W ( N O ) I H [ P ( O P h ) 3 ] w i t h t h e aluminum h y d r i d e r e a g e n t o v e r n i g h t r e s u l t s o n l y i n p a r t i a l d e c o m p o s i t i o n o f t h e s t a r t i n g n i t r o s y l h y d r i d e a n d no f o r m a t i o n o f t h e d e s i r e d p r o d u c t . 60 C H 0 C 1 - o r [ C p W ( N 0 ) H ] 2 ( u - H ) 2 + 2 L 2 CpW(N0)H 2L (2-8) PhH The complex C p w ( N O ) H 2 [ P ( O P h ) 3 ] Is a n o r a n g e , d i a m a g n e t i c , r e l a t i v e l y a i i — s t a b l e s o l i d w h i c h i s s o l u b l e i n most common, o r g a n i c s o l v e n t s . An IR s p e c t r u m o f a C H 2 C 1 2 s o l u t i o n o f t h i s compound ( T a b l e 2-1) has a b s o r p t i o n s due t o b o t h t e r m i n a l h y d r i d e and t e r m i n a l n i t r o s y l l i g a n d s . I t s *H NMR s p e c t r u m ( T a b l e 2-11) shows a Cp t o h y d r i d e H atom r a t i o o f 5:2 a n d has a h y d r i d e r e s o n a n c e p a t t e r n q u a l i t a t i v e l y v e r y s i m i l a r t o t h o s e o f t h e CpW(NO)IHL c o m p l e x e s ( s e e a b o v e ) . T h i s compound, t h e r e f o r e , l i k e l y has a c o n v e n t i o n a l " f o u r - l e g g e d p i a n o - s t o o l " s t r u c t u r e w i t h two e q u i v a l e n t , m u t u a l l y t r a n s , h y d r i d e l i g a n d s , i . e . P r o t o n NMR m o n i t o r i n g o f t h e r e a c t i o n o f [ C p W ( N O ) H ] 2 ( u - H ) 2 w i t h P ( O M e ) 3 i n C&D& s u g g e s t s t h a t i t p r o c e e d s a n a l o g o u s l y t o t h a t o f P ( O P h ) 3 ( e q . 2-6 a n d 2 - 7 ) , a l b e i t more r a p i d l y . The o n l y d i f f e r e n c e i s t h a t i n t h e p r e s e n c e o f t h e s t e r i c a l l y l e s s d emanding p h o s p h i t e , t h e p u r p l e i n t e r m e d i a t e 61 [CpW(NO) { P ( O M e ) 3 ) ] 2 ( u - H ) 2 i s ^ o r m e c | a s a m i x t u r e o f i s o m e r s ( d e s i g n a t e d A a n d B i n T a b l e 2-1 I ) . The i s o m e r s show r e s o n a n c e s c o n s i s t e n t w i t h t h e i r h a v i n g s t r u c t u r e s a n a l o g o u s t o t h a t i n F i g . 2-6, w i t h t h e P ( O M e ) 3 l i g a n d s c i s t o e a c h o t h e r i n i s o m e r A a n d t r a n s i n i s o m e r B. B o t h i s o m e r s a p p e a r t o d i s p r o p o r t i o n a t e i n s o l u t i o n a t room t e m p e r a t u r e ( t h e s t e r i c a l l y c rowded A more r a p i d l y t h a n B) t o f o r m C p W ( N O ) H 2 [ P ( O M e ) 3 ] w i t h t h e same t r a n s d i h y d r i d e s t r u c t u r e a s t h e P ( OPh> 3 complex d e s c r i b e d a b o v e . No o t h e r h y d r i d e c o m p l e x e s o f t u n g s t e n a r e d e t e c t a b l e i n t h e f i n a l s o l u t i o n . None o f t h e s e P(OMe> 3 compounds have been i s o l a t e d i n a p u r e f o r m . G. P r e p a r a t i o n and P r o p e r t i e s o f [ C p W ( N O ) B r 2 ] 2 . The y i e l d s o f a l l t h e h y d r i d e p r e p a r a t i o n s d i s c u s s e d a b o v e a r e n o t v e r y s a t i s f a c t o r y . In p a r t i c u l a r , i t was e s p e c i a l l y d e s i r e d t o r a i s e t h e y i e l d o f [CpW(NO)H] ( u - H ) 2 s o t h a t i t s p o t e n t i a l l y i n t e r e s t i n g c h e m i s t r y c o u l d be c o n v e n i e n t l y s t u d i e d . I t was f e l t t h a t one c o n t r i b u t i n g f a c t o r t o t h e low y i e l d s o f a l l t h e p r e p a r a t i o n s i s t h e low s o l u b i l i t y o f t h e [ C p W ( N O ) I 2 ] 2 s t a r t i n g m a t e r i a l i n t h e r e a c t i o n s o l v e n t s and t h e c o n s e q u e n t n e c e s s i t y o f p e r f o r m i n g t h e r e a c t i o n s a t room t e m p e r a t u r e . T h e r e f o r e , t h e bromo a n a l o g u e was p r e p a r e d i n t h e hope t h a t i t w o u l d be more s o l u b l e (on t h e g r o u n d s o f s m a l l e r s i z e and lower m o l e c u l a r w e i g h t ) an d t h e r e a c t i o n s c o u l d t h e n be t r i e d a t lower t e m p e r a t u r e . 62 The p r e p a r a t i o n o f [ C p W ( N O ) B r 2 ] 2 by t h e a d d i t i o n o f a s t o i c h i o m e t r i c amount o f a B r 2 / C H 2 C 1 2 s o l u t i o n t o Cpw(CO) 2(NO) p r o c e e d s a n a l o g o u s l y t o t h a t o f [CpW(NO)I ] * 1 * (Scheme 2-1 I ) . Scheme 2-1 I CpW(C0) 2(N0) v c o = 2010, 1927, v N Q = 1655 cm B r 2 / C H 2 C l 2 - CO C p w ( C O ) ( N 0 ) B r 2 v C Q = 2099, v N Q = 1693 cm" 1 - CO Cpw(N0)Br, vMr, = 1655 cm" 1 The IR bands d e s c r i b e d i n t h e E x p e r i m e n t a l S e c t i o n may be a s s i g n e d t o s t a r t i n g CpW(C0> 2(N0), t h e C p W ( C O ) ( N O ) B r 2 i n t e r m e d i a t e a n d t h e f i n a l CpW(NO)Br 2 ( s e e b e l o w ) . The p a r t i c u l a r l y u n u s u a l f e a t u r e o f t h i s r e a c t i o n i s t h a t t h e f i n a l g r e e n r e a c t i o n s o l u t i o n d e p o s i t s a brown, a n a l y t i c a l l y p u r e , m i c r o c r y s t a l 1 i n e s o l i d , w h i c h i s t h e [ C p W ( N O ) B r 2 ] 2 p r o d u c t . T h i s m a t e r i a l i s much more a i r - s e n s i t i v e t h a n i t s i o d o a n a l o g u e a n d , a l t h o u g h I t may be r a p i d l y h a n d l e d a n d w e i g h e d i n a i r a s a s o l i d , s u c h e x p o s u r e must be b r i e f . S o l u t i o n s a r e s u f f i c i e n t l y a i r - s e n s i t i v e t h a t c o m p l e t e d e c o m p o s i t i o n o f t h e complex o c c u r s w i t h i n f i v e m i n u t e s upon e x p o s u r e t o a i r . The brown complex i s c o n s i d e r a b l y more s o l u b l e In most n o n - a l i p h a t i c , n o n - c o o r d i n a t i n g o r g a n i c s o l v e n t s t h a n i s [CpW(NO)1 2 3 2 t o y i e l d b r i l l i a n t g r e e n 63 c o l o u r e d s o l u t i o n s r e m i n i s c e n t o f C p W ( N 0 ) 2 C l . ( 3 0 * In c o o r d i n a t i n g s o l v e n t s , s u c h a s a c e t o n e , [ C p W ( N O ) B r 2 ] 2 d i s s o l v e s t o i n s t a n t l y g i v e o r a n g e s o l u t i o n s o f what p r e s u m a b l y i s t h e s o l v a t e d monomer, CpW(NO)Br 2L ( L = s o l v e n t ) . The IR s p e c t r u m o f t h e dromo complex i n C H 2 C 1 2 shows a s i n g l e v N 0 a t 1655 c m - 1 , 8 cm * lower t h a n t h a t o f i t s i o d o a n a l o g u e . I n t e r e s t i n g l y , t h e *H NMR s p e c t r u m o f CpW(NO)Br 2 d i s s o l v e d i n C DC1 3 shows t h e e x p e c t e d s i n g l e t ( a t S - 6.35), b u t t h i s peak i s s u f f i c i e n t l y 183 n a r r o w t h a t c o u p l i n g o f t h e eye 1 o p e n t a d i e n y 1 p r o t o n s t o w c a n 2 be o b s e r v e d ( J ^ w = 1.8 Hz - F i g . 2 - 7 ) . Re i n s p e c t i o n o f t h e s p e c t r u m o f t h e i o d o compound shows t h e same phenomenon ( C D C l ^ , 6 2 = 6.29, J H W = 1.8 H z ) . None o f t h e o t h e r eye 1 o p e n t a d i e n y 1 t u n g s t e n compounds d i s c u s s e d i n t h i s t h e s i s have n a r r o w enough eye 1 o p e n t a d i e n y 1 r e s o n a n c e s f o r t h i s c o u p l i n g t o be o b s e r v a b l e . U n l i k e [CpW(NO) 1 2 3 2 » * 1 ^ t n e l o w - r e s o l u t i o n , e 1 e c t r o n - 1 m p a c t mass s p e c t r u m o f [ C p W ( N O ) B r 2 ] 2 ( p r o b e t e m p e r a t u r e = 150°C) has no p e a k s t h a t c a n be a t t r i b u t e d t o a d i - t u n g s t e n s p e c i e s , w i t h t h e 81 184 h i g h e s t mass p e a k s (m/z = 439; B r , W ) , o b s e r v e d b e i n g due t o t h e monomeric i o n [ C p W ( N O ) B r 2 ] + ( ( P / 2 ) + ) . The u n u s u a l b r o w n / g r e e n s o l i d / s o l u t i o n c o l o u r c h a r a c t e r i s t i c o f [ C p W ( N O ) B r 2 ] 2 when compared t o [ C p W ( N O ) I 2 ] 2 , w h i c h f o r m s d a r k y e l l o w - b r o w n s o l u t i o n s f r o m t h e brown s o l i d , 1ed us t o s p e c u l a t e t h a t t h e bromo compound m i g h t have a d i f f e r e n t s o l u t i o n s t r u c t u r e . T h e r e f o r e , q u a l i t a t i v e U V - v i s s p e c t r a o f t h e two 64 6.40 */ * 6.30 S(ppm) F i g . 2-7. The 80-MHz lh NMR s p e c t r u m o f C p W ( N 0 ) B r 2 i n CDC1 3 2 s h o w i n g J H W = 1.8 Hz. 65 compounds were r u n i n C H ^ C l g ( F i g - 2 - 8 ) . A t c o n c e n t r a t i o n s —3 —5 a p p r o p r i a t e f o r s u c h s p e c t r a (10 t o 10 M), s o l u t i o n s o f t h e i o d o compound a r e b r i g h t y e l l o w i n c o l o u r , w h i l e t h o s e o f t h e bromo a r e a p a l e y e l l o w - g r e e n . A l t h o u g h no a t t e m p t t o measure e x t i n c t i o n c o e f f i c i e n t s was made, i t was c l e a r t h a t much l e s s c o n c e n t r a t e d s o l u t i o n s o f t h e i o d o complex were n e e d e d t o o b t a i n good s p e c t r a . I n s p e c t i o n o f t h e s e ( F i g . 2-8) shows t h a t t h e y a r e q u a l i t a t i v e l y v e r y s i m i l a r , e x c e p t t h e p e a k s f o r t h e i o d o compound a r e s h i f t e d ~100 nm t o lower e n e r g y . The d-d t r a n s i t i o n s may be a s s i g n e d t o t h e weak bands a t 698 a n d 772 nm f o r t h e bromo a n d i o d o compounds, r e s p e c t i v e l y , w h i l e a number o f much more i n t e n s e c h a r g e - t r a n s f e r band's may be s e e n a t h i g h e r e n e r g i e s . The s p e c t r o p h o t o m e t r i c r e a s o n f o r t h e d i f f e r e n t c o l o u r s i n s o l u t i o n i s now a p p a r e n t . The c o l o u r o f t h e bromo compound i s g o v e r n e d by t h e weak d-d t r a n s i t i o n whose maximum i s j u s t w i t h i n t h e v i s i b l e r e g i o n (400-700 nm), w h i l e t h a t o f t h e more i n t e n s e l y c o l o u r e d i o d o compound i s g o v e r n e d by t h e much s t r o n g e r c h a r g e - t r a n s f e r band a t 447 nm. T h i s band has s h i f t e d f r o m t h e u l t r a v i o l e t r e g i o n f o r t h e bromo complex i n t o t h e v i s i b l e r e g i o n f o r t h e i o d o a s p a r t o f t h e a b o v e m e n t i o n e d 100 nm s h i f t . The o v e r a l l s i m i l a r i t y o f t h e s p e c t r a s u g g e s t no r a d i c a l s t r u c t u r a l d i f f e r e n c e between t h e two c o m p l e x e s i n s o l u t i o n . The most o b v i o u s p o s s i b l e s t r u c t u r a l d i f f e r e n c e between two s u c h compounds w o u l d be a monomer/dimer d i f f e r e n t i a t i o n . The [CpW(NO)I_]_ complex was f o r m u l a t e d a s a d i m e r on t h e b a s i s o f 66 1 1 1 1 1 1 r 300 400 500 600 700 800 900 Wavelength (nm) F i a . 2-8. U V - v i s i b l e s p e c t r a o f CpW(N0)Br 2 ( ) a n d C p W ( N 0 ) I z ) In C H 2 C 1 2 . t h e 1 8 - e l e c t r o n r u l e and t h e o b s e r v a t i o n o f p e a k s i n t h e mass s p e c t r u m due t o d i - m e t a l l i c c o n t a i n i n g f r a g m e n t s . * 1 * The f i r s t compound o f t h i s t y p e , [ C p M o ( N O ) I 2 3 2 , was f o r m u l a t e d a s a d i m e r on t h e same b a s i s . * 3 2 3 * However, t h e t r i s - p y r a z o l y l b o r a t e a n a l o g u e s a r e b e l i e v e d t o be d i m e r s when t h e p y r a z o l e r i n g s a r e u n s u b s t i t u t e d ( e . g . [ ( H B p z 3 ) M o ( N O ) I 2 3 2 ) b u t monomers when t h e s e r i n g s a r e p a r t i a l l y m e t h y l s u b s t i t u t e d ( e . g . C H B ( 3 , 5 - M e 2 p z ) 3 ] M o ( N O ) I 2 ) . * 3 2 b * The l a t t e r c o n c l u s i o n s were b a s e d on s o l u b i l i t y p r o p e r t i e s a n d s o l u t i o n m o l e c u l a r w e i g h t measurements on t h e s u b s t i t u t e d compounds. A d d i t i o n a l l y , Cp*W(NO)I 2 was r e c e n t l y p r e p a r e d i n o u r l a b o r a t o r y ( s e e c h a p t e r 4) a n d shown t o e x i s t a s a monomer b o t h i n t h e s o l i d - s t a t e a n d i n C H 2 C 1 2 s o l u t i o n . * 3 3 * I t i s c l e a r f r o m t h e f a c t t h a t t h e e l e c t r o n - i m p a c t mass- s p e c t r u m o f [ C p W ( N O ) B r 2 ] 2 shows no d i - t u n g s t e n f r a g m e n t s t h a t a ny ( p r e s u m a b l y ) h a l i d e b r i d g e s h o l d i n g s u c h a d i m e r t o g e t h e r must be weaker i n t h i s compound t h a t i n i t s i o d o a n a l o g u e . However, a l t h o u g h t h e bromo compound i s much more s o l u b l e t h a n t h e i o d o , i t i s s t i l l n o t s o l u b l e enough f o r a s o l u t i o n m o l e c u l a i — w e i g h t / 3 4 ) d e t e r m i n a t i o n . ' N e v e r t h e l e s s , o u r b e l i e f i s t h a t [ C p W ( N O ) B r 2 3 2 e x i s t s a s a brown d i m e r i n t h e s o l i d - s t a t e , b u t p r o b a b l y d i s s o c i a t e s s u b s t a n t i a l l y upon d i s s o l u t i o n t o g i v e g r e e n s o l u t i o n s o f t h e monomer, C p W ( N O ) B r 2 ? a l t h o u g h t h e e v i d e n c e i s n o t v e r y c o n c l u s i v e . The s i m i l a r i t y o f t h e U V - v i s s p e c t r a o f t h e bromo a n d i o d o compounds wo u l d t h e r e f o r e s u g g e s t t h a t t h e l a t t e r . 68 t o o , f o r m s a monomer In s o l u t i o n . T h e s e s u g g e s t i o n s a r e s u p p o r t e d by r e c e n t e l e c t r o c h e m i c a l s t u d i e s w h i c h show t h e s i m i l a r i t i e s o f t h e c y c l i c voltammograms o f t h e CpM(NO)X 2 s p e c i e s a n d by t h e p r e p a r a t i o n o f a s e r i e s o f [ C p f U N O X ^ ] * r a d i c a l (35) a n i o n s . ' A d d i t i o n a l l y , t h e o b s e r v a t i o n o f o r a n g e c o l o u r e d s o l u t i o n s when [C p W C N O B r ^ J g , s d i s s o l v e d i n c o o r d i n a t i n g s o l v e n t s ( e . g . a c e t o n e ) i s s u g g e s t i v e o f t h e f o r m a t i o n o f a CpW(NO)Br 2L (where L = s o l v e n t ) s p e c i e s . T h i s i s t h e same c o l o u r a s t h o s e o b s e r v e d f o r t h e CpW(NO)X 2L (X=I, H, L = t e r t i a r y p h o s p h i n e o r p h o s p h i t e ) s e r i e s o f c o m p l e x e s d i s c u s s e d e a r l i e r . H. P r e p a r a t i o n a n d P r o p e r t i e s o f CpW(NO)BrH[P(OPh) ] . R e g a r d l e s s o f w h e t h e r [ C p W ( N O ) B r 2 ] 2 e x i s t s a s a monomer o r d i m e r i n s o l u t i o n , i t d o e s meet t h e a b o v e s t a t e d o b j e c t i v e o f g r e a t e r s o l u b i l i t y t h a n i t s i o d o a n a l o g u e . The f i r s t s t e p i n a s s e s s i n g i t s u t i l i t y a s a s t a r t i n g m a t e r i a ) f o r h y d r i d e s y n t h e s i s was t o p r e p a r e t h e most e a s i l y i s o l a t e d a n a l o g u e t o a known i o d o compound. C o n s e q u e n t l y , C p W ( N O ) B r H [ P ( O P h ) 3 ] was p r e p a r e d , a t room t e m p e r a t u r e , i n a manner e x a c t l y a n a l o g o u s t o t h a t o f C p W ( N O ) I H [ P ( O P h ) 3 ] ( s t e p s a a n d b. Scheme 2-1 a b o v e and r e f . 2 ) . The bromo compound i s a b r i g h t , o r a n g e - r e d c r y s t a l l i n e m a t e r i a l whose a i l — s e n s i t i v i t y , s o l u b i l i t y a n d m a s s - s p e c t r a l p r o p e r t i e s a r e a n a l o g o u s t o t h o s e o f i t s i o d o r e l a t i v e . I t s o t h e r s p e c t r o s c o p i c p r o p e r t i e s a r e g i v e n i n T a b l e s 2-1 a n d 2-1 I a n d i t i s i n f o r m a t i v e t o compare them w i t h t h o s e o f 69 C p W ( N O ) l H [ P ( O P h ) 3 ] . F o r e a s e o f c o m p a r i s o n t h e s e d a t a have been p a r t i a l l y r e l i s t e d i n T a b l e 2 — I I I . P r i m a r i l y , t h e s e s p e c t r a l d a t a i n d i c a t e t h a t t h e bromo a n d i o d o compounds a r e 1 s o s t r u c t u r a l . However, t h e r e a r e some i n t e r e s t i n g c o m p a r i s o n s t h a t c a n be made. I n f r a r e d s p e c t r a (CH C l , s o l u t i o n ) o f t h e two T a b l e 2-1 I 1. C o m p a r a t i v e S p e c t r o s c o p i c D a t a f o r t h e C p w ( N O ) X H [ P ( O P h ) 3 J C o m p l e x e s . X I Br 1 R ( C H 2 C 1 2 ) V N Q 1643 1636 (cm" 1) \>WH 1883 1869 lH NMR ( C 6 D 6 ) <JCp 4.85 4.84 (6:ppm, J:Hz) 6W-H -2.06 0.20 l jHW 5 4 4 8 lJHP 112 112 3 1 P { 1 H } NMR ( C f e D 6 ) 69 115.5 120.2 («:ppm, J:Hz) 1 J p w 363 360 compounds show d e c r e a s e s i n b o t h t h e v (7 cm a n d v (14 cm *) v i b r a t i o n a l f r e q u e n c i e s upon s u b s t i t u t i o n o f B r f o r I. A d e c r e a s e i n v̂ ,„. i s u s u a l l y a s c r i b e d t o a n i n c r e a s e i n e l e c t r o n NU d e n s i t y on t h e m e t a l c e n t r e , t h e r e b y p e r m i t t i n g more b a c k - b o n d i n g (36) i n t o t h e NO n* o r b i t a l . The o b s e r v e d r e d u c t i o n i n v i n i s NO 70 o p p o s i t e t o e x p e c t a t i o n , a s s u b s t i t u t i o n o f I by t h e more (31) e l e c t r o n e g a t i v e Br (2.5 v s . 2 . 8 ) v ' w o u l d be a n t i c i p a t e d t o d i m i n i s h t h e e l e c t r o n d e n s i t y on t h e t u n g s t e n c e n t r e a v a i l a b l e f o r b a c k - b o n d i n g . The r e a s o n f o r t h e o b s e r v a t i o n o f t h e o p p o s i t e t r e n d i s n o t c l e a r . The d e c r e a s e i n v W H i s more i n l i n e w i t h e x p e c t a t i o n s , a s t h e d r a i n i n g o f m e t a l e l e c t r o n d e n s i t y o n t o t h e Br atom s h o u l d weaken t h e w-H bond. The h y d r i d e r e g i o n s o f t h e NMR s p e c t r a a r e a l s o i n t e r e s t i n g t o compare. S u b s t i t u t i o n o f I by Br s h i f t s 6^ by + 2.26 ppm. E l e c t r o n e g a t i v i t y c o n s i d e r a t i o n s w o u l d l e a d one t o a n t i c i p a t e s u c h a d e s h i e l d i n g , b u t t h e s e a r g u m e n t s a r e u s u a l l y n o t u s e f u l when d i s c u s s i n g (38) t r a n s i t i o n - m e t a l h y d r i d e s . On t h e o t h e r hand, t h e d e c r e a s e i n 1 J H W i s c o n s i s t e n t w i t h t h e t r e n d o b s e r v e d f o r t h e CpW(NO)IHL co m p l e x e s w i t h d e c r e a s i n g d o n o r a b i l i t y o f L d i s c u s s e d a b o v e . The i n i t i a l o b j e c t i v e o f t u r n i n g t o t h e bromo a n a l o g u e s was t o improve t h e y i e l d s o f h y d r i d e c o m p l e x e s . U n f o r t u n a t e l y , a y i e l d o f o n l y 13% was o b t a i n e d i n t h e p r e p a r a t i o n o f C p W ( N O ) B r H [ P ( O P h ) 3 ] — l e s s t h a n o n e - t h i r d o f t h a t o b t a i n e d f o r t h e i o d o compound. L i k e w i s e , numerous a t t e m p t s t o p r e p a r e [ C p W ( N 0 ) H ] 2 ( v i - H ) 2 i n C H 2 C l 2 / t o l u e n e a t 0°C f r o m [ C p W ( N O ) B r 2 ] 2 o n l y g a v e v e r y low y i e l d s o f p o o r q u a l i t y m a t e r i a l . R e a c t i o n t e m p e r a t u r e s lower t h a n 0°C were n o t a c c e s s i b l e b e c a u s e t h e d i b r o m o compound became t o o i n s o l u b l e a t a b o u t t h i s t e m p e r a t u r e f o r t h e r e a c t i o n t o be p r a c t i c a b l e . A t t e m p t s t o u s e [ C p w ( N O ) B r 2 ] 2 a s a s t a r t i n g m a t e r i a l f o r h y d r i d e s y n t h e s i s were 71 t h e r e f o r e a b a n d oned. I_. The C y c l i c Voltammogram o f [CpW (NO) I 2 ] 2 . In h e r p r e l i m i n a r y work, J . C . Ox l e y e x p l o r e d a number o f (2) d i f f e r e n t r o u t e s t o some o f t h e s e h y d r i d e c o m p l e x e s . As she s o c o r r e c t l y p o i n t e d o u t , t h e l o w - y i e l d s t e p i n a l l t h e r o u t e s a t t e m p t e d , i n c l u d i n g t h o s e d e s c r i b e d i n t h i s t h e s i s , was a l w a y s t h e h a l i d e / h y d r i d e m e t a t h e s i s . In a d d i t i o n t o b e i n g m e t a t h e s i s r e a g e n t s , h y d r i d e c o m p l e x e s s u c h a s N a [ H ? A l ( O C H 2 C H 2 O C H 3 ) 2 ] c a n a c t a s r e d u c i n g a g e n t s . In f a c t , Na[H 2Al(OCH 2CH 2OCH 3 > 2 3 has been shown t o work a l m o s t a s w e l l a s Na amalgam as a r e d u c i n g a g e n t i n t h e p r e p a r a t i o n o f C p M o ( N 0 ) L 2 c o m p l e x e s ( L = t e r t i a r y p h o s p h i n e ) f r o m [ C p M o ( N O ) I 2 ] 2 ( 3 9 ) ( e q . 2 - 9 ) . Sometime a f t e r t h e s y n t h e t i c work d e s c r i b e d i n t h i s c h a p t e r was c o m p l e t e d , t h e c y c l i c (35) voltammogram (CV) o f CpW(NO)I 2 was r u n v ' i n C H 2 C 1 2 and t h i s a p p e a r s t o o f f e r some e x p l a n a t i o n f o r t h e low y i e l d s . A CV Na/Hg o r N a [ H 2 A 1 ( O C H 2 C H 2 O C H 3 ) 2 ] [CpMo(NO) I 2 ] 2 + 4 L • - 2 CpMo(NO)l_ 2 (2-9) THF i s shown i n F i g . 2-9 and, a s c a n be s e e n , t h e r e a r e a t l e a s t two r e d u c t i o n waves a t r e l a t i v e l y low p o t e n t i a l s (-0.34 a n d -0.63 V v s . S C E ) . The e a s e o f t h e s e r e d u c t i o n s s u g g e s t s t h e m e t a t h e s i s g o e s v i a an e l e c t r o n t r a n s f e r mechanism, o r , a t t h e v e r y l e a s t . 7 2 0 -1 -2 Volts vs S C E F i g . 2-9. The ( r e d u c t i v e ) c y c l i c voltammogram o f CpWCNO)^ i n C H 2 C 1 2 u s i n g a P t bead e l e c t r o d e a n d B u 4 N P F 6 a s t h e s u p p o r t e l e c t r o l y t e . S c a n r a t e = 0.4 V s - 1 . * 3 5 , 4 1 * an e l e c t r o n t r a n s f e r r e a c t i o n i s c o m p e t i n g w i t h m e t a t h e s i s . The f a c t t h a t t h e r e a c t i o n between CpW(NO)I^ a n d N a [ H 2 A l ( O C H 2 C H 2 O C H 3 ) 2 3 t o f o r m [CpW(NO)I] £(u-H) i s i n s t a n t a n e o u s i s a l s o c o n s i s t e n t w i t h an e l e c t r o n t r a n s f e r mechanism. As F i g . 2-9 shows, t h e f i r s t r e d u c t i o n wave i s c o m p l e t e l y i r r e v e r s i b l e and so e l e c t r o n t r a n s f e r f r o m N a [ H 2 A l ( O C H 2 C H 2 O C H 3 ) 2 ] t o CpW(NO)I 2 must r e s u l t i n an u n s t a b l e s p e c i e s t h a t r a p i d l y u n d e r g o e s c h e m i c a l c h a n g e . The low y i e l d s f o r t h e m e t a t h e s i s r e a c t i o n s c an t h e r e f o r e be e x p l a i n e d by s u g g e s t i n g t h a t t h i s change removes t h e t u n g s t e n r e a g e n t f r o m any pathway l e a d i n g t o t h e m e t a t h e s i s p r o d u c t , [ C p W ( N O ) n 2 ( y - H ) 2 . The d e s i r e d p r o d u c t i s o b t a i n e d , t h e r e f o r e , o n l y b e c a u s e t h e m e t a t h e s i s i s e x t r e m e l y r a p i d and c a n compete w i t h t h e e l e c t r o n t r a n s f e r pathway. F u r t h e r s t u d i e s t o c l a r i f y t h i s i s s u e a r e underway by o t h e r members o f o u r r e s e a r c h (35) g r o u p . 74 J . R e f e r e n c e s a n d N o t e s 1. L e g z d i n s , P.; M a r t i n , D.T.; N u r s e , C R . I n o r g . Chem. 1980, 19, 1560-1564. 2. O x l e y , J . C Ph.D. D i s s e r t a t i o n , The U n i v e r s i t y o f B r i t i s h C o l u m b i a , 1983. 3. S h r i v e r , D.F.; D r e z d z o n , M.A. "The M a n i p u l a t i o n o f A i r - S e n s i t i v e Compounds", 2nd e d . ; W i 1 e y - I n t e r s c i e n c e : T o r o n t o , 1986. 4. Merck D e u t e r a t e d S o l v e n t s f o r NMR C a t a l o g u e , MSD I s o t o p e s , M o n t r e a l , Que, P r i c e L i s t 47C, p 7. 5. N i x o n , J . F . ; P i d c o c k , A. Annu. Rev. Nuc1. Magn. Reson. S p e c t r o s c . 1969, 2 2 , 345. 6. N a [ H 2 A l ( 0 C H 2 C H 2 0 C H 3 ) 2 ] was p u r c h a s e d a s a 3.4 M s o l u t i o n i n t o l u e n e f r o m t h e A l d r i c h C h e m i c a l Co. u n d e r t h e t r a d e name R e d - A l . 7. I t i s i n t e r e s t i n g t o n o t e t h a t [ C p W ( N 0 ) I 2 ] 2 d o e s a p p e a r t o r e a c t w i t h N a [ H 2 A l ( O C H g C H g O C H ^ ) 2 ] i n C H 2 C 1 2 w i t h o u t a n y n o t i c e a b l e i n t e r f e r e n c e o f t h e h a l o g e n a t e d s o l v e n t . 8. GC-MS a n a l y s i s o f C 5 H 1 Q was done on a Nermag RIO-10 s p e c t r o m e t e r u s i n g a 30-m Carbowax c a p i l l a r y c olumn a t 1 ° C 9. Hames, B.W.; L e g z d i n s , P.; O x l e y , J . C . I n o r g . Chem. 1980, 1 9 , 1565-1571. 10. Adams, O.M. " M e t a l L i g a n d a n d R e l a t e d V i b r a t i o n s " ; Edward A r n o l d L t d . : London, 1967; pp 1-25 and r e f e r e n c e s t h e r e i n . 11. C o o p e r , C.B.; S h r i v e r , D.F.; Onaka, S. Adv. Chem. S e r . 75 1978, 167, 232-247. 12. B e c k e r , E.D. " H i g h R e s o l u t i o n NMR", 2nd e d . ; A c a d e m i c P r e s s : New Y o r k , 1980; C h a p t e r 7. 13. J e s s o n , J . P . i n "The H y d r o g e n S e r i e s , V o l . 1. T r a n s i t i o n - M e t a l H y d r i d e s " , M u e t t e r t i e s , E . L . , Ed.; M a r c e l D e k k e r : New Y o r k , 1971; C h a p t e r 4, p 79. 14. T j measurements were o b t a i n e d w i t h t h e a s s i s t a n c e o f Mr. J . Ba l atom" on a m o d i f i e d N i c o 1 e t - O x f o r d H-270 s p e c t r o m e t e r u s i n g a 180°-'t-90° p u l s e s e q u e n c e . The a b s o l u t e s i g n a l i n t e n s i t i e s were p r o c e s s e d u s i n g s t a n d a r d N i c o l e t s o f t w a r e . 15. Adam, M.J.; H a l l , L.D. J . O r g a n o m e t a l . Chem. 1980, 186, 289-296. 16. Tolman, C.A. Chem. Rev. 1977, 77, 313-348 a n d r e f e r e n c e s t h e r e i n. 17. Kubacek, P.; Hoffmann, R.; H a v l a s , Z. O r g a n o m e t a l 1 i c s 1982, 1, 180-188 a n d r e f e r e n c e s t h e r e i n . 18. K a l c k , P.; P o i l b l a n c , R . J . J . O r g a n o m e t a l . Chem. 1970, 24, 445-452 a n d r e f e r e n c e s t h e r e i n . 19. S l a t e r , S.G.; L u c k , R.; Schumann, B.F.; D a r e n s b o u r g , M. O r g a n o m e t a l 1 i c s 1982, 1, 1662-1666. 20. S c h a t z , P.F. RACCOON 2.0; Moore, J.W. d i r e c t o r ; P r o j e c t SERAPHIM; E a s t e r n M i c h i g a n U n i v e r s i t y : Y p s i l a n t i , MI, 48197, 1984. 21. a) K a e s z , H.D.; S a i l l a n t , R.B. Chem. Rev. 1972, 72. 231-281 b) J o n e s , S.B.; P e t e r s e n , J . L . I n o r g . Chem. 1981, 20, 2889- 76 2894 and r e f e r e n c e s t h e r e i n . 22. S i n c e t h e i s o t o p o m e r c o n t a i n i n g two Jw n u c l e i i s s o s c a r c e (and was n e v e r o b s e r v e d i n o u r s y s t e m s due t o t h e low s o l u b i l i t y o f t h e s e c o m p l e x e s ) , t h e r e l a t i v e p r o p o r t i o n s o f i s o t o p o m e r s h a v i n g z e r o and one W n u c l e u s w o u l d be 74.8:25.2. 23. D e u b z e r , B.; K a e s z , H.D. J ^ Am. Chem. S o c . 1968, 90, 3276- 3277. 24. Reasons f o r d e p i c t i n g t h e W 2 ( y - H ) 2 i n t e r a c t i o n u s i n g t h e " f u s e d " r e p r e s e n t a t i o n w i l l be d i s c u s s e d i n c h a p t e r 3. 25. a) X - r a y s t r u c t u r e : C h u r c h i l l , M.R.; Chang, S.W.-Y. I n o r g . Chem. 1974, 1 3 , 2413-2419. b) n e u t r o n s t r u c t u r e : Wei, C - Y.; Marks, M.W.; Bau, R.; K i r t l e y , S.W.; B i s s o n , O.E.; H e n d e r s o n , M.E.; K o e t z l e , T.F. I b i d 1982, 2 1 , 2556-2565. 26. A l t , H.G.; Mahmoud, K.A.; R e s t , A . J . Angew. Chem. I n t . Ed. E n g l . 1983, 2 2 , 544-545. 27. L e g z d i n s , P.; M a r t i n , J . T . ; O x l e y , J . C . Q r g a n o m e t a l 1 i c s 1985, 4, 1263-1271. 28. GC-MS a n a l y s i s f o r H £ was done on a K r a t o s MS80 s p e c t r o m e t e r s c a n n i n g c o n t i n u o u s l y a t a r a t e o f 1 s c a n / s u s i n g a 30 m, DB-1 c a p i l l a r y column w i t h 5 uL c o a t i n g a t 0 ° C . 29. T h i s i s i n c o n t r a s t w i t h t h e p r e v i o u s l y r e p o r t e d r a t i o o f 5:2 a n d t h e p r e v i o u s l y a s s i g n e d s t r u c t u r e o f c i s - C p W ( N O ) H 2 [ P ( O P h ) 3 ] . ( 2 ) 30. L e g z d i n s , P.; M a l i t o , J . T . I n o r g . Chem. 1975, 1 4 , 1875-1878 77 and r e f e r e n c e s t h e r e i n . 31. C o t t o n , F.A.; W i l k i n s o n , G. "Advanced I n o r g a n i c C h e m i s t r y " , 4 t h e d . ; W i 1 e y - I n t e r s c i e n c e : T o r o n t o , 1980. pp 657-669. 32. a) K i n g , R.B. O r g . Mass. S p e c t r o m . 1969, 2, 401-412 a n d r e f e r e n c e s t h e r e i n , b) M c C l e v e r t y , J.A.; Seddon, 0.; B a i l e y , N.A.; W a l k e r , N.W. J ^ Chem. S o c . , Da 1 t o n T r a n s . 1976, 898-908. 33. E i n s t e i n , F.W.B.; J o n e s , R.A.; Dr y d e n N.H. p e r s o n a l commun i c a t i o n . 34. C l a r k , E.P. I n d . Eng. Chem., A n a l . Ed. 1941, 13, 820-821. 35. R i c h t e r - A d d o , G.B. p e r s o n a l c o m m u n i c a t i o n . 36. C h i s h o l m , M.H.; C o t t o n , F.A.; E x t i n e , M.W.; K e l l y , R.L. I n o r g . Chem. 1979, 18, 116-119 a n d r e f e r e n c e s t h e r e i n . 37. P a u l i n g L. "The N a t u r e o f t h e C h e m i c a l Bond", 3 r d e d . ; C o r n e l l U n i v e r s i t y P r e s s : I t h a c a , New Y o r k , 1960, p 90. 38. Buckingham, A.D.; S t e p h e n s , P . J . J_;_ Chem. S o c . 1964, 2747- 2759. 39. H u n t e r , A.D.; L e g z d i n s , P. O r g a n o m e t a l 1 i c s 1986, 5, 1001- 1009. 40. A f u l l a n a l y s i s o f t h e CV o f [ C p W ( N O ) I 2 ] 2 i s o u t s i d e t h e s c o p e o f t h i s t h e s i s . 41. L e g z d i n s , P.; W a s s i n k , B. O r g a n o m e t a l 1 i c s 1984, 3, 1811- 1817. 78 CHAPTER 3 Qn t.hg lH Nuc 1 e a r M a g n e t i c R e s o n a n c e S p e c t r a o f O r q a n o m e t a 1 1 i c T u n g s t e n H y d r i d e s In t h e l a s t c h a p t e r , t h e s y n t h e s e s a n d c h a r a c t e r i z a t i o n s o f CCpW(NO)IH] 2, [ C p w ( N 0 ) H 2 ] 2 a n d [CpW(NO)H{P(OPh) 3 ) ] 2 W E R E d i s c u s s e d . D u r i n g t h i s work, one o f t h e c l a s s i c p r o b l e m s i n b i m e t a l l i c h y d r i d e c h e m i s t r y was e n c o u n t e r e d — n a m e l y , d e t e r m i n i n g t h e mode o f a t t a c h m e n t o f t h e h y d r i d e l i g a n d s t o t h e m e t a l c e n t r e s . I n t r y i n g t o e s t a b l i s h t h e s t r u c t u r e o f a b i m e t a l l i c h y d r i d e c o m p l ex, a n y i n v e s t i g a t o r must d e a l w i t h two q u e s t i o n s : 1) A r e t h e H atoms a t t a c h e d i n a t e r m i n a l o r b r i d g i n g f a s h i o n ? a n d 2) Even i f t h e p h y s i c a l p r o p e r t i e s o f t h e complex i n s o l u t i o n s u g g e s t t h e p r e s e n c e o f a b r i d g i n g H 1 i g a n d , Is t h i s a t r u l y s t a t i c l i n k a g e o r i s i t a t i m e - a v e r a g e d s t r u c t u r e r e f l e c t i n g t h e o c c u r r e n c e o f r a p i d f l u x i o n a l p r o c e s s e s s u c h a s H u H 1 A . 1, M—M' ^ M—M ;F± M — M ? As i n o u r c a s e , when one o f t h e m e t a l s i n v o l v e d Is t u n g s t e n , t h e p r i n c i p a l t o o l e m p l o y e d t o a t t e m p t t o answer t h e s e q u e s t i o n s i s *H NMR s p e c t r o s c o p y , s i n c e t u n g s t e n has a n a t u r a l l y o c c u r r i n g t o o (14.47. a b u n d a n t ) , s p i n 1/2 i s o t o p e , O JW. Arguments a b o u t t h e n a t u r e o f t h e W-H i n t e r a c t i o n i n b i m e t a l l i c compounds have i n v o l v e d b o t h t h e c h e m i c a l s h i f t s o f t h e h y d r i d e r e s o n a n c e s a n d 1 183 t h e m a g n i t u d e s o f t h e H- W c o u p l i n g c o n s t a n t s o b s e r v e d In t h e 1 (28) s o l u t i o n H NMR s p e c t r a o f t h e s e s p e c i e s . However, t h e r e has 79 been c o n s i d e r a b l e u n c e r t a i n t y a s t o how t h e s e NMR p a r a m e t e r s a r e a f f e c t e d by t h e b r i d g i n g o r t e r m i n a l n a t u r e o f t h e H l i g a n d s * 3 3 * a s w e l l a s by t h e o t h e r l i g a n d s p r e s e n t i n t h e c o m p l e x . In t h i s c h a p t e r , *H NMR a r g u m e n t s a r e made t h a t e l i m i n a t e much o f t h i s u n c e r t a i n t y . F o r o u r d i - t u n g s t e n c o m p l e x e s , we, t o o , had t o answer t h e two q u e s t i o n s p o s e d a b o v e . F o r t u n a t e l y , o u r p r o b l e m was s i m p l i f i e d by t h e u n i q u e n a t u r e o f [ CpW(NO)H 23 2. As d i s c u s s e d i n c h a p t e r 2, a n d w i l l be d e a l t w i t h f u r t h e r i n t h i s c h a p t e r , t h i s compound i s more c o r r e c t l y r e p r e s e n t e d a s [ C p W ( N O ) H ] 2 ( y - H ) 2 and has b o t h b r i d g i n g a n d t e r m i n a l h y d r i d e l i g a n d s t h a t a r e s t a t i c . M o r e o v e r , t h e d i s t i n c t i v e *H NMR s p e c t r a l p a r a m e t e r s o f t h i s c omplex have a l l o w e d us t o d e v e l o p c r i t e r i a w i t h w h i c h t o r e i n t e r p r e t numerous *H NMR s p e c t r a o f b i m e t a l l i c o r g a n o t u n g s t e n h y d r i d e s r e p o r t e d i n t h e l i t e r a t u r e . In d o i n g s o , t h e s t a t i c o r f l u x i o n a l c h a r a c t e r s o f a number o f s u c h s p e c i e s have been d e c i p h e r e d , some o f whose s t r u c t u r e s i n s o l u t i o n have n o t b een known w i t h c e r t a i n t y f o r o v e r 20 y e a r s . F u r t h e r m o r e , i t has been 1 183 f o u n d t h a t t h e m a g n i t u d e s o f e x p e r i m e n t a l l y o b s e r v e d H- W c o u p l i n g c o n s t a n t s p e r m i t r e a s o n a b l e e s t i m a t e s o f t h e t y p e s o f f l u x i o n a l p r o c e s s e s o p e r a t i n g a n d , o c c a s i o n a l l y , t h e a p p r o x i m a t e t i m e s c a l e s i n v o l v e d . F i n a l l y , a n d p e r h a p s most i m p o r t a n t l y , i t w i l l be d e m o n s t r a t e d t h a t w i t h i n c e r t a i n , w e l l - d e f i n e d f a m i l i e s o f compounds t h e d e p e n d e n c e o f t h e m a g n i t u d e o f 'Jui. on t h e n a t u r e o f t h e W-H l i n k c a n o f t e n be r a t i o n a l i z e d i n t e r m s o f 80 s t r a i g h t f o r w a r d b o n d i n g a r g u m e n t s . B e c a u s e o f t h e c e n t r a l i m p o r t a n c e o f [ C p W ( N O ) H ] 2 ( y - H ) 2 t o t h e o v e r a l l d i s c u s s i o n , t h e r e s u l t s o f a s i n g l e c r y s t a l X - r a y a n a l y s i s o f t h i s compound w i l l be p r e s e n t e d f i r s t . R e s u l t s and P i s c u s s i o n A. C r y s t a l a n d M o l e c u l a r S t r u c t u r e s o f [ C p W ( N O ) H ] 2 ( y - H ) 2 . The complex [ C p W ( N O ) H ] 2 ( y - H ) 2 was p r e p a r e d a s d e s c r i b e d i n c h a p t e r 2 and s m a l l s i n g l e - c r y s t a l s s u i t a b l e f o r X - r a y a n a l y s i s were grown by s l o w e v a p o r a t i o n u n d e r N 2 o f a s a t u r a t e d C H 2 C 1 2 s o l u t i o n o f t h e compound a t room t e m p e r a t u r e i n a t h r e e - n e c k f l a s k c l o s e d w i t h a s h u t gas i n l e t t u b e a n d two u n p u n c t u r e d Suba- (2) S e a l s e p t a v ( C H 2 C 1 2 l o s s o c c u r r e d v i a a b s o r p t i o n o f t h e s o l v e n t v a p o u r by t h e s e p t a ) . D e t a i l s o f t h e d a t a c o l l e c t i o n and r e f i n e m e n t have been p u b l i s h e d e l s e w h e r e . ' The c r y s t a l s t r u c t u r e o f [ C p W ( N O ) H ] 2 ( y - H ) 2 c o n s i s t s o f d i s c r e t e m o l e c u l a r u n i t s s e p a r a t e d by normal i n t e r m o l e c u l a r c o n t a c t d i s t a n c e s . E a c h u n i t , two v i e w s o f w h i c h a r e shown i n F i g . 3-1 a n d 3-2, c o n s i s t s o f a c e n t r o s y m m e t r i c d i m e r o f t h e f o r m Cp(NO)(H)W(y-H) 2W(H)(NO)Cp whose a t o m i c c o o r d i n a t e s a n d i m p o r t a n t s t r u c t u r a l p a r a m e t e r s a r e g i v e n In T a b l e s 3-1 a n d 3-11. The W-N- O g r o u p s a r e e s s e n t i a l l y l i n e a r ( 1 7 4 ( 1 ) ° ) , w i t h t h e s h o r t W-N ( 1 . 7 5 3 ( 1 1 ) A) a n d l o n g N-0 ( 1 . 2 1 8 ( 1 6 ) A) bond l e n g t h s i n d i c a t i n g t h e e x i s t e n c e o f c o n s i d e r a b l e b a c k - b o n d i n g f r o m t h e e l e c t r o n - r i c h 81 F i g . 3-1. View o f t h e m o l e c u l a r s t r u c t u r e o f [CpW(NO)H] 2(y-H) H(B) a n d H(T) a r e shown i n o b s e r v e d ( b u t u n r e f i n e d ) p o s i t i o n s . 0 F i g . 3-2. End v i e w o f [ C p W ( N O ) H ] ? ( y - H ) ? down t h e W-W a x i s . 82 T a h l P 3-1. A t o m i c C o o r d i n a t e s f o r [CpW(NO)H] 2(M-H) 2, Atom W N 0 C( 1) C ( 2 ) C ( 3 ) C ( 4 ) C ( 5 ) H(T) H(B) 0.17165(5) 0.2563(14) 0.3282(17) 0.3499(17) 0.2024(22) 0.1876(20) 0.3226(20) 0.4247(16) 0. 182 -0.049 0.04140(6) -0.1300(16) -0.2363(18) 0.3538(19) 0.4023(20) 0.3124(24) 0.2090(24) 0.2425(21) -0.150 -0.022 0.16400(8) 0.0122(19) -0.0860(23) 0.2323(26) 0.2673(29) 0.4711(32) 0.5598(23) 0.4117(23) 0.351 0. 168 C r y s t a l D a t a : t r i c l i n i c s y s t e m , PI s p a c e g r o u p , a = 8.542(1) A, b = 6.607(2) A, c = 5.838 A, a = 9 4 . 6 4 ( 2 ) ° , £ = 1 0 8 . 0 6 ( 1 ) ° , Y = 9 8 . 7 0 ( 2 ) ° . b H y d r i d e p o s i t i o n s e s t i m a t e d f r o m t h e e l e c t r o n - d e n s i t y d i f f e r e n c e maps, b u t n o t r e f i n e d ( s e e t e x t a n d r e f . 3 ) . T a b l e 3-1 I. I m p o r t a n t I n t e r a t o m i c D i s t a n c e s (A) a n d A n g l e s (deg) a,b f o r [ C p W ( N O ) H ] 2 ( y - H ) 2 , W-W W-N W'-W-N W'-W-CP 2.9032(9) 1 .753( 1 1 ) 9 9 . 5 ( 4 ) 127.8 N-0 W-CP W-N-0 N-W-CP 1.218(16) 2.019 174.3(10) 126.6 P r i m e s i n d i c a t e atoms r e l a t e d t o t h o s e g i v e n i n T a b l e 3-1 by t h e t r a n f o r m a t i o n x , y , z •»• - x , - y , - z . CP i s t h e c e n t r o i d o f C ( 1 ) - C ( 5 ) : ( 0 . 2 9 7 4 , 0.3040, 0.3884). 83 m e t a l c e n t r e s t o t h e n i t r o s y l l i g a n d s . ' Th e s e s t r u c t u r a l f e a t u r e s a r e c o n s i s t e n t w i t h t h e r e l a t i v e l y low n i t r o s y l - s t r e t c h i n g f r e q u e n c y (1599 c m - 1 i n C H 2 C 1 2 ) o b s e r v a b l e i n t h e IR s p e c t r u m o f t h e compound ( s e e c h a p t e r 2 ) . The most i n t e r e s t i n g p a r t o f t h i s m o l e c u l a r s t r u c t u r e i s t h e W 2 H 4 9 r o u P i n 9 ' T n e t u n g s t e n - t u n g s t e n s e p a r a t i o n o f 2.9032(8) A i s l e s s t h a n t h a t o f t h e W-W s i n g l e bond ( 3 . 2 2 2 ( 1 ) A) i n (5) [ C p W ( C O ) 3 ] 2 , a n d r a t h e r g r e a t e r t h a n t h e Mo=Mo t r i p l e bond (2.448(1) A) i n t h e most c l o s e l y r e l a t e d s p e c i e s , [ C p M o ( C O ) 2 ] 2 . T h e m o l e c u l a r s t r u c t u r e o f t h e t u n g s t e n a n a l o g u e , [ C p W ( C O ) 2 ] 2 , o f t h i s l a t t e r compound, has n o t y e t been r e p o r t e d , b u t i t i s p r o b a b l e t h a t i t s Wsw d i s t a n c e i s s i m i l a r t o t h e Mo=Mo bond l e n g t h i n t h e molybdenum complex due t o t h e " l a n t h a n i d e c o n t r a c t i o n . " ^ ' In f a c t , t h e W-W bond l e n g t h i n t h e d i h y d r i d e d i m e r r e s e m b l e s t h e 3.0162(11) A s e p a r a t i o n f o u n d i n t h e v a l e n c e i s o e l e c t r o n i c a n i o n [ { W ( C 0 ) 4 } 2 ( u - H ) 2 J » t h e r e b y i n d i c a t i n g s u b s t a n t i a l m e t a l - m e t a l b o n d i n g i n [ C p W ( N O ) H ] 2 ( u - H ) 2 ( s e e b e l o w ) . The p o s i t i o n s o f t h e Cp and NO g r o u p s , and t h e m e t a l - m e t a l a x i s ( F i g . 3-1) l e a v e a " h o l e " i n e a c h t u n g s t e n s c o o r d i n a t i o n s p h e r e , s u g g e s t i n g t h e p r e s e n c e o f one t e r m i n a l h y d r i d e 1 i g a n d on e a c h m e t a l c e n t r e . T a k e n t o g e t h e r w i t h t h e *H NMR s p e c t r u m d i s c u s s e d i n c h a p t e r 2 and t h e c r y s t a 1 1 o g r a p h i c c e n t r e o f symmetry, t h i s f u r t h e r i m p l i e s t h e e x i s t e n c e o f two b r i d g i n g h y d r i d e l i g a n d s between t h e t u n g s t e n atoms. T h e s e c o n c l u s i o n s a r e g i v e n q u a l i f i e d s u p p o r t by t h e o b s e r v a t i o n o f 84 r e g i o n s o f i n c r e a s e d e l e c t r o n - d e n s i t y i n t h e e x p e c t e d p l a c e s i n t h e d i f f e r e n c e m a p s , * 3 * - b u t none o f t h e h y d r i d e atom p o s i t i o n s c o u l d be s u c c e s s f u l l y r e f i n e d . * 3 * N e v e r t h e l e s s , r e a s o n a b l e p o s i t i o n s f o r t h e b r i d g i n g and t e r m i n a l h y d r i d e l i g a n d s (H(B) and H(T) r e s p e c t i v e l y ) c o u l d be a s s i g n e d and t h e y a r e g i v e n i n T a b l e 3-1 and F i g . 3-1 a n d 3-2. The p l a n e d e f i n e d by w, H ( B ) , W and W'(B) l i e s s t a g g e r e d between N'O' a n d H(T) ( F i g . 3-2) a s w o u l d be e x p e c t e d on t h e b a s i s o f s i m p l e s t e r i c c o n s i d e r a t i o n s a n d l e n d s c r e d e n c e t o t h e a s s i g n e d l o c a t i o n s o f t h e b r i d g i n g h y d r i d e l i g a n d s . By a n a l o g y w i t h t h e s o l i d - s t a t e s t r u c t u r e o f [ { W ( C O ) 4 ) 2 ( y - H ) 2 ] 2 ~ , * 8 * i t i s b e l i e v e d t h a t H(B) a n d H'(B) a r e i n d e e d e q u i d i s t a n t f r o m t h e two t u n g s t e n c e n t r e s a n d t h a t t h e b r i d g i n g s y s t e m s a r e r e g u l a r . As d i s c u s s e d i n c h a p t e r 2, [ C p W ( N O ) H ] 2 ( y - H ) 2 e x i s t s i n s o l u t i o n a s a m i x t u r e o f two i s o m e r s , A a n d B ( r a t i o ~1.3:1 a t 2 0 ° C ) , a n d t h e s o l i d - s t a t e s t r u c t u r e f o u n d h e r e i s t h a t o f i s o m e r A. S i n c e a c r y s t a l o f A was s u b j e c t e d t o X - r a y a n a l y s i s , t h e p o s s i b i l i t y a r i s e s t h a t i n t h e s o l i d - s t a t e , [ C p W ( N O ) H ] 2 ( y - H ) 2 may e x i s t s o l e l y a s t h i s i s o m e r and t h a t i s o m e r B i s f o r m e d o n l y upon d i s s o l u t i o n o f t h e compound i n v a r i o u s s o l v e n t s . We b e l i e v e t h a t t h i s i s u n l i k e l y s i n c e t h e r e l a t i v e p r o p o r t i o n s o f A and B a r e t h e same i n C D C 1 3 a n d C^Dg. Hence, i t i s more l i k e l y t h a t b o t h A a n d B a r e f o r m e d d u r i n g t h e i n i t i a l s y n t h e s i s o f t h e complex and i t s i s mere c h a n c e t h a t a c r y s t a l o f A was s e l e c t e d f o r X - r a y ana l y s i s . 85 B. B o n d i n g i n t h e w 2 ( u - H ) 2 U n i t o f [ C p w ( N O ) H ] 2 ( y - H ) 2 . C o n v e n t i o n a l l y , t h e b r i d g i n g s y s t e m i n [ C p W ( N O ) H ] 2 ( y - H ) 2 w o u l d be f o r m u l a t e d a s w==w t h e f o r m a l W=W d o u b l e bond b e i n g i n v o k e d s o t h a t e a c h m e t a l c e n t r e c o u l d a t t a i n t h e f a v o u r e d 18- (9) v a l e n c e e l e c t r o n c o n f i g u r a t i o n . I d e n t i c a l b r i d g i n g s y s t e m s h a ve a l s o been p r o p o s e d f o r [ ( W ( C O ) 4 > 2 ( y - H ) 2 ] Z a n d [ C p W ( C O ) ] 2 ( y - H ) 2 . ( 1 0 ) However, t h e o n l y r e l a t e d s y s t e m t o have been s u b j e c t e d t o d e t a i l e d t h e o r e t i c a l a n a l y s i s t o d a t e i s t h e H os===os l i n k i n (y-H) 2 0 s 3 (CO) j Q . On t h e b a s i s o f F e n s k e - H a l l m o l e c u l a r o r b i t a l c a l c u l a t i o n s and t h e g a s - p h a s e u l t r a v i o l e t p h o t o e l e c t r o n s p e c t r u m o f ( y - H ) 2 0 s 3 ( C O ) j Q , Sherwood and H a l l * 1 1 ' c o n c l u d e d t h a t t h e m a j o r p a r t o f t h e b o n d i n g i n t h e O s 2 ( y - H ) 2 s y s t e m i s composed o f two t h r e e - c e n t r e , t w o - e l e c t r o n Os-H-Os bonds w i t h an a d d i t i o n a l " t _ - t _ " b o n d i n g i n t e r a c t i o n between 2g 2g t h e m e t a l c e n t r e s . In a d d i t i o n , however, t h e y n o t e d s i g n i f i c a n t h y d r o g e n - h y d r o g e n a n t i - b o n d i n g i n t e r a c t i o n s . B e c a u s e o f t h e s e r e s u l t s a n d o u r o b s e r v a t i o n s d i s c u s s e d l a t e r i n t h i s c h a p t e r t h a t t h i s t y p e o f W 2 ( y - H ) 2 s y s t e m has a c o n s i d e r a b l y d i f f e r e n t e f f e c t on ^J j _ | W t h a n w o u l d be e x p e c t e d f r o m i t s r e p r e s e n t a t i o n a s p r i m a r i l y two i n d e p e n d e n t t h r e e - c e n t r e , t w o - e l e c t r o n W-H-W b r i d g e s , we b e l i e v e t h a t t h e p l a n a r W 2 ( y - H ) 2 e n t i t y i s b e s t c o n s i d e r e d a s a s i n g l e , f o u i — c e n t r e u n i t . To r e f l e c t t h i s u n i t y , H we t h e r e f o r e p r o p o s e t h e " f u s e d " n o t a t i o n w^=w t o r e p r e s e n t H t h e b r i d g i n g s y s t e m i n [ C p W ( N O ) H ] 2 ( y - H ) 2 . Such a n i n t e r a c t i o n r e s u l t s i n a f o r m a l t u n g s t e n - t u n g s t e n bond o r d e r somewhat g r e a t e r 86 t h a n one, a s i s r e f l e c t e d by t h e W-W s e p a r a t i o n o b s e r v e d i n t h e s o l i d - s t a t e , a b o v e . T h a t t h i s W 2 ( u - H ) 2 i n t e r a c t i o n i s q u i t e s t r o n g i s a l s o s u g g e s t e d by t h e r i g i d i t y o f t h e complex i n s o l u t i o n ( s e e b e l o w ) . F i n a l l y , t h i s l i n k a g e i s a l s o p r o b a b l y a i d e d by t h e p r e s e n c e o f t h e NO l i g a n d s , w h i c h a r e known s t r o n g w - a c i d s . ( 4 > L i k e t h e CO g r o u p s i n ( u - H ) 2 0 s 3 ( C O ) l Q , ( 1 1 ) t h e n i t r o s y l l i g a n d s c a n , i n p r i n c i p l e , remove W-W it* a n t i b o n d i n g e l e c t r o n d e n s i t y a n d t h e r e b y i n c r e a s e t h e n e t m e t a l - m e t a l b o n d i n g . O b v i o u s l y , t h e c o n f i r m a t i o n o f t h e s e i n f e r e n c e s must a w a i t a t h e o r e t i c a l a n a l y s i s o f t h e b o n d i n g i n [ C p W ( N O ) H ] 2 ( u - H ) 2 . C. The lH NMR S p e c t r u m o f [ C p W ( N O ) H ] 2 ( u - H ) 2 . The a s s i g n m e n t o f t h e *H NMR s p e c t r u m o f [ C p W ( N O ) H ] ^(u-H) 2 has been d i s c u s s e d i n c h a p t e r 2 i n some d e t a i l . However, t h o r o u g h a n a l y s i s o f t h i s s p e c t r u m y i e l d s c o n s i d e r a b l y more i n f o r m a t i o n t h a n mere a s s i g n m e n t o f t h e b r i d g i n g and t e r m i n a l n a t u r e o f t h e h y d r i d e l i g a n d s . F i r s t l y , i t c a n be s e e n t h a t 1 2 o b s e r v e d v a l u e s o f t h e J H W a n d J H W c o u p l i n g c o n s t a n t s a r e i n t h e r a n g e o f 90-100 Hz a n d 13-15 Hz r e s p e c t i v e l y ( s e e T a b l e 2- I I ) . S e c o n d l y , a n d v e r y i m p o r t a n t l y , t h e s p e c t r u m shows t h a t b o t h i s o m e r s A and B o f [ C p W ( N O ) H ] 2 ( u ~ H ) 2 a r e s t e r e o c h e m l c a 1 1 y r i g i d on t h e NMR t i m e s c a l e . T h i s c a n be c o n c l u d e d b e c a u s e o f o b s e r v a t i o n s o f w e l l - r e s o l v e d *H-*H c o u p l i n g amongst t h e h y d r i d e l i g a n d s . In f a c t , f r o m t h i s , a r e a s o n a b l e e s t i m a t e f o r t h e minimum l i f e t i m e o f ( e . g . ) i s o m e r B w i t h r e s p e c t t o 87 i n t r a m o l e c u l a r H(T) a n d H(B) e x c h a n g e c a n be c a l c u l a t e d t o be t * 90 ms, s i n c e Av = 1 J m * 2.5 H z . ( 1 2 ) T h e r e f o r e , t h i s s p e c t r u m i n d i c a t e s t h a t f o r a g i v e n e l e c t r o n i c e n v i r o n m e n t i n b i m e t a l l i c c o m p l e x e s o f t h i s t y p e , 1 183 1) t h e m a g n i t u d e o f t h e H- W c o u p l i n g i s e s s e n t i a l l y i n d e p e n d e n t o f w h e t h e r t h e h y d r i d e 1 i g a n d i s a t t a c h e d In a b r i d g i n g o r t e r m i n a l f a s h i o n ; 1 183 2) one-bond H- W c o u p l i n g i s g r e a t e r t h a n two-bond; and 3) t h e r e s o n a n c e s due t o b r i d g i n g h y d r i d e s a p p e a r u p f i e l d o f t h o s e due t o t e r m i n a l h y d r i d e s . T h e s e k e y r e s u l t s , p a r t i c u l a r l y 1 ) , c o u p l e d w i t h t h e s p e c t r a l p a r a m e t e r s o f a p p r o p r i a t e monomeric t u n g s t e n h y d r i d e s , now e n a b l e us t o r e a n a l y z e t h e *H NMR s p e c t r a o f a number o f b i m e t a l l i c t u n g s t e n h y d r i d e c o m p l e x e s t h a t have been r e p o r t e d i n t h e l i t e r a t u r e o v e r t h e y e a r s . F i r s t , however, we must d i s c u s s what s o r t o f s p e c t r a l p a t t e r n s w o u l d be e x p e c t e d f o r g i v e n s i t u a t i o n s a n d how o u r r e s u l t s s h e d l i g h t on t h e s e p a t t e r n s . D. *H NMR S p e c t r o s c o p i c C r i t e r i a f o r E l u c i d a t i n g t h e S t r u c t u r e s o f B i m e t a l l i c O r g a n o t u n g s t e n H y d r i d e s i n S o l u t i o n . F o r a w^H s p i n s y s t e m , t h e *H NMR s p e c t r u m s h o u l d c o n s i s t o f a n e q u a l l y s p a c e d , f i v e - p e a k p a t t e r n h a v i n g a n I n t e g r a t e d i n t e n s i t y r a t i o o f 0.5:12.3:74.4:12.3:0.5 r e g a r d l e s s o f w h e t h e r t h e s y s t e m i n v o l v e s a s t a t i c , b r i d g e d W-H-W l i n k o r i s u n d e r g o i n g r a p i d H-W-W W-W-H f l u x i o n a l i t y . ( 1 3 J The f u n d a m e n t a l 88 d i f f e r e n c e between t h e two c a s e s i s t h a t i n t h e s t a t i c s i t u a t i o n , J o b s d = l j H ( B ) - W w n 1 1 e i n t h e f 1 u x i o n a l c a s e J o b s d = 1 2 l / 2 ( J H ( T j _ w + JH(T)-W* a s s n o w n i n F , " a ' 3 - 3 * A n a l y s e s o f h e t e r o b i m e t a l 1 i c s p i n s y s t e m s o f t h e t y p e WHM g i v e s i m i l a r c o n c l u s i o n s , a l t h o u g h f o r t h e s e s y s t e m s o n l y a t h r e e - 1 i n e *H NMR p a t t e r n ( i n t e n s i t y r a t i o = 7.7:85.6:7.7) due t o c o u p l i n g t o l 8 3W 1 183 w o u l d be e x p e c t e d . R e a s o n a b l e e s t i m a t e s o f t h e t h r e e H- W c o u p l i n g c o n s t a n t s i n v o l v e d i n a l l t h e s e c a s e s a r e o b t a i n a b l e by a n a l y s i s o f t h e *H s p e c t r a o f a p p r o p r i a t e monomeric h y d r i d o - t u n g s t e n c o m p l e x e s a n d by a p p l i c a t i o n o f t h e p r i n c i p l e s d e r i v e d f r o m o u r a n a l y s i s o f t h e s p e c t r u m o f [ C p W ( N O ) H ] 2 ( y - H ) 2 , a b o v e . H a v i n g t h e s e e s t i m a t e s o f l J H ( T ) _ w » l j H ( B ) - W a n d 2 j H ( T ) - W 1 n h a n d ( s e e T a b l e 3-1 I I ) , we a r e i n a p o s i t i o n t o j u d g e w h e t h e r a p a r t i c u l a r b i m e t a l l i c o r g a n o t u n g s t e n h y d r i d e i s s t a t i c o r f l u x i o n a l i n s o l u t i o n ( w i t h r e s p e c t t o t h e e x c h a n g e o f H l i g a n d s between m e t a l c e n t r e s ) on t h e NMR t i m e s c a l e i f t h e a p p e a r a n c e o f i t s *H s p e c t r u m d o e s n o t r e s o l v e t h i s q u e s t i o n u n a m b i g u o u s l y . F u r t h e r m o r e , I f t h e b i m e t a l l i c complex i s j u d g e d t o be f l u x i o n a l , t h e m a g n i t u d e o f J o b s e r v e d e n a b l e s us t o make r e a s o n a b l e e s t i m a t e s o f t h e t y p e s o f f l u x i o n a l p r o c e s s e s i n v o l v e d a n d , on o c c a s i o n , t h e i r a p p r o x i m a t e t i m e s c a l e s . The s y s t e m s whose r e p o r t e d *H NMR s p e c t r a we have a n a l y z e d a r e g r o u p e d a c c o r d i n g t o f a m i l i e s i n T a b l e s 3-IV a n d 3-VI I. T h e s e g r o u p i n g s c o n t a i n most o f t h e b i m e t a l l i c t u n g s t e n h y d r i d e s a n d r e l a t e d monomeric c o m p l e x e s t o be f o u n d i n t h e l i t e r a t u r e t o 89 Static: J o b s r 1 J H B W Fluxional: J o b s = \ • Jobs ;obs' 0.5 Jobs 12.3 744 12.3 Calculated Peak Intensities 0.5 F i g . 3-3. Expected lH NMR p a t t e r n f o r s t a t i c and f l u x i o n a l W-H-W systems, the out e r l i n e s being drawn t w i c e t h e i r a c t u a l s i z e f o r c l a r i t y . d ate. In a d d i t i o n t o the chemical formula o f each complex and the r e l e v a n t 'rl NMR data, s t a t i c r e p r e s e n t a t i o n s o f the tung s t e n - hydrogen bonding i n t e r a c t i o n s have been i n c l u d e d s i n c e they a re c e n t r a l t o many o f the arguments presented below. These " f u s e d " bonding r e p r e s e n t a t i o n s a r e not, however, intended t o r e f l e c t the s t r u c t u r a l dynamics o f the complexes In s o l u t i o n , but r a t h e r what 90 T ^ h l e 3-111. 1 183 A p p r o x i m a t e H- W C o u p l i n g C o n s t a n t s E x p e c t e d f o r S t e r e o c h e m i c a 1 1 y R i g i d O r g a n o t u n g s t e n H y d r i d e s . family of compds nature of W - H linkage conventnl reprsntn fused" reprsntn approximate expected V i H - " ' w PI J (Hz) Cp 2 W CpW(CO) 3 W(CO) 5 CpW(NO) 2 CpW(NO)' W - H W - H W = = M W - H / N W - H W - H H W - H n W=^=M H H W | M H W - H H W=^=M H H * M JL W M W - H n H H W - H W - H H H H 75 65 20 100 75 40 80 55 40 55 15 60 40 200 20 50-90 70-100 55 The r a t i o n a l e b e h i n d t h e u s e o f t h e f u s e d r e p r e s e n t a t i o n f o r t h e v a r i o u s W-H l i n k a g e s i s p r e s e n t e d i n t h e t e x t . B e c a u s e o f t h e v a r i e t y o f o t h e r l i g a n d s c o o r d i n a t e d t o t h e CpW(NO) f r a g m e n t , t h i s f a m i l y o f compounds e x h i b i t s more v a r i a t i o n i n t h e e x p e c t e d n « J H w v a l u e s . 91 t h e b o n d i n g w o u l d be f f t h e compound were s t a t i c . In t h e 1 183 f o l l o w i n g d i s c u s s i o n , a l l t h e H- W c o u p l i n g c o n s t a n t s a r e assumed t o have t h e same s i g n , a l t h o u g h no d e t e r m i n a t i o n s o f s u c h s i g n s have been r e p o r t e d i n t h e l i t e r a t u r e . However, s p i n t i c k l i n g e x p e r i m e n t s on [ C p * w ( N O ) H ] ( p - H ) 2 [ C p # W ( N O ) ( C H 2 S 1 M e 3 ) ] d i s c u s s e d i n c h a p t e r 4 show t h a t f o r t h i s s y s t e m , a t l e a s t , 1 1 2 JH(B)-W* JH(T)-W a n c l J H ( T ) - W a l 1 n a v e "the same s i g n , s u g g e s t i n g t h a t t h e a b o v e a s s u m p t i o n i s v a l i d . E . Cp 2W D e r i v a t i v e s ( T a b l e 3-IV) T h i s f a m i l y o f compounds p r o v i d e s , p e r h a p s , t h e most unambiguous s e r i e s o f o r g a n o t u n g s t e n h y d r i d e s f o r a n a l y s i s . C o n s i d e r a t i o n o f t h e lh NMR p a r a m e t e r s i n T a b l e 3-IV f o r t h e Cp 2W d e r i v a t i v e s w h i c h a r e u n q u e s t i o n a b l y r i g i d * 2 4 * i n s o l u t i o n on t h e NMR t i m e s c a l e l e a d s t o t h e a p p r o x i m a t e n ^ H ^ v a l u e s l i s t e d i n T a b l e 3-1 I I f o r t h i s f a m i l y . T h e s e a p p r o x i m a t e c o u p l i n g c o n s t a n t s c a n be u s e d t o p r e d i c t t h e s o l u t i o n m o l e c u l a r s t r u c t u r e s o f t h e v a r i o u s f l u x i o n a l s p e c i e s i n t h i s f a m i l y . 1 183 The o b s e r v e d H- W c o u p l i n g c o n s t a n t o f 45 Hz f o r t h e [ ( C p W H ) 2 ( y - H ) { u ( n 5 - C 5 H 4 - n 5 - C 5 H 4 ) } ] + c a t i o n a t a m b i e n t t e m p e r a t u r e i s c o n s i s t e n t w i t h t h e s y s t e m u n d e r g o i n g t e r m i n a l - t e r m i n a l h y d r o g e n e x c h a n g e H—w—w—H ;=i H—w—w—H H H F o r s u c h a n e x c h a n g e , J H W ( p r e d i c t e d ) = 1/6 (3 x ! J + 3 x 2 j H W > • 1/6 (3 x 65 + 3 x 20) Hz = 42.5 Hz, In e x c e l l e n t a g r e e m e n t w i t h t h e o b s e r v e d v a l u e . T h i s e x c h a n g e 92 T a b l e 3-1V. T u n g s t e n H y d r i d e Der i v a t i v e s . H NMR P a r a m e t e r s f o r Cp 2W complex "•/'H-"'W r*(°C) tolv W - H interaction'' *' (ppm) n r (Hz) JM (Hz) ref C p , W H j [ C p 3 W H , ] + Cp,W(H)Ph C p 2 W ( C H , ) 2 C p j W H 2 W ( C O ) 5 CpjWHj-MoCCO), C p j M o H r W ( C O ) 5 K C p W H ^ - H N ^ ' - C ^ - V - C H , ) ! ] * [Cr^WtM-HJjPttPEtjXPh))* [Cp,HW(„-H)Pt (PEt , ) , (Ph) ] + [CpjW^-HJjRMPPhj) : ]* |CpWU, f f : l-5-i r -C 5 H<)0 1 -H) J IrH(PPh J ) 2 r (CpW(H)(M,<r:l-5-i r-C,H <)(M-H)IrH(dppe)(PPh 3)r C p j W H y A l E l j C p j W H j Z n C l j - D M F C , H 6 cone H C I W— H, -12.28 I 73.2 H A , -6.44 1 47.8'' C 6 D 6 W - H C t D t W - C H j T H F "L -co.": T H F T H F C D 3 C N f - M j I }-<--{ A . -30 C D J C I J -20 CD,C1 2 H—W W—M "=f=<p M— W^Pt CDjCI 5 JL C D J C I J V» C D 2 C I 2 C 6 H , H— W^I> — M 6 I D M F »—j—Zn H » , -6.08 1 N R 1 80 2 6.0 1 63.0 2 19.2 1 65.8 2 19.6 111 0.24 15.2 * ' ' « » • J N R N R N R -16.0' H A . -14.1 1 99.1 H B , -17.1 1 101.1 -18.7* -18.11' H A , -16.41 1 92 H,,-18.28 1 ~90 H c . -24.55 2 N O -15.88' -12.43 -13.0 1 ~72 1 76.0 45 59.7 107 38 14,15 U 16 17 15 15 15 1B 19 19 20,21 21 21 22 23 a Ambient t e m p e r a t u r e s u n l e s s i n d i c a t e d o t h e r w i s e . b The W-H b o n d i n g i n t e r a c t i o n s a r e d i s c u s s e d i n d e t a i l i n t h e t e x t . NO = n o t o b s e r v e d ( i . e . , t h e c i t e d p a p e r s p e c i f i c a l l y s t a t e s 1 183 t h a t no H- W c o u p l i n g was o b s e r v e d ) . NR = n o t r e p o r t e d ( i . e . , no m e n t i o n w h a t s o e v e r i s made o f t h i s p a r a m e t e r ) . T h i s c o u p l i n g c o n s t a n t may be t o o low by a f a c t o r o f 2 ( c f . r e f 1 5 ) . The complex i s f l u x i o n a l on t h e NMR t i m e s c a l e a t t h e i n d i c a t e d t e m p e r a t u r e a n d a l l h y d r i d e H's a r e e q u i v a l e n t . 93 p r o b a b l y p r o c e e d s v i a a s y m m e t r i c a l l y b r i d g e d W-H-W i n t e r m e d i a t e , b u t t h e i n t e r m e d i a t e d o e s n o t p o s s e s s a s i g n i f i c a n t l i f e t i m e on t h e NMR t i m e s c a l e a n d Is t h e r e f o r e u n d e t e c t a b l e . A s i m i l a r e x c h a n g e mechanism, H — W — I r — H ; = ± H — W — I r — H I . I H H may be i n v o k e d f o r t h e [CpWH(p,o: l - 5 - r | - C 5 H 4 ) (u-H) I r H ( d p p e ) - ( P P h 3 ) ] + c a t i o n a t room t e m p e r a t u r e t o a c c o u n t f o r i t s o b s e r v e d J.... o f 38 Hz. F o r b o t h t h e s e c a s e s a n a p p r o x i m a t e maximum rlW l i f e t i m e f o r t h e e x c h a n g i n g s p e c i e s c a n be c a l c u l a t e d t o be T * 5 (12) ms, s i n c e Av = AJ * (65-20) = 45 Hz. T h i s same t y p e o f c a l c u l a t i o n c a n be done f o r a l l t h e e x c h a n g i n g s p e c i e s d i s c u s s e d i n t h i s c h a p t e r . The f l u x i o n a l i t y o f t h e [ C p 2 H W ( u - H ) P t ( P E t 3 ) 2 ( P h ) ] + c a t i o n a t - 2 0 ° C i s c l e a r l y d i f f e r e n t f r o m t h a t j u s t c o n s i d e r e d s i n c e i t s J H W v a l u e i s 59.7 Hz. T h i s o b s e r v a t i o n may be r e a s o n a b l y w e l l a c c o u n t e d f o r by i n v o k i n g e i t h e r o f t h e e x c h a n g e mechanisms shown be 1ow, i . e . H — W — P t 5 = ± H — W — P t — H I H 1 2 f o r w h i c h J H W ( p r e d i c t e d ) = 1/4 (3 x J H ( T ) _ W + J H ( T ) - W ) = 1/4 (3 x 65 + 20) Hz » 54 Hz, o r H H — W — P t 5 = ^ ^ v . | H — W Pt H 1 1 f o r w h i c h J H W ( p r e d i c t e d ) * 1/4 (3 x J H ( T ) _ W + J H ( B ) - W ) = 1/4 (3 x 65 + 65) Hz * 65 Hz, i f i t i s assumed t h a t ^ ( j ) ^ * l j H ( B ) _ w a s i s t r u e f o r [ C p W ( N O ) H ] 2 ( u - H ) 2 . B o t h t h e s e t y p e s o f f l u x i o n a l i t y a r e a l s o c o n s i s t e n t w i t h t h e l i m i t e d v a r i a b l e 94 t e m p e r a t u r e *H NMR d a t a on t h i s c o m p l e x . * * ^ ' The *H NMR s p e c t r u m o f [ C p 2 W ( y - H ) 2 R h ( P P h 3 ) 2 ] + i n C D 2 C 1 2 a t a m b i e n t t e m p e r a t u r e i s p a r t i c u l a r l y i n t e r e s t i n g i n t h a t i t i n d i c a t e s b o t h h y d r i d e l i g a n d s t o be e q u i v a l e n t ( r a t h e r t h a n t h e e x p e c t e d AA'MXX' (= HH'RhPP' s y s t e m ) and t h e r e f o r e f l u x i o n a l , a n d d i s p l a y s a l a r g e J * H W v a l u e o f 107 Hz. As c a n be s e e n f r o m T a b l e 3-1 I I and f r o m a g e n e r a l p e r u s a l o f T a b l e s 3-IV t o 3-VI1, a t u n g s t e n - h y d r i d e I n t e r a c t i o n t h a t c a n be w r i t t e n ( i n s t a t i c f o r m ) a s w—i|r—M a l w a y s shows a *H-*^W c o u p l i n g c o n s t a n t c o n s i d e r a b l y H g r e a t e r t h a n t h a t f o r I t s monomerIc p a r e n t . The o b s e r v a t i o n o f H s u c h a l a r g e c o u p l i n g f o r t h i s w=^=Rh l i n k a g e i m m e d i a t e l y H s u g g e s t s what t y p e o f f l u x i o n a l I t y i s o c c u r r i n g . I f t h i s compound were u n d e r g o i n g W = Rh ^ = ± ^ W = Rh H' f l u x i o n a l i t y , t h e n J H W ( p r e d i c t e d ) = 1/2 ( I j H ( T ) - W + 2 j H ( T ) - W ) = 1/2 ( 1 0 0 + 2 0 ) Hz = 60 H z — a l o n g way f r o m t h e o b s e r v e d v a l u e . On t h e o t h e r hand, i f t h e e x c h a n g e p r o c e s s i n v o l v e s t h e two h y d r i d e l i g a n d s m a i n t a i n i n g d i r e c t I n t e r a c t i o n w i t h b o t h m e t a l c e n t r e s ( e . g . by s p i n n i n g a b o u t t h e m e t a l - m e t a l a x i s ) , t h e n J nw ( p r e d i c t e d ) = 1/2 ( 1 ^ H ( B ) . W + l j H ( B ) - W ) = 1 / 2 ( 1 0 ° + 1 0 0 ) H z = 100 H z — v e r y much i n a g r e e m e n t w i t h o b s e r v a t i o n . An i d e n t i c a l (20 21) c o n c l u s i o n was r e a c h e d by t h e o r i g i n a l i n v e s t 1 g a t o r s * ' on t h e b a s i s o f v a r i a b l e t e m p e r a t u r e *H NMR s t u d i e s . The L e w i s a d d u c t c o m p l e x e s o f Cp 2WH 2 ( e . g . C p 2 W H 2 » A l E t 3 a n d C p 2 W H 2 » Z n C l 2 » D M F ) p r e s e n t a d i f f e r e n t a n d i n t e r e s t i n g s i t u a t i o n . 95 T h e s e c o m p l e x e s have t r a d i t i o n a 1 1 y been assumed t o i n v o l v e a ( 2 2 ) s i m p l e W-»M d o n o r bond o f t h e s o r t i n v o k e d f o r t h e C p 2 H 2 W - » M ( C 0 ) 5 compounds. ' T h i s i s b e c a u s e i n t h e o r i g i n a l r e p o r t on t h i s t y p e o f compound (on C p ^ W H ^ A l M e 3 ) . t h e IR s p e c t r u m (KBr d i s c ) showed a d e c r e a s e i n v W H upon c o m p l e x a t i o n (1912 t o 1898 c m - 1 ) w h i c h was t h o u g h t t o be t o o s m a l l f o r t h e H's t o have gone f r o m t e r m i n a l t o b r i d g i n g . ' However, a r e c e n t , l o w - t e m p e r a t u r e (-166°C) X - r a y c r y s t a l a n a l y s i s o f C p 2 W H 2 » A 1 M e ^ (26) shows t h i s a s s u m p t i o n t o be i n c o r r e c t . ' F o r t h i s s t r u c t u r e , a l l t h e atoms i n c l u d i n g t h e h y d r i d e l i g a n d s c o u l d be r e f i n e d , a n d i t showed t h e s e l i g a n d s t o be t r u l y b r i d g i n g — i . e . C p 2 W ( u - H ) 2 A l M e 3 . An e a r l i e r s t r u c t u r e o f C p 2 M o H 2 » Z n B r 2 « D M F (27) showed e s s e n t i a l l y t h e same t h i n g . ' S i m p l e e l e c t r o n - c o u n t i n g on t h e s e compounds shows t h a t t h e y c a n n o t have a f o r m a l l y meta1- H m e t a l d o u b l e - b o n d t y p e o f s t r u c t u r e , e . g . w=j=*i a n d t h i s i s H r e f l e c t e d i n t h e o b s e r v e d J v a l u e s (~75 Hz v s . 100 H z ) . HW H R a t h e r , t h e s e compounds have a f o r m a l l y s i n g l y bonded w—j— AI 1 H t y p e o f l i n k a g e w h i c h a p p e a r s t o e x h i b i t c o u p l i n g s e s s e n t i a l l y u n c h a n g e d f r o m t h o s e o f t h e m o n o n u c l e a r p r e c u r s o r . More w i l l be s a i d a b o u t t h i s l a t e r i n t h e d i s c u s s i o n . One f i n a l p o i n t c o n c e r n i n g t h e d a t a In T a b l e 3-IV r e q u i r e s d i s c u s s i o n . T h i s i s t h a t t h e c h e m i c a l s h i f t s o f t h e i n d i v i d u a l r e s o n a n c e s due t o t h e h y d r i d e 1 f g a n d s a r e u n r e l i a b l e g u i d e s t o t h e i r b r i d g i n g o r t e r m i n a l n a t u r e s . S i g n a l s due t o s t a t i c h y d r i d e s t e r m i n a l l y bound t o t h e Cp 2 w m o i e t y c a n be f o u n d f r o m 96 6 -6 t o -15 ppm, w h e r e a s t h o s e due t o s t a t i c , b r i d g i n g h y d r i d e s r a n g e f r o m -12 t o -18 ppm. A l t h o u g h t h i s a g r e e s w i t h t h e g e n e r a l l y o b s e r v e d t r e n d o f b r i d g i n g h y d r i d e s e x h i b i t i n g s i g n a l s u p f i e l d o f t h o s e due t o t e r m i n a l H l i g a n d s , * 2 8 ' i t r e m a i n s t h a t t h e o v e r l a p p i n g o f t h e s e two r e g i o n s means t h a t t h e c h e m i c a l s h i f t o f J u s t a s i n g l e s i g n a l c a n n o t be e m p l o y e d w i t h c e r t a i n t y t o d e t e r m i n e w h e t h e r a h y d r i d e i s b r i d g i n g o r t e r m i n a l . In a d d i t i o n , i n c a s e s o f f l u x i o n a l m o l e c u l e s , t h e c h e m i c a l s h i f t s p r o v i d e no i n f o r m a t i o n w h a t s o e v e r a b o u t w h e t h e r t h e f l u x i o n a l i t y i n v o l v e s t e r m I n a l - t e r m 1 n a 1 , t e r m i n a l - b r i d g i n g o r b r i d g i n g - b r i d g i n g e x c h a n g e w h i l e , a s we h a v e s e e n , t h e o b s e r v e d J i s n W q u i t e i n f o r m a t i v e on t h i s p o i n t . T h e s e same c o n c l u s i o n s a p p l y t o t h e o t h e r f a m i l i e s o f o r g a n o t u n g s t e n h y d r i d e s w h i c h a r e c o n s i d e r e d b e l o w . F. CpW(CO) 3 D e r i v a t i v e s ( T a b l e 3-V) 1 183 A l t h o u g h t h e m a g n i t u d e s o f t h e H- W c o u p l i n g c o n s t a n t s o b s e r v e d f o r t h i s f a m i l y a r e s m a l l e r t h a n t h o s e f o r t h e Cp 2W d e r i v a t i v e s , a s i m i l a r t y p e o f a n a l y s i s i s p o s s i b l e . The model c o m p l e x , CpW(C0) 3H, e x h i b i t s 'J h w o f -37 Hz, w h i c h i n c r e a s e s t o 48 Hz upon r e p l a c e m e n t o f one o f t h e CO l i g a n d s by t h e s t r o n g l y b a s i c PMe 3. T h i s Is p r e s u m a b l y a m a n i f e s t a t i o n o f t h e I n c r e a s e d s - e l e c t r o n d e n s i t y a t t h e m e t a l c e n t r e i n t h i s l a t t e r complex ( s e e s e c t i o n I ) . As f o r t h e C p - W - c o n t a i n i n g compounds, H i n v o l v e m e n t o f d e r i v a t i v e s o f t h i s f a m i l y i n w=^=w H 97 T a b l e 3-V. T u n g s t e n H y d r i d e *H NMR P a r a m e t e r s f o r C p w ( C O ) 3 Der i v a t i v e s . complex 7* ( ° C ) solv W - H interaction' tc (ppm) VIH_IIIW ./(Hz) (Hz) ref CpW(CO) jH « > - C p W ( C O ) 2 ( P M e 3 ) H r ™ / u - C p W ( C O ) 2 ( P M e 3 ) H CpW(PMe, )H 5 C p W ( P M e , ) 2 ( , J - C 5 H , ) H [|CpW(CO),|2(^-H))* [|CpW(CO) ] |(M -H)|CpMo(CO) 3|] + (CpW(CO) 2 ] 2 (^ -H)( M -OMe) (|CpW(CO ) 2 | 2 ( M -H ) ( M -MeCCMe) ) + [CpW(CO) 2 HM-H)( M -CHMe)[Pt(PMej) 2 ] isomer i isomer ii -70 -38 -38 - 8 0 C p ( C O ) 2 W C H ( P M e 3 ) - C H C O M e -30 -30 -20 C 6 H , 2 C D C l j C , D , C , D , C . D 6 C 6 D 6 cone H£0A cone H 2 S 0 4 ( C D 3 ) 2 C O (CD 3 ) 2 CO CD 2 CI 2 CD 2 C1 2 CD 2 CI 2 W - H W - H W - H W - H W - H W - H H H Hh H X M IS* -7.33 -7 .3 -8.32 -7.51 -3.95 -7.35 -24.77 -22.88 -10.56 -18.5 -7.77 -8.29 2.49 37.7 36.7' 48.0 48.0 42.5 40 38.6' 38.0' 57.4 32 53 56 3.2 29 30 31 31 32 32 33 33 34 35 36 37 [ (Ph jPC 5 H 4 )W(CO) 3 H] + [CpW(CO) 2 ] : (p -H) 2 [ ( n ' - C j M e j J W t C O j h ^ - H ) , CpW(CO) 3 (SnMe 3 ) -30 C F 3 C O O H (CD 3 ) 2 CO (CD 3 ) 2 CO Q H , W - H H ( W=̂=W ) M ( ( „ ! - C 5 / / j ) W W - S n - C « 3 2.01 -7.15 -13.24 -9.30 N R 0.52 4.5 36 83.1* 82.8 1.4 ~0 .6 38 10 10 39 a Ambient t e m p e r a t u r e s u n l e s s i n d i c a t e d o t h e r w i s e , b The W-H b o n d i n g i n t e r a c t i o n s a r e d i s c u s s e d i n d e t a i l i n t h e t e x t . c NR = n o t r e p o r t e d ( i . e . , t h e c i t e d p a p e r makes no m e n t i o n w h a t s o e v e r o f t h i s p a r a m e t e r ) . 183 d W s a t e l l i t e s were r e p o r t e d t o c o n s t i t u t e ~14% o f t h e t o t a l i n t e g r a t e d a r e a o f t h e r e s o n a n c e . 183 e W s a t e l l i t e s were r e p o r t e d t o c o n s t i t u t e ~24% o f t h e t o t a l i n t e g r a t e d a r e a o f t h e r e s o n a n c e . 98 i n t e r a c t i o n s m a r k e d l y i n c r e a s e s f o r example, t o ~83 Hz f o r [ C p w ( C O ) 2 ] 2 ( y - H ) 2 . The c o m p l e x e s l i s t e d i n T a b l e 3-V t h a t c a n be r e p r e s e n t e d a s H h a v i n g 3 - c e n t r e , 2 - e l e c t r o n JL b r i d g e s c o n s t i t u t e a most W M i n t e r e s t i n g c l a s s . T h e s e compounds f a l l i n t o two c a t e g o r i e s : u n s u p p o r t e d a n d s u p p o r t e d . In t h e f o r m e r , t h e two c o m p l e x e s w h i c h c o n t a i n s u c h a n u n s u p p o r t e d b r i d g e , [ { C p W ( C O ) 3 } ( y - H ) { C p M ( C O ) 3 } ] + (M=W o r Mo), show 1H- 1 8 3W c o u p l i n g c o n s t a n t s o f 38.6 a n d 38.0 Hz, w h i c h a r e s i m i l a r t o t h o s e o b s e r v e d f o r t h e monomeric s p e c i e s . I f t h e s e s y s t e m s were f l u x i o n a l , t h e n J H W ( p r e d i c t e d ) = 1/2 C 1 * ^ + 2 j H w > = 1/2 (40 + 15) Hz = 27.5 Hz i f i t Is assumed t h a t two-bond 1H- 1 8 3W c o u p l i n g i n t h e s e s y s t e m s i s s i m i l a r t o t h a t f o u n d f o r Cp 2W d e r i v a t i v e s . The o n l y two-bond d a t a a v a i l a b l e f o r t h e C p W ( C 0 ) 3 f a m i l y i n v o l v e c o u p l i n g t h r o u g h a c a r b o n c e n t r e * * H z ) * 3 ^ * — a s c a n o f t h e l i m i t e d d a t a i n T a b l e s 3-IV t o 3-VII s u g g e s t t h a t t h r o u g h - c a r b o n c o u p l i n g s a r e g e n e r a l l y l e s s t h a n t h r o u g h - m e t a l . N e v e r t h e l e s s , t h e o b s e r v a t i o n o f c o u p l i n g o f t h e m a g n i t u d e e x p e c t e d f o r a monomer s u g g e s t s t h a t t h e [ { C p W ( C O ) 3 ) ( y - H ) { C p M ( C O ) 3 } ] + c a t i o n s i n s o l u t i o n a r e s t a t i c w i t h r e s p e c t t o h y d r i d e 1 i g a n d e x c h a n g e . In t h e s e c o n d c a t e g o r y a r e t h o s e c o m p l e x e s i n w h i c h t h e f o r m a l l y e l e c t r o n - d e f i c i e n t , 3 - c e n t r e , 2 - e l e c t r o n b r i d g e i s s u p p o r t e d by some o t h e r b r i d g i n g 1 i g a n d . S u p e r f i c i a l l y , t h e b r i d g e s In [ C p w ( C O ) 2 ] 2 ( y - H ) ( y - O M e ) a n d [ C p w ( C 0 ) 2 ] ( y - H ) - ( y - C H M e ) [ P t ( P M e 3 ) 2 ] e a c h a p p e a r t o be a c o m b i n a t i o n o f a 99 s e p a r a t e , 3 - c e n t r e , 2 - e l e c t r o n b r i d g e and a n e l e c t r o n - s u f f i c i e n t (u-OMe) o r (u-CHMe) b r i d g e . However, t h e s e c o m p l e x e s e x h i b i t *H- 183 W c o u p l i n g s some 20 Hz g r e a t e r t h a n t h o s e f o r t h e u n s u p p o r t e d s y s t e m s . N e v e r t h e l e s s t h e s e v a l u e s a r e s t i l l ~25 Hz l e s s t h a n H t h o s e o b s e r v e d f o r t h e w^=w g r o u p i n g i n t h i s f a m i l y . To H r e f l e c t t h e s e f a c t s , we b e l i e v e t h a t t h e s e two s u p p o r t e d , p l a n a r b r i d g i n g s y s t e m s a r e b e s t v i e w e d a s s i n g l e , f o u r c e n t r e g r o u p i n g s H H a s t h e f u s e d r e p r e s e n t a t i o n s w = ^ = P t a n d w = T l w i m p l y , r a t h e r t h a n a s , f o r example, w c ~ ? M o r w N " ~ 7 m • These f u s e d X ? s y m b o l s a l s o v i s u a l l y s u g g e s t t h e s i m i l a r i t y o f t h e s e l i n k a g e s t o H / l 1 \ t h e M-4-M b r i d g e , w h i c h Sherwood and H a l l have d e s c r i b e d a s b e i n g f u n d a m e n t a l l y t h e same, a l t h o u g h t h e M=*=M i n t e r a c t i o n was shown t o be weaker. I n t e r e s t i n g l y , t h i s i n t u i t i v e l y a g r e e s w i t h t h e o b s e r v e d t r e n d i n c o u p l i n g c o n s t a n t s . When t h e b r i d g e H i n c o r p o r a t e s a p e r p e n d i c u l a r a c e t y l e n e t o g i v e i n + l l ft ̂ — C{CpW(CO) 2) 2(y-H)(u-MeCCMe)] , t h e 1 H - O JW c o u p l i n g c o n s t a n t r e v e r t s b a c k t o t h a t o f an u n s u p p o r t e d b r i d g e , s u g g e s t i n g t h e removal o f p l a n a r i t y f r o m t h e s u p p o r t e d b r i d g e r e s u l t s i n a W-H-W i n t e r a c t i o n t h a t i s e s s e n t i a l l y t h e same a s an u n s u p p o r t e d one. S i n c e t h e u n s u p p o r t e d 3 - c e n t r e , 2 - e l e c t r o n l i n k a g e s a p p e a r t o be s t a t i c i n s o l u t i o n , i t i s b e l i e v e d t h a t t h e s u p p o r t e d ones a r e n o n - f 1 u x i o n a 1 a s w e l l . 100 G. W ( C O ) 5 D e r i v a t i v e s ( T a b l e 3-VI) The o b v i o u s p a r e n t monomer p r e s e n t l y known i n t h i s f a m i l y i s [ H W ( C O ) 5 ] ~ , an d i t e x h i b i t s ' j ^ = 53.4 Hz. S u r p r i s i n g l y , t h i s p a r a m e t e r d o e s n o t c hange s i g n i f i c a n t l y upon r e p l a c e m e n t o f a c a r b o n y l 1 i g a n d by a p h o s p h i n e o r a p h o s p h i t e . N e v e r t h e l e s s , H when t h e s e s p e c i e s engage In 3 - c e n t r e , 2 - e l e c t r o n JL W M 1 183 l i n k a g e s , t h e r e i s a d e c r e a s e i n t h e o b s e r v e d H- W c o u p l i n g c o n s t a n t t o 38-45 Hz. A t f i r s t g l a n c e , t h i s w o u l d a p p e a r t o be s u g g e s t i v e o f t e r m i n a 1 - t e r m i n a 1 h y d r o g e n e x c h a n g e ( a s f o r t h e a n a l o g o u s C P 2 W d e r i v a t i v e s d i s c u s s e d e a r l i e r ) . In s u c h a s i t u a t i o n , J H W ( p r e d i c t e d ) = 1/2 ( 1 J H W + 2 J H W ) = 1/2 (54 + 15) Hz (49) = 34.5 Hz. However, t h e s t a t i c n a t u r e o f [{W(CO) 4P(OMe) 3}(y-H){W(CO ) 5 } 3 _ i s e s t a b l i s h e d u n a m b i g u o u s l y by t h e o b s e r v a t i o n o f two d i s t i n c t 1H- 1 8 3W c o u p l i n g c o n s t a n t s , a f a c t a t t r i b u t e d t o t h e p r e s e n c e o f a n a s y m m e t r i c h y d r i d e b r i d g e . * 4 1 ' F u r t h e r m o r e , v a r i a b l e - t e m p e r a t u r e *H NMR s t u d i e s o f [ W ( C O ) 5 ] ( y - H ) [ A u P P h g ] have c o n f i r m e d t h e a b s e n c e o f h y d r i d e 1 i g a n d e x c h a n g e i n t h i s c o m p o u n d . * 4 5 ' By a n a l o g y , i t t h e r e f o r e seems l i k e l y t h a t a l l t h e r e l a t e d s p e c i e s l i s t e d i n T a b l e 3-VI a r e a l s o s t a t i c . T h i s a p p a r e n t c o n t r a v e n t i o n o f t h e p r i n c i p l e s e s t a b l i s h e d f o r t h e o t h e r f a m i l i e s may p o s s i b l y be e x p l a i n e d by t h e f a c t t h a t t h e p a r e n t In t h i s c a s e Is a m o n o anion, w h i l e t h e p a r e n t s i n a l l t h e o t h e r c a s e s a r e n e u t r a l . The a n i o n i c n a t u r e o f [HWCCO)^] - w o u l d u n d o u b t e d l y r e s u l t i n i n c r e a s e d s - e l e c t r o n d e n s i t y a t t h e m e t a l c e n t r e o v e r what w o u l d be e x p e c t e d i n a 101 T a b l e 3-V1. T u n g s t e n H y d r i d e l h NMR P a r a m e t e r s f o r W ( C 0 ) 5 Der i v a t i v e s . complex 7" C C ) solv IHW(CO)j) - C D j C N [HW(CO) 4|P(OMe),|]- C D j C N [HW(CO) 4 (PMe 5 ) ] - C D j C N [|W(CO),|,0.-H)]- T H F ' [ | W ( C O ) 5 | ( M - H ) | M O ( C O ) 3 | ] - T H F [|W(CO)j|((i-H)|Cr(CO)s|]- T H F [|W(CO) 4P(OMe),| 2(M-H)]- C D j C N [|W(CO)4P(OMe),|0i-H)|Cr(CO)5|]- C D , C N ) [|W(CO)4P(OMe),|(M-H)|W(COJ5|]- C D J C N [W(CO),(NO)|P(OMe),|](i.-H)[W(CO) J] C D C I J [ W ( C O ) 5 ] ( „ - H ) [ A U P P h 3 ] C D 2 C I 2 [W(CO) 5 ] ( M -H)[Cp 2 Ta(CO)] C 6 D 6 , I|W(CO) 5HFe(CO) 4H|]- T H F [W(CO), ] (M-CO)(M- i7 1 -CH,C t H,Me-4)0. - «Jppm)[Re(CO) J ] - 2 0 C D J C I J W - H interaction* 5 (ppm) n V '" -" ' w / (Hz ) (Hz) ref [ | W ( C O ) 4 | 2 ( M - H ) 2 ) J - W ( C O ) 5 ( P M e P h 2 ) (CD , ) 2 CO C H 2 C l j W - H W - H W - H W - F e - H H W - P - C H j -4 .2 1 53.4 40 -4 .5 1 54 41 -3 .6 1 54 41 -12.52 1 41.9' 42 - 1 2 . 3 7 1 42.3 42 -15.43 1 ~ 4 0 42 -11.9 1 45.2 4 3 0 -14.4 1 38.4 41 -12.2 1 42, 45.6' 41 -12.50 I 39.5 44 -2.69 1 46 45 -15.48 1 42.5 46 -11.8 2 15.0 47 -3.69 1 48 48 - 4 . 0 1 6 2 " / 43 2.21 3 2.1 3 9 a Ambient t e m p e r a t u r e s u n l e s s I n d i c a t e d o t h e r w i s e . b The W-H b o n d i n g i n t e r a c t i o n s a r e d i s c u s s e d i n t h e t e x t . 183 c W s a t e l 1 i t e s were r e p o r t e d t o c o n s t i t u t e ~24% o f t h e t o t a l i n t e g r a t e d a r e a o f t h e r e s o n a n c e . 1 183 d Two s e p a r a t e H- W c o u p l i n g c o n s t a n t s a r e o b s e r v a b l e due t o t h e asymmetry o f t h e co m p l e x . e See t e x t f o r d i s c u s s i o n o f t h i s s p e c i e s , f R e d e t e r m i n e d v a l u e . n e u t r a l s p e c i e s * a n d t h i s c o u l d be t h e c a u s e o f t h e u n e x p e c t e d l y l a r g e v a l u e o f The most a p p r o p r i a t e p a r e n t f o r t h i s f a m i l y c o u l d t h e r e f o r e be ( n 2 - H 2 ) W ( C O ) 3 ( P C y 3 ) 2 (Cy • c y c l o h e x y l ) . 183 U n f o r t u n a t e l y , p r o b a b l y b e c a u s e o f d i p o l a r b r o a d e n i n g , W 102 s a t e l l i t e s o f t h e ty^-H^ r e s o n a n c e were n o t o b s e r v a b l e . * 5 0 ' I f 183 c o u p l i n g t o W i s e v e r o b s e r v e d , i t i s p r e d i c t e d t h a t t h e c o u p l i n g c o n s t a n t w i l l be i n t h e v i c i n i t y o f 40-45 Hz ( s u c h c o u p l i n g may more c o n c e i v a b l y be o b s e r v a b l e i n t h e (n -HD) a n a l o g u e ) . B e c a u s e o f t h e w e l l - k n o w n i s o l o b a l a n a l o g y between A u P P h 3 a n d H , * 5 1 ' t h e a b o v e m e n t i o n e d [ W ( C 0 ) 5 ] ( u - H ) [ A u P P h 3 ] 2 ( p e r h a p s b e t t e r d e s c r i b e d a s {r\ - H A u P P h 3 ) W ( C O ) 5 ) may t h e r e f o r e be a s u i t a b l e p a r e n t "monomer." An a l t e r n a t i v e p a r e n t i s one o f t h e r e c e n t l y r e p o r t e d H W ( C 0 ) x ( N 0 ) ( P R 3 ) 4 _ X (x = 3 o r 2) c o m p l e x e s , however t h e v a l u e s were n o t i n c l u d e d i n t h e r e p o r t . * 5 2 ' The [ { W ( C O ) 5 } « { F e ( C O ) 4 H } ] ~ a n i o n i s q u i t e a n i n t e r e s t i n g s p e c i e s . I t was o r i g i n a l l y f o r m u l a t e d a s [ { W ( C 0 ) 5 } - ( u - H ) { F e ( C O ) 4 } ] ~ * 4 7 a ) b u t was l a t e r r e f o r m u l a t e d a s h a v i n g " c o n s i d e r a b l e Fe-H t e r m i n a l c h a r a c t e r " on t h e b a s i s o f i t s s o l i d - s t a t e m o l e c u l a r s t r u c t u r e . * 4 7 d ' In s o l u t i o n , some b r i d g i n g c h a r a c t e r was a t t r i b u t e d t o t h e h y d r i d e 1 i g a n d b e c a u s e o f " t h e d i s t i n c t i v e h i g h f i e l d p o s i t i o n o f t h e h y d r i d e r e s o n a n c e (-11.8 ppm) a n d a d e f i n i t e ( a l b e i t s m a l l , 15.0 Hz) W-H c o u p l i n g . " * 4 7 0 ' As has been n o t e d e a r l i e r , t h e c h e m i c a l s h i f t i s n o t a p a r t i c u l a r l y u s e f u l c r i t e r i o n t o u s e i n t h e s e s i t u a t i o n s . S i n c e t h e o b s e r v e d c o u p l i n g c o n s t a n t i s o f t h e m a g n i t u d e e x p e c t e d f o r 2 • J u i i t we b e l i e v e t h a t d i r e c t W-H i n t e r a c t i o n In HW [ { W ( C O ) 5 ) « { F e ( C O ) 4 H } ] ~ i s n e g l i g i b l e . More r e c e n t l y , t h e o r i g i n a l I n v e s t i g a t o r s o f t h e s y s t e m have a l s o a d o p t e d t h i s v i e w . * 5 3 ' 103 P r e v i o u s I n v e s t i g a t o r s have r e p o r t e d v a l u e s f o r [ { W ( C O ) 4 ) 2 ( y - H ) 2 ] 2 _ o f 3 2 ( 8 b ) a n d 30.4 H z . * 4 3 a ) T h e s e numbers H seemed t o o low f o r what w o u l d be e x p e c t e d f o r a w=̂ =w g r o u p i n g ( s e e a b o v e ) . C o n s e q u e n t l y , we have r e d e t e r m i n e d t h i s c o u p l i n g c o n s t a n t a n d f o u n d i t t o be 62 Hz, t h a t I s , t w i c e t h e p u b l i s h e d v a l u e . * 4 3 0 ' T h i s m a g n i t u d e i s more i n l i n e w i t h t h e t r e n d s i n H- W c o u p l i n g f o u n d f o r t h e o t h e r f a m i l i e s o f o r g a n o t u n g s t e n h y d r i d e s ( T a b l e 3-11 I ) . H. C p w ( N 0 ) x (x - 2 o r 1) D e r i v a t i v e s ( T a b l e 3 - V I I ) . T h i s g e n e r a l c l a s s o f compounds may be d i v i d e d I n t o d i n i t r o s y l a n d m o n o n i t r o s y l s p e c i e s . C o n t r a r y t o t h e o r i g i n a l r e p o r t , * 5 4 3 ' t h e *H NMR s p e c t r u m o f t h e p a r e n t d i n i t r o s y l h y d r i d e . CpW(NO) 2H ( F i g . 3-4) shows a ! J H W o f 200 H z , * 5 4 b ) b y f a r t h e l a r g e s t v a l u e y e t o b s e r v e d f o r t h i s p a r a m e t e r . However, t h e b i n u c l e a r d e r i v a t i v e s [{CpW(NQ) 2}(y—H){CpM(NO) 2 } ] + (M=Mo, W) e x h i b i t c o u p l i n g s o n l y s l i g h t l y g r e a t e r t h a n o n e - h a l f t h a t o f t h e p a r e n t . T h i s i m m e d i a t e l y i m p l i e s t h e o c c u r r e n c e o f t e r m i n a l - t e r m i n a l H e x c h a n g e , H H W — M ; = £ W — M 1 2 f o r w h i c h J H W ( p r e d i c t e d ) = 1/2 ( <J H(T ) -w + J H ( T ) - w ' = 1/2 (200 + 15) Hz = 107.5 Hz, a v a l u e n o t f a r f r o m t h o s e o b s e r v e d . A r e a s o n a b l e e s t i m a t e f o r t h e maximum l i f e t i m e o f e a c h i s o m e r c o n t a i n i n g a t e r m i n a l M-H i s t * 1.2 ms, s i n c e Av = AJ * 185 H z . * 1 2 ) 104 T a b l e 3 - V I I . T u n g s t e n H y d r i d e 'H NMR P a r a m e t e r s f o r CpW(NO) (x = 2 o r 1) D e r i v a t i v e s ViH_u>w complex CpW(NO) jH [|CpW(NO)2|,(/i-H)]+ [|CpW(NO)2|(M-H)|CpMo(NO)2|]+ CpW(NO)IH|P(OPh)j| » r a « - C p W ( N O ) H 2 | P ( O P h ) j | [CPW(NO)1]2(M-H)2 [CpW(NO)H] 2 ( M -H ) 2 isomer A 7 " ( 0 C ) isomer B [CpW(NO)|P(OPh),|] 2(M-H) 2 Cp(NO)(Cl )W|CHCHC(0)Me| -20 solv C D 2 N 0 2 CDJNOJ CDCIj C D C l j CDCIj C D C l j CDCI j C 6 D 6 CD 2 C1 2 W-H W-H H-W-H , - w = r w H W=±=W w = ± = w < X M w—j—w 6 (ppm) n •>(Hz) J** (Hz) ref 2.67 1 200*/ Si -8.33 -8.92 114.2' m.(/ 13 13 -2.04 -1.82 1 1 54 88 55 55 -1 .21 '* 1 1 88.3 70.8 55 H A , 6.99 H x , -2.05 1 2 1 9S? - 1 3 9 3 " 55 H A , 6.55 H M . 1.39 H x , -5.94 1 2 1 1 99f ~ 1 5 92' 96' 55 1.32 55' 55 7.64 2 8.8 56 a Ambient t e m p e r a t u r e s u n l e s s i n d i c a t e d o t h e r w i s e . b The W-H b o n d i n g i n t e r a c t i o n s a r e d i s c u s s e d i n d e t a i l i n t h e t e x t . c R e d e t e r m i n e d v a l u e . 183 d W s a t e l 1 i t e s were r e p o r t e d t o c o n s t i t u t e ~24% o f t h e t o t a l i n t e g r a t e d a r e a o f t h e r e s o n a n c e . 183 e The W s a t e l 1 i t e s f o r m an AA'X s y s t e m ; s e e t e x t f o r a d i s c u s s i o n o f t h i s s p e c i e s . 183 f W s a t e l l i t e s were r e p o r t e d t o c o n s t i t u t e ~14% o f t h e t o t a l i n t e g r a t e d a r e a o f t h e r e s o n a n c e . 9 J o b s d = 1 / 2 ( l j H ( X ) - W + l j H ( X ' ) - W ) - 105 —I 1 1 1 1 I I I I 1_ J|_ll_l =0.7 Hz >(ppm) Fi f j - a=A. The 80-MHz *H NMR s p e c t r u m o f CpW(NO) 2H i n CgDg. The monomeric m o n o n i t r o s y l compounds l i s t e d i n T a b l e 3-VI I 1 183 d i s p l a y c o n s i d e r a b l y s m a l l e r H- W c o u p l i n g c o n s t a n t s . N e v e r t h e l e s s , t h e s e v a l u e s a r e l a r g e r t h a n t h o s e f o u n d f o r a n a l o g o u s Cpw(CO) 3H d e r i v a t i v e s ( T a b l e 3 - V ) . F o r t h e m o n o n i t r o s y l compounds, t h e f a c t t h a t C p w ( N O ) H 2 [ P ( O P h ) 3 ] e x h i b i t s a l a r g e r c o u p l i n g t h a n d o e s C p W ( N O ) l H [ P ( O P h ) 3 ] i s a g a i n p r o b a b l y a m a n i f e s t a t i o n o f g r e a t e r s - e l e c t r o n d e n s i t y a t t h e m e t a l c e n t r e o f t h e f o r m e r compound. T h i s i s c o n s i s t e n t w i t h t h e e l e c t r o n i c c h a n g e s e x p e c t e d when a t e r m i n a l H 1 i g a n d i s f o r m a l l y r e p l a c e d by t h e more e l e c t r o n e g a t i v e I 1Igand. As was d i s c u s s e d In c h a p t e r 106 2, t h e s e r i e s CpW(NO)IH(PR 3) (R=OPh, OMe, Ph, Me) shows an i n c r e a s e i n t h e 1 ^ r ) W c o u p l i n g a s t h e e l e c t r o n d o n a t i n g a b i l i t y o f t h e p h o s p h i n e i n c r e a s e s ( T a b l e 2 - 1 1 ) — t h i s , a g a i n , i s a s e x p e c t e d ( s e e b e l o w ) . The lH NMR s p e c t r u m o f [ C p W ( N O ) I H ] 2 ( F i g . 2-1) u n e q u i v o c a l l y e s t a b l i s h e s t h a t t h e complex f s r i g i d In s o l u t i o n o n t h e NMR t i m e s c a l e a n d t h a t t h e h y d r i d e l i g a n d s a r e b r i d g i n g . T h i s i s b e c a u s e t h e 1 8 3W s a t e l l i t e s e x h i b i t a n AA'X p a t t e r n , w i t h t h e H's 183 i n e q u i v a l e n t i n t h e i s o t o p o m e r s w i t h one W n u c l e u s , w i t h f u l l y r e s o l v e d c o u p l e d ( T a b l e 2-1 I) a nd t h e s a t e l l i t e s i n t e g r a t i n g t o ~257. o f t h e t o t a l h y d r i d e i n t e g r a t i o n . In o u r o r i g i n a l p a p e r on (57) t h e s u b j e c t , t h i s complex was f o r m u l a t e d a s [ C p w ( N O ) ] 2 ( y - H ) 2 ( u - I ) 2 . The g r e a t e r u n d e r s t a n d i n g o f 1H- 1 8 3W c o u p l i n g c o n s t a n t s d e v e l o p e d s i n c e t h e n l e a d s us t o r e f o r m u l a t e t h i s compound a s [ C p W ( N O ) I ] 2 ( y — H ) 2 , w i t h a s t r u c t u r e c l o s e l y a k i n t o t h a t o f [CpW(N0) H ] 2 ( y - H ) < ? ( F i g . 2-4) a n d c o n t a i n i n g t h e H f a m i l i a r w=^w b r i d g i n g g r o u p . * 5 8 * The r e a s o n s f o r t h i s a r e t w o - f o l d . F i r s t l y , t h e j " H W v a l u e s e x h i b i t e d by [ C p W ( N O ) I ] 2 ( y — H ) 2 a r e o n l y s l i g h t l y l e s s t h a n t h o s e d i s p l a y e d by [ C p W ( N O ) H ] 2 ( y - H ) 2 , a n d t h i s s l i g h t d e c r e a s e i s e x p e c t e d upon f o r m a l I f o r H s u b s t i t u t i o n ( s e e a b o v e ) . S e c o n d l y , i n v o l v e m e n t H o f a CpW(NO)IH m o i e t y i n a w=^=w I n t e r a c t i o n w o u l d be e x p e c t e d 1 1 8 3 H t o r e s u l t i n i n c r e a s e d H- W c o u p l i n g c o n s t a n t s r e l a t i v e t o t h o s e e x h i b i t e d by r e l a t e d monomers, and J u s t s u c h an i n c r e a s e i s o b s e r v e d . As m e n t i o n e d i n c h a p t e r 2, however, i t h as n o t y e t 107 p r o v e n p o s s i b l e t o grow c r y s t a l s o f t h i s compound s u i t a b l e f o r an X - r a y c r y s t a 1 1 o g r a p h i c a n a l y s i s i n o r d e r t o r e s o l v e t h i s i s s u e . As a n a s i d e , i f [CpW(NO) I ] 2 ( y - H ) 2 i s t n e c o r r e c t f o r m u l a t i o n f o r t h i s compound, t h i s b r i n g s up an i n t e r e s t i n g b o n d i n g q u e s t i o n . A s s u m i n g t h a t t h e s t a r t i n g m a t e r i a l f o r t h i s compound, [ C p W ( N O ) I 2 ] 2 t i s a monomer i n s o l u t i o n a s d i s c u s s e d i n c h a p t e r 2 , t h e n m e t a t h e s i s o f a n I ~ by a n H" i n t h e p r e p a r a t i o n w o u l d l e a d t o t h e f o r m a t i o n o f CpW(NO)IH, w h i c h must s u b s e q u e n t l y d i m e r i z e . D i m e r I z a t i o n l e a d s t o s e v e r a l p o s s i b l e p r o d u c t s , t h e most o b v i o u s o f w h i c h a r e [ C p W ( N O ) H ] 2 ( y - I ) 2 , [ C p W I H ] 2 ( y - N O ) 2 a n d [CpW(NO)I3 2(u-H) 2. The f i r s t two o f t h e s e have e l e c t r o n - s u f f i c i e n t b r i d g i n g s y s t e m s , w h i l e t h e l a s t , t h e a p p a r e n t s t r u c t u r e , has a f o r m a l l y e 1 e c t r o n - d e f i c i e n t b r i d g e . Why t h a t t h i s e l e c t r o n - d e f i c i e n t s y s t e m a p p e a r s t o . b e f a v o u r e d o v e r e l e c t r o n - s u f f i c i e n t s y s t e m s i s i n t r i g u i n g a n d i t w o u l d be most i n t e r e s t i n g t o s e e some t h e r m o d y n a m i c d a t a a n d t h e o r e t i c a l c a l c u l a t i o n on t h e s u b j e c t . The work d e s c r i b e d i n c h a p t e r 2 on s y s t e m , e s t a b l i s h e d t h a t , i n s o l u t i o n , t h e two h y d r i d e l i g a n d s a r e e x c h a n g i n g r a p i d l y on t h e NMR t i m e s c a l e s o a s t o m a i n t a i n , on a v e r a g e , a t r a n s o r i e n t a t i o n w i t h r e s p e c t t o t h e p h o s p h i t e p h o s p h o r u s a t o m s . I f t h e y were u n d e r g o i n g r a p i d t e r m i n a l - t e r m i n a l e x c h a n g e , t h a t i s . H [CpW(N0){P(0Ph)o }3?(M-H),, w h i c h c o n t a i n s a b r i dg i ng H H' W — W W — W H H 108 1 183 t h e n t h e o b s e r v e d H- W c o u p l i n g c o n s t a n t o f 55 Hz wou l d i m p l y J H W ( o b s e r v e d ) = 1/2 ( ! J H W + 2 j H w ) f a n d t h e r e f o r e 5 5 = 1/2 ( l j H w + 15) Hz, y i e l d i n g a v a l u e o f *«J H W = 95 Hz. T h i s i s h i g h e r t h a n t h o s e u s u a l l y f o u n d f o r t e r m i n a l W-H l i n k a g e s i n t h i s c l a s s ( T a b l e s 3-1 I I a n d 3 - V I I ) ( e x c l u d i n g HW(w-H)2WH s y s t e m ) . C o n s e q u e n t l y , t h e n o n r i g i d i t y o f [ C p W ( N O ) { P ( O P h ) 3 ) ] 2 ( p - H ) 2 l i k e l y i n v o l v e s t h e two b r i d g i n g h y d r i d e l i g a n d s e x c h a n g i n g by s p i n n i n g a b o u t t h e m e t a l - m e t a l a x i s a n d m a i n t a i n i n g d i r e c t c o n t a c t w i t h b o t h m e t a l c e n t r e s i n a manner a n a l o g o u s t o t h a t s u g g e s t e d f o r [ C p 2 W ( y - H ) 2 R h ( P P h 3 ) 2 ] + d i s c u s s e d a b o v e . As n o t e d i n p a s s i n g a b o v e , a l l t h e n i t r o s y l c o m p l e x e s l i s t e d 1 183 i n T a b l e 3-VII e x h i b i t H- W c o u p l i n g s t h a t a r e c o n s i d e r a b l y g r e a t e r t h a n t h o s e shown by a n a l o g o u s c a r b o n y l compounds ( T a b l e 3 - V ) . T h i s i s p r o b a b l y a m a n i f e s t a t i o n o f t h e f a c t t h a t NO l i g a n d s a p p e a r t o be much s t r o n g e r d o n o r s o f o e l e c t r o n d e n s i t y (59) t h a n a r e CO g r o u p s . Such d o n a t i o n by t h e n i t r o s y l s w o u l d be e x p e c t e d t o i n c r e a s e t h e t u n g s t e n c e n t r e s v a l e n c e s - e l e c t r o n d e n s i t y a n d , c o n s e q u e n t l y , ( s e e b e l o w ) . In a d d i t i o n , t o 1 183 t h e i r e f f e c t o n t h e H- W c o u p l i n g c o n s t a n t s , t h e NO g r o u p s a l s o i n f l u e n c e t h e c h e m i c a l s h i f t s o f t h e r e s o n a n c e s due t o t h e h y d r i d e l i g a n d s . The s i g n a l s r a n g e f r o m +7 t o -2 ppm f o r s t a t i c , t e r m i n a l h y d r i d e s a n d f r o m +1.4 t o -6 ppm f o r s t a t i c , b r i d g i n g h y d r i d e s f o r t h e c o m p l e x e s g i v e n i n T a b l e 3 - V I I . T h e s e a r e s u b s t a n t i a l l y d o w n f i e l d o f t h o s e e x h i b i t e d by most o f t h e o t h e r o r g a n o t u n g s t e n h y d r i d e s c o n s i d e r e d i n t h i s s t u d y . In t e r m s o f 109 t h e c h e m i c a l s h i f t o f t h e h y d r i d e 1 i g a n d , t h e s e n i t r o s y l c o m p l e x e s seem t o be between t h e e l e c t r o n - r i c h l a t e r t r a n s i t i o n m e t a l h y d r i d e s a n d t h e e l e c t r o n - p o o r e a r l y t r a n s i t i o n - m e t a l h y d r i d e s ( s e e c h a p t e r 1 ) . W h i l e t h e g e n e r a l t r e n d o f b r i d g i n g h y d r i d e s i g n a l s b e i n g u p f i e l d o f t e r m i n a l h y d r i d e s i g n a l s a l s o h o l d s f o r t h e h y d r i d o n i t r o s y l c o m p l e x e s , t h e f a c t r e m a i n s t h a t t h e c h e m i c a l s h i f t o f a s i n g l e h y d r i d e r e s o n a n c e i s n o t a p a r t i c u l a r l y u s e f u l i n d i c a t o r o f t h e b r i d g i n g o r t e r m i n a l n a t u r e o f t h e H 1 I g a n d . ( 6 0 ) J u s t i f i c a t i o n f o r U s i n g " F u s e d " B o n d i n g R e p r e s e n t a t i o n s . A l t h o u g h t h e t h e o r e t i c a l f a c t o r s t h a t i n f l u e n c e t h e m a g n i t u d e s o f one-bond, m e t a l - h y d r o g e n c o u p l i n g c o n s t a n t s h a v e n o t been s t u d i e d i n d e t a i l , * ^ * ' more g e n e r a l a n a l y s e s o f o ne-bond / £2 ) s p i n - s p i n c o u p l i n g s h a v e a p p e a r e d . I t has b e en shown t h a t t h i s i n t e r a c t i o n i s u s u a l l y d o m i n a t e d by t h e F e r m i c o n t a c t t e r m , w h i c h , i n t u r n , i s d o m i n a t e d by t h e p o l a r i z a b l 1 i t y o f t h e bond ( i . e . t h e amount o f s - c h a r a c t e r i n t h e bond) an d t h e v a l e n c e s - e l e c t r o n d e n s i t i e s a t t h e c o u p l e d n u c l e i . In t h e c a s e o f t r a n s i t i o n - m e t a 1 - p h o s p h o r u s c o u p l i n g , i t has b e en s u g g e s t e d t h a t t h e p o l a r i z a b l 1 i t y f a c t o r p r e d o m l n a t e s . * 6 3 ' I f t h e s e a n a l y s e s h o l d t r u e f o r o n e - b o n d t u n g s t e n - h y d r o g e n c o u p l i n g s , t h e n i n c r e a s e s i n t h e m e t a l s b o n d i n g components an d v a l e n c e s - e l e c t r o n d e n s i t i e s a t t h e m e t a l a n d h y d r o g e n n u c l e i s h o u l d be r e f l e c t e d i n i n c r e a s e d m a g n i t u d e o f 1 J ' H w . In f a c t , t h i s l a t t e r 110 f a c t o r has b e e n n o t e d i n s e v e r a l o f t h e f a m i l i e s o f t u n g s t e n h y d r i d o n i t r o s y l c o m p l e x e s d i s c u s s e d a b o v e . I n s p e c t i o n o f t h e d a t a summarized i n T a b l e 3-1 I I shows t h a t t h e m a g n i t u d e s o f * ^ H u d e p e n d on t h e n a t u r e o f t h e t u n g s t e n - h y d r o g e n i n t e r a c t i o n a n d d e c r e a s e i n t h e o r d e r H H H H W ^ = M > W = J U M > ĴL̂  « W — | — M RJ W — H H C H H w i t h i n e a c h f a m i l y o f compounds. The f a c t t h a t t h e W ^ = M b r i d g i n g s y s t e m s e x h i b i t t h e l a r g e s t H- W c o u p l i n g s u g g e s t s i t p o s s e s s t h e g r e a t e s t s - c h a r a c t e r o f a l l t h e s e i n t e r a c t i o n s . T h i s s u p p o s i t i o n i s g i v e n I n d i r e c t s u p p o r t by t h e r e s u l t s o f t h e c a l c u l a t i o n s on ( y - H ) 2 0 s 3 ( C O ) 1 Q w h i c h show t h a t t h e a n a l o g o u s p l a n a r ( y - H ) 2 0 s 2 b o n d i n g u n i t c o n t a i n s a s u b s t a n t i a l amount o f Os 6s c h a r a c t e r . * 1 1 * S u r p r i s i n g l y enough, o n l y r e c e n t l y have d e t a i l e d m o l e c u l a r o r b i t a l c a l c u l a t i o n s on t r a n s i t i o n - m e t a l s H i n v o l v e d i n u n s u p p o r t e d JL 3 - c e n t r e , 2 - e l e c t r o n M M I n t e r a c t i o n s a p p e a r e d In t h e l i t e r a t u r e . * 6 4 * T h i s d i s c u s s i o n on t h e [ { M ( C O ) 5 ) 2 ( w - H ) ] ~ s p e c i e s s u g g e s t s t h a t t h e o r b i t a l s t h a t make up t h e M(y-H)M b r i d g e c o n t a i n , a t most, o n l y a v e r y s m a l l amount o f m e t a l s - c h a r a c t e r . T h i s a p p e a r s t o be r e f l e c t e d i n t h e s m a l l e r c o u p l i n g s o b s e r v e d f o r t h e s e s y s t e m s . O f c o u r s e , d e t a i l e d , c o m p a r a t i v e c a l c u l a t i o n s a r e n e c e s s a r y t o c o n f i r m t h e s e a r g u m e n t s . A t l e a s t a s i m p o r t a n t a s t h e s e p o i n t s i s t h e t r e n d i n H c o u p l i n g c o n s t a n t s w h i c h i n d i c a t e s t h a t W = ^ = M g r o u p i n g s do n o t s i m p l y i n v o l v e two s e p a r a t e , t h r e e - c e n t r e , t w o - e l e c t r o n ji^ H W ' M 1 1 1 ( o r v v — — ) g r o u p s a s i s i m p l i e d by t h e i r r e p r e s e n t a t i o n a s H W===M . T h e r e f o r e , t h e y a r e b e s t v i e w e d a s s i n g l e , f o u i — H H c e n t r e u n i t s , a n d t h e r e f o r e t h e w=i=M n o t a t i o n i s s u g g e s t e d . I H [ T h e w—h-M r e p r e s e n t a t i o n was c o n s i d e r e d , b u t r e j e c t e d , s i n c e H t h i s c o u l d be v i e w e d a s i n v o l v i n g d i h y d r o g e n a s a 1 i g a n d , ( 5 0 * 6 6 , 6 7 ' a c o n n o t a t i o n we wanted t o a v o i d . ] F o r s i m i l a r r e a s o n s , t h e " f u s e d " r e p r e s e n t a t i o n s a r e e m p l o y e d t h r o u g h o u t t h i s t h e s i s . One p r i m a r y a d v a n t a g e o f t h i s n o t a t i o n i s t h a t e a c h l i n e f r o m an atom r e p r e s e n t s one o r b i t a l c o n t r i b u t e d by t h a t atom t o t h e b o n d i n g i n t e r a c t i o n , j u s t a s i n t h e f a m i l i a r t h r e e - c e n t r e , H H t h r e e - o r b i t a l M - ^ M d e s c r i p t i o n . C o n s e q u e n t l y , M=^=M H i n d i c a t e s a f o u i — c e n t r e , s i x - o r b i t a l i n t e r a c t i o n ( a s t h e H c a l c u l a t i o n s on ( y - H ) 2 0 s 3 ( C O ) j Q show), M - | - M a f o u r - c e n t r e , H f o u i — o r b i t a l i n t e r a c t i o n , a n d s o o n . The s i m p l e s t way o f d e d u c i n g t h e a p p r o p r i a t e " f u s e d " r e p r e s e n t a t i o n f o r any g i v e n d i n u c l e a r s i t u a t i o n i s t o u s e t h e i d e a o f a p r o t o n a t e d m e t a l - m e t a l b o n d . * 3 3 , 6 8 ' T h a t i s , t o p e r f o r m a normal e l e c t r o n (9) c o u n t ' on t h e m o l e c u l e a f t e r c o n s i d e r i n g i t t o have l o s t a n y b r i d g i n g h y d r o g e n s a s p r o t o n s , l e a v i n g t h e m o l e c u l e a n i o n i c ( a s s u m i n g , o f c o u r s e , i t was n e u t r a l t o b e g i n w i t h ) . The b r i d g i n g h y d r i d e s a r e t h e n a d d e d by f o r m a l p r o t o n a t i o n o f t h e r e s u l t i n g m e t a l - m e t a l bond t o g i v e t h e " f u s e d " p i c t u r e , a s i n 112 C p v b-H~~1 O N » » W = W r * N O * 2 H + "'Cp O f c o u r s e , t h e number o f e l e c t r o n s i n v o l v e d i n t h e b o n d i n g i n t e r a c t i o n c a n n o t be i n f e r r e d d i r e c t l y f r o m t h e n o t a t i o n . H However, t h e JL s y s t e m i s g e n e r a l l y b e l i e v e d t o i n v o l v e two M M (9) e l e c t r o n s , a n d t h e c a l c u l a t i o n s on ( y - H ) 2 O s 3 ( C O ) 1 Q do s u g g e s t H t h a t t h e M=^=M i n t e r a c t i o n d o e s i n v o l v e f o u r e l e c t r o n s * 1 1 * a s H t h i s c o u n t i n g t e c h n i q u e I m p l i e s . We t h e r e f o r e f e e l t h a t t h e " f u s e d " n o t a t i o n i s a u s e f u l , a c c u r a t e a n d s i m p l e r e p r e s e n t a t i o n o f t h e s e e l e c t r o n - d e f i c i e n t b r i d g i n g s y s t e m s . J . Summary The u n i q u e n a t u r e o f [ C p W ( N O ) H ] 2 ( y - H ) 2 » a l o n g w i t h t h e a n a l y s i s o f a l a r g e amount o f d a t a on t u n g s t e n h y d r i d e s i n t h e l i t e r a t u r e , has a l l o w e d us t o g a i n c o n s i d e r a b l e i n s i g h t i n t o t h e f a c t o r s t h a t g o v e r n t h e m a g n i t u d e o f o b s e r v e d t u n g s t e n - h y d r o g e n c o u p l i n g c o n s t a n t s i n mono and d i n u c l e a r s y s t e m s . I t c a n now be s e e n t h a t t h e o b s e r v a t i o n o f t h e s i z e o f t h e s e c o u p l i n g s c a n g e n e r a l l y g i v e a n e x c e l l e n t i d e a o f t h e t y p e o f m e t a l - h y d r o g e n i n t e r a c t i o n i n v o l v e d when s u c h c o u p l i n g s a r e compared w i t h o t h e r s o f t h e a p p r o p r i a t e f a m i l y . I t has been shown t h a t i n a g i v e n 113 C p v H H ON'-W+Wr-NO H' T "-cp e l e c t r o n i c e n v i r o n m e n t , 1 ̂ ( t e r m i na 1 )-W " 1 J H ( b r i d g i n g ) - W > 2 jHW and t h a t e s t i m a t e s f o r t h e s e v a l u e s may be o b t a i n e d f r o m t h e *H NMR s p e c t r a o f t h e a p p r o p r i a t e monomeric p a r e n t . U s i n g t h e s e , a l a r g e number o f o b s e r v e d c o u p l i n g s c a n be e x p l a i n e d on t h e b a s i s o f s t a t i c i n t e r a c t i o n s o r s p e c i f i c t y p e s o f f l u x i o n a l pathways i n v o l v i n g e x c h a n g e o f h y d r i d e s between m e t a l c e n t r e s , a n d t h a t some i d e a o f t h e t i m e s c a l e s o f t h e s e f 1 u x i o n a l I t i e s may be o b t a i n e d . Not s u r p r i s i n g l y , i t was f o u n d t h a t compounds w i t h 4- H c e n t r e , 6 - o r b i t a l I n t e r a c t i o n s , W = ^ = M a r e c o n s i d e r a b l y l e s s H H f l u x i o n a l t h a n t h o s e w i t h 3 - c e n t r e , 3 - o r b i t a l î̂  b r i d g i n g  s y s t e m s . I n f e r e n c e s r e g a r d i n g f l u x i o n a l i t y drawn i n t h i s way a r e g e n e r a l l y c o n s i s t e n t w i t h e x c h a n g e mechanisms s u g g e s t e d on t h e b a s i s o f v a r i a b l e t e m p e r a t u r e NMR s t u d i e s . A l t h o u g h b r i d g i n g h y d r i d e l i g a n d s g e n e r a l l y show c h e m i c a l s h i f t s i n a r e a s u p f i e l d o f t h o s e due t o t e r m i n a l o n e s , t h e f a c t t h a t t h e s e r e g i o n s a l w a y s o v e r l a p e v e n i n a n y one p a r t i c u l a r f a m i l y means t h a t a p a r t i c u l a r r e s o n a n c e c a n n o t be u s e d d i a g n o s t i c a l l y t o d e t e r m i n e t h e b r i d g i n g o r t e r m i n a l n a t u r e o f a p a r t i c u l a r h y d r i d e 1igand i n a c omplex. The m a g n i t u d e o f t h e H- W c o u p l i n g s a p p e a r s t o be i n f l u e n c e d p r i m a r i l y by t h e v a l e n c e s - e l e c t r o n d e n s i t i e s a t t h e t u n g s t e n c e n t r e a n d t h e s - o r b i t a l component o f t h e b o n d i n g . W i t h i n a g i v e n f a m i l y o f b i m e t a l l i c t u n g s t e n h y d r i d e s , t h e s e c o u p l i n g s d e c r e a s e i n t h e o r d e r H H H H W = | = M > W=j|=M > * W - j - M « W - H H C 1 14 T h i s f a c t s u g g e s t s t h a t t h e f o u r g r o u p s t h a t c o n t a i n b r i d g i n g h y d r i d e l i g a n d s a r e b e s t t h o u g h t o f a s s i n g l e u n i t s h e l d t o g e t h e r b y d e l o c a l i z e d b o n d i n g w h i c h e x t e n d s o v e r a 11 t h e atoms i n v o l v e d i n t h e b r i d g e . T h i s c o n c l u s i o n s u p p o r t s v a r i o u s m o l e c u l a r o r b i t a l c a l c u l a t i o n s i n t h e l i t e r a t u r e on some o f t h e s e b r i d g i n g s y s t e m s . To c o n v e y t h e u n i t a r y v i e w , t h e u s e o f t h e s e " f u s e d " r e p r e s e n t a t i o n s f o r t h e i n t e r a c t i o n s i s s u g g e s t e d . F i n a l l y , i t may be n o t e d t h a t s i m i l a r t r e n d s may e x i s t f o r t h e c o u p l i n g o f h y d r i d e s t o o t h e r t r a n s i t i o n - m e t a l c e n t r e s ; f o r example, * < J U O K i s g r e a t e r f o r R n = * = R h t h a n f o r Rh (69) 1 15 K. R e f e r e n c e s a n d N o t e s 1. T r a n s i t i o n M e t a l H y d r i d e s : M u e t t e r t i e s , E . L . E d . ; M a r c e l D e k k e r : New Y o r k , 1971. a n d r e f e r e n c e s t h e r e i n . 2. S u b a - S e a l s e p t a a r e o b t a i n a b l e f r o m t h e A l d r i c h C h e m i c a l Co., I n c . 3. 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I t i s p o s s i b l e t h a t t h e m a g n i t u d e o f J H W may be i n c r e a s e d f r o m i t s u s u a l v a l u e (<15 Hz) i n t h e c a s e o f a p a r t i c u l a r l y e l e c t r o n - r i c h d a t i v e bonded s y s t e m : [ ( O C ) 3 W ( y - d p p m ) 2 P t ( H ) (CI ) ] w i t h W<-Pt-H a n d 2 J H W = 30 Hz ( C D 2 C 1 2 , - 9 0 ° C ) — s e e : B l a g g , A.; Shaw, B.L. J . Chem. S o c , D a l t o n T r a n s . 1987, 221-226. 50. Kubas, G.L.; Ryan, R.R.; Swanson, B . J . ; V e r g a m i n i , P . J . ; Wasserman, H.J. J ^ Am. Chem. S o c . 1984, 106, 451-452. 51. L o S c h i a v o , S.; B r u n o , G.; N l c o l d , F.; P i r a t no, P.; F a r a o n e , F. O r g a n o m e t a l 1 i c s 1985, 4, 2091-2096 and r e f e r e n c e s t h e r e i n . 52. B e r k e , H.; K u n d e l , P. Z. N a t u r f o r s c h . B 1986, 40, 527-531. 53. a) A r n d t , L.W.; D a r e n s b o u r g , M.Y.; F a c k l e r , J . P . ; L u s k , R . J . ; M a r l e r , D.O. ; Youngdahl,, K.A. J_j_ Am. Chem. S o c . 1985, 1 0 7 , 7218-7219. b) A r n d t , L.W.; D a r e n s b o u r g , M.Y.; D e l o r d , 120 T.; B a n c r o f t , B.T. I b i d 1986, 108, 2617-2627. c) See a l s o : Hal p i n , C.F.; H a l l , M.B. I b i d 1986, 108, 1695-1696. 54. a) L e g z d i n s , P.; M a r t i n , D.T. I n o r g . Chem. 1979, 18, 1250- 1254. b) R e d e t e r m i n e d 80-MHz lh NMR o f CpW(N0) oH ( C D , - ) : 6 C. D O 4.96 ( d , 5H, C 5JH 5, 3 J H H = 0.7 H z ) , 2.67 ( s e x t e t , 1H, W-H.. 1 J H W = 200 H z ) . 55. See c h a p t e r 2. 56. A l t , H.G.; Hagen, H.J.; K l e i n , H.-P.; T h e w a l t , U. Angew. Chem.. I n t . E d . E n g l . 1984, 2 3 , 809-810. 57. L e g z d i n s , P.; M a r t i n J . T . ; O x l e y , J . C . Q r g a n o m e t a l 1 i c s 1985, 4, 1263-1271. 58. A s i m i l a r t y p e o f s t r u c t u r e has a l s o been p r o p o s e d f o r [ C p * I r C l ] 2 ( y - H ) 2 on t h e b a s i s o f i n f r a r e d l a b e l l i n g s t u d i e s — s e e : G i l l , D.S.; M a i t l i s , P.M. J . Q r g a n o m e t a l . Chem. 1975, 87, 359-364. 59. a) Hubbard, J . L . Ph.D. D i s s e r t a t i o n , The U n i v e r s i t y o f A r i z o n a , 1982. b) H a r t l e y , F.R. Chem. S o c . Rev. 1972, 2 , 163-179. 60. A s t r i k i n g i l l u s t r a t i o n o f t h i s f a c t i s p r o v i d e d i n t h e r e p o r t o f W 2 H ( 0 - i - P r ) 4 ( y - C 4 M e 4 ) ( y - C P h ) , a d i t u n g s t e n complex c o n t a i n i n g a s t a t i c , t e r m i n a l W-H g r o u p w h i c h e x h i b i t s a *H NMR r e s o n a n c e a t <$ +20.42 ppm. T h i s i s a p p r o x i m a t e l y 10 ppm d o w n f i e l d f r o m t h e W 2(u-H) s i g n a l s e x h i b i t e d by t h e h i gh-ox i d a t i on s t a t e a 1kox i d e s o f t h e t y p e [ W 2 ( y - H ) ( Q - i - P r ) 7 ] 2 a n d N a [ W 2 ( y - H ) ( 0 - i - P r ) 8 ] * d i g l y m e — s e e : 121 C h i s h o l m , M.H.; E i c h h o r n , B.W.; Huffman, J . C . J . Chem. S o c . . Chem. Commun. 1985, 861-863 and r e f e r e n c e s t h e r e i n . 61. F o r b r i e f d i s c u s s i o n s , s e e : a) G r e e n , M.L.H.; J o n e s , D .J. Adv. I n o r g . Chem. Radiochem. 1965, 7, 1 1 5 - 1 8 3 — i n p a r t i c u l a r , s e e pp 128-131. b) A t k i n s , P.W.; G r e e n , J . C ; G r e e n , M.L.H. J± Chem. S o c . A 1968, 2275-2280. c ) C h u r c h , M.J.; Mays, M.J. J . Chem. S o c . A 1970, 1938-1941 and r e f e r e n c e s t h e r e i n . 62. a) P o p l e , J.A.; S a n t r y , D.P. M o l . P h y s . 1964, 8, 1-18. b) K o w a l e w s k i , J . Annu. Rev. Nuc1. Magn. Reso n . S p e c t r o s c . 1982, 12, 82-176. 63. P r e g o s i n , P.S.; Kunz, R.W. i n NMR. Bas i c P r i nc i p i e s a n d P r o g r e s s ; D i e h l , P.; F l u c k , E.; K o s f e l d , R., E d s . ; S p r i n g e r - V e r l a g : New Y o r k , 1979; V o l . 16. 64. J e z o w s k a - T r z e b i a t o w s k a , B.; N i s s e n - S o b o c i n s k a , B. J . Q r g a n o m e t a l . Chem. 1987, 322, 3 3 1 - 3 5 0 — f o r f u r t h e r d i s c u s s i o n , s e e r e f . 65. 65. a) [ { M ( C O ) 5 } 2 ( j i - H ) ] ~ : A l b r i g h t , T.A. T e t r a h e d r o n 1982, 38, 1 3 3 9 - 1 3 8 8 — i n p a r t i c u l a r , s e e p 1349. F o r t h e f r o n t i e r m o l e c u l a r o r b i t a l s o f t h e M(CO> 5 f r a g m e n t , s e e b) Hay, J . P . J . Am. Chem. S o c . 1978, 100, 2411-2417. c ) E l i a n , M.; Hoffmann, R. I n o r g . Chem. 1975, 14, 1058-1076. 66. M o r r i s , R.H.; Sawyer, J . F . ; S h i r a l i a n , M.; Z u b k o w s k i , J.D. J . Am. Chem. S o c . 1985, 107, 5581-5582 a n d r e f e r e n c e s t h e r i n . 122 67. C r a b t r e e , R.H.; L a v i n , M.; B o n n e v o i t , L. J ^ Am. Chem. S o c . 1986, 108, 4032-4037. 68. a ) Handy, L.B.; R u f f , J.K.; D a h l , L . F . J j . Am. Chem. S o c . 1970, 92, 7312-7326. b) C h u r c h i l l , M.R.; DeBoer, B.G.; R o t e l l a , F . J . I n o r q . Chem. 1976, 15, 1843-1853. 69. F r y z u k , M.D. O r g a n o m e t a l 1 I c s 1982, |, 408-409. 123 C h a p t e r 4 S t a b 1 e A l k y 1 H y d r i d e Complexes o f T u n g s t e n The y i e l d s o f t h e h y d r i d e p r e p a r a t i o n s f r o m t h e m e t a t h e s i s r e a c t i o n s o f [ C p W ( N O ) I 2 ] 2 d i s c u s s e d i n c h a p t e r 2 were n o t s a t i s f a c t o r y . In p a r t i c u l a r , t h e [ C p W ( N O ) H ] 2 ( y - H ) 2 compound, w h i c h has t h e p o t e n t i a l t o e x h i b i t much I n t e r e s t i n g c h e m i s t r y , c o u l d o n l y be p r e p a r e d i n s u c h a low y i e l d (~107.) a n d t h r o u g h s u c h a t e d i o u s p r o c e d u r e s o a s t o make t h e e x t e n s i v e i n v e s t i g a t i o n o f i t s c h e m i s t r y i m p r a c t i c a l . C o n s e q u e n t l y , a n o t h e r s y n t h e t i c r o u t e i n t o t h i s a r e a was h i g h l y d e s i r a b l e . W h i l e t h e work d e s c r i b e d i n c h a p t e r s 2 a n d 3 was i n p r o g r e s s , o t h e r work f r o m o u r l a b o r a t o r y d e t a i l e d t h e p r e p a r a t i o n o f t h e u n i q u e compounds C p l i ( N O ) R 2 (li=Mo, W a n d R=bulky a l k y l ) v i a r e a c t i o n 4 - 1 . T h e compounds were i s o l a t e d In r e a s o n a b l e RMgX H 2 0 [CpM(NO) I 2 ] 2 ^ [ C p M ( N O ) R 2 ] 2 . M g X 2 ^2 CpM(NO)R 2 (4-1) y i e l d s , p a r t i c u l a r l y C p W ( N O ) ( C H 2 S 1 M e 3 ) 2 , w h i c h was o b t a i n e d i n g r e a t e r t h a n 70% y i e l d . T h e s e a r e u n u s u a l l y s t a b l e , 1 6 - e l e c t r o n compounds t h a t h a v e an a v a i l a b l e , o p e n c o o r d i n a t i o n s i t e a n d have been shown t o e x h i b i t i n t e r e s t i n g r e a c t i v i t y w i t h s e v e r a l s m a l l m o l e c u l e s , i n c l u d i n g 0 2 , ( 2 ) S g ( 3 ) a n d N 0 . ( 4 ) I t was hoped, t h e r e f o r e , t h a t h y d r o g e n o l y s i s o f t h i s compound ( h y d r i d e p r e p a r a t i o n r o u t e # 1 — c h a p t e r 1) wo u l d r e s u l t 124 i n t h e f o r m a t i o n o f [ C p W ( N O ) H ] 2 ( y - H ) 2 ( e q . 4 - 2 ) . P r e l i m i n a r y H 2 2 CpW (NO) ( C H 2 S i M e 3 ) 2 [CpW (NO)H] 2 (p-H) 2 + 2 M e 4 S i (4-2) ? r e a c t i o n s a t low H 2 p r e s s u r e s (<60 p s i g ) r e s u l t e d o n l y i n d e c o m p o s i t i o n and t h e d e s i r e d p r o d u c t was n o t o b t a i n e d . However, when t h i s r e a c t i o n was a t t e m p t e d i n t h e p r e s e n c e o f a t e r t i a r y p h o s p h i n e ( o r p h o s p h i t e ) , P P 3 » n o v e l p r o d u c t s o f t h e f o r m C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P R 3 ) were o b t a i n e d . T h e s e p r e p a r a t i o n s a n d a s s o c i a t e d c h e m i s t r y o f t h e p r o d u c t c o m p l e x e s f o r m p a r t o f t h e work d e s c r i b e d i n t h i s c h a p t e r . F o r r e a s o n s t h a t w i l l become c l e a r i n t h e d i s c u s s i o n , t h i s work was e x t e n d e d t o t h e Cp* a n a l o g u e s and a d e s c r i p t i o n o f t h i s s y s t e m , i n c l u d i n g t h e p r e p a r a t i o n s o f t h e r e l e v a n t s t a r t i n g m a t e r i a l s , c o n s t i t u t e t h e r e m a i n d e r o f t h e c h a p t e r . E x p e r i menta1 S e c t i on S t a n d a r d t e c h n i q u e s e m p l o y e d were d e t a i l e d i n c h a p t e r 2. T e t r a m e t h y 1 s 1 1 a n e was i d e n t i f i e d u s i n g a Carbowax 20M 12m c a p i l l a r y column i n a H e w l e t t - P a c k a r d HP 5880A L e v e l 4 gas c h r o m a t o g r a p h w i t h h e l i u m c a r r i e r gas and an o v e n t e m p e r a t u r e o f 5 0 ° C . Carbon-13 NMR s p e c t r a were r u n on a V a r i a n XL-300 s p e c t r o m e t e r o p e r a t i n g a t 75.429-MHz r e f e r e n c e d t o C^Dg a t 128.00 (5) ppm o r CD^NO, a t 62.8 ppm a n d a r e r e p o r t e d i n ppm d o w n f i e l d 125 f r o m TMS. C p W ( N O ) ( C H 2 S i M e 3 ) 2 , ( 1 ' 6 ) C 5 M e 5 H ( 7 ) and N a C 5 M e 5 ( 8 ) were p r e p a r e d a s d e s c r i b e d i n t h e l i t e r a t u r e . The p h y s i c a l and s p e c t r o s c o p i c p r o p e r t i e s o f a l 1 new compounds p r e p a r e d a r e g i v e n i n T a b l e s 4-1 and 4-11. CAUTION: The g l a s s F i s h e r - P o r t e r p r e s s u r e v e s s e l s must be h a n d l e d w i t h c a r e a s t h e m a n u f a c t u r e r d o e s n o t s p e c i f y a s a f e o p e r a t i n g p r e s s u r e and t h e y a r e n o t e q u i p p e d w i t h any a u t o m a t i c p r e s s u r e r e l i e f s y s t e m . P r e p a r a t i o n o f C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) L ( L = P ( O P h ) 3 , P M e P h 2 ) . C p W ( N O ) ( C H 2 S i M e 3 ) (0.30 g, 0.66 mmol) was d i s s o l v e d w i t h s t i r r i n g i n h e x a nes (10 mL) and c a n n u i a t e d i n t o a 300 mL F i s h e r - P o r t e r v e s s e l t h a t had been e v a c u a t e d and f i l l e d w i t h H 2 t h r e e t i m e s . A s t o i c h i o m e t r i c amount o f L (0.66 mmol, 0.18 mL P ( O P h ) 3 o r 0.12 mL PMePh 2) was t h e n a d d e d v i a s y r i n g e t o t h e F i s h e i — P o r t e r v e s s e l , w h i c h was s u b s e q u e n t l y p r e s s u r i z e d t o ~80 p s i g H^. The v e s s e l was t h e n a g i t a t e d f o r a few moments t o a l l o w m i x i n g o f L a n d s p e e d s o l u b i l i z a t i o n o f t h e H 2, and l e f t s t a n d i n g w i t h no s t i r r i ng. L = P ( 0 P h ) 3 : O v e r t h e c o u r s e o f t h e r e a c t i o n , t h e i n i t i a l d a r k p u r p l e s o l u t i o n g r a d u a l l y l i g h t e n e d t o a v e r y p a l e p u r p l e w i t h a c o n c o m i t a n t d e p o s i t i o n o f a p a l e y e l l o w powdery p r e c i p i t a t e . A f t e r 2 h t o t a l r e a c t i o n t i m e , t h e p r e s s u r e i n t h e v e s s e l was r e l i e v e d and t h e m other l i q u o r c a n n u i a t e d away f r o m t h e p r e c i p i t a t e . The r e a c t i o n v e s s e l was t h e n o p e n e d i n a i r and t h e p r e c i p i t a t e t r a n s f e r r e d i n t o a n i t r o g e n - f i l l e d f l a s k . The 126 p r e c i p i t a t e was washed w i t h h e x a nes (3 x 10 mL) u n d e r a n d d r i e d u n d e r vacuum (0.05 mm Hg, 2 h) t o y i e l d 0.29 g (657. y i e l d ) o f y e l l o w m i c r o c r y s t a l 1 i n e C p W ( N O ) ( H ) ( C H ^ S i M e 3 ) [ P ( O P h ) 3 ] • L=PMePh 2: As t h e r e a c t i o n p r o c e e d e d , t h e i n i t i a l d a r k p u r p l e s o l u t i o n c h a n g e d t o a deep red-brown c o l o u r a s s e v e r a l l a r g e , r e d - b r o w n b r i c k - s h a p e d c r y s t a l l i n e masses f o r m e d on t h e b o t t o m o f t h e v e s s e l , a l o n g w i t h some o t h e r , amorphous m a t e r i a l . A f t e r 3 h t o t a l r e a c t i o n t i m e , t h e p r e s s u r e was r e l i e v e d a n d t h e mother l i q u o r c a n n u l a t e d away f r o m t h e s o l i d m a t e r i a l , whereupon t h e F i s h e r - P o r t e r v e s s e l was o p e n e d i n a i r a n d t h e b r i c k - s h a p e d masses c a r e f u l l y and q u i c k l y t r a n s f e r r e d t o a n i t r o g e n - f i l l e d f l a s k . T h i s c r y s t a l l i n e m a t e r i a l was t h e n t a k e n up i n E t 2 0 , f i l t e r c a n n u l a t e d t o remove a s m a l l amount o f d a r k c o l o u r e d i n s o l u b l e m a t e r i a l a n d t h e f i l t r a t e s l o w l y c o n c e n t r a t e d u n d e r vacuum t o g i v e a s m a l l amount o f y e l l o w , m i c r o c r y s t a l 1 i n e C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e P h 2 ) . S i n g l e c r y s t a l s o f t h i s m a t e r i a l s u i t a b l e f o r X - r a y a n a l y s i s were grown i n l e s s t h a n 1 h f r o m C H 2 C 1 2 / h e x a n e s a t - 2 5 ° C . P r e p a r a t i o n o f C p W ( N O ) ( H ) [ P ( 0 P h ) 2 ( 0 C 6 H 4 ) ] . T h i s compound was p r e p a r e d by c o m b i n i n g C p W ( N O ) ( C H 2 S i M e ^ ) , P ( 0 P h ) 3 a n d h"2 a s a b o v e (on o n e - h a l f t h e s c a l e ) , b u t l e t t i n g t h e r e a c t i o n p r o c e e d f o r 4 d a y s a t room t e m p e r a t u r e . T h i s r e s u l t e d i n an a l m o s t c o l o u r l e s s s o l u t i o n a b o v e a y e l l o w m i c r o c r y s t a l 1 i n e c r u s t y p r e c i p i t a t e . The hexanes were removed u n d e r r e d u c e d 127 p r e s s u r e ( i n t h e F i s h e r - P o r t e r v e s s e l ) , Et^O was a d d e d a n d t h e v e s s e l a g i t a t e d t o h e l p b r e a k up t h e h a r d c r u s t y r e s i d u e enough t o a l l o w b o t h t h e s o l i d a n d s o l u t i o n t o be p o u r e d I n t o a n i t r o g e n f i l l e d f l a s k . The E t ^ O was t h e n removed u n d e r vacuum an d t h e s o l i d m a t e r i a l r e c r y s t a l 1 i z e d o v e r n i g h t f r o m t o l u e n e a t - 2 5 ° C . The p r o d u c t was washed o n c e w i t h h e x anes (10 mL) a n d d r i e d o v e r n i g h t (0.005 mm Hg) t o g i v e y e l l o w , m i c r o c r y s t a l 1 i n e C p W ( N O ) ( H ) [ P ( O P h ) 2 ( O C 6 H 4 ) ] . X - r a y q u a l i t y s i n g l e c r y s t a l s o f t h i s compound were grown by s l o w e v a p o r a t i o n o f a C^Dg s o l u t i o n i n an NMR t u b e c a p p e d by a septum p u n c t u r e d w i t h a n e e d l e i n a i r a t room t e m p e r a t u r e . R e a c t i o n s o f C p W ( N O ) ( C H 2 S i M e 3 ) 2 , H 2 a n d L ( L = P ( O P h ) 3 , PMePh 2) i n an NMR Tube. To a s m a l l , N 2 - f i l l e d S c h l e n k t u b e was a d d e d C p W ( N O ) ( C H 2 S i M e 3 ) 2 (-0.01 g, -0.04 mmol), CgDg (~2 mL) a n d (by s y r i n g e ) an a p p r o x i m a t e l y s t o i c h i o m e t r i c amount o f L (12 uL P ( O P h ) 3 o r 9 yL P M e P h 2 ) . T h i s m i x t u r e was s t i r r e d u n t i l a homogeneous s o l u t i o n was o b t a i n e d a n d p a r t o f t h i s s o l u t i o n (9) c a n n u i a t e d i n t o a t h i c k - w a 1 1 e d v NMR t u b e u n t i l ~3 cm o f s o l u t i o n was i n t h e t u b e . The s o l u t i o n was t h e n f r e e z e - p u m p - t h a w d e g a s s e d t h r e e t i m e s , f o l l o w i n g w h i c h 1 atm o f was a l l o w e d I n t o t h e NMR t u b e a t - 1 9 6 ° C and t h e t u b e f l a m e s e a l e d . A f t e r t h e m i x t u r e had r e a c h e d room t e m p e r a t u r e ( r e s u l t i n g i n an H 2 p r e s s u r e o f ~4 a t m ) , 'H a n d 3 l P NMR s p e c t r a were o b t a i n e d o v e r t h e c o u r s e 128 o f ~60 h w i t h i n t e r m i t t e n t s h a k i n g o f t h e NMR t u b e . E q u i l i b r i u m between CpW (NO) ( C h ^ S i Me 3) 2 a n d PMePhj,. A m i x t u r e o f C p W ( N O ) ( C H ? S i M e 3 ) 2 (0.0244 g, 5.38 x 1 0 ~ 2 mmol), PMePh 2 (10 uL, ~5.4 x 1 0 ~ 2 mmol), a n d t o l u e n e - d Q (0.90 mL) was p l a c e d i n a n NMR t u b e , f r e e z e - p u m p - t h a w d e g a s s e d t h r e e t i m e s a n d t h e t u b e f l a m e - s e a l e d u n d e r vacuum. P r o t o n a n d 3 1 P { 1 H ) NMR s p e c t r a were t h e n o b t a i n e d a t t e m p e r a t u r e s f r o m - 8 5 ° C t o 2 5 ° C . P r e p a r a t i o n o f C p » W ( C 0 ) 2 ( N O ) . ( 1 0 ' 1 1 •* T h i s compound was p r e p a r e d by t h e s t a n d a r d method u s e d f o r C p W ( C 0 ) 2 ( N 0 ) ( 1 2 ) i n 92.7% y i e l d u s i n g i s o l a t e d , c r y s t a l l i n e N a C 5 M e 5 . ( 8 ) P r e p a r a t i o n o f Cp»W(NO)I . ( 1 3 ' To a w e l l s t i r r e d s o l u t i o n o f Cp*W(C0) 2(NO) (10.02 g, 24.7 mmol) i n t o l u e n e (100 mL) was a d d e d I 2 (6.34 g, 24.8 mmol) i n 4 p o r t i o n s w h i l e v i g o u r o u s gas e v o l u t i o n o c c u r r e d (CAUTION; t h i s CO gas s h o u l d be v e n t e d t o t h e fume h o o d ) . A f t e r g a s e v o l u t i o n had s i g n i f i c a n t l y s u b s i d e d , a d a r k r e d - b r o w n m i c r o c r y s t a l 1 i n e p r e c i p i t a t e was o b s e r v e d b e n e a t h a d a r k r e d - b r o w n s o l u t i o n . The s o l u t i o n was s t i r r e d u n d e r a s l i g h t d y n a m ic vacuum w h i l e warming w i t h a warm w a t e r b a t h . The i n i t i a l p r e c i p i t a t e e v e n t u a l l y r e d i s s o l v e d a n d was r e p l a c e d by a b r i l l i a n t - g r e e n ( b e l o w room t e m p e r a t u r e ) o r g o l d ( a b o v e room t e m p e r a t u r e ) c o l o u r e d 129 m i c r o c r y s t a 1 1 i n e p r e c i p i t a t e o v e r t h e c o u r s e o f s e v e r a l h o u r s a s t h e t o l u e n e s o l v e n t was s l o w l y r e d u c e d i n volume. A f t e r ~3 h o f pumping a n d p e r i o d i c a d d i t i o n s o f t o l u e n e when t h e s o l u t i o n volume d r o p p e d b e l o w ~50 mL, t h e volume o f s o l v e n t was r e d u c e d t o ~20 mL under vacuum a n d t h e r e s u l t i n g p r e c i p i t a t e c o l l e c t e d by f i l t r a t i o n , washed w i t h s m a l l a l i q u o t s o f E t 2 0 (5 mL e a c h ) u n t i l t h e f i l t r a t e was no l o n g e r d a r k brown and f i n a l l y w i t h h e x anes (3 x 20 mL). The p r e c i p i t a t e was d r i e d under vacuum (0.005 mm Hg, 2 h) t o y i e l d 12.6 g (84.67.) o f g r e e n o r g o l d t h e r m o c h r o m i c m i c r o c r y s t a l 1 i n e C p * W ( N 0 ) I 2 . P r e p a r a t i o n o f C p * W ( N 0 ) ( C H 2 S i M e 3 ) 2 . T h i s p r e p a r a t i o n i s a s l i g h t m o d i f i c a t i o n o f t h a t f o r C p W ( N O ) ( C H 2 S i M e 3 ) 2 . ( 1 , 6 ) To a r a p i d l y s t i r r i n g g r e e n o r g o l d s u s p e n s i o n o f C p * W ( N 0 ) I 2 (12.6 g, 21.2 mmol) i n E t 2 0 (150 mL) was ad d e d 43 mL o f 1.0 M M e 3 S i C H 2 M g C l ( 1 4 ) (43 mmol) d r o p w i s e f r o m a s y r i n g e . The m i x t u r e d a r k e n e d t o a red-brown c o l o u r a s soo n a s t h e a d d i t i o n o f t h e G r i g n a r d r e a g e n t had s t a r t e d a n d a d a r k c o l o u r e d p r e c i p i t a t e began t o a p p e a r . A f t e r ~ l / 2 h o f s t i r r i n g t h e s u s p e n s i o n , ~4 mL o f N 2 ~ p u r g e d d e i o n i z e d H 2 0 was a d d e d v i a s y r i n g e t h r o u g h a septum whereupon t h e s o l u t i o n t u r n e d p u r p l e and a w h i t e p r e c i p i t a t e was d e p o s i t e d o v e r t h e c o u r s e o f ~ i h. The volume o f t h e m i x t u r e was t h e n r e d u c e d t o -20 mL u n d e r vacuum a n d t r a n s f e r r e d by c a n n u l a t o t h e t o p o f a 15 x 4 cm F l o r i s i l column made up i n 4:1 h e x a n e s : E t _ o s o l v e n t . The r e s i d u e a t t h e b o t t o m 130 o f t h e r e a c t i o n f l a s k was t h e n e x t r a c t e d w i t h 3 x 10 mL p o r t i o n s o f 4:1 h e x a n e s '.Et^O and t h i s t r a n s f e r r e d by c a n n u l a t o t h e t o p o f t h e c o l u m n . The column was t h e n s l o w l y e l u t e d w i t h a 4:1 h e x a n e s : E t 2 0 m i x t u r e c a u s i n g t h e d e v e l o p m e n t o f a b r o a d d a r k p u r p l e band and a s m a l l e r , r e d d i s h y e l l o w s e c o n d band. The two bands were c o l l e c t e d s e p a r a t e l y w i t h t h e s e c o n d band b e i n g e l u t e d o f f t h e column u s i n g p u r e E t 2 0 . The volume o f t h e s o l u t i o n c o n t a i n i n g t h e f i r s t band was r e d u c e d under vacuum t o ~15 mL and s t o r a g e o v e r n i g h t a t - 2 5 ° C i n d u c e d t h e c r y s t a l l i z a t i o n o f C p * W ( N 0 ) ( C H 2 S i M e 3 ) 2 - The mother l i q u o r was t h e n removed f r o m t h i s c r y s t a l l i n e m a t e r i a l a t - 2 5 ° C by c a n n u l a t i o n a n d t h e c r y s t a l s washed w i t h 5 mL c o l d h e x a nes t o g i v e 5.62 g o f p r o d u c t a f t e r d r y i n g (0.05 mm Hg, 2 h ) . R e d u c i n g t h e volume o f t h e c o m b i n e d mother l i q u o r and w a s h i n g s t o ~2 mL a n d s t o r a g e a t - 2 5 ° C o v e r n i g h t i n d u c e d f u r t h e r c r y s t a l l i z a t i o n . T h e s e c r y s t a l s were i s o l a t e d by c a n n u l a removal o f t h e mother l i q u o r a t - 2 5 ° C and w a s h i n g o n c e w i t h ~2 mL c o l d h e x a nes a n d d r y i n g t o g i v e a f u r t h e r 1.20 g o f p r o d u c t f o r a t o t a l y i e l d o f 6.82 g (61.47. y i e l d ) o f d a r k p u r p l e , c r y s t a l l i n e C p * w ( N 0 ) ( C H 2 S i M e 3 ) 2 . The s o l u t i o n c o n t a i n i n g t h e s e c o n d band was t a k e n t o d r y n e s s u n d e r vacuum and t h e r e s i d u e r e c r y s t a l 1 i z e d f r o m h e x a n e s t o g i v e a s m a l l number o f c o l o u r l e s s c r y s t a l s i d e n t i f i e d by e l e m e n t a l a n a l y s i s and IR and NMR s p e c t r o s c o p i e s a s Cp*W(0)- (CH,Si M e . , ) . * 1 5 ) 131 P r e p a r a t i o n o f Cp*W ( N O ) ( H ) ( C h ^ S i M e 3 ) ( P M e 3 ) . C p * W ( N O ) ( C H 2 S i M e 3 ) (3.00 g, 5.7 mmol) was d i s s o l v e d i n h e x a nes (15 mL) i n a 100-mL 3-necked f l a s k and t h e n c a n n u l a t e d i n t o a 300 mL F i s h e r - P o r t e r v e s s e l t h a t had been e v a c u a t e d a n d f i l l e d t h r e e t i m e s w i t h H 2 . The 100-mL f l a s k was r i n s e d w i t h h e x a n e s (5 mL) and t h e r i n s i n g s c a n n u l a t e d i n t o t h e F i s h e r - P o r t e r v e s s e l . P M e 3 (~3 mL, ~30 mmol) was t h e n s y r i n g e d i n t o t h e v e s s e l a n d 80 p s i g a d d e d . The c o n t e n t s o f t h e p r e s s u r e v e s s e l were s t i r r e d f o r ~3 h a s t h e c o l o u r c h a n g e d f r o m d a r k p u r p l e t o r e d - brown and a r e d - b r o w n powder p r e c i p i t a t e d . The p r e s s u r e was t h e n c a r e f u l l y r e l i e v e d and t h e s u s p e n s i o n c a n n u l a t e d u n d e r N 2 i n t o a S c h l e n k t u b e , f o l l o w i n g w h i c h t h e F i s h e i — P o r t e r v e s s e l was washed w i t h 2 x 10 mL h e x a n e s and t h e w a s h i n g s a d d e d t o t h e s u s p e n s i o n . The s o l v e n t volume i n t h e s u s p e n s i o n was t h e n r e d u c e d t o ~10 mL u n d e r r e d u c e d p r e s s u r e and t h e mother l i q u o r d i s c a r d e d by c a n n u l a . R e c r y s t a 1 1 i z a t i o n o f t h e r e s u l t i n g s o l i d f r o m C H 2 C 1 2 / h e x a n e s gave 1.35 g o f d a r k c o l o u r e d we 11-formed s i n g l e c r y s t a l s o f Cp*W(NO)(H)(CH 2 s i Me^)(PMe^) w h i c h a f u r t h e r c r y s t a l l i z a t i o n f r o m C H 2 C 1 2 / h e x a n e s l i g h t e n e d t o b r i g h t y e l l o w . The d a r k r e d - b r o w n mother l i q u o r f r o m t h e f i r s t r e c r y s t a 1 1 i z a t i o n was d r i e d u n d e r vacuum, t a k e n up i n . a n a p p r o x i m a t e l y 6:1 h e x a n e s : C H 2 C l 2 m i x t u r e a n d p u t on a 10 x 2 cm A l u m i n a V column made up i n h e x a n e s . E l u t i o n f i r s t w i t h h e x a n e s c a u s e d t h e d e v e l o p m e n t o f a s m a l l d a r k r e d - b r o w n band w h i c h was d i s c a r d e d . S u b s e q u e n t e l u t i o n w i t h a 6:1 h e x a n e s ^ H ^ C l , m i x t u r e gave a 132 s e c o n d band w h i c h was c o l l e c t e d and f r o m w h i c h c o u l d be c r y s t a l l i z e d a f u r t h e r 0.24 g o f y e l l o w , m i c r o c r y s t a 1 1 i n e C p * W ( N 0 ) ( H ) ( C H 2 S i M e 3 ) ( P M e 3 ) f o r a t o t a l y i e l d o f 1.59 g ( 5 4 . 0 % ) . P r e p a r a t i o n o f C p * W ( N O ) ( P M e 3 ) 2 . T h i s compound was p r e p a r e d v i a t h e Na/Hg r e d u c t i o n o f C p*W(NO)I 2 i n t h e p r e s e n c e o f an e x c e s s o f PMe 3 by t h e method o f H u n t e r and L e g z d i n s * 1 6 * i n 32% y i e l d a s a b r i g h t o r a n g e , v e r y a i r - s e n s i t i v e , m i c r o c r y s t a 1 1 i n e s o l i d . T h e r m o l y s i s o f C p * W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e 3 ) i n CgHg. C p * W ( N 0 ) ( H ) ( C H 2 S i M e 3 ) ( P M e 3 ) (0.10 g) was p l a c e d i n a S c h l e n k t u b e i n a g l o v e box and t h e t u b e c l o s e d w i t h a new S u b a - S e a l septum. Benzene (15 mL) was t h e n a d d e d v i a s y r i n g e t h r o u g h t h e septum and t h e S c h l e n k t u b e p u t i n a 40°C warm w a t e r b a t h o v e r n i g h t , r e s u l t i n g i n v e r y l i t t l e c o l o u r c h a n g e . A f t e r t h e b e n z e n e s o l v e n t was removed u n d e r vacuum, t h e o i l y r e s i d u e was r e c r y s t a l 1 i z e d f r o m C H 2 C 1 2 / h e x a n e s t o y i e l d a s m a l l amount o f r e d - b r o w n m i c r o c r y s t a 1 1 i n e C p * W ( N 0 ) ( H ) ( C ^ H g ) ( P M e 3 ) . O x i d a t i o n o f Cp*W(NO)(H)(CH 2 s i M e 3 ) ( P M e 3 ) w i t h AgBF^. A few c r y s t a l s o f C p * W ( N 0 ) ( H ) ( C H 2 S i M e 3 ) ( P M e 3 ) were d i s s o l v e d i n C f e o 6 (~2 mL) i n a s m a l l S c h l e n k t u b e and a s p a t u l a t i p f u l l o f f i n e l y d i v i d e d AgBF^ a d d e d . A s i l v e r m i r r o r i m m e d i a t e l y a p p e a r e d and t h e s o l u t i o n t u r n e d f r o m o r a n g e t o o r a n g e - r e d . The v o l a t i l e 133 m a t e r i a l was t r a p - t o - t r a p d i s t i l l e d o f f , a n a l y z e d by GC, GC-MS and 'H NMR s p e c t r o s c o p y and f o u n d t o c o n t a i n p r i n c i p a l l y (CHgj^s i a s t h e r e a c t i o n p r o d u c t . P r e p a r a t i o n s o f [ C p * w ( N O ) H ] 2 ( y - H ) 2 a n d [ C p » W ( N O ) H ] ( u - H ) 2 [ C p * W ( N O ) ( C H 2 S i M e 3 ) ] . In a g l o v e box, C p * W ( N O ) ( C H 2 S i M e 3 ) 2 (2.00 g, 3.82 mmol) was l o a d e d i n t o a 300 mL P a r r m i n i - r e a c t o r and h e x a n e s (10 mL) was a d d e d . The r e a c t o r was c l o s e d i n t h e g l o v e box and t h e n p r o p e r l y t i g h t e n e d up on t h e b e n c h . H y d r o g e n (920 p s i g ) was i n t r o d u c e d i n t o t h e r e a c t o r a n d t h e c o n t e n t s s t i r r e d f o r 20 min. The p r e s s u r e was t h e n r e l i e v e d , t h e r e a c t o r o p e n e d i n a i r and t h e c o n t e n t s q u i c k l y p o u r e d i n t o a n i t r o g e n - c o n t a i n i n g S c h l e n k t u b e . The r e a c t o r was r i n s e d w i t h C H 2 C 1 2 (10 mL) and t h e r i n s i n g s a d d e d t o t h e o t h e r m a t e r i a l . The r e s u l t i n g s o l u t i o n was t a k e n t o d r y n e s s u n d e r vacuum l e a v i n g a r e d-brown g l a s s . A d d i t i o n o f ~10 mL o f hexanes f o l l o w e d by v i g o u r o u s t r i t u r a t i o n w i t h a metal s p a t u l a gave an o r a n g e - b r o w n m i c r o c r y s t a I 1 i n e powder b e n e a t h a d a r k r e d - b r o w n s o l u t i o n . The s o l u t i o n was c a n n u l a t e d away and t h e powder d r i e d u n d e r vacuum. R e c r y s t a 1 1 i z a t i o n o f t h i s powder f r o m t o l u e n e - h e x a n e s a t - 2 5 ° C g a v e a s m a l l amount o f a n a l y t i c a l l y p u r e o r a n g e m i c r o c r y s t a 1 1 i n e [Cp*W(NO)H] ( y - H ) 2 . Two f u r t h e r r e c r y s t a 1 1 i z a t i o n s o f t h e mother l i q u o r f r o m t h e f i r s t r e c r y s t a 1 1 i z a t i o n a l l o w e d t h e i s o l a t i o n o f a s m a l l amount o f a n a l y t i c a l l y p u r e r e d c r y s t a l l i n e 134 [ C p « W ( N O ) H ] ( u - H ) 2 [ C p * W ( N O ) ( C H 2 S i M e 3 ) ] . S m a l l , " h a l f - m o o n " s h a p e d s i n g l e c r y s t a l s o f t h i s l a t t e r compound were grown f r o m a C e l i t e - f i l t e r e d CD.,NO„ s o l u t i o n a t - 2 5 ° C . 135 Table 4-1. Analytical, Infrared and Nass Spectral Data for the Complexes analytical data C H N Coiplex calcd found calcd found calcd found CpH(N0)(H)(CH2Sir1e3)[P(0Ph)3] 47.87 48.00 4.76 4.84 2.07 2.12 CpK(MO)(H)(CHzSihe3)(PllePh2l 46.57 46.52 5.33 5.33 2.47 2.51 CpW(NO)(H)[P(OPh)2(OC6H4)] 46.88 46.90 3.42 3.40 2.38 2.52 Cp f V (M»l 19.92 19.86 2.51 2.44 2.32 2.40 Cp,M(NO)(CH2SiHe3)2 41.30 41.03 7.12 7.30 2.66 2.67 Cp*«(0) 2(CH 2SiNe 3) 38.37 38.20 5.98 5.99 0.00 0.00 Cp'K(NO)(H)(CH2SiHe3)(PHe3) 39.77 39.82 7.07 6.96 2.73 2.59 Cp'y(HO)(Prle3)2 38.34 37.99 6.64 6.48 2.79 2.60 [Cp*K(N0)H] 2(»-H) 2 34.21 33.90 4.88 4.89 3.99 4.04 [Cp'K(HO)H](y-H)2(Cp,ll{HO)(CH2Sir1e3)] 36.56 36.83 5.62 5.56 3.55 3.50 136 Table 4-1 (Cont'd) IR data low resolution aass spectrin Coiplex phase v M 0 ( c . - ' ) v„ H(c.-') •/z probe te«p as s i g ' t Cp«{HO)(H)(CH 2SiHe 3)(P(OPh) 3] Nu jo I 1579 1837 CH 2CI 2 1601 1836 Cp«(NO)(H)(CH 2SiHe 3)(PHePh 2) Nujol 1553 1838 479 80 (P-CH 2SiHe 3! (P- H e 4 S i ) + CH 2CI 2 1560 1865 CpW(NO)(H)[P(OPh) 2(OC 6H 4)] Nujol 1611 1856 589 100 (P) +,(P-H) + CH 2CI 2 1626 1850 Cp*«(N0)l 2 Nujol 1627 952 120 ( 2 P - I 2 ) + CH 2CI 2 1629 Cp'H(HO)(CH 2SiNe 3) 2 Nujol ( s o l i d ) 9 1549 523 120 ( P ) + Nujol (sol") 1572 CH 2CI 2 1543 Cp*K(N0)(H)(CH 2SiHe 3)(PHe 3) Nujol 1547 1852 b CH 2CI 2 1545 1850 Cp«H(N0)(H)(C 6H 5)(PHe 3) Nujol 1551 1813 425 150 ( P - W + CH 2CI 2 C 1560 or 1550 1807 Cp'K(H0)(P(le 3) 2 Nujol 1514, 1505 CH 2CI 2 1498 137 T a b l e 4-1 (Cont'd) [CP' IKNOIHJ. IB-H) [Cp«y(HO)H] (n-HJ^Cp'KIHO) ( C H 2 S i H e 3 ) } N u j o l I 5 7 5 ( s ) , I 5 3 3 N ) 1898 C H Z C I Z t 5 6 6 ( s ) , I533(sh) 1902 N u j o l I 5 7 4 ( s h ) , I 5 5 9 ( s ) 1910 C H . C L 1557 1921 a C p ' K ( N O ) C H 2 S i H e 3 ) 2 p a r t i a l l y d i s s o l v e s i n N u j o l upon l u l l i n g . b See t e x t f o r a d i s c u s s i o n o f t h i s HSS s p e c t r i n . c The v i s o v e r l a p p e d by a r o a a t i c r i n g v i b r a t i o n bands. 138 Table 4-11. HHP Data f o r the Complexes Coaplex nucleus a s s g ' t i ( J , Hz) C p « ( « 0 ) ( H ) ( C H S i « e 3 ) [ P ( 0 P h ) 3 ] H CpM(NO)(H)(CH2SiRe3)(PHePh2) H Cp 4 . 6 5 ( s , 5) P ( 0 P h ) 3 6 . 7 - 7 . 3 (• , 15) S l'5£ 3 0.56 ( s , 9) K C ^ B 0.07 (ddd, 1, 2 J H ( A ) H ( B ) 3 2 J s 9 . 6 , 4 J a H(A)P ° ' H|A)K ""A 0.87 (ddd, 1, \ m m 2 J * 7) H ( B ) « ' 1 3 C { ' H ) K - H , - 2 . 4 9 (ddd, 1, 2 J H ( l ( ) p = ipso PhC 152.03 ( d , 2 J c p = 8 . 9 ) ortho PhC 129.80 (s) • e t a PhC 122.29 ( d , 4 J c p = 4 . 5 ) para PhC 125.06 (s) Cp 96.42 ( d , 2 J c p = 2.1) S i H e 3 3.49 (s) « C H 2 S i - 1 4 . 8 8 {d, 3 J c p = 1 9 . 5 , 3 , P { ' H ) 127.42 ( s , ' j p | ) r 353) ' H CP 5.02 ( s , 5) PHePJ^ 7-7 .6 (• , 10) PhePh2 1.70 ( d , 3 , 2 J H p = 8 . 0 ) s l 3 , 2 , J H ( A ) H ( « ) 1 3 \ 2 , 8) . 3 , 3 J H ( B ) p = 3 0 . 8 , "H(U)M = 47) CM 139 Table 4-1i (Cont'd) SiHe 3 0.37 (s, 9) »Ctt AH B -0.24 (ddd, 1. 2 J H ( A ) ( | ( B ) = 13.5, \ h ) m - 2. 3 2 JH{A)P "- 7' 5 , JH(A)« * 5 ) H C H A « 6 - " • L 5 ( D D D ' L ' 3 J H | B ) H ( H ) = 7 ' 5 ' 3 J H ( B ) P = 2 4 ' 5 ' H-H^ -0.47 (ddd, I, 2 J H ( „ ) p = 89.5, * J H ( M ) H = <8-5) I 3 C { ' H ) ipso PhC, 139.50 (d, ' j ^ = 45) ipso PhC 2 137.79 (d, 'j c p = 46) ortho PhC, 133.36 (d, 2 J c p = II) ortho PhC 2 131.87 (d, 2 J C p = 10) •eta PhC, 128.48 (d, 3 J C p = 10) •eta PhC £ 128.31 (d, 3 J C p = 9) para PhC, 130.14 (d, 4 J c p = 2) para PhC 2 129.52 (d, 4 J C p = I) Cp 95.68 (d, 2 J c p = 2) PHePh 16.16 (d, 'acp = 29) SiMe 3 3.69 (s) HCH 2Si -8.97 (d, 2 J c p = 13, ' j ^ = 66) ^Pl'H} 7.49 (s, l J H = 202) 1 4 0 Table 4-11 (Cont'd) CpH(N0)(H)[P(0Ph) 2(0C 6H 4)] H P(0Ph)(0C 6H 4) 6.7-7.5 (a, 14) Cp 4.78 (d, 5, 3 J H p * 0.6) K-H^ -1.85 (d, 1, Z J H p = 100.3, 'j H | ( = 54.7) 3Vn) 176 (s, 'j p i ( = 345) Cp*M(N0)l 2 lH CjBe^ 1.62 (s) I 3 C { ' H ) C,l1e, 116.92 (s) C ^ 12.36 (s) Cp'H(NO ) ( C H 2Sille 3) 2 * H CjHej 1.51 (s, 15) SiHe 3 0.36 (s, 18) "VB • ' - 5 4 l°< 2 J H ( A ) H . B ) - , 0 ' 9 ) B I 3 C ( ' H) C Cjdej 110.16 (s) CjBej 9.83 (s, 'J C h * 128) SiBe 3 2.83 (s, ' j ^ = 118, ' j ^ , = 51) •£H Si 62.70 (s, ' j = 120,116, ' j ^ = l j C 5 i = 4 6 ) 141 Table 4-II (Cont'd) Cp««(0) 2(CH 2Sihe 3) I 3 C ( ' H J C ^ KCH 2Si ^ e 5 Sf He 3 1.67 (s, 15) 0.38 (s, 9, Z J H S j = 6.4) 0.42 (s, 2, Z J H | J = 10.7) 116.50 (s) 10.36 (s) 0.80 (s, ' J C 5 J = 32) HCH2Si 24.39 (s, ' J c y = 135) Cp»«(NO)(H)(CH,SiHe,)(PHeJ *H C ^ 1.77 (s, 15) PHe 3 1.09 (d, 9, 2 J H p . S'$£ 3 0.48 (s, 9) Kh\ -0.97 (ddd, 1, 2 J ( 3 jH(A)P = l 6 - 7 , Z' -0.68 (ddd, 1, ^ 2 jH(B)« = 8- U -1.25 (ddd, 1, 2J{ M e 5 105.02 (d, 2 J c p = CjHej 10.79 (s) P«e 3 18.90 (d, ' J c p » : Si«e 3 4.02 Is, ' J c s , = 'H(A)H(B) 1 l 3 , 4 , 3 jH(A)H(«) = ' H M ) H = 7 , 8 ) H(B)H(W) = 6" 7 , JH(B)P = 2 4 , 9 H ( U )P = 8 7 - 9 , l j H m n = 5 6 ' 6 ) , 3 C { ' H ) M , .   ' J R O = 2 ) 49) 142 «CH 2Si -5.73 (d, 2 J C p = 14, ' J C | ( = 40) 3 1 P { ' H ) -28.74 (s, ' j p i | = 195) Cp*H(NO)(H)(C 6H 5)(PHe 3) *H 1.62 (s, 15) PKe 3 1.15 (d, 9, Z J H p = 9.3) CgHj 7.1-8.0 (a, 5) K-Hy 5.15 (d, 1, 2 J H p = 97.0, ' j ^ 79) 3 1 P{'H} -3.14 (s, ' j p i ( = 201) Cp'«(NO)(PHe 3) 2 'H CjKej 1.91 (s, 15) Pflt 3 1.34 ( i d , 9, 2 J H p = 7.55, 4 J H p , 0.05, 2 J p p , = -9.6, |N| = 7.6 Hz) 3 I P { ' H ) -22.56 (s, ' j p i | = 454) OPHe 3 e !H 0.88 (d, 2 J H p = 12.8) I 3 C{ 'H) 17.85 (d, ' J C P = 68.6) 3 1 P{ 'H) 33.52 (s) [Cp'H(NO)H] 2(|i-H) 2 f *H isoaer A: CjHej 2.03 (s, 15) H-H x-« -0.05 (•, 2) 143 Table 4-1! (Cont'd) isoaer B : H in C02C12 C 5 % H - H X - H i S M e r A: C 5 ^ 5 2.03 (s, 15) 7.41 (a, 2) 4.56 (a, 1) 9 2.22 (s, 15) 2 2 7.44 (a, 2, J H { A ) ( ) ( X ) = 5.5, J „ ( A ) H ( X . , « 8.0, JH(A)H(A') = , ' 0 , J H ( X ) H = 9 2 , J H ( X ) « 1 1 5 1 -0.33 (a, 2, \ X ) H ( r ) - l . 5 . mi\llw* f 1, [CpfH(MO)H](ii-H) [Cp fM(NO)(CH 2SIHe 3)] H J H ( X ' ) H ' = 9 3 ) isoaer B : C 5 ^ 5 2.22 (s, 15) 6.89 (dd, 2, 2 J ( l jH(A)« 1 9 6 ) n 4.11 (td, 1, 1 J, y-H x-« -4.84 (td, 1) S ^ I A ) 1.79 (s, 15) ^ ( B ) 2.04 (s, 15) 0.46 (s, 9) 7.21 (dd, 1) H(A)H(N) S 5 * 0 , J H ( A ) H ( X ) = 8 • 4 , : 2.3, ' j * 90) h H ( H ) H ( X ) ' H(H)W ' 144 Table 4-11 (Cont'd) 13C('H} in C D 3 N 0 2 5.61 (dd, 1) KCH^HgSi 0.01 (d, 1) K C H ^ S i -1.24 (dd, 1) y-H.-y -6.43 ( d i , 1) S^IA) 1.93 (s, 15) S^IB) 2.14 (s, 15) S i 5 i 3 -0.06 (s, 9, 2<i{ y-Hg 6.57 (dd, 1, 2J{ y - i ^ - y yct^HgSi KHJJjSI y-H.-y CJJ., C ^ C5**5 % Si He, WCH2Si HSi " 'HtA)H(E) 9* 0 , 2 jH(D)H(E) = 5 - ° * , JH(E)y(B) = ,"'0' 2 j H ( E ) y ( A ) = "- 5 ) 5.30 (dd, 1, ' J H ( A ) H ( 0 ) = 2.5, * < > m m « 93.5, l jH(0)y(B) = 8 4• 0 , -0.13 (d, I, 2 J H ( B ) H ( C ) = 12.5, 2 J H ( C ) y ( A ) = 6 , 5 ) -1.39 (dd, 1, 3 J H { A ) H ( B ) « 3.0, \ m [ k ) ' - • 7.5) -6.36 (d., 1, ' J H ( A ) M ( A ) - 78.5, \ ( k ) m - 83.5) 112.63 (s) 110.62 (s) 11.28 (s) 10.60 (s) 2.79 (s) 31.74 (s) 145 Table 4-11 (Cont'd) a A l l NOR data recorded in C f c0 f c unless otherwise noted. 183 b * s a t e l l i t e s obscured by overlap of Cp* resonance. c ' j [ H data froa the gated decoupled spectrua. d Proton phosphine resonances fora an XJiAX'g pattern; |N| is the separation of the two aost intense p e a k s . " 6 ' e OPHe^ was prepared by the aethod of Steube and co-workers. f See text for a discussion of t h i s species. g S/N r a t i o not high enough to f i n d t h i s resonance. 2 h J u u not resolved. 146 R e s u 1 t s and D i s c u s s i o n H y d r o g e n a t i o n a t r e l a t i v e l y low p r e s s u r e s (60-80 p s i g ) o f CpW(NO)(CH^SiMe 3)2 w i t h no L e w i s b a s e p r e s e n t , w h e t h e r done on a p r e p a r a t i v e s c a l e o r NMR t u b e s c a l e , does n o t r e s u l t i n [CpW(NO)H] 2(y-H)2 o r o t h e r r e a d i l y i d e n t i f i a b l e n o v e l p r o d u c t , b u t o n l y i n t h e f o r m a t i o n o f an i n t r a c t a b l e t a n m a t e r i a l . S u r p r i s i n g l y enough, t h e o n l y compound e v e r i s o l a t e d f r o m t h i s (2) r e a c t i o n was a v e r y low y i e l d o f C p W ( O ) 2 ( C H 2 S i M e 3 ) , ' w i t h t h e oxo l i g a n d s p r e s u m a b l y coming e i t h e r f r o m t h e NO 1 i g a n d o f t h e s t a r t i n g m a t e r i a l o r f r o m some a d v e n t i t i o u s 0 2 . ^ 1 8 ^ A. C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) L ( L = P ( O P h ) 3 , PMePh^) H y d r o g e n o l y s i s o f C p W ( N O ) ( C H 2 S i M e 3 ) 2 a t -60 p s i g i n t h e p r e s e n c e o f one e q u i v a l e n t o f a b u l k y L e w i s b a s e , L, r e s u l t s i n t h e i s o l a t i o n o f modest y i e l d s o f C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) L ( e q . 4-3 s t e p c , Scheme 4 - 1 ) . h e x a n e s , RT CpW(NO) ( C H 2 S i M e 3 ) 2 + L — - CpW( NO) (H) ( C H 2 S i Me 3 )L (4- 3 h, 60 p s i g H 2 -TMS T h e s e a r e b r i g h t y e l l o w , c r y s t a l l i n e s o l i d s t h a t a r e ( f o r L= PMePh 2) s t a b l e i n a i r a t 0°C and un d e r N 2 a t 20 ° C f o r a t l e a s t s i x months ( t h e complex w i t h L = P ( 0 P h ) 3 v e r y s l o w l y u n d e r g o e s a t h e r m a l d e c o m p o s i t i o n — s e e s e c t i o n B ) . They a r e o n l y s l i g h t l y 147 Scheme 4-1 Cp'M(NO)1 RMgX [C p ' M ( N O ) R 2 ] 2 . M g X 2 Cp'=Cp o r Cp» R=CH_Si Me-, H 2 0 Cp'M(NO)R, H 2 ( 6 0 - 8 0 p s i g ) L / c C p ' M ( N O ) ( H ) ( R ) L H 2 (~900psig) cT [ C p ' M ( N O ) H ] 2 ( p - H ) 2 + [ C p ' M ( N O ) H ] ( w - H ) 2 [ C p ' M ( N O ) ( C H 2 S i M e 3 ] s o l u b l e i n h e x a n e s a n d E t 2 0 , b u t q u i t e s o l u b l e i n more p o l a r o r g a n i c s o l v e n t s t o f o r m somewhat a i r - s e n s i t i v e s o l u t i o n s . The IR s p e c t r a o f t h e s e compounds ( T a b l e 4-1) show s t r o n g , low f r e q u e n c y n i t r o s y l s t r e t c h i n g bands (1550-1600 c m - 1 ) i n d i c a t i v e o f l i n e a r NO g r o u p s a n d s u g g e s t i v e o f c o n s i d e r a b l e amounts o f (19) W-»N0 b a c k - d o n a t i o n . Much weaker, t e r m i n a l W-H s t r e t c h i n g b ands (1836-1865 cm ') a r e a l s o v i s i b l e . A d d i t i o n a l l y , i n N u j o l mul1 s p e c t r a , two medium s t r e n g t h bands a t ~1240 a n d ~1250 c m - 1 a r e o b s e r v e d w h i c h a r e c h a r a c t e r i s t i c o f t h e C H 2 S i M e 3 1 i g a n d . * 2 0 ^ The e l e c t r o n - I m p a c t mass s p e c t r u m o f C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e P h 2 ) u n f o r t u n a t e l y d o e s n o t show a n y p e a k s due t o a p a r e n t i o n , b u t r a t h e r a h i g h e s t - m a s s p a t t e r n w i t h i t s most i n t e n s e peak a t m/z = 479, w h i c h i s an o v e r l a p o f t h e p a t t e r n s e x p e c t e d f o r ( P - C H 2 s i M e 3 ) + a n d ( P - M e 4 S i ) + . 148 The H NMR s p e c t r a o f t h e s e compounds a r e p a r t i c u l a r l y i n f o r m a t i v e . In a d d i t i o n t o t h e e x p e c t e d p e a k s f o r t h e Cp, L and Si M e ^ p r o t o n s , an i n t e r e s t i n g p a t t e r n i s o b s e r v e d f o r t h e W-CH_2 a n d m e t a 1 - h y d r i d e p e a k s — t h i s r e g i o n i s shown i n F i g . 4-1 f o r L=PMePh 2. The most s t r i k i n g f e a t u r e i s t h e s i m i l a r i t y o f t h e c h e m i c a l s h i f t s f o r t h e m e t h y l e n e and h y d r i d e p r o t o n s . F o r t u n a t e l y , a t 400-MHz, t h e r e s o n a n c e s a r e s u f f i c i e n t l y r e s o l v e d t o f o r m an e f f e c t i v e l y f i r s t - o r d e r s p e c t r u m . C o u p l i n g i s o b s e r v e d between t h e two i n e q u i v a l e n t m e t h y l e n e p r o t o n s , t h e h y d r i d e p r o t o n , t h e 3 1 P n u c l e u s o f L, and 1 8 3W, g i v i n g t h e o b s e r v e d s u p e r p o s i t i o n o f a 2 4 - 1 i n e p a t t e r n on a 4 8 - 1 i n e p a t t e r n . A l l t h e c o u p l i n g c o n s t a n t s ( T a b l e 4-1 I) c a n t h e r e f o r e be c a l c u l a t e d i n a s t r a i g h t f o r w a r d manner. As may be s e e n , t h e m e t h y l e n e p r o t o n s (H^ a n d Hg) e a c h e x h i b i t m a r k e d l y d i f f e r e n t c o u p l i n g t o t h e h y d r i d e p r o t o n (H w> and t h e p h o s p h o r u s - 3 1 n u c l e u s . T h i s b e h a v i o u r f o r v i c i n a l c o u p l i n g (H-C-W-H and H-C-w- P) Is r e m i n i s c e n t o f t h a t o b s e r v e d f o r o r g a n i c e t h a n e (H-C-C-H) f r a g m e n t s w h i c h a r e u n d e r s t o o d i n t e r m s o f t h e w e l l - k n o w n K a r p l u s (74) e q u a t i o n . ' A l t h o u g h i t i s u n l i k e l y t h a t t h e t r u e K a r p l u s e q u a t i o n h o l d s a c r o s s t h e H-C-W-H s y s t e m (an d , o f c o u r s e , i t c a n n o t a c r o s s t h e H-C-W-P f r a g m e n t ) , t h e p r i n c i p l e o f a l a r g e r 3 J f o r a s m a l l d i h e d r a l a n g l e i s w e l l - e s t a b l i s h e d a nd i t i s p o s s i b l e t h a t a " K a r p l u s - 1 i k e " r e l a t i o n may h o l d f o r o r g a n o m e t a 1 1 i c s y s t e m s . On t h i s b a s i s , a r e a s o n a b l e i d e a o f t h e r e l a t i v e o r i e n t a t i o n s o f H^, Hg, H^ a n d P may be o b t a i n e d a nd a Newman 149 -0.'25 -0.50 b(ppm) Cp Ph,MeP SiMe-3 WHg NO F i g . 4-1. A s e c t i o n o f t h e 400-MHz H NMR s p e c t r u m o f C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e P h 2 ) i n C 6 D 6 s h o w i n g t h e r e s o n a n c e s due t o t h e h y d r i d e a n d Q-C p r o t o n s , a l o n g w i t h a Newman p r o j e c t i o n down t h e a-C-W a x i s s h o w i n g t h e p o s s i b l e o r i e n t a t i o n o f t h e l i g a n d s b a s e d on t h e o b s e r v e d c o u p l i n g c o n s t a n t s . 150 p r o j e c t i o n down t h e C-W bond s h o w i n g t h i s i s a l s o g i v e n i n F i g . 4-1 . The most o b v i o u s p r o b a b l e m o l e c u l a r s t r u c t u r e s f o r C p W ( N O ) ( H ) ( C H ^ S i M e 3 ) L a r e c o n v e n t i o n a l , f o u r - l e g g e d p i a n o - s t o o l s . The l a r g e two bond c o u p l i n g between t h e h y d r i d e a n d p h o s p h o r u s n u c l e i ( J = 90-117 Hz) i s i n d i c a t i v e o f a c i s o r i e n t a t i o n o f t h e H a n d L l i g a n d s i n t h e b a s e o f t h e p i a n o - s t o o l ( s e e c h a p t e r 2 ) . However, n e i t h e r t h e NMR s p e c t r a n o r a n y o t h e r s p e c t r o s c o p i c t e c h n i q u e i n d i c a t e s w h e t h e r t h e H a n d CH^SiMe^ l i g a n d s a r e m u t u a l l y c i s o r t r a n s . Our e x p e c t a t i o n i s t h a t t h e y s h o u l d be t r a n s on t h e b a s i s t h a t t h e e l e c t r o n - w i t h d r a w i n g NO a n d e l e c t r o n - d o n a t i n g L l i g a n d s s h o u l d be t r a n s . T h e r e f o r e , s i n g l e c r y s t a l s o f C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e P h 2 ) s u i t a b l e f o r X - r a y a n a l y s i s were grown and t h e s t r u c t u r a l a n a l y s i s was p e r f o r m e d by R.H. J o n e s and F.W.B. E i n s t e i n o f Simon E r a s e r U n i v e r s i t y . ( A l l t h e X - r a y a n a l y s e s d i s c u s s e d i n t h i s c h a p t e r were p e r f o r m e d by J o n e s an d E i n s t e i n a n d t h e d e t a i l s o f t h e d a t a c o l l e c t i o n a n d r e f i n e m e n t w i l l be r e p o r t e d e l s e w h e r e . ) Two v i e w s o f t h e s o l i d - s t a t e m o l e c u l a r s t r u c t u r e o f C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e P h 2 ) a r e shown i n F i g . 4-2 a n d s e l e c t e d bond a n g l e s a n d bond l e n g t h s a r e g i v e n i n T a b l e 4-1 I I. As may be s e e n , t h i s c omplex d o e s a d o p t a c o n v e n t i o n a l p i a n o - s t o o l s t r u c t u r e . The g e o m e t r y o f t h e WNO l i n k a g e i s s i m i l a r t o t h a t o f [ C p W ( N O ) H ] 2 ( y - H ) 2 ( c h a p t e r 3 ) , a g a i n i n d i c a t i n g c o n s i d e r a b l e W-»N0 (19) b a c k b o n d i n g . The W-N-O a n g l e i s c l o s e t o l i n e a r , a l t h o u g h 151 s l i g h t l y more b e n t h e r e t h a n i n t h e d i h y d r i d e d i m e r ( 1 7 0 . 4 ( 9 ) ° v s . 1 7 4 . 3 ( 1 0 ) ° ) . The m o l e c u l e i s a l s o q u i t e c rowded, a s i s T a b l e 4-1 I 1 I m p o r t a n t I n t e r a t o m i c D i s t a n c e s (A ) a n d A n g l e s (deg) f o r C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e P h 2 ) W-N W-C(6) W-P W-N-0 N-W-P N-W-CP C(6)-W-CP 1.781(8) 2.246(11) 2.492(3) 170.4(9) 103.3(3) 123.8 110.6 N-0 W-CP N-W-C(6) C(6)-W-P P-W-CP W-C(6 ) - S i 1.213(11) 2.023 94.7(9) 79.7(5) 129.5 123.2(5) r e f l e c t e d i n t h e W-C( 6 ) - S i a n g l e o f 123.2(5) w h i c h i s a marked d e p a r t u r e f r o m t h e e x p e c t e d t e t r a h e d r a l a n g l e o f 1 0 9 . 6 ° . U n f o r t u n a t e l y , t h e h y d r i d e 1 i g a n d c o u l d n o t be l o c a t e d f r o m t h e X - r a y a n a l y s i s . However, i f a f o u r - l e g g e d p i a n o - s t o o l s t r u c t u r e i s assumed, t h e n t h e r e a p p e a r s t o be a " h o l e " i n t h e m e t a l s c o o r d i n a t i o n s p h e r e where t h e h y d r i d e may be l o c a t e d . The m o l e c u l e has been o r i e n t e d i n F i g . 4-2b s o a s t o p l a c e t h i s h o l e t o t h e r i g h t o f t h e W atom ( c f . F i g . 4 - 1 2 ) . T h i s empty c o o r d i n a t i o n s i t e c a n be b e t t e r s e e n i n F i g . 4-3, w h i c h shows i t t o be t r a n s t o t h e C H 2 S i M e 3 1 i g a n d , t h u s s u p p o r t i n g o u r e x p e c t a t i o n . O f c o u r s e , t h e compound i s c h i r a l a n d t h e v i e w s shown i n F i g . 4-2 a n d 4-3 a r e o f o n l y one o f t h e e n a n t i o m e r s . The C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) L c o m p l e x e s a r e members o f t h e v e r y s m a l l c l a s s o f i s o l a b l e t r a n s i t i o n - m e t a l a l k y l h y d r i d e compounds and a r e t h e f i r s t h y d r i d o a l k y l n i t r o s y l compounds known f o r a ny 152 F i g . 4-2. SNOOP I d i a g r a m s of" t h e m o l e c u l a r s t r u c t u r e o f C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e P h 2 ) . a) View s h o w i n g t h e NO, C H 2 S i M e 3 a n d PMePh 2 l i g a n d s s p r e a d o u t . b) View s h o w i n g t h e h o l e where t h e h y d r i d e h y d r o g e n atom i s p r o b a b l y l o c a t e d t o t h e r i g h t ( c f . F i g . 4 - 1 2 ) . 153 F i g . 4-3. S t i c k d i a g r a m o f t h e s t r u c t u r e o f C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e P h 2 ) a s v i e w e d f r o m d i r e c t l y a b o v e t h e p l a n e o f t h e Cp r i n g s h o w i n g t h e h o l e where t h e h y d r i d e h y d r o g e n atom i s p r o b a b l y l o c a t e d t o t h e r i g h t o f t h e t u n g s t e n atom ( c f . F i g . 4 - 1 3 ) . m e t a l . The o n l y o t h e r t u n g s t e n a l k y l h y d r i d e c o m p l e x e s i n t h e l i t e r a t u r e a r e t h e t u n g s t e n o c e n e d e r i v a t i v e s , Cp 2W(R)H, whose c h e m i s t r y was e x t e n s i v e l y i n v e s t i g a t e d by G r e e n a n d c o - w o r k e r s i n t h e 1970's. S t r u c t u r a l l y , t h e most c l o s e l y r e l a t e d s p e c i e s a r e C p R e ( C O ) 2 ( H ) ( C H 2 C 6 H 5 ) , r e p o r t e d by F i s c h e r a n d F r a n k i n f 22) 1978, ' and CpRe(CO) ( H ) ( M e ) , m e n t i o n e d by Yang and Bergman i n 1 9 8 3 . ( 2 3 } O f t h e s e Re compounds, o n l y CpRe (CO) -(H) (CH^C^-Hc ) has 154 been c h a r a c t e r i z e d c r y s t a 1 1 o g r a p h i c a 1 1 y . As w i t h o u r W compound, t h e h y d r i d e H atom was n o t l o c a t e d i n t h e s t r u c t u r e , * 2 4 * however, t h e r e i s a " h o l e " i n t h e m e t a l s c o o r d i n a t i o n s p h e r e t r a n s ( a s s u m i n g a f o u r - l e g g e d , p i a n o - s t o o l g e o m e t r y ) t o t h e b e n z y l g r o u p and t h e complex i s t h e r e f o r e i s o s t r u c t u r a l t o t h e W one. T h i s Re compound i s much l e s s s t e r i c a l l y c rowded t h a n C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e P h 2 ) , a s i s e v i d e n c e d by t h e Re-C-C a n g l e ( a c r o s s t h e b e n z y l g r o u p ) b e i n g much l e s s d i s t o r t e d ( 1 1 4 . 8(8)°) away f r o m t h e t e t r a h e d r a l a n g l e . T h i s i s n o t s u r p r i s i n g s i n c e , i n t h e W compound, a r e l a t i v e l y b u l k y PMePh 2 g r o u p f o r m a l l y r e p l a c e s a CO 1 i g a n d on t h e Re. U n l i k e t h e W complex, u n i q u e ^JLJLJ c o u p l i n g i s n o t o b s e r v e d between t h e h y d r i d e n u c l e u s and t h e nn i n d i v i d u a l Q - c a r b o n p r o t o n s f o r e i t h e r Re compound. T h e r e f o r e t h e e x t r e m e c r o w d i n g i n CpW(NO)(H)(CH 2S i M e 3 ) ( P M e P h 2 ) and t h e "Karp1 u s - 1 i k e " c o u p l i n g s o b s e r v e d i n t h e *H s p e c t r u m s u g g e s t t h a t t h i s a l k y l h y d r i d e complex i s l e s s f l u x i o n a l i n s o l u t i o n t h a n t h e Re c o m p l e x e s and t h a t i t i s u n l i k e l y t h a t t h e r e i s s u b s t a n t i a l r o t a t i o n a b o u t t h e W-CH 2SiMe 3 bond. As a c l a s s , a l k y l and t h e r e l a t e d a c y l h y d r i d e compounds a r e v e r y i m p o r t a n t b e c a u s e t h e y a r e i m p l i c a t e d i n a number o f homogeneous, c a t a l y t i c r e a c t i o n s s u c h a s o l e f i n h y d r o g e n a t i o n and h y d r o f o r m y l a t i o n . v ' U s u a l l y , however, h y d r i d o a l k y l c o m p l e x e s a r e p r o n e t o u n d e r g o r e a d y r e d u c t i v e e l i m i n a t i o n , much more so (26) t h a n r e l a t e d d i a l k y l o r d i h y d r i d e compounds. B e c a u s e o f t h e p a u c i t y o f i s o l a b l e c o m p l e x e s o f t h i s c l a s s , l i t t l e i s known 155 / 27) a b o u t t h e i r c h e m i s t r y v ' and so f u r t h e r s t u d y o f t h e s e c o m p l e x e s i s o f c o n s i d e r a b l e i n t e r e s t . I t i s w o r t h w h i l e t o s p e c u l a t e a s t o why t h e s e C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) L compounds a r e so s t a b l e . T hermodynamica11y, a l k y l h y d r i d e s a r e g e n e r a l l y b e l i e v e d t o be u n s t a b l e w i t h r e s p e c t t o a l k a n e l o s s , i . e . M(R) (H) •* M + RH, ( 2 6 ) a l t h o u g h t h i s r e a c t i o n i s l e s s f a v o u r e d f o r t h i r d - r o w t r a n s i t i o n m e t a l compounds b e c a u s e o f t h e i r g r e a t e r M-C bond s t r e n g t h s t h a n (26) f o r f i r s t - and s e cond-row a n a l o g u e s . ' C o n s e q u e n t l y , i s o l a b l e c o m p l e x e s o f t h i s t y p e a r e c o n s i d e r e d t o be k i n e t i c a l l y s t a b l e f 27) f o r any o f s e v e r a l r e a s o n s . F i r s t l y , r e d u c t i v e e l i m i n a t i o n is n o t f a c i l e i f t h e a l k y l and h y d r i d e l i g a n d s a r e t r a n s , as< i n t r a n s - N i ( H ) ( M e ) [ P ( C 6 H j j ) 3 ] 2 ( C 6 H n = eye 1 o h e x y 1 ) ( 2 8 ) and t r a n s - P t ( H ) ( R ) ( P R 3 ' ) 2 . ( 2 9 , 3 0 ) R e l a t e d c i s compounds u n d e r g o r e d u c t i v e e l i m i n a t i o n r e a d i l y ; f o r example, c_i_s-Pt (H) (Me) ( P P h 3 ) 2 l o s e s methane i n t r a m o l e c u 1ar1y a t - 2 5 ° C . ^ 3 1 ^ S e c o n d l y , e l i m i n a t i o n may n o t o c c u r e v e n f r o m a c i s a l k y l h y d r i d e i f t h e complex i s s t e r e o c h e m i c a l l y r i g i d . F o r example, 6 - c o o r d i n a t e c o m p l e x e s s u c h a s c_Ls-Ir (H) ( C H 2 C ( 0 ) H ) ( P M e 3 ) 3 C l a r e s t a b l e even upon e x t e n d e d h e a t i n g a t 1 0 0 ° C . ^ 3 2 ^ The k i n e t i c s o f t h e r e d u c t i v e e l i m i n a t i o n f r o m t h e r e l a t e d Rh s p e c i e s showed e l i m i n a t i o n t o o n l y o c c u r a f t e r l o s s o f one o f t h e p h o s p h i n e l i g a n d s , f o r m i n g a n o n r i g i d 5- c o o r d i n a t e i n t e r m e d i a t e . T h i r d l y , i n t r a m o l e c u l a r e l i m i n a t i o n may n o t o c c u r i f t h e r e s u l t i n g m e t a 1 - c o n t a i n i n g p r o d u c t i s h i g h l y u n s t a b l e . N o r t o n an d c o - w o r k e r s h ave e x t e n s i v e l y s t u d i e d a l k a n e 156 l o s s f r o m c i s - Q s ( H ) ( R ) ( C 0 > 4 and shown t h a t i t goe s v i a an (33) i n t e r m o l e c u l a r pathway, t h u s n o t a l l o w i n g t h e f o r m a t i o n o f t h e u n s t a b l e O s ( C O ) 4 f r a g m e n t . In l i g h t o f t h e above r e s u l t s , t h e s t a b i l i t y o f t h e C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) L c o m p l e x e s c a n be c o n s i d e r e d . A l t h o u g h t h e a l k y l and h y d r i d e l i g a n d s a r e d e s c r i b e d a s t r a n s a c r o s s t h e b a s e o f a f o u r - l e g g e d p i a n o - s t o o l , t h e y a r e r e a l l y n o t t r a n s i n an o c t a h e d r a l s e n s e and t h e r e a r e c e r t a i n l y no i n t e r v e n i n g l i g a n d s between t h e two t o p r e v e n t e l i m i n a t i o n . T h e r e f o r e t h e Ni and P t t r a n s argument a b o v e does n o t h o l d h e r e . As has been n o t e d e a r l i e r , a r e a s o n a b l e c a s e may be made f o r t h e CpW(NO)(H)(CH^SiMe^)L compounds t o be n o n - f l u x i o n a 1 i n s o l u t i o n . In s p i t e o f t h e f a c t t h a t t h e y a r e f o r m a l l y 7 - c o o r d i n a t e , t h e s e an d t h e r e l a t e d CpW(NO)lHL c o m p l e x e s d i s c u s s e d i n c h a p t e r 2, u n l i k e t h e CpM (CO) 2l_H c o m p o u n d s , * 3 4 * do n o t i n t e r c o n v e r t between c i s a nd t r a n s i s o m e r s and a p p e a r t o p r e f e r t o e x i s t i n o n l y one f o r m . I t may w e l l be, t h e r e f o r e , t h i s r i g i d i t y t h a t s t a b i l i z e s t h e s e compounds enough t o make them i s o l a b l e . As f o r t h e t h i r d p o s s i b l e r e a s o n f o r k i n e t i c s t a b i l i t y , a t t h i s p o i n t t h e r e i s no way o f e s t i m a t i n g t h e p o t e n t i a l s t a b i l i t y o f t h e CpW(NO)L f r a g m e n t t h a t w o u l d r e s u l t f r o m i n t r a m o l e c u l a r M e 4 S i r e d u c t i v e e l i m i n a t i o n and s o any d i s c u s s i o n on t h i s i s p r e m a t u r e . 157 6. T h e r m o l y s i s o f C p W ( N O ) ( H ) ( C h ^ S i M e 3 ) [ P ( O P h ) 3 ] . When C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) [ P ( O P h ) 3 ] i s warmed g e n t l y i n hex a n e s s o l u t i o n , t h e m i x t u r e g r a d u a l l y l i g h t e n s i n c o l o u r and p a l e y e l l o w , m i c r o c r y s t a l 1 i n e C p W ( N O ) ( H ) [ P ( O P h ) 2 ( O C 6 H 4 ) ] (34) p r e c i p i t a t e s o u t o f s o l u t i o n ( e q . 4 - 4 ) . 50°C C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) [ P ( O P h ) 3 ] ^ C p W ( N O ) ( H ) [ P ( O P h ) 2 ( O C g H 4 ) ] 12 h + M e 4 S i (4-4) T h i s m a t e r i a l has v e r y s i m i l a r p h y s i c a l p r o p e r t i e s t o t h o s e o f t h e h y d r i d o a l k y l c o m p l e x e s d i s c u s s e d a bove, e x c e p t i t i s c o n s i d e r a b l y l e s s s o l u b l e i n common o r g a n i c s o l v e n t s . I t s IR s p e c t r u m shows s i m i l a r v N Q and v W H p e a k s , b u t , o f c o u r s e , i t l a c k s t h e bands a t t r i b u t a b l e t o t h e C H 2 S i M e 3 1 i g a n d . T h a t t h i s compound i s an o r t h o m e t a 1 1 a t e d s p e c i e s was f i r s t s u g g e s t e d by i t s 3lP{1h} NMR s p e c t r u m ( 6 p = 176 ppm) when compared w i t h t h a t o f i t s a l k y l h y d r i d e p r e c u r s o r (<5p = 127 p p m ) — s e e T a b l e 4-1 I . I t (36) i s g e n e r a l l y a c c e p t e d t h a t , among c l o s e l y r e l a t e d s p e c i e s , when a mo n o d e n t a t e p h o s p h i n e c h e l a t e s t o f o r m a 5-membered r i n g , a s u b s t a n t i a l d o w n f i e l d s h i f t i s o b s e r v e d i n i t s p h o s p h o r u s - 3 1 13 1 NMR s p e c t r u m . In an a t t e m p t t o c o n f i r m t h i s , a C{ H) NMR s p e c t r u m was r u n i n t h e hope t h a t t h i s w ould show d i r e c t c o u p l i n g 183 between W a n d t h e r i n g c a r b o n atom a t t a c h e d t o i t . U n f o r t u n a t e l y , t h e low s o l u b i l i t y o f t h i s complex i n C^D^ 13 1 p r e v e n t e d a u s e f u l C{ H) s p e c t r u m f r o m b e i n g c o l l e c t e d . 158 T h e r e f o r e , i n o r d e r t o c o n f i r m t h e s t r u c t u r e , a s i n g l e c r y s t a l X- r a y a n a l y s i s was p e r f o r m e d on c r y s t a l s grown f r o m CH^C1^/hexanes a t - 2 5 ° C . The s t r u c t u r a l a n a l y s i s d o e s i n d e e d show t h a t t h i s m a t e r i a l i s C p W ( N O ) ( H ) [ P ( 0 P h ) 2 ( 0 C 6 H 4 ) ] and two v i e w s o f t h e m o l e c u l a r s t r u c t u r e a r e shown i n F i g . 4-4 w h i l e s e l e c t e d bond d i s t a n c e s a nd a n g l e s a r e g a t h e r e d i n T a b l e 4-IV. A l t h o u g h t h e s e d e p i c t i o n s a r e T a b l e 4-1V I m p o r t a n t I n t e r a t o m i c D i s t a n c e s (A) and A n g l e s (deg) f o r CpW(NO)(H)[P(OPh) 2 ( O C 6 H 4 ) ] W-N 1.795(6) N-0(1) 1.194(8) W-C(12) 2.221(6) W-CP 2.024 W-P 2.380(2) P-0(2) 1.603(4) P-0(3) 1.583(4) P-0(4) 1.611(5) 0 ( 2 ) - C ( l l ) 1.413(7) 0 ( 3 ) - C ( 2 1 ) 1 .420(7) 0 ( 4 ) - C ( 3 1 ) 1.413(8) W-N-0(1) 173.7(5) N-W-C(12) 92.6(2) N-W-P 96.0(2) C(12)-W-P 72.6(2) N-W-CP 125.6 P-W-CP 136.6 C(12J-W-CP 112.6 W-P-0(2) 112.6(2) W-P-0(3) 1 14.9(2) W-P-0(4) 122.1(2) P - 0 ( 2 ) - C ( 1 1 ) 112.8(4) 0 ( 2 ) - C ( 1 1 ) - C ( 1 2 ) 119.3(5) C ( 1 1 ) - C ( 1 2 ) - W 122.6(4) P - 0 ( 3 ) - C ( 2 1 ) 128.5(4) P - 0 ( 4 ) - C ( 3 1 ) 121.2(4) t h e o p p o s i t e e n a n t i o m e r t o t h o s e g i v e n f o r C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e P h 2 ) , i t i s a p p a r e n t t h a t t h e ge o m e t r y i s r e m a r k a b l y s i m i l a r . The W-N and N-0 d i s t a n c e s a r e t h e same ( w i t h i n e x p e r i m e n t a l e r r o r ) , w h i l e t h e o r t h o m e t a l l a t e d complex has a s l i g h t l y more l i n e a r W-N-0 l i n k a g e . I n s p e c t i o n o f t h e ge o m e t r y o f t h e p h o s p h i t e m o i e t y shows t h a t o r t h o m e t a l 1 a t i o n has 159 F i g . 4 - 4 . SNOOPI d i a g r a m s o f t h e m o l e c u l a r s t r u c t u r e o f C p W ( N O ) ( H ) [ P ( 0 P h ) 2 ( 0 C 6 H 4 ) ] . a ) View s h o w i n g t h e o r t h o m e t a l l a t e d p h o s p h i t e 1 i g a n d . b) View s h o w i n g t h e h o l e where t h e h y d r i d e h y d r o g e n atom i s p r o b a b l y l o c a t e d t o t h e r i g h t ( c f . F i g . 4 - 1 2 ) . The Ph g r o u p a t t a c h e d t o 0 ( 4 ) has been o m i t t e d f o r c l a r i t y . 160 n o t s t r a i n e d t h i s 1 i g a n d i n a n y w e l l - d e f i n e d f a s h i o n . F o r example, t h e w-P-0 a n g l e s a r e 1 1 2 . 6 ( 2 ) , 114.9(2) a n d 122.1(2) f o r 0 ( 2 ) , 0 ( 3 ) a n d 0 ( 4 ) r e s p e c t i v e l y . S i n c e t h e 0 ( 4 ) phenoxy g r o u p i s n o t t h e one i n v o l v e d i n t h e c h e l a t i o n , t h i s s u g g e s t s t h a t t h e s e m a g n i t u d e s o f a n g l e d i f f e r e n c e s a r e n o t s i g n i f i c a n t . A g a i n , a s w i t h C p W ( N O ) ( H ) ( C H 2 S 1 M e 3 ) ( P M e P h 2 ) , t h e h y d r i d e H was n o t l o c a t e d , however, t h e o r t h o m e t a l l a t e d complex a l s o shows a " h o l e " i n t h e e x p e c t e d p l a c e i n t h e m e t a l s c o o r d i n a t i o n s p h e r e a n d t h i s i s shown a s b e f o r e i n F i g . 4-4b and F i g . 4-5. C. R e a c t i o n s o f C p W ( N O ) ( C H g S i M e 3 ) 2 , H£ and L i n NMR T u b e s . The f u l 1 c o u r s e o f t h e h y d r o g e n a t i o n r e a c t i o n o f C p W ( N O ) ( C H 2 S i M e 3 ) 2 l e a d i n g t o C p W ( N O ) ( H ) [ P ( O P h ) 2 ( 0 C 6 H 4 ) ] was f o l l o w e d i n a s e a l e d NMR t u b e by b o t h *H a n d 3 1 P NMR s p e c t r o s c o p y and s e r i e s ' o f t h e s e s p e c t r a a r e shown i n F i g . 4-6 a n d 4-7. As shown, t h e r e a c t i o n s were e x t r e m e l y c l e a n a n d t h e o v e r a l l c o u r s e i s summarized i n Scheme 4-1 I. As t h e r e a c t i o n p r o c e e d e d , t h e r e s o n a n c e s due t o C p W ( N O ) ( C H 2 S i M e 3 ) 2 (marked "A" i n F i g . 4-6) were g r a d u a l l y r e p l a c e d w i t h t h o s e due t o t h e h y d r i d o a l k y l c omplex ("B" i n t h e f i g u r e s ) w i t h t h e c o n c o m i t a n t f o r m a t i o n o f M e „ S i . As t h e r e a c t i o n c o n t i n u e d , t h e a l k y l h y d r i d e r e s o n a n c e s 4 were t h e m s e l v e s r e p l a c e d w i t h t h o s e due t o t h e f i n a l o r t h o m e t a l l a t e d p r o d u c t ("C" i n F i g . 4-6 a n d 4-7) a s more Me„Si 4 f o r m e d . T h e s e s p e c t r a i l l u s t r a t e t h a t no o t h e r s p e c i e s were p r o d u c e d i n s i g n i f i c a n t q u a n t i t i e s . B e c a u s e i t i s d i f f i c u l t t o 161 F i g . 4 - 5 . S t i c k d i a g r a m o f t h e s t r u c t u r e o f C p W ( N O ) ( H ) [ P ( 0 P h ) 2 ( 0 C 6 H 4 ) ] a s v i e w e d f r o m d i r e c t l y a b o v e t h e p l a n e o f t h e Cp r i n g s h o w i n g t h e h o l e where t h e h y d r i d e h y d r o g e n atom i s p r o b a b l y l o c a t e d t o t h e r i g h t o f t h e t u n g s t e n atom ( c f . F i g . 4 - 1 3 ) . (9) a d e q u a t e l y mix t h e c o n t e n t s o f a n NMR t u b e o f t h e t y p e u s e d , ' t h e r e a c t i o n t o p r o d u c e t h e a l k y l h y d r i d e complex was c o n s i d e r a b l y s l o w e r ( s e e b e l o w ) h e r e t h a n on a p r e p a r a t i v e s c a l e . T h i s r e s u l t e d i n t h e f o r m a t i o n o f t h e o r t h o m e t a 1 1 a t i o n p r o d u c t b e i n g c o m p e t i t i v e w i t h t h a t o f t h e h y d r i d o a l k y l a n d s o r e s o n a n c e s due t o a l 1 t h r e e m e t a l - c o n t a i n i n g s p e c i e s were o b s e r v e d 162 A=CpW(N0)(CH2SiMe3)2 B=CpW(NO)(H)(CH2SiMe3)[P(OPh)3] C = CpW(NO)(H)[P(OPh)2(OC6Ĥ )] A B A B A J L B Start TMS J L B A 1 hour TMS B —r- 6 B B 60 hours C B TMS JfJJf JUL i 0 — r --2 F i a . 4 - 6 , 6(ppm) The 300-MHz *H NMR s p e c t r u m o f t h e r e a c t i o n between C p W ( N O ) ( C H 2 S i M e 3 ) 2 . P ( 0 P h ) 3 a n d H g s h o w i n g t h e s u c c e s s i v e f o r m a t i o n o f C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) [ P ( O P h ) 3 ] and C p W ( N O ) ( H ) [ P ( O P h ) 2 ( O C g H ^ ) ] . 163 A=free P(OPh)3 B=CpW(NO)(H)(CH2SiMe3)[P(OPh)3] C = CpW(NO)(H)[P(OPh)2(OC6H4)] A t=Oh B t = 1 1 /oh B I I I | I I I I | I I I ! | I I I I I I I 1 I | I I I I | I I I I | I I I I | I I I I | I I I I | I I I I | I 160 150 140 ' AJLU— t = A5'/2h 170 { 130 PPM F i a . 4-7. The 121.421-MHz 3 1 P { 1 H } NMR s p e c t r u m o f t h e r e a c t i o n b e tween C p W ( N O ) ( C H 2 S i M e 3 ) 2 . P ( 0 P h ) 3 a n d H 2 s h o w i n g t h e s u c c e s s i v e f o r m a t i o n o f C p W ( N O ) ( H ) ( C H 2 s i M e 3 ) [ P ( O P h ) 3 ] a n d C p W ( N O ) ( H ) [ P ( O P h ) 2 ( O C 6 H 4 ) ] . 164 Scheme 4-11 C p W ( N O ) ( C H 2 S i M e 3 ) 2 H „ , P(OPh) C 6 D 6 - TMS C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) [ P ( O P h ) 3 ] C 6 D 6 TMS C p W ( N O ) ( H ) [ P ( O P h ) 2 ( O C 6 H 4 ) ] s i m u l t a n e o u s l y i n some o f t h e s p e c t r a . P r e p a r a t i v e l y , C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) [ P ( O P h ) 3 ] c o u l d be i s o l a t e d w i t h o u t a n y c o n t a m i n a t i o n f r o m t h e o r t h o m e t a l l a t e d complex i f t h e r e a c t i o n was done on a r e l a t i v e l y s m a l l s c a l e ( s e e E x p e r i m e n t a l S e c t i o n ) an d i f t h e r e a c t i o n t i m e was k e p t s h o r t (<3 h ) . In l i g h t o f t h e NMR s t u d y , a n d w i t h t h e a d d i t i o n a l o b s e r v a t i o n t h a t t h e h y d r o g e n a t i o n r e a c t i o n was s u b s t a n t i a l l y s l o w e d when lower p r e s s u r e s o f were u s e d ( e . g . 15 p s i g v s . 60 p s i g ) , a r e a s o n a b l e a n d s t r a i g h t f o r w a r d mechanism f o r t h e r e a c t i o n c a n be p r o p o s e d (Scheme 4-1 I I ) . T h i s i n v o l v e s f i r s t t h e s l o w o x i d a t i v e a d d i t i o n o f H 2 t o t h e 1 6 - e l e c t r o n C p W ( N O ) ( C H 2 S i M e 3 ) 2 t o f o r m a d i h y d r i d o d i a l k y l complex t h a t r a p i d l y r e d u c t i v e l y e l i m i n a t e s M e 4 S i t o f o r m t h e C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) t r a n s i e n t . When no L i s p r e s e n t , t h i s 165 m a t e r i a l r a p i d l y decomposes ( s e e a b o v e ) , b u t i t may be r e a d i l y t r a p p e d by a s u i t a b l e L e w i s b a s e . A l t h o u g h t h e a l k y l h y d r i d e c o m p l e x e s a r e r e a s o n a b l y s t a b l e a n d i s o l a b l e , t h e y do a p p a r e n t l y s l o w l y r e d u c t i v e l y e l i m i n a t e Me^Si a n d , when L = P ( O P h ) 3 » t h e r e s u l t i n g C p W ( N O ) [ P ( O P h ) 3 ] t h e n u n d e r g o e s o r t h o m e t a l l a t i o n t o g i v e t h e o b s e r v e d f i n a l p r o d u c t . When an a t t e m p t was made t o f o l l o w t h e h y d r o g e n a t i o n o f t h e a l k y l complex i n t h e p r e s e n c e o f PMePh 2 i n a n NMR t u b e , t h e r e a c t i o n was f o u n d t o be much l e s s c l e a n t h a n when L = P ( O P h ) 3 > S i g n a l s due t o b o t h Me^Si a n d CpW(NO)(H)(CHgSi M e 3 ) ( P M e P h 2 ) d i d a p p e a r i n t h e s p e c t r a , a l o n g w i t h numerous o t h e r p e a k s i n t h e c y c l o p e n t a d i e n y l a n d s i l y l m e t h y l r e g i o n s . A p p a r e n t l y PMePh 2 i s a much l e s s e f f i c i e n t t r a p p i n g a g e n t f o r t h e C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) f r a g m e n t . The o b s e r v a t i o n t h a t t h i s NMR t u b e r e a c t i o n was much l e s s c l e a n t h a n i n t h e P ( O P h ) 3 c a s e was In a g r e e m e n t w i t h o b s e r v a t i o n s on t h e p r e p a r a t i v e s c a l e . In t h e l a t t e r s i t u a t i o n , t h e r e a c t i o n s o l u t i o n t u r n e d f r o m t h e I n t e n s e p u r p l e c o l o u r o f t h e C p W ( N O ) ( C H 2 S i M e 3 ) 2 t o a deep c h e r r y r e d when L=PMePh 2, r a t h e r t h a n t h e y e l l o w c o l o u r o b s e r v e d when L = P ( O P h ) 3 . The o n l y way f o u n d f o r o b t a i n i n g p u r e a l k y l h y d r i d e when PMePh 2 was u s e d was n o t t o s t i r t h e s o l u t i o n a n d a l l o w C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e P h 2 ) t o c r y s t a l l i z e o u t o f s o l u t i o n a s i t f o r m e d . T h i s c r y s t a l l i n e m a t e r i a l , w h i c h f o r m e d a r e m a r k a b l e b r i c k - s h a p e d mass a t t h e b o t t o m o f t h e f l a s k , t h e n had t o be p i c k e d o u t m a n u a l l y f r o m t h e a c c o m p a n y i n g powdery p r e c i p i t a t e 166 a n d r e c r y s t a 1 1 i z e d . Scheme 4-1 I I C p W ( N O ) ( C H 2 S i M e 3 ) 2 + H 2 s l o w f a s t TMS [ C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) ] f a s t +L C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) L s 1 ow - TMS [CpW(NO)L] f a s t i f L=P(OPh) 16e" [ C p W ( N O ) ( H ) 2 ( C H 2 S i M e 3 ) 2 ] 18e" 16e 18e 16e C p W ( N O ) ( H ) [ P ( O P h ) 2 ( O C 6 H 4 ) ] 18e" D. The E q u i l i b r i u m Between C p W ( N O ) ( C H 2 S i M e 3 ) 2 a n d PMePh 2. When t h e NMR t u b e c o n t a i n i n g CpW(NO)(CH 2Si M e 3 ) 2 a n d PMePh 2 was u n d e r g o i n g t h e f r e e z e - p u m p - t h a w d e g a s s i n g c y c l e s In p r e p a r a t i o n f o r t h e h y d r o g e n a t i o n r e a c t i o n d i s c u s s e d a b o v e , i t was o b s e r v e d t h a t , a t low t e m p e r a t u r e s , t h e m i x t u r e r e v e r s l b l y c h a n g e d f r o m t h e p u r p l e o f t h e a l k y l c omplex t o a y e l l o w c o l o u r r e m i n i s c e n t o f C p W ( N O ) ( C H 2 S i M e 3 ) 2 ( P M e 3 ) . ( 3 7 ) T h i s s u g g e s t e d t h a t t h e a d d u c t CpW(NO)(CH 2si M e 3 ) 2 ( P M e P h 2 ) i s f o r m e d a t low t e m p e r a t u r e a n d s o a *H a n d 3 1 P { 1 H } NMR s t u d y o f t h i s e q u i l i b r i u m 167 T a b l e 4-V. The E q u i l i b r i u m D a t a f o r t h e R e a c t i o n Between C p W ( N O ) ( C H 2 S i M e 3 ) 2 a n d PMePhg i n t o l u e n e - d g . T ( ° C ) K j a ( L m o l - 1 ) K 2 a AG j D ( k J m o l - 1 ) A G 2 ° ( k J m o l - 1 ) 25 0 C - - 0 0 C - - -25 4.4 0 d -3.1 -50 22 0 d -5.7 -75 78 0.70 -7.2 0.59 -85 120 1.6 -7.5 -0.74 a s e e t e x t f o r d e f i n i t i o n s o f K j a n d K 2 b AG = - R T l n K c no a p p r e c i a b l e a d d u c t A f o r m a t i o n d no a p p r e c i a b l e a d d u c t B f o r m a t i o n was u n d e r t a k e n . Sample s p e c t r a a r e g i v e n i n F i g . 4-8, w h i l e t h e a p p r o p r i a t e e q u i l i b r i u m d a t a a r e l i s t e d i n T a b l e 4-V. T h e s e d a t a show t h a t , i n f a c t , two d i f f e r e n t low t e m p e r a t u r e a d d u c t s a r e f o r m e d (A and B ) . T h i s i s summarized i n e q . 4-5, where R 2= C p W ( N O ) ( C H 2 S i M e 3 ) 2 , P = f r e e PMePhg, a n d R g P A and R 2 P Q a r e t h e a d d u c t s . T h e s e two a d d u c t s a r e i n d i s t i n g u i s h a b l e i n t h e 'H NMR s p e c t r a . T h e y b o t h g i v e two, s i l y l m e t h y l p e a k s ( l a b e l l e d X j and X 2 i n F i g . 4-8) w h i c h do n o t change i n i n t e n s i t y r e l a t i v e t o e a c h 168 a) m T—I—r-r-j—I—I—I—I—|—Hi—I—I—|—I—I—I—I—[—I—I—I—1—|—1—I—I—rh—I—r—i—1—|—r 0 -5 -10 -15 -20 -25 PPM -30 F i g , /t-ft. V a r i a b l e t e m p e r a t u r e lH and 3 1 P { 1 H } NMR s p e c t r a ( t o l u e n e - d Q ) s h owing t h e e q u i l i b r i u m between C p W ( N O ) ( C H 2 S i M e 3 ) 2 and PMePh 2. a) 'HY - 2 5 ° C ; b) 3 1 P { 1 H } , - 2 5 ° C ; c ) 'H, - 8 5 ° C ; d) P C'H}, - 8 5 ° C . R 2 S f r e e C p W ( N O ) ( C H g S i M e 3 ) 2 ; P = f r e e PMePh 2; X j , X 2 = c o i n c i d e n t a l SiMe_ 3 p e a k s ('H s p e c t r a ) f o r a d d u c t s A and B ; A, B = 3 1 P { 1 H } p e a k s c o r r e s p o n d i n g t o a d d u c t s A and B . Note t h e s l i g h t t e m p e r a t u r e d e p e n d e n c e o f t h e 'H and 3 1P{ 1H) c h e m i c a l s h i f t s . K K 2 (4-5) a n d K 2 = f R 2 P B ] C R 2 ] C P ] o t h e r a s t h e t e m p e r a t u r e i s l o w e r e d . The d i f f e r e n t a d d u c t s m a n i f e s t t h e m s e l v e s i n t h e 3*P{*H} s p e c t r a , where ( a t - 8 5 ° C ) 6 A = 3.91, ! J p w =« 145 Hz a n d 6Q = 4.66, 1 J p w * 157 Hz (A i s t h e h i g h e r t e m p e r a t u r e a d d u c t and B i s t h e l o w e r ) . The most o b v i o u s p o s s i b i l i t i e s f o r A a n d B a r e c i s a n d t r a n s i s o m e r s . We t h i n k t h i s u n l i k e l y b e c a u s e a p h o s p h i n e t r a n s t o t h e s t r o n g i r - a c i d NO s h o u l d e x h i b i t a m a r k e d l y d i f f e r e n t 3 * P c h e m i c a l s h i f t t h a n i f i t were t r a n s t o a m i l d l y e l e c t r o n - d o n a t i n g a l k y l g r o u p . We have a l s o s e e n t h a t , i n f o u i — l e g g e d p i a n o - s t o o l s t r u c t u r e s o f t h i s t y p e , a t r a n s o r i e n t a t i o n i s p r e f e r r e d a n d i t i s l i k e l y t h a t b o t h A a n d B a r e t r a n s a d d u c t s . T h i s m o l e c u l e i s u n d o u b t e d l y v e r y c r owded a n d t h e c l o s e s i m i l a r i t i e s o f t h e *H a n d 3 1 P { 1 H } s p e c t r a o f t h e a d d u c t s s u g g e s t t h a t t h e y d i f f e r o n l y i n how t h e l i g a n d s a r e " l o c k e d t o g e t h e r " i n a r i g i d s t r u c t u r e . The o b s e r v a t i o n t h a t CpW(NO)(H)(CH^S i M e ^ ) [ P ( O P h ) 3 ] l o s t M e 4Sf a n d under w e n t i n t e r m o l e c u l a r C-H bond a c t i v a t i o n ( o r t h o m e t a l 1 a t i o n ) s u g g e s t e d t h e p o s s i b i l i t y t h a t t h e s e compounds may be p r e c u r s o r s f o r i n t e r m o l e c u l a r r e a c t i v i t y . P h o t o c h e m i c a l 1y i n d u c e d i n t e r m o l e c u l a r a c t i v a t i o n i s c u r r e n t l y a n a r e a o f c o n s i d e r a b l e a c t i v i t y a nd much has a p p e a r e d i n t h e 170 l i t e r a t u r e . However, t h e r m a l a c t i v a t i o n i s a much rarsr phenomenon an d i t was o f i n t e r e s t , t h e r e f o r e , t o i n v e s t i g a t e t h i s p o s s i b i l i t y . A r e n e C-H bond a c t i v a t i o n has b een o b s e r v e d t o be ( 3 9 ) t h e most f a c i l e — i n f a c t , t h e Cp 2W f r a g m e n t was f o u n d t o (21) i n d u c e s u c h a r e a c t i o n b o t h t h e r m a l l y and p h o t o c h e m i c a 1 1 y . U n f o r t u n a t e l y , t h e r m o l y s i s o f C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e P h 2 ) i n CgHg d i d n o t r e s u l t i n t h e i d e n t i f i c a t i o n o f a n y C-H a c t i v a t i o n p r o d u c t . N u c l e a r m a g n e t i c r e s o n a n c e a n a l y s i s o f t h e non- v o l a t i l e s showed o n l y low y i e l d s o f f r e e P M e P h 2 , ( 4 0 ) O P M e P h 2 , ( 4 1 ) and C p W ( N O ) ( P M e P h 2 ) 2 ( 1 6 ) i n t h e lH a n d 3 1 P { 1 H } s p e c t r a amongst a p l e t h o r a o f d e c o m p o s i t i o n p r o d u c t s . G e n e r a l l y s p e a k i n g , most known C-H bond a c t i v a t i n g s p e c i e s c o n t a i n r e l a t i v e l y e l e c t r o n - r i c h m e t a l c e n t r e s s u c h a s Re, Rh a n d I r . C o n s e q u e n t l y , i t was f e l t t h a t i n c r e a s i n g t h e e l e c t r o n d e n s i t y on t h e CpW(NO)L f r a g m e n t w o u l d r e n d e r i t more p r o n e t o u n d e r g o i n t e r m o l e c u l a r o x i d a t i v e a d d i t i o n o n c e M e 4 S i had b een l o s t . The o b v i o u s r o u t e t o t r y was t h e r e f o r e w i t h a s t r o n g e r p h o s p h i n e d o n o r s u c h a s P M e 3 . * 4 8 * However, PMe 3 f o r m s an a d d u c t a t room t e m p e r a t u r e w i t h C p W ( N O ) ( C H g S i M e 3 ) 2 ( 3 7 ) a n d i t t h u s b l o c k s t h e s i t e f o r t h e i n i t i a l H 2 r e a c t i o n . I s o l a t e d C p W ( N O ) ( C H 2 S i M e 3 ) 2 ( P M e 3 ) do e s l o s e some PMe 3 upon d i s s o l u t i o n , r e f o r m i n g a s m a l l amount o f t h e d i a l k y l c o m p l e x . When s u c h a m i x t u r e was h y d r o g e n a t e d , some o f t h e d e s i r e d h y d r i d o a l k y l compound c o u l d be i d e n t i f i e d by *H NMR s p e c t r o s c o p y , b u t t h e r e a c t i o n was v e r y s l o w a n d t h e d e s i r e d p r o d u c t c o u l d n o t be 171 s e p a r a t e d . T h e r e f o r e , t h i s r o u t e was abandoned. T h e s e e x p e r i m e n t s d i d p r o v i d e s u p p o r t , however, f o r t h e i n i t i a l s t e p i n t h e h y d r o g e n o l y s i s r e a c t i o n b e i n g o x i d a t i v e a d d i t i o n o f H 2 t o t h e 1 6 - e l e c t r o n C p W ( N O ) ( C H 2 S i M e 3 ) 2 r a t h e r t h a n d i r e c t H 2 a t t a c k on t h e m e t a l - c a r b o n bond. S i n c e c h a n g i n g t h e p h o s p h i n e i n t h i s s y s t e m d i d n o t o f f e r a p r o m i s i n g r o u t e t o a more e l e c t r o n - r i c h m e t a l c e n t r e , i t was d e c i d e d t o t u r n t o t h e a n a l o g o u s Cp* s y s t e m . P e n t a m e t h y l c y c l o p e n t a d i e n y l c o m p l e x e s a r e g e n e r a l l y a c c e p t e d t o have more e l e c t r o n - r i c h m e t a l c e n t r e s and t o e n j o y g r e a t e r t h e r m a l s t a b i l i t y t h a n t h e i r p e r h y d r o r e l a t i v e s . * 4 2 * The r e m a i n d e r o f t h i s c h a p t e r d i s c u s s e s t h i s s y s t e m , i n c l u d i n g t h e p r e p a r a t i o n o f t h e a p p r o p r i a t e s t a r t i n g m a t e r i a l s . E. Cp*W(NO)I 2. V e r y l i t t l e Cp* c h e m i s t r y o f t h e g r o u p 6 n i t r o s y l s h as been r e p o r t e d . O n l y t h e p r e p a r a t i o n a n d X - r a y c r y s t a l s t r u c t u r e o f Cp*W(CO> 2(NO) have been p u b l i s h e d . * 1 0 * The s y n t h e s i s o f t h e d e s i r e d i o d o p r e c u r s o r t o t h e a l k y l h y d r i d e s t a r t i n g m a t e r i a l C p * w ( N O ) ( C H 2 S i M e 3 ) 2 ( s t e p s a a n d b Scheme 4 - 1 ) , Cp*W(NO)I 2, has been d i s c u s s e d , a l o n g w i t h s e v e r a l o f i t s L e w i s b a s e a d d u c t s (L= t e r t i a r y p h o s p h i n e o r p h o s p h i t e ) . * 1 3 * D u r i n g t h e p r e p a r a t i o n o f t h i s c o m p l e x f o r t h e work d e s c r i b e d h e r e , a number o f i n t e r e s t i n g f e a t u r e s were o b s e r v e d . The s t a n d a r d p r e p a r a t i o n o f t h e C p M ( N O ) I 2 ~ t y p e compounds 172 i n v o l v e s t h e a d d i t i o n o f a s t o i c h i o m e t r i c amount o f ^ t o a ( 1 2 ) C H 2 C 1 2 s o l u t i o n o f CpM(CO) 2(NO) ( s e e p 6 3 ) . One e q u i v a l e n t o f CO i s i m m e d i a t e l y e v o l v e d , y i e l d i n g C p M ( C O ) ( N O ) 1 2 , w h i c h t h e n l o s e s t h e s e c o n d e q u i v a l e n t more s l o w l y a s t h e C H 2 C 1 2 s o l v e n t i s (43) removed u n d e r g e n t l e vacuum. The C p M ( C O ) ( N O ) 1 2 c o m p l e x e s have n o t y e t p r o v e n i s o l a b l e . In t h e c a s e o f Cp*W(CO) 2(NO), t h e s e c o n d CO l o s s i s much more d i f f i c u l t and t h e C H 2 C 1 2 i s u s u a l l y c o m p l e t e l y removed u n d e r vacuum b e f o r e a l l t h e CO i s r e l e a s e d . C o n s e q u e n t l y , i t was d e c i d e d t o u s e t h e 1ess-vo1 a t i 1 e s o l v e n t t o l u e n e f o r t h i s r e a c t i o n . When t h i s i s done, s h o r t l y a f t e r a l l t h e I 2 has been a d d e d t o t h e o r a n g e Cp*W(CO) 2(NO) s o l u t i o n , a d a r k red-brown m i c r o c r y s t a 1 1 i n e p r e c i p i t a t e , p r e s u m a b l y Cp*W(CO) (NO) I 2 < 4 4 ) (IR s u p e r n a t a n t \>co = 2052, v N Q = 1676 c m - 1 ) , f o r m s o u t o f t h e deep red-brown s o l u t i o n . As t h e r e a c t i o n m i x t u r e i s f u r t h e r s t i r r e d and g e n t l y warmed un d e r a s l i g h t d y namic vacuum, t h i s m a t e r i a l r e d i s s o l v e s and e v e n t u a l l y C p * W ( N 0 ) I 2 p r e c i p i t a t e s a s t h e s o l v e n t volume i s r e d u c e d . T h i s complex i s i s o l a t e d by f i l t r a t i o n a n d must be t h o r o u g h l y washed w i t h E t 2 0 t o remove an y r e s i d u a l I 2 , o t h e r w i s e a t t e m p t s t o p r e p a r e C p * W ( N O ) ( C H 2 S i M e 3 ) 2 a r e f u t i l e . P h y s i c a l l y , p u r e C p * W ( N 0 ) I 2 i s a most u n u s u a l s p e c i e s . I t i s t h e r m o c h r o m i c , b e i n g b r i g h t g r e e n a t t e m p e r a t u r e s a t , o r b elow, ~20°C, w h i l e i t r e v e r s i b l y t u r n s t o a d i r t y - g o l d c o l o u r a b o v e ~ 2 5 ° C . T h i s c h ange o c c u r s b o t h i n s o l u t i o n i n non- c o o r d i n a t i n g s o l v e n t s s u c h a s t o l u e n e and C H 2 C 1 2 a n d i n t h e 173 s o l i d - p h a s e w h e t h e r u n d e r vacuum o r when e x p o s e d t o a i r o r an N 2 a t m o s p h e r e . I n t e r e s t i n g l y , no c h a n g e s i n t h e p o s i t i o n s o f t h e N O - s t r e t c h i n g f r e q u e n c i e s a r e o b s e r v e d i n t h e IR s p e c t r a o f e i t h e r t h e N u j o l m u l l o r C H 2 C 1 2 s o l u t i o n p h a s e s a s t h e t e m p e r a t u r e i s a l t e r e d . As w e l l , v a r i a b l e t e m p e r a t u r e *H NMR s p e c t r a i n t o l u e n e - d show no s u b s t a n t i a l c h ange i n t h e p o s i t i o n o f t h e Cp* r e s o n a n c e , o n l y t h e u s u a l s l i g h t t e m p e r a t u r e d e p e n d e n c e o f s h i f t e x p e c t e d f o r a c o n v e n t i o n a l compound. Indeed, t h e o n l y p h y s i c a l t e c h n i q u e t h a t r e f l e c t s t h e o b s e r v e d c o l o u r change i s , n a t u r a l l y , t h e U V - v i s i b l e a b s o r p t i o n s p e c t r u m ( F i g . 4 - 9 ) . As c a n be s e e n , t h e s p e c t r o p h o t o m e t r f c d i f f e r e n c e i s n o t v e r y l a r g e ; n e v e r t h e l e s s i t i s a p p a r e n t l y s u f f i c i e n t f o r t h e e f f e c t t o be s t a r t l i n g t o t h e e y e . The most o b v i o u s p o s s i b l e e x p l a n a t i o n f o r t h i s t h e r m o c h r o m i s m i s a monomer-dimer e q u i l i b r i u m . However, r e c e n t o (45) s o l u t i o n m o l e c u l a r - w e i g h t s t u d i e s ( a t 23 C) a n d an X - r a y c r y s t a l l o g r a p h i c a n a l y s i s * 4 6 * i n d i c a t e t h a t t h e compound i s a monomer b o t h i n s o l u t i o n a n d a s a s o l i d . I t t h e r e f o r e a p p e a r s t h a t t h e c o l o u r c h a n g e i s n o t due t o any c h e m i c a l c h a n g e , b u t r a t h e r t o some s u b t l e e l e c t r o n i c f a c t o r a s y e t u n e x p l a i n e d . I n t e r e s t i n g l y , t h e EI mass s p e c t r u m o f t h i s compound ( T a b l e 4-1) shows a h i g h e s t mass peak a t 952 ( ( 2 P - I 2 ) + ) , w h i c h s u g g e s t s t h e complex may u n d e r g o a g g l o m e r a t i o n i n t h e g a s p h a s e a n d t h a t mass s p e c t r a o f t h e s e t y p e s o f compounds a r e p r o b a b l y n o t a u s e f u l 174 g u i d e t o t h e i r m o l e c u l a r i t y i n t h e s o l i d s t a t e . 0 . 2 0 0 n 2 0 . 1 0 0 c D i_ O (f) X) < 0 . 0 0 0 - 1 LEGEND — 8 . 5 ° C — 3 0 5 ° C 3 0 0 4 0 0 5 0 0 6 0 0 7 0 0 Wavelength (nm) 8 0 0 F i a . 4-9. V a r i a b l e t e m p e r a t u r e U V - v i s f b l e s p e c t r u m o f Cp*W(N0)I i n C H 2 C 1 2 . L i k e i t s p e r h y d r o a n a l o g u e , C p * W ( N 0 ) I 2 i s s u f f i c i e n t l y a i r - s t a b l e f o r i t t o be r e a d i l y h a n d l e d i n a i r a s a s o l i d . I t 1s somewhat more a i r - s e n s i t i v e i n s o l u t i o n . S o l u t i o n s a r e e a s i l y f o r m e d i n a l l n o n - a l i p h a t i c common o r g a n i c s o l v e n t s t o f o r m g r e e n o r g o l d c o l o u r e d m i x t u r e s . C o o r d i n a t i n g s o l v e n t s s u c h a s a c e t o n e do n o t f o r m t h e r m o c h r o m i c s o l u t i o n s b u t i n s t e a d i m m e d i a t e l y y i e l d o r a n g e s o l u t i o n s , p r e s u m a b l y o f C p * W ( N 0 ) I 2 L ( L = s o l v e n t ) . U n l i k e 175 [CpW(NO)1 2 3 2, Cp*W(NO)I 2 i s somewhat t h e r m a l l y s e n s i t i v e a n d c a n n o t be s t o r e d f o r e x t e n d e d p e r i o d s o f t i m e . A s h e l f - l i f e o f o n l y 1-2 months a t 0°C i s p r a c t i c a l — t h i s i s d e c r e a s e d somewhat a t room t e m p e r a t u r e . The p r o d u c t o f t h e d e c o m p o s i t i o n i s a d a r k - g r e e n , a l m o s t b l a c k m a t e r i a l t h a t has n o t y e t been i d e n t i f i e d . F. C p * W ( N O ) ( C H 2 S i M e 3 ) 2 The p r e p a r a t i o n o f b, Scheme 4-1) i s a n a l o g o u s t o t h a t o f t h e p e r h y d r o s p e c i e s . * 1 , 6 * C p * W ( N O ) ( C H 2 S i M e 3 ) 2 ( e q . 4-6; s t e p s a a n d RMgX H 2 0 Cp*W(NO)I 2 -1/2 [ C p » W ( N 0 ) R 2 ] 2 « M g X 2 -Cp*W(NO)R 2 (4-6) In t h i s r e a c t i o n , somewhat more H 2 0 i s needed i n t h e s e c o n d s t e p t o c l e a v e t h e [ C p * W ( N O ) ( C H 2 S i M e 3 ) 2 3 2 « M g X 2 a d d u c t t h a n i n t h e Cp c a s e . A d d i t i o n a l l y , c h r o m a t o g r a p h y o f t h e f i n a l r e a c t i o n m i x t u r e must be done w i t h some c a r e , a s a s m a l l amount o f (2) C p * W ( 0 ) 2 ( C H 2 S i M e 3 ) f o r m a t i o n a l w a y s o c c u r s a n d t h e two p r o d u c t s have s i m i l a r c h r o m a t o g r a p h i c p r o p e r t i e s . The C p * W ( N O ) ( C H 2 S i M e 3 ) 2 p r o d u c t i s i s o l a t e d e i t h e r by c r y s t a l l i z a t i o n f r o m p u r e h e x a n e s a t - 2 5 ° C , o r s i m p l y by d r y i n g u n d e r vacuum t h e s o l u t i o n c o n t a i n i n g t h i s c o m p l e x a f t e r i t e l u t e s f r o m t h e col u m n . I f t h e s e p a r a t i o n f r o m t h e oxo compound i s good, t h i s l a t t e r t e c h n i q u e i s p r e f e r r e d b e c a u s e t h e r e i s u s u a l l y c o n s i d e r a b l e y i e l d l o s s o f C p * W ( N O ) ( C H 2 S i M e 3 ) 2 due t o i t s v e r y h i g h s o l u b i l i t y i n h e x a n e s . F o r example, >0.8 g o f t h e d i a l k y l c omplex c a n be 176 c r y s t a l l i z e d f r o m <1 mL o f h e x a n e s s o l u t i o n . The C p * W ( N O ) ( C H 2 S i M e 3 ) 2 compound i s an i n t e n s e l y c o l o u r e d , p u r p l e m i c r o c r s y t a l 1 i n e m a t e r i a l t h a t i s e x t r e m e l y s o l u b l e i n a l l common o r g a n i c s o l v e n t s . As a s o l i d , i t may be h a n d l e d r a p i d l y i n a i r , b u t i t s s o l u t i o n s a r e q u i t e a i r - s e n s i t i v e . S o l u t i o n IR s p e c t r a show one s t r o n g NO s t r e t c h i n g band (1543 c m - 1 i n C H 2 C 1 2 ) and t h e p o s i t i o n o f t h e band shows t h e same d e p e n d e n c y on t h e s o l v e n t a c c e p t o r number a s do t h e CpM(NO)L 2 (L = t e r t i a r y p h o s p h i n e o r p h o s p h i t e ) c o m p l e x e s . ' 1 6 ' T h a t i s , e v e n t h o u g h t h i s m a t e r i a l i s a f o r m a l l y u n s a t u r a t e d , 1 6 - e l e c t r o n compound, i t (47) s t i l l shows s i g n i f i c a n t L e w i s b a s e p r o p e r t i e s . N u j o l m u l l IR s p e c t r a o f C p * W ( N O ) ( C H 2 S i M e 3 ) 2 u s u a l l y show two v N Q bands a t 1549 a n d 1572 cm 1 t h e l a t t e r b e i n g due t o d i s s o l u t i o n o f t h e complex i n N u j o l , a s w e l l a s t h e u s u a l bands f o r t h e C H 2 S i M e 3 1 i g a n d . ^ 2 0 * The *H NMR s p e c t r u m o f t h i s compound shows t h e e x p e c t e d Cp* a n d s i l y l m e t h y l p e a k s , a s w e l l a s two d o u b l e t s f o r t h e d i a s t e r e o t o p i c a-C p r o t o n s ( F i g . 4 - 1 0 ) . One o f t h e s e d o u b l e t s i s p a r t i a l l y o b s c u r e d by t h e Cp* r e s o n a n c e ( i n C^D^ s o l u t i o n ) a n d may o n l y be s e e n on a low f i e l d ( e . g . 80-MHz) s p e c t r o m e t e r . In a d d i t i o n t o g e m i n a l c o u p l i n g a n d two-bond c o u p 1 i n g t o W, s l i g h t s h o u l d e r s a r e o b s e r v a b l e on t h e d o u b l e t s t h a t may be a s c r i b e d t o f o u i — b o n d H-H c o u p l i n g ( a c r o s s t h e m e t a l ) — t h u s t h e s e p r o t o n s a c t u a l l y f o r m a n AA'XX' s p i n s y s t e m ( e x c l u s i v e o f W) b u t t h e r e s o n a n c e s a r e n o t s u f f i c i e n t l y r e s o l v e d f o r a l l t h e c o u p l i n g c o n s t a n t s t o be c a l c u l a b l e . 177 T 1 1 1 0 -1 (5 ppm F i g . 4-10. The 80-MHz H NMR s p e c t r u m o f C p « W ( N 0 ) ( C H 2 S i M e 3 ) 2 i n C 6 D 6 ' W i t h C p * W ( N 0 ) ( C H 2 S i M e 3 ) 2 i n hand, a h y d r o g e n o l y s 1 s r e a c t i o n i n a n NMR t u b e i n t h e p r e s e n c e o f P ( 0 P h > 3 ( i . e . s i m i l a r t o t h a t In Scheme 4-11) was a t t e m p t e d . Some a l k y l h y d r i d e f o r m a t i o n was o b s e r v e d , b u t no o r t h o m e t a l 1 a t i o n p r o d u c t c o u l d be d e t e c t e d i n t h e r e a c t i o n m i x t u r e , a s a p l e t h o r a o f p r o d u c t s ( i n c l u d i n g Me^Si) were o b s e r v e d . I n s p e c t i o n o f t h e m o l e c u l a r s t r u c t u r e o f C p w ( N O ) ( H ) [ P ( 0 P h ) 2 ( 0 C 6 H 4 ) ] ( F i g . 4-4) o f f e r s a p o s s i b l e r e a s o n 178 f o r t h i s . As may be s e e n , one o f t h e p h e n y l g r o u p s i n t h i s s t r u c t u r e p o i n t s up t o w a r d s t h e eye 1 o p e n t a d i e n y 1 r i n g — i t may be t h a t t h e Cp* m e t h y l s p r e v e n t t h e p h o s p h i t e f r o m a d o p t i n g t h e c o n f o r m a t i o n t h a t w o u l d a l l o w o r t h o m e t a l 1 a t i o n . C o n s e q u e n t l y , when C p * W ( N O ) ( H ) ( C H 2 S i M e 3 ) [ P ( O P h ) 3 3 l o s e s Me 4S1, t h e r e s u l t i n g f r a g m e n t c a n n o t t r a p i t s e l f a n d o t h e r r e a c t i o n s o c c u r . G. C p * W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e 3 ) . As d i s c u s s e d e a r l i e r , i n t h e s e a r c h f o r a n e l e c t r o n - r i c h m e t a l c e n t r e , PMe 3 i s a most d e s i r a b l e p h o s p h i n e f o r o u r s y s t e m . * 4 8 ) F o r t u n a t e l y , PMe 3 d o e s n o t c o o r d i n a t e t o C p * W ( N O ) ( C H 2 S i M e 3 ) 2 e v e n a t - 8 5 ° C i n t o 1 u e n e - d Q a n d s o h y d r o g e n o l y s i s o f t h i s d i a l k y l was c a r r i e d o u t i n t h e p r e s e n c e o f PMe 3 ( e q . 4-7; s t e p c , Scheme 4 - 1 ) . U s i n g e x c e s s P M e 3 , * 4 9 ^ t h i s r e a c t i o n p r o c e e d s s m o o t h l y t o g i v e good (547.) y i e l d s o f C p * W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e 3 ) . L i k e t h e o t h e r a l k y l h y d r i d e c o m p l e x e s i s o l a t e d , t h i s i s a y e l l o w , c r y s t a l 1 i n e m a t e r i a l t h a t 80 p s i g H 2 C p * W ( N 0 ) ( C H 2 S i M e 3 ) 2 + x s PMe 3 - C p * w ( N 0 ) ( H ) ( C H 2 S 1 M e 3 ) ( P M e 3 ) h e x a n e s , 3 h (4-7) - TMS i s a i l — s t a b l e i n t h e s o l i d p h a s e , b u t somewhat a i r - s e n s i t i v e i n s o l u t i o n . I t i s s o l u b l e i n a l l c o n v e n t i o n a l o r g a n i c s o l v e n t s , w i t h t h e s o l u b i l i t y i n c r e a s i n g i n t h e o r d e r h e x a n e s < E t 2 0 179 ( s l i g h t ) < b e n z e n e < Ch^C]^. T h i s compound e x h i b i t s a s t r o n g n i t r o s y l s t r e t c h i n g a b s o r p t i o n i n t h e IR s p e c t r u m ( T a b l e 4-1) a t 1545 c m - 1 ( C H 2 C 1 2 s o l u t i o n ) , some 15 c m - 1 lower t h a n t h a t o b s e r v e d f o r C p * W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e P h 2 ) , s u g g e s t i n g t h a t a n (19) i n c r e a s e i n m e t a l e l e c t r o n - d e n s i t y has been a c h i e v e d . The mass s p e c t r u m o f an a n a l y t i c a l l y p u r e sample o f t h i s complex shows a t u n g s t e n - c o n t a i n i n g h i g h e s t mass p a t t e r n c e n t r e d a t m/z = 603, 90 mass u n i t s a b o v e t h e m o l e c u l a r w e i g h t . In a d d i t i o n , numerous n o n - t u n g s t e n - c o n t a i n i n g e n v e l o p e s o f p e a k s a p p e a r up t o m/z = 912, i n d i c a t i n g t h a t t h i s complex u n d e r g o e s e x t e n s i v e i o n - m o l e c u l e r e a c t i o n s . The lH NMR s p e c t r u m o f C p * w ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e 3 ) ( T a b l e 4- I I ) shows t h e same f e a t u r e s e x h i b i t e d by t h e o t h e r monomeric a l k y l h y d r i d e c o m p l e x e s , i n c l u d i n g t h e c l o s e l y b u n c h e d p a t t e r n f o r t h e a-C p r o t o n s a n d t h e h y d r i d e r e s o n a n c e s . S i n c e t h e X - r a y a n a l y s i s o f t h e s t r u c t u r e o f C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e P h 2 ) d o e s n o t d e f i n i t i v e l y e s t a b l i s h t h e p o s i t i o n o f t h e h y d r i d e 1 i g a n d , i t was hoped t h a t a n NOE d i f f e r e n c e e x p e r i m e n t on C p * W ( N 0 ) ( H ) ( C H 2 S i M e 3 ) ( P M e 3 ) m i g h t p r o v e u s e f u l i n t h i s r e g a r d . i f t h e p h o s p h i n e i s c i s t o b o t h t h e h y d r i d e a n d a l k y l l i g a n d s , t h e n t h e p h o s p h i n e m e t h y l s s h o u l d be c l o s e ( i n s p a c e ) t o t h e a-C a n d h y d r i d e p r o t o n s and s o i r r a d i a t i o n o f t h e PMe 3 *H s i g n a l s (6 = 1.09 ppm) s h o u l d i n d u c e a p o s i t i v e n u c l e a r O v e r h a u s e r e f f e c t . As F i g . 4-11 shows, when t h i s i r r a d i a t i o n i s p e r f o r m e d , a p o s i t i v e NOE i s o b s e r v e d f o r t h e h y d r i d e s i g n a l , a s 180 w e l l a s f o r one o f t h e a-C p r o t o n s (Hg i n T a b l e 4-1 I ) . Not o n l y d o e s t h i s e x p e r i m e n t p r o v i d e f u r t h e r e v i d e n c e f o r t h e t r a n s p i a n o - s t o o l c o n f i g u r a t i o n , b u t i t a l s o c o n f i r m s t h e a s s i g n m e n t s o f H A a n d H 0 t h a t were o r i g i n a l l y b a s e d on d i h e d r a l a n g l e a n d c o u p l i n g c o n s t a n t a r g u m e n t s ( s e e s e c t i o n A) w i t h H p o i n t i n g away f r o m t h e p h o s p h i n e 1 i g a n d a n d Hg g e n e r a l l y p o i n t i n g t o w a r d s i t ( F i g . 4 - 1 ) . In o r d e r t o f u r t h e r c o n f i r m t h e s t r u c t u r e , a s i n g l e - c r y s t a l X - r a y a n a l y s i s o f C p * W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e 3 ) ( a t a t e m p e r a t u r e o f ~200 K) was p e r f o r m e d . A SNOOPI d i a g r a m o f t h e s o l i d - s t a t e m o l e c u l a r s t r u c t u r e o f t h i s m a t e r i a l i s shown i n F i g . 4-12 a n d i m p o r t a n t bond d i s t a n c e s a n d a n g l e s a r e g i v e n i n T a b l e 4-VI. C o m p a r i s o n o f t h e a n g l e s a n d d i s t a n c e s f o r t h i s compound w i t h t h o s e o f C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e P h 2 ) ( F i g . 4-2 a n d T a b l e 4 - 1 I I ) shows t h e s e c o m p l e x e s t o be r e m a r k a b l y i s o s t r u c t u r a 1 . The i m p o r t a n t a n a l o g o u s bond d i s t a n c e s ( i . e . W-N, N-0, W-P a n d W-C Q) a r e a l l t h e same w i t h i n e x p e r i m e n t a l e r r o r , a s a r e t h e bond a n g l e s ( i . e . w-N-O, N-w-C Q, N-W-P a n d P-W-C Q). The o n l y i m p o r t a n t s t a t i s t i c a l l y s i g n i f i c a n t bond a n g l e d i f f e r e n c e i s t h a t a r o u n d t h e a - c a r b o n atom ( W - C ( 6 ) - S i = 123.2(5) v s . W - C ( l l ) - S i = 119.8(3) f o r CpPMePh 2 v s . C p » P M e 3 ) . T h i s a n g l e i s s l i g h t l y l e s s d i s t o r t e d away f r o m t h e t e t r a h e d r a l a n g l e i n t h e C p » W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e 3 ) c a s e t h a n f o r C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e P h 2 ) , a s m i g h t be e x p e c t e d f o r t h e l e s s b u l k y p h o s p h i n e , * 4 8 * a l t h o u g h t h e m o l e c u l e i s s t i l l v e r y c rowded. 181 I I I I I I I I I I I I I I I I I I I I I I [ I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I -0.50 -0.60 -0.70 -0.80 -0.90 -1.00 -1.10 -1.20 -1 .30 -1.40 -1.50 PPM F i g . 4-11. NOE d i f f e r e n c e e x p e r i m e n t on Cp*W(NO)(H)(CH^Si M e 3 ) ( P M e 3 ) . O n l y t h e W-CH^CHg-Si and W-Jdw r e g i o n o f t h e *H NMR s p e c t r u m i s shown (300-MHz, C & D 6 ) . a) Normal s p e c t r u m ; b) NOE d i f f e r e n c e s p e c t r u m upon i r r a d i a t i o n o f t h e PMe^ s i g n a l a t & = 1.09 ppm. See t e x t f o r c o m p l e t e d i s c u s s i o n . T a b l e 4-VI. I m p o r t a n t I n t e r a t o m i c D i s t a n c e s ( A ) a n d A n g l e s (deg) f o r C p * W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e 3 ) W-N ' W-C(11) W-P H d ) - C ( l l ) 1.771(5) 2.248(6) 2.494(2) 3.80 ( n o n - b o n d i n g ) N-0 W-H(1) W-CP 1.223(7) 1 .75 2.045 W-N-0 169.1(5) 8 1 . 1 ( 2 ) N-W-C(1 1 ) P-W-H(1) 94.0 ( 2 ) 61.9 102.3(2) C(11)-W-P H(1)-W-N 90. 1 142.8 1 12.0 96.9 N-W-P N-W-CP P-W-CP H(1)-W-C(11) 121.0 132.4 C(11)-W-CP H(1)-W-CP W-C(11)-S i 119.8(3) F o r t u n a t e l y , t h e h y d r i d e h y d r o g e n was l o c a t e d ( a l t h o u g h n o t r e f i n e d ) i n t h e s t r u c t u r e o f C p * W ( N 0 ) ( H ) ( C H 2 S i M e 3 ) ( P M e 3 ) . F i g . 4-12 has been o r i e n t e d s o t h a t t h i s h y d r o g e n i s t o t h e r i g h t i n t h e p i c t u r e , a n d a view f r o m a b o v e t h e m o l e c u l e i s g i v e n i n F i g . 4-13. T h e s e v i e w s c o n f i r m t h a t t h e compound d o e s have a t r a n s c o n f i g u r a t i o n i n a s e v e r e l y d i s t o r t e d f o u r - l e g g e d p i a n o - s t o o l . D i r e c t c o m p a r i s o n s o f F i g . 4-2b a n d 4-4b w i t h F i g . 4-12 a n d F i g . 4-3 a n d 4-5 w i t h F i g . 4-13 show t h a t C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e P h 2 ) a n d CpW(NO)(H)[P(OPh)^(OC^H^)] must a l s o have t h e same s t r u c t u r e s . E x a m i n a t i o n o f F i g . 4-12 shows t h a t t h e c r o w d i n g o f t h e b a s a l l i g a n d s r e s u l t s i n a v e r y i n t e r e s t i n g s i t u a t i o n . In o r d e r t o r e l i e v e t h e s t e r i c s t r a i n , t h e H a n d C H 2 s i M e 3 l i g a n d s have been moved away f r o m e a c h o t h e r , r e s u l t i n g i n an H ( l ) - C ( l l ) n on- b o n d i n g d i s t a n c e o f 3.80 A . T h i s i s p a r t i c u l a r l y i n t e r e s t i n g i n l i g h t o f t h e f a c t t h a t Me.Si c a n be i n d u c e d t o e l i m i n a t e f r o m t h e 183 F i g . 4-12. SNOOPI d i a g r a m o f t h e m o l e c u l a r s t r u c t u r e o f C p * W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e 3 ) . The m o l e c u l e i s o r i e n t e d w i t h t h e h y d r i d e h y d r o g e n ( H ( l ) ) t o t h e r i g h t ( c f . F i g . 4-2b a n d 4 - 4 b ) . F i g . 4-13. S t i c k d i a g r a m o f t h e s t r u c t u r e o f C p * W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M E 3 ) a s v i e w e d f r o m d i r e c t l y a b o v e t h e p l a n e o f t h e Cp* r i n g — n o t e t h e p o s i t i o n o f t h e h y d r i d e h y d r o g e n , H ( l ) ( c f . F i g . 4-3 a n d 4 - 5 ) . 184 c o m p l e x ( s e e p 186). I f r e d u c t i v e e l i m i n a t i o n Is i n t r a m o l e c u l a r t h e s t a b i l i t y o f t h i s a l k y l h y d r i d e may be b e c a u s e t h e C ( l l ) a n d H ( l ) atoms must move a l o n g way b e f o r e t h e y c a n bond ( s e e F i g . 4 14). A l t e r n a t i v e l y , t h i s l o n g C-H d i s t a n c e s u g g e s t s t h a t p e r h a p an i n t e r m o l e c u l a r mechanism may be o p e r a t i v e ( s e e s e c t i o n A ) . A a t h i r d p o s s i b i l i t y , t h e r e may be a s l o w e q u i l i b r i u m between t h e t r a n s f o r m a n d a c i s , w i t h t h e c i s u n d e r g o i n g r a p i d i n t r a m o l e c u l a r r e d u c t i v e e l i m i n a t i o n and t h u s e s c a p i n g d e t e c t i o n In a n y e v e n t , i t w o u l d c e r t a i n l y be o f i n t e r e s t t o i n v e s t i g a t e t h e mechanism o f t h e Me^Si e l i m i n a t i o n r e a c t i o n . F i g . 4-14. S i d e v i e w o f t h e s t r u c t u r e o f C p * W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e 3 ) . Note how f a r H ( l ) a n d C ( l l ) must move i n o r d e r t o r e d u c t i v e l y e l i m i n a t e . 185 H. Thermal C-H A c t i v a t i o n I n v o l v i n g C p * W ( N O ) ( H ) ( C H 2 S 1 M e 3 ) ( P M e 3 ) . As we had hoped, t h e r m o l y s i s o f Cp*W(NO)(H)(CHgS i M e^)(PMe 3) i n CgHg d o e s r e s u l t i n t h e l o s s o f Me^Si (by *H NMR s p e c t r o s c o p y ) a n d t h e f o r m a t i o n o f C p * W ( N O ) ( H ) ( C 6 H 5 ) ( P M e 3 ) ( e q . 4 - 8 ) . A l t h o u g h C 6 H 6 , - M e 4 S i Cp*W(NO) (H) ( C H 2 S i M e 3 ) (PMe 3) -Cp*W(NO) (H) ( C 6 H 5 ) (PMe 3) 4 0 ° C , 22 h (4-8) t h i s r e a c t i o n i s q u i t e c l e a n by *H NMR s p e c t r o s c o p y , o n l y a s m a l l amount o f Cp*W(NO)(H)(C_H C)(PMe,) was i s o l a t e d due t o t h e c o n c o m i t a n t f o r m a t i o n o f a v e r y p e r s i s t e n t o i l a n d a s m a l l amount o f C p * W ( N O ) ( P M e 3 ) 2 . ( 5 4 , 5 5 J The i n t e r m o l e c u l a r a c t i v a t i o n p r o d u c t has v e r y s i m i l a r p h y s i c a l p r o p e r t i e s t o t h e h y d r i d o a l k y l c o m p l e x e s a l r e a d y d i s c u s s e d . The N u j o l m u l l IR s p e c t r u m l a c k s t h e bands a t t r i b u t a b l e t o t h e C H 2 S i M e 3 I i g a n d , ( 2 0 } a n d s t r o n g b ands due t o t h e p h e n y l C-C bond s t r e t c h e s a n d t h e a p p e a r a t 1560 a n d 1550 c n i " 1 ( 5 1 ) i n C H 2 C 1 2 s o l u t i o n , t h u s m a k i n g s p e c i f i c a s s i g n m e n t o f t h e p o s i t i o n o f t h e n i t r o s y l band i m p o s s i b l e ( T a b l e 4 - 1 ) . The *H NMR s p e c t r u m e x h i b i t s t h e W-H r e s o n a n c e a t 6 = 5.15 ppm ( F i g . 4 - 1 5 ) , a s u b s t a n t i a l d o w n f i e l d s h i f t f r o m t h e 6 = -1.25 ppm o f t h e s t a r t i ng m a t e r i a 1. When t h i s compound i s k e p t 1n C^Dg a t room t e m p e r a t u r e o v e r t h e c o u r s e o f s e v e r a l weeks, t h e p h e n y l H a n d h y d r i d e p e a k s d i s a p p e a r a n d a r e r e p l a c e d by a s i n g l e t due t o C^Hg. As t h i s o c c u r s , t h e Cp* a n d PMe 3 p e a k s a r e u n a f f e c t e d , 186 a s Is t h e p o s i t i o n o f t h e r e s o n a n c e i n t h e P{ H} NMR s p e c t r u m . However, t h i s l a t t e r s p e c t r u m t u r n s i n t o a 1:1:1 t r i p l e t , a nd t h e r e f o r e t h e s e d a t a s u g g e s t t h a t t h e WCDMCgD^) a n a l o g u e i s b e i n g f o r m e d c l e a n l y a f t e r t h e o r i g i n a l compound r e d u c t i v e l y e l i m i n a t e s b e n z e n e . I n t e r e s t i n g l y , when C p * W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e 3 ) i s t h e r m o l y z e d i n C 6 D 6 i n s t e a d o f CgHg, TMS i s p r o d u c e d , b u t t h e r e a c t i o n i s much l e s s c l e a n a n d numerous p e a k s a r e o b s e r v e d i n t h e Cp* r e g i o n o f t h e *H NMR s p e c t r u m . T h i s s u g g e s t s t h a t t h e o x i d a t i v e a d d i t i o n o f t h e C-D I I | I T I I | I I | | | I 1 I I | I I I I | I I I I | I I I I | I I I I | I I I I ) I I I I | I I t I [ II II | I II I | I I I I | I I I I | I I I I | ' ' 8 0 7.0 6.0 S.O 4.0 3.0 2.0 £ 1.0 PPM F i g . 4-15. The 300-MHz H NMR s p e c t r u m o f C p » W ( N 0 ) ( H ) ( C 6 H 5 ) ( P M e 3 ) i n CgDg. The i n s e t s show t h e p h e n y l (6 = 7 t o 8) a n d h y d r i d e (<S = 5.15) r e s o n a n c e s . 187 bond i s more d i f f i c u l t t h a n t h a t o f t h e C-H bond, i n l i n e w i t h t h e e x p e c t e d d e u t e r i u m i s o t o p e e f f e c t . The c o n d i t i o n s e mployed i n t h i s i n t e r m o l e c u l a r a c t i v a t i o n a r e c o n s i d e r a b l y m i l d e r t h a n t h o s e c i t e d i n two r e c e n t r e p o r t s o f (52) therma1 b e n z e n e C-H a c t i v a t i o n , a n d so we were e n c o u r a g e d t o t r y o t h e r s u b s t r a t e s . However, t h e r m o l y s i s o f C p * W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e 3 ) i n t o l u e n e r e s u l t s i n a l a r g e number o f p r o d u c t s (by *H NMR s p e c t r o s c o p y ) . Two s e t s o f r e s o n a n c e s w i t h t h e same p a t t e r n a r e o b s e r v e d i n a s i m i l a r r e g i o n o f t h e s p e c t r u m t o t h a t o f t h e h y d r i d e peak o f C p * W ( N O ) ( H ) ( C ^ H ^ ) ( P M e 3 ) , i nd i c a t i ng t h a t some a c t i v a t i on o f t h e ar o m a t i c r i n g o f t o 1uene o c c u r s , however, we were u n s u c c e s s f u l a t i s o l a t i n g t h e (53) p r o d u c t s . U n f o r t u n a t e l y , t h e r m o l y s i s o f C p * W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e 3 ) i n t h e p r e s e n c e o f n-hexane, c y c l o h e x a n e o r CH^ i n C^Djg d o e s n o t r e s u l t i n t h e o b s e r v a t i o n o f any C-H a c t i v a t i o n p r o d u c t . The o n l y i d e n t i f i a b l e p r o d u c t s a r e ( S 4 SS} C p » W ( N O ) ( P M e 3 ) 2 , I 3 * ' 3 3 ' f r e e P M e 3 a n d f r e e OPMe 3. T h e r m o l y s i s was a l s o t r i e d i n t h e p r e s e n c e o f P P h 3 t o s e e i f a r e n e a c t i v a t i o n w o u l d o c c u r i n p r e f e r e n c e t o p h o s p h i n e b i n d i n g . The *H NMR s p e c t r u m shows no e v i d e n c e f o r C-H a c t i v a t i o n a nd t h e 3 1 P { 1 H ) s p e c t r u m i n d i c a t e s a m i x t u r e o f C p * W ( N O ) ( P M e 3 ) 2 (6* p = -22.56, 1 J p w = 454 H z ) , C p * W ( N O ) ( P P h 3 ) 2 ( 6 p = 42.21, 1 J p w = 491 Hz) and C p » W ( N O ) ( P M e 3 ) ( P P h 3 ) ( * p p h 3 = 48.24, l J p ] f j = 474, 2 J p p = 8 Hz, *PMe3 = - 2 3 * 9 6 » l j p w = 4 6 6 H z * i s f o r m e d , w i t h t h e l a t t e r p redomi n a t i ng. 188 S i n c e most s u c c e s s f u l i n t e r m o l e c u l a r C-H a c t i v a t i o n i s (38) p h o t o c h e m i c a 1 1 y i n i t i a t e d , t h e p h o t o l y s i s ( H a n o v i a lamp) o f C p * W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e 3 ) was a t t e m p t e d . T h i s r e s u l t e d o n l y i n t h e l o s s o f a l l n i t r o s y l c o n t a i n i n g s p e c i e s and d e c o m p o s i t i o n i n t o a n I n t r a c t a b l e brown o i l . In a n o t h e r e f f o r t t o i n d u c e i n t e r m o l e c u l a r r e a c t i v i t y , s o n i c a t i o n was t r i e d i n t h e hope t h a t t h e t r a n s i e n t h i g h - t e m p e r a t u r e s i n v o l v e d i n t h i s p r o c e s s m i g h t p r o v e u s e f u 1 . ( 5 7 ) S o n i c a t i o n o f Cp*W(NQ)(H)(CHgSi M e 3 ) ( P M e 3 ) i n ^ 6 H 6 i n a n u l - t r a s o n i c c l e a n i n g b a t h ( t h e o n l y s o n i c s o u r c e (57) a v a i l a b l e ) d i d g i v e t h e a c t i v a t i o n p r o d u c t , b u t i n d e p e n d e n t e x p e r i m e n t s showed t h a t t h i s was m e r e l y t h e r e s u l t o f t h e warming t o ~40°C o f t h e w a t e r b a t h i n t h e c l e a n e r a n d t h e r e f o r e t h e c o n v e n t i o n a l t h e r m a l r e a c t i o n . K. The Redox C h e m i s t r y o f C p * W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e 3 ) . In a l a s t a t t e m p t t o i n v o k e C-H a c t i v a t i o n , t h e c a t a l y t i c o x i d a t i o n o f C p « W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e 3 ) w i t h A g + B F 4 ~ i n C 6 H 6 was t r i e d . I t was hoped (Scheme 4-IV) t h a t o x i d a t i o n o f t h e a l k y l h y d r i d e t o a more r e a c t i v e 1 7 - e l e c t r o n r a d i c a l c a t i o n ( s t e p a) w o u l d c a u s e Me^Si e l i m i n a t i o n ( s t e p b) a t a low t e m p e r a t u r e . The r e s u l t i n g 1 5 - e l e c t r o n s p e c i e s m i g h t t h a n be r e d u c e d by t h e s t a r t i n g c omplex ( s t e p c ) , g e n e r a t i n g Cp*W(NO)PMe 3 ? w h i c h w o u l d t h e n a d d C^Hg ( s t e p d ) , a n d t h e 1 7 - e l e c t r o n r a d i c a l c a t i o n , t h u s f o r m i n g a c a t a l y t i c c y c l e . U n f o r t u n a t e l y , t h i s d i d n o t work. However, c y c l i c vo1tammograms (CV's) r u n In c o n j u n c t i o n w i t h t h i s 189 a t t e m p t s u g g e s t t h a t s t e p s a a n d b o f Scheme 4-IV a r e r e a s o n a b l e a n d t h i s e l e c t r o c h e m i s t r y w i l l now be d i s c u s s e d . G e o r g e R i c h t e i — Addo o f o u r r e s e a r c h g r o u p r a n t h e CV's i n C H ^ C l ^ a t a complex —5 c o n c e n t r a t i o n o f ~5 x 10 M, u s i n g 0.1 M Bu^NPFg s u p p o r t e l e c t r o l y t e w i t h a P t b e a d e l e c t r o d e and r e f e r e n c e d t o t h e S C E . ( 5 8 ) When t h e CV i s r u n o v e r p o s i t i v e p o t e n t i a l s a t a r e l a t i v e l y s l o w s c a n s p e e d ( F i g . 4-16a), an i r r e v e r s i b l e o x i d a t i o n wave Is o b s e r v e d a t E s 0.88 V. T h i s i s a c o n s i d e r a b l y lower p o t e n t i a l pa Scheme 4-1V W * ( H ) ( C H 2 S i M e 3 ) - e [ W ( H ) ( C H 2 S i M e 3 ) ] b [ W * ] ' + - Me.Si 4 W » ( H ) ( C H 2 S 1 M e 3 ) C 6 H 6 W ( H ) ( C 6 H 5 ) W « = C p » W ( N 0 ) ( P M e 3 ) t h a n t h o s e o b s e r v e d f o r t h e C p M ( N 0 ) 2 X s p e c i e s ( 5 9 ) ( e . g . 1.38 V f o r CpW(N0) 2Me), r e f l e c t i n g t h e more e l e c t r o n - r i c h m e t a l c e n t r e o f t h e a l k y l h y d r i d e c o m p l e x . A s t h e s c a n r a t e i s i n c r e a s e d . 190 e) T 1 1 1 0 + 1 0 Volts vs SCE C y c l i c vo1tammograms o f t h e o x i d a t i o n o f C p * W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e 3 ) i l l u s t r a t i n g t h e i n c r e a s i n g l y r e v e r s i b l e c h a r a c t e r a s t h e s c a n r a t e 1 i n c r e a s e d . S c a n r a t e s ( V s - 1 ) : a) 2; b) 10; c ) 20; d) 40; e) 80; f ) 120; g) 160. 191 t h e CV b e g i n s t o show some r e v e r s i b l e c h a r a c t e r ( F i g . 4 - 1 6 ). A p l o t o f t h e c o r r e c t e d peak c a t h o d i c c u r r e n t d i v i d e d by t h e c o r r e c t e d peak a n o d i c c u r r e n t ( i / i ) v e r s u s t h e s c a n r a t e * 6 1 * p c pa g i v e s a s t r a i g h t l i n e w i t h a p o s i t i v e s l o p ( F i g . 4 - 1 7 ) . T h i s (62) i n d i c a t e s t h a t a r e v e r s i b l e c h a r g e t r a n s f e r ( E p ) f o l l o w e d by a n i r r e v e r s i b l e c h e m i c a l c hange ( C { ) i s o c c u r r i n g ( i . e . an E p C . m e c h a n i s m ) . T r e a t m e n t o f Cp*W(NO)(H)(CH^Si Me^)(PMe^) w i t h AgBF^ i n CgDg r e s u l t s i n t h e immediate d e p o s i t i o n o f a s i l v e r m i r r o r a n d a c o l o u r change i n t h e s o l u t i o n f r o m y e l l o w t o r e d - b r o w n . P r o t o n NMR, GC a n d GC-MS a n a l y s e s o f t h e v o l a t i l e s a f t e r vacuum d i s t i l l a t i o n show t h e p r i m a r y p r o d u c t t o be Me^Si ( a few o t h e r , v e r y m i n o r , s i l y l m e t h y l p e a k s were o b s e r v e d i n t h e *H NMR s p e c t r u m ) . I n f r a r e d a n a l y s i s o f t h e n o n - v o l a t i l e r e s i d u e t a k e n up i n C F ^ C ^ shows o n l y a v e r y s m a l l band i n t h e NO r e g i o n , i n d i c a t i n g t h e p r e s e n c e o f no s i g n i f i c a n t t u n g s t e n n i t r o s y l c o n t a i n i n g s p e c i e s . T a k e n t o g e t h e r , t h e s e r e s u l t s s u g g e s t t h a t s t e p s a a n d b i n Scheme 4-IV do o c c u r . S uch o x i d a t i v e l y i n d u c e d e l i m i n a t i o n s a r e known, b u t few e x a m ples have been s t u d i e d i n d e t a i l . * 6 3 * In o u r s y s t e m , t h e 1 5 - e l e c t r o n [CpW(NO)(PMe^)] + p r o d u c e d u n f o r t u n a t e l y i s n o t a p r e c u r s o r f o r C-H bond a c t i v a t i o n ( i . e . s t e p s c a n d d o f Scheme 4-IV do n o t o c c u r ) . S c a n n i n g t h e CV t o n e g a t i v e p o t e n t i a l s shows a c o m p l e t e l y f e a t u r e l e s s voltammogram o u t t o t h e s o l v e n t l i m i t (~-2 V ) . T h i s i n d i c a t e s t h a t C p * W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e 3 ) i s v e r y d i f f i c u l t t o r e d u c e . T r e a t m e n t o f t h e r e l a t e d , a n d l e s s e l e c t r o n - r i c h . 192 C p W ( N O ) ( H ) [ P ( O P h ) 2 ( O C 6 H 4 ) ] w i t h Na/Hg i n THF f o r 48 h does n o t r e s u l t i n any change i n t h e IR s p e c t r u m and p r e s u m a b l y no r e a c t i o n . 0.62 - i 1 0.43 H 1 1 1 1 1 1 1 1 19.95 31.62 50.12 79.43 125.89 Scan Rate (V/s) log scale F i g . 4-17. P l o t o f t h e c o r r e c t e d c a t h o d i c peak c u r r e n t d i v i d e d by t h e c o r r e c t e d a n o d i c peak c u r r e n t ( 1 „ „ / i _ = ) a s a * pc' pa f u n c t i o n o f t h e s c a n r a t e f o r t h e o x i d a t i o n o f C p * W ( N 0 ) ( H ) ( C H 2 S i M e 3 ) ( P M e 3 ) . The p o s i t i v e s l o p e i n d i c a t e s an E J.C i mechanism. ( 6 1 , 6 2 ^ ( D a t a p o i n t s t a k e n f r o m p l o t s s i m i l a r t o F i g . 4 - 1 6 ) . 193 J . H y d r o g e n o l y s i s o f C p * W ( N O ) ( C H 2 5 i M e 3 ) 2 W i t h No L P r e s e n t . The work d e s c r i b e d i n t h i s c h a p t e r so f a r stemmed f r o m t h e a t t e m p t t o p r o d u c e C C p W ( N O ) H ] 2 ( u - H ) 2 v i a t h e h y d r o g e n o l y s i s o f C p W ( N O ) ( C H 2 S i M e 3 ) 2 . A l t h o u g h t h i s was u n s u c c e s s f u l i n t h e u n s u b s t i t u t e d c y c l o p e n t a d i e n y l s y s t e m , i t was d e c i d e d t o t r y a n a l o g o u s r e a c t i o n s w i t h t h e Cp* s y s t e m . When C * p W ( N O ) ( C H 2 S i M e 3 ) 2 was t r e a t e d w i t h a low p r e s s u r e o f H 2 (-80 p s i g — t h e same p r e s s u r e u s e d f o r t h e a l k y l h y d r i d e p r e p a r a t i o n s ) f o r -3 h i n hexanes o r CgHg, c o m p l e t e d e c o m p o s i t i o n was n o t t h e r e s u l t . The *H NMR s p e c t r u m o f t h e r e s i d u e i n C^D- a f t e r r e moval 6 6 o f t h e r e a c t i o n s o l v e n t under vacuum showed t h a t a complex m i x t u r e o f compounds was o b t a i n e d , a l o n g w i t h some d e c o m p o s i t i o n m a t e r i a l . Most p r o m i s i n g l y , a number o f s m a l l p e a k s i n t h e s p e c t r u m c o u l d be o b s e r v e d t h a t showed H- W c o u p l i n g c h a r a c t e r i s t i c o f me t a l h y d r i d e s . D e c o u p l i n g e x p e r i m e n t s i n d i c a t e d t h a t a t l e a s t 5 h y d r i d e c o n t a i n i n g compounds were p r e s e n t , a l o n g w i t h numerous o t h e r s p e c i e s . A t t e m p t s t o c h r o m a t o g r a p h t h e s e r e a c t i o n m i x t u r e s r e s u l t e d o n l y i n t r a c e q u a n t i t i e s o f n o n - h y d r i d e m a t e r i a l s b e i n g s e p a r a t e d , b u t i n t o o s m a l l q u a n t i t i e s a n d i n t o o impure a f o r m t o be i d e n t i f i a b l e , e x c e p t f o r some C p * W ( O ) 2 ( C H 2 S i M e 3 ) . A p p r o x i m a t e l y t h e same complex m i x t u r e was o b s e r v e d when t h e r e a c t i o n was done u n d e r -4 atm o f H 2 i n C f iD 6 i n a s e a l e d NMR t u b e . However, when t h e H 2 p r e s s u r e was i n c r e a s e d t o -920 p s i g (-63 a t m ) , t h e r e a c t i o n was c o m p l e t e i n un d e r 20 min a n d a much 194 l e s s c o m p l i c a t e d m i x t u r e was o b t a i n e d . When t h e r e a c t i o n was done i n h e x a n e s , a red-brown p r e c i p i t a t e f o r m e d a l o n g w i t h a v e r y i n t e n s e l y c o l o u r e d r e d - brown s o l u t i o n . Removal o f t h e s o l v e n t u n d e r vacuum and s e v e r a l f r a c t i o n a l c r y s t a l l i z a t i o n s f r o m t o 1uene/hexanes a l l o w e d t h e i s o l a t i o n o f two a n a l y t i c a l l y p u r e compounds i n v e r y s m a l l q u a n t i t i e s . The lower y i e l d a nd l e s s s o l u b l e m a t e r i a l was i d e n t i f i e d a s [ C p * W ( N O ) H J 2 ( y - H ) 2 a n d t h e more s o l u b l e i d e n t i f i e d a s [ C p * W ( N O ) H ] ( u - H ) 2 [ C p * W ( N O ) ( C H 2 S i M e 3 ) ] ( e q . 4-9? s t e p d, Scheme 4 - 1 ) . T h e s e two compounds a r e v e r y s i m i l a r i n c o l o u r a n d s o l u b i l i t y a nd a r e d i f f i c u l t t o s e p a r a t e . ( I t s h o u l d be n o t e d t h a t i n t h e *H NMR s p e c t r u m (C..D,-) t h e C-Me,- r e s o n a n c e o f [ C p * W ( N O ) H ] 2 ( y - H ) 2 i s c o i n c i d e n t a l ( e v e n a t 400-MHz) w i t h one o f CP1 H R * H,(920 psig) V V Cp* W ( N O ) ( C H 2 S i M e 3 ) 2 ON—W=+=W — N O hexanes y ,\ * ^ — H H Cp ( 4 " 9 ) 20*C. 20 min R=H = CH2SiMe3 t h e C 5 M e 5 r e s o n a n c e s o f [ C p * W ( N 0 ) H ] ( y - H ) 2 [ C p * W ( N 0 ) ( C H 2 S i M e 3 ) ] , making i t d i f f i c u l t t o a s s e s s when a q u a l i t y sample o f t h e l a t t e r has been o b t a i n e d . ) 195 K. [ C p * W ( N O ) H ] 2 ( u - H ) 2 . A n a l y t i c a l l y p u r e [ C p * w ( N O ) H j 2 ( u - H ) 2 i s a r e d - b r o w n powder t h a t i s s l i g h t l y s o l u b l e i n hexanes and E t 2 0 , somewhat more s o i n b e n z ene and r e a d i l y d i s s o l v e s i n more p o l a r s o l v e n t s s u c h a s C H 2 C 1 2 . The m a t e r i a l i s e a s i l y h a n d l e d i n a i r a s a s o l i d , b u t f o r m s s l i g h t l y a i r - s e n s i t i v e s o l u t i o n s . I t i s c o n s i d e r a b l y more s o l u b l e i n c o n v e n t i o n a l o r g a n i c s o l v e n t s t h a n i s i t s p e r h y d r o a n a l o g u e [ C p W ( N O ) H ] 2 ( y - H ) 2 , b u t c o m p l e t e s o l u b i l i z a t i o n i n , f o r example, C^D^ i s q u i t e s l o w and t h e m i x t u r e u s u a l l y must be warmed t o o b t a i n a c l e a r s o l u t i o n . Once t h e s o l u t i o n has become c l e a r , c o o l i n g back t o room t e m p e r a t u r e g e n e r a l l y d o e s n o t i n d u c e r e p r e c i p i t a t i o n . The IR s p e c t r a o f [ C p * w ( N O ) H ] 2 ( y - H ) 2 show some i n t e r e s t i n g f e a t u r e s ( T a b l e 4 - 1 ) . In a d d i t i o n t o t h e e x p e c t e d bands f o r a t e r m i n a l h y d r i d e 1 i g a n d , t h e s p e c t r a show two d i s t i n c t n i t r o s y l s t r e t c h i n g v i b r a t i o n s i n b o t h C H 2 C 1 2 s o l u t i o n and N u j o l m u l l p h a s e s , w i t h t h i s phenomenon b e i n g more p r o m i n e n t i n t h e l a t t e r . The h i g h e r f r e q u e n c y band (1571 cm 1 i n N u j o l m u l l ) i s a l w a y s s t r o n g e r , b u t t h e r e l a t i v e i n t e n s i t i e s o f t h e bands v a r y . The r e a s o n f o r t h e s e two bands i s n o t c l e a r . U n l i k e C p * W ( N O ) ( C H 2 S i M e 3 ) 2 , t h i s m a t e r i a l i s n o t s o l u b l e enough t o f o r m a s o l u t i o n i n N u j o l . T h e r e f o r e , t a k e n i n c o n j u n c t i o n w i t h t h e i n f o r m a t i o n g a i n e d f r o m t h e *H NMR s p e c t r a ( s e e b e l o w ) , t h e most l i k e l y p o s s i b i l i t y i s t h a t t h e more i n t e n s e , h i g h e r f r e q u e n c y band i s due t o [ C p * w ( N O ) H ] - ( y - H ) 0 , w h i l e t h e lower f r e q u e n c y 196 r e s o n a n c e i s due t o an i s o m e r w i t h no b r i d g i n g h y d r i d e l i g a n d s . The IR s p e c t r u m o f [ C p W ( N O ) H ] 2 ( y - H ) 2 shows o n l y one v N Q band a t 1599 cm ' ( C H 2 C 1 2 s o l u t i o n ) , 33 cm" 1 above t h a t s e e n h e r e , r e f l e c t i n g t h e e x p e c t e d i n c r e a s e i n W-*NO b a c k b o n d i n g upon moving f r o m t h e Cp t o Cp* s y s t e m . The *H NMR s p e c t r u m o f [ C p * W ( N O ) H ] 2 ( v - H ) 2 i n C 6 D 6 ( F i g . 4- 18) shows t h a t , a s f o r t h e p e r h y d r o compound, two i s o m e r s a r e p r e s e n t . T h e s e two i s o m e r s show t h e same AA'XX' ( i s o m e r A) and A 2MX ( i s o m e r B) h y d r i d e p a t t e r n s a s b e f o r e , b u t t h e r a t i o o f A:B i s ~9:1 i n t h i s c a s e r a t h e r t h a n t h e ~1.4:1 s e e n f o r t h e Cp c o m p l e x e s . The Cp* r e s o n a n c e s f o r t h e two i s o m e r s a r e c o i n c i d e n t a l e v e n a t 400-MHz, a l t h o u g h t h e h y d r i d e p e a k s a r e wel1 s e p a r a t e d . However, t h e h y d r i d e p e a k s f o r i s o m e r B a r e o f s u c h 183 low i n t e n s i t y t h a t t h e W s a t e l l i t e s a r e n o t d i s c e r n a b l e a n d, i n f a c t , t h e e x p e c t e d h i g h - f i e l d h y d r i d e s i g n a l c a n n o t be f o u n d . I n t e r e s t i n g l y , u n l i k e i n t h e Cp s y s t e m , t h e r a t i o o f i s o m e r s A and B c h a n g e s when a d i f f e r e n t NMR s o l v e n t i s u s e d . The *H s p e c t r u m o f [ C p * W ( N O ) H ] 2 ( y - H ) 2 i n C D 2 C 1 2 shows t h i s r a t i o t o be ~3:1, w i t h A s t i l l p r e d o m i n a n t . The i n c r e a s e d p r o p o r t i o n o f B 183 a l l o w e d t h e o b s e r v a t i o n and i n t e g r a t i o n o f t h e W s a t e l l i t e s f o r t h e two d o w n f i e l d r e s o n a n c e s o f t h e A 2 M X p a t t e r n ( i . e . on A 2 and M), a s w e l l a s p e r m i t t i n g t h e l o c a t i n g o f t h e h i g h - f i e l d X p a r t o f t h e s p e c t r u m — u n f o r t u n a t e l y , t h e s i g n a l : n o i s e r a t i o was 183 n o t s u f f i c i e n t f o r t h e W s a t e l l i t e s o f t h e l a t t e r t o be s e e n . The s i m i l a r i t i e s o f t h e o v e r a l l p a t t e r n s a n d t h e i n d i v i d u a l 197 8 6 & ppm * ^ F i g . 4-1B. The 400-MHz H NMR o f [ C p « W ( N O ) H ] 2 ( u - H ) 2 i n CgDg. "A" a n d "B" r e f e r t o t h e h y d r i d e r e s o n a n c e s f o r i s o m e r s A a n d B. One o f t h e h y d r i d e r e s o n a n c e s o f i s o m e r B i s n o t v i s i b l e . See t e x t f o r c o m p l e t e d i s c u s s i o n . c o u p l i n g c o n s t a n t s i n t h e H NMR s p e c t r a o f i s o m e r s A and B f o r b o t h t h e Cp and Cp* s y s t e m s i n d i c a t e t h a t t h e s e compounds a r e i s o s t r u c t u r a 1 ( s e e F i g . 2 - 4 ) . The f a c t t h a t t h e A:B r a t i o i s s o l v e n t d e p e n d e n t f o r [ C p * W ( N 0 ) H ] 2 ( y - H ) 2 i s s u 9 9 e s - t i v e ° ^ a n e q u i l i b r i u m o f t h e s o r t g i v e n i n e q . 4-10. I n t e r c o n v e r s i o n between t h e two i s o m e r s must [ C p * W ( N O ) H 2 ] 2 (4-10) [ C p * W ( N O ) H ] 2 ( U - H ) 2 [ C p » W ( N O ) H ] 2 ( y - H ) 2 i somer A i somer B be s l o w on t h e NMR t i m e s c a l e , however, s i n c e f u l l y r e s o l v e d h y d r i d e - h y d r i d e c o u p l i n g i s o b s e r v e d , and a minimum l i f e t i m e o f x * 0.2 s ( J = 1 H z — s e e T a b l e 4-1 I a n d c h a p t e r 3) may be c a l c u l a t e d f o r one m o l e c u l e t o be i n a p a r t i c u l a r i s o m e r i c f o r m . I f t h e i n t e r c o n v e r s i o n p a s s e s t h r o u g h an u n b r i d g e d Cp(N0)H 2w=WH 2(NO)Cp d i m e r , t h i s must have a t r a n s i e n t e x i s t e n c e a s i t i s n o t d e t e c t a b l e i n t h e NMR sample. I f t h e i s o m e r i z a t i o n d o e s t a k e p l a c e v i a t h i s complex, t h e n s c r a m b l i n g between b r i d g i n g and t e r m i n a l h y d r i d e s w o u l d be e x p e c t e d . A s p i n - s a t u r a t i o n t r a n s f e r e x p e r i m e n t on t h e h y d r i d e r e s o n a n c e s o f i s o m e r A i n CgD^ shows no t r a n s f e r a t a l l , a n d , c o u p l e d w i t h a T j e x p e r i m e n t t h a t shows T j (H b r i d g i n g ) = 0.98 s, T j (H t e r m i n a l ) = 1.42 s and T j ( C p * ) = 2.49 s f o r t h i s i s o m e r , s u g g e s t s t h a t i s o m e r i z a t i o n v i a an u n b r i d g e d s p e c i e s i s s l o w and t h e l i f e t i m e s o f A a n d B a r e a t l e a s t o f t h e o r d e r o f s e c o n d s . Indeed, t h i s i s 199 what we b e l i e v e i s o c c u r r i n g . The IR s p e c t r a , a s d i s c u s s e d a b o v e , show two n i t r o s y l s t r e t c h i n g b a n d s . However, i n C H ^ C ^ ( o r C D 2 C I 2 ) t h e lower f r e q u e n c y band i s o f t o o low an i n t e n s i t y t o be due t o t h e l e s s a b u n d a n t iso m e r B — i t i s l i k e l y t h a t t h e V N Q bands f o r A a n d B a r e c o i n c i d e n t a l . T h i s low f r e q u e n c y NO band i s t h e r e f o r e p r o b a b l y due t o v e r y s h o r t l i v e d [Cp*W(NO)H 2 ] ^ , w h i c h c a n be d e t e c t e d on t h e f a s t IR t i m e s c a l e b u t n o t on t h e much s l o w e r NMR t i m e s c a l e ( s e e c h a p t e r 3 ) . T h i s h y d r o g e n o l y s i s method o f p r e p a r i n g [ C p * W ( N 0 ) H ] 2 ( u - H ) 2 o n l y p r o d u c e d a v e r y s m a l l y i e l d o f t h i s m a t e r i a l . T h e r e f o r e , s e v e r a l a t t e m p t s were made i n t h i s Cp* s y s t e m t o t r y t h e m e t a t h e s i s method u s i n g i n c h a p t e r 2. T r e a t m e n t o f Cp*W ( N 0 ) l 2 w i t h one e q u i v a l e n t o f N a [ H 2 A l ( O C H 2 C H 2 O C H 3 ) 2 3 d i d r e s u l t i n t h e f o r m a t i o n o f t h e i n t e n s e l y g r e e n c o l o u r e d s o l u t i o n e x p e c t e d f o r [ C p * W ( N O ) I ] 2 ( g - H ) 2 a n d workup o f t h e m i x t u r e i n t h e same manner a s d e s c r i b e d i n c h a p t e r 2 gave a g r e e n m i c r o c r y s t a 1 1 i n e p r o d u c t . However, t h e *H NMR s p e c t r u m showed t h i s m a t e r i a l t o c o n t a i n many p r o d u c t s i n a d d i t i o n t o t h e i o d o h y d r i d e d i m e r (6{.u = -0.62 ( s ) , 1 8 3 w s a t e l l i t e s f o r m AA'X p a t t e r n , ! J H H , = 4 . 5 , ! J w = 9 3 . 5 , ljH'W = 6 8 , 5 H z — s e e c n a p t e r 2 ) . A t t e m p t s t o r e c r y s t a 1 1 i z e t h i s m i x t u r e r e s u l t e d o n l y i n d e c o m p o s i t i o n . When t h e g r e e n s o l u t i o n , a b o v e , was t r e a t e d w i t h a s e c o n d e q u i v a l e n t o f N a [ H 2 A l ( O C H 2 C H 2 O C H 3 ) 2 ] i n an a t t e m p t t o p r e p a r e [Cp*W(NO)H] 2(ii-H) 2» a l l n i t r o s y l bands were l o s t f r o m t h e IR s p e c t r u m a n d s o t h i s r o u t e was a bandoned. 200 L. [ C p * W ( N O ) H ] ( u - H ) 2 [ C p * W ( N O ) ( C H 2 S i M e 3 ) ] . The s e c o n d p r o d u c t o b t a i n e d f r o m t h e h y d r o g e n o l y s i s o f C p * W ( N O ) ( C H 2 S i M e 3 > 2 i s t h e n o v e l d i n u c l e a r a l k y l h y d r i d e complex [ C p * W ( N O ) H ] ( y - H ) 2 [ C p " W ( N O ) ( C H 2 S i M e 3 ) ] . T h i s i s a b r i g h t , r e d - o r a n g e c r y s t a l l i n e m a t e r i a l t h a t i s somewhat more s o l u b l e t h a n i s [ C p * W ( N 0 ) H ] 2 ( y - H ) 2 . The compound a p p e a r s t o be a i l — s t a b l e a s a s o l i d , b u t f o r m s s l i g h t l y a i r - s e n s i t i v e o r a n g e s o l u t i o n s . I t s N u j o l IR s p e c t r u m ( T a b l e 4-1) shows a v e r y s t r o n g v N 0 band a t 1559 cm a s w e l l a s a weak t e r m i n a l h y d r i d e s t r e t c h v 1 1 L 1 a t 1910 WH cm * a n d weak bands a t t r i b u t a b l e t o t h e C H 2 S i M e 3 1 i g a n d a t 1252 and 1242 cm 1 . ^ 0 ) U n l i k e t h e m o n o n u c l e a r s p e c i e s , t h e e l e c t r o n impact mass s p e c t r u m e x h i b i t s a ( P - H ) + i o n , s u g g e s t i n g t h a t Me^Si e l i m i n a t i o n i s l e s s f a v o u r e d . S i n g l e c r y s t a l s o f t h i s d i n u c l e a r s p e c i e s s u i t a b l e f o r a n X- r a y c r y s t a 1 1 o g r a h i c a n a l y s i s were grown f r o m a f i l t e r e d C D 3 N 0 2 s o l u t i o n a t - 2 5 ° C . I t i s e s s e n t i a l t h a t t h i s s o l u t i o n be w e l l - f i l t e r e d ( i . e . t h r o u g h C e l i t e ) b e f o r e c r y s t a l g r o w t h i s a t t e m p t e d , a s [ C p * W ( N 0 ) H ] ( y - H ) 2 C C p » W ( N 0 ) ( C H 2 S i M e 3 ) ] shows a g r e a t t e n d e n c y t o n u c l e a t e a b o u t any s u s p e n d e d m a t e r i a l . Two v i e w s o f t h e m o l e c u l a r s t r u c t u r e o f t h i s compound a r e shown i n F i g . 4-19 a n d s e l e c t e d bond d i s t a n c e s , a n g l e s and t o r s i o n a n g l e s a r e g i v e n i n T a b l e 4 — V I I I . As w i t h t h e o t h e r a l k y l h y d r i d e c o m p l e x e s whose s t r u c t u r e s have been d i s c u s s e d i n t h i s c h a p t e r , t h e WNO l i n k a g e s i n t h i s complex show s u b s t a n t i a l d e v i a t i o n s f r o m 1 i n e a r i t y , w i t h t h e s e b e i n g t h e most b e n t 201 (~166°). The two W-N-0 a n g l e s i n t h e a s y m m e t r i c m o l e c u l e do n o t show a n y s t a t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e between them, however. In c o m p a r i s o n w i t h t h e s t r u c t u r e o f [ C p W ( N O ) H ] 2 ( y - H ) 2 d i s c u s s e d i n c h a p t e r 3, t h e s e g r o u p i n g s show s t a t i s t i c a l l y t h e same W-N a n d N-0 d i s t a n c e s , b u t t h e W-N-0 a n g l e s i n t h e d i n u c l e a r a l k y l h y d r i d e complex a r e more b e n t by ~ 8 ° , s u g g e s t i n g g r e a t e r (19) W-*NO ba c k d o n a t i o n i n t h e l a t t e r compound. T h i s i s a l s o r e f l e c t e d i n t h e 42 c m - 1 (1599 t o 1557 cm" 1 C H 2 C 1 2 s o l u t i o n ) d e c r e a s e i n t h e NO s t r e t c h i n g f r e q u e n c y . The W-W s e p a r a t i o n i n [ C p * W ( N O ) H ] ( y - H ) 2 [ C p * W ( N O ) ( C H 2 S i M e 3 ) ] i s 2.984(1) A, s i g n i f i c a n t l y l o n g e r t h a n t h e 2.9032(8) A f o u n d f o r T a b l e 4-VI I. I m p o r t a n t I n t e r a t o m i c D i s t a n c e s (A), A n g l e s (deg) and T o r s i o n A n g l e s (deg) f o r [ C p * W ( N 0 ) H ] ( y - H ) 2 [ C p » W ( N 0 ) ( C H 2 S i M e 3 ) ] . W(1)-W(2) W ( l ) - N ( l ) W ( 1 ) - N ( l ) - 0 ( 1 ) C P ( 1 ) - W ( 1 ) - N ( 1 ) W(2)-C(21) W(2)-N(2) W ( 2 ) - N ( 2 ) - 0 ( 2 ) W(1)-W(2)-C(21 ) W ( 2 ) - C ( 2 1 ) - S i C P ( 2 ) - W ( 2 ) - C ( 2 1 ) 2.984(1) 1.757(15) 165.8(11) 101.7 2.227(15) 1 .756(17) 166.4(13) 111.2(6) 122.1(9) 108.3 W d ) - C P ( l ) N ( 1 ) - 0 ( 1 ) W(2)-W(1)-N(1) CP(1)-W(1)-W(2) W(2)-CP(2) N ( 2 ) - 0 ( 2 ) W(1)-W(2)-N(2) N ( 2 ) - W ( 2 ) - C ( 2 1 ) C P ( 2 ) - W ( 2 ) - N ( 2 ) CP(2)-W(2)-W(1) 1 .997 1.225(17) 101.7(4) 129.2 2.057 1.242(19) 98.2(4) 93.5(7) 119.0 122.8 C P ( 1 ) - W ( 1 ) - W ( 2 ) - C P ( 2 ) 119 C P ( 1 ) - W ( 1 ) - W ( 2 ) - C ( 2 1 ) 111 CP(1)-W(1)-W(2)-N(2) 14 N(1)-W(1)-W(2)-CP(2) 26 N(1)-W(1)-W(2)-C(21) 104 N(1)-W(1)-W(2)-N(2) 159 202 [CpW(NO)H]2(u-H)2« I n a d e t a i l e d t h e o r e t i c a l s t u d y , Sherwood and H a l l * 6 4 * have shown t h a t t h e d i r e c t m e t a l - m e t a l i n t e r a c t i o n i n t h e c l o s e l y r e l a t e d O s 2 ( y - H ) 2 b r i d g e o f H 2 O s 3 ( C O ) 1 0 i s s t r e n g t h e n e d by t h e i r - a c i d i t y o f t h e c a r b o n y l l i g a n d s , w h i c h remove m e t a l - m e t a l a n t i b o n d i n g e l e c t r o n d e n s i t y . The f a c t t h a t t h e W-W d i s t a n c e i n t h e d i n u c l e a r a l k y l h y d r i d e complex i s l o n g e r t h a n t h a t i n [ C p W ( N O ) H ] 2 ( y - H ) 2 may t h e r e f o r e be t h e r e s u l t o f t h e f o r m e r h a v i n g more e l e c t r o n d e n s i t y t o c o n t r i b u t e i n t o m e t a l - m e t a l a n t i b o n d i n g o r b i t a l s . L i k e t h e o t h e r a l k y l h y d r i d e compounds r e p o r t e d i n t h i s c h a p t e r , t h i s m o l e c u l e i s s t e r i c a l l y c r o w d e d , p a r t i c u l a r l y a r o u n d W(2). T h i s i s r e f l e c t e d i n t h e d i s t o r t i o n o f t h e a n g l e a b o u t C ( 2 1 ) f r o m t h e t e t r a h e d r a l a n g l e t o 1 2 2 . 1 ( 9 ) ° . U n f o r t u n a t e l y , t h e h y d r i d e h y d r o g e n s c o u l d n o t be l o c a t e d by t h e X - r a y a n a l y s i s , b u t t h e p o s i t i o n o f t h e t e r m i n a l h y d r i d e c a n be a p p r o x i m a t e l y a s s i g n e d by t h e o b s e r v a t i o n o f a " h o l e " i n t h e c o o r d i n a t i o n s p h e r e o f W ( l ) . However, t h e s t r u c t u r e d o e s n o t g i v e a n y s u g g e s t i o n w h a t s o e v e r o f f u r t h e r h y d r i d e l i g a n d s . I t i s t h e *H NMR s p e c t r u m t h a t i s d e f i n i t i v e a s t o t h e e x i s t e n c e o f t h e t h r e e h y d r i d e atoms. T h e r e a r e e x t r e m e l y few d i n u c l e a r h y d r i d o a l k y l c o m p l e x e s i n t h e l i t e r a t u r e . The most e x t e n s i v e l y s t u d i e d o f t h e s e i s ( O C ) 4 ( H ) O s O s ( C H 3 ) ( C O ) 4 by N o r t o n , ( 3 3 a ) b u t t h i s i s n o t s t r i c t l y a n a l o g o u s b e c a u s e t h e a l k y l a n d h y d r i d e l i g a n d s a r e on d i f f e r e n t m e t a l c e n t r e s . More c l o s e l y r e l a t e d a r e t h e [ C p 2 Z r ( R ) ^ ( v - H ^ c o m p l e x e s t h a t a p p e a r t o be d i m e r s a s s o l i d s a n d p a r t i a l l y 203 F i g . 4-19. SNOOPI diagrams o f the molecular s t r u c t u r e o f [Cp«W(NO)H](w-H) 2[Cp*W(NO)(CH 2SiMe 3)]. a) View showing a s i d e view o f the molecule; b) View with a l l Cp* and SiMe_ methyl groups d e l e t e d . 2 0 4 d i s s o c i a t e d i n s o l u t i o n . * 6 5 ^ The most c l o s e l y r e l a t e d s p e c i e s * ^ ^ r e p o r t e d t o d a t e Is t h e s t r u c t u r a l l y c h a r a c t e r i z e d [ C p 2 W ( y - H ) 2 P t ( P E t 3 ) ( P h ) ] + , ( 6 7 ) w h i c h was b r i e f l y d i s c u s s e d i n c h a p t e r 3. T h i s seems t o be t h e o n l y o t h e r complex known t h a t H H c o n t a i n s a M=*==M-R g r o u p i n g , a l t h o u g h an ( R 3 S i ) P t = t = P t ( S i F ? 3 ) a r r a n g e m e n t h a s been o b s e r v e d . V e r y l i t t l e i s known a b o u t d i n u c l e a r r e d u c t i v e e l i m i n a t i o n ^ ^ 3 ) a n d s o t h e s t u d y o f s u c h p o t e n t i a l r e a c t i v i t y on [ C p * W ( N O ) H ] ( y - H ) 2 [ C p * W ( N O ) ( C H 2 S i M e 3 ) ] , e s p e c i a l l y i n c o m p a r i s o n w i t h t h e r e l a t e d m o n o n u c l e a r compounds, i s o f g r e a t f u t u r e i n t e r e s t . M. The *H NMR S p e c t r u m o f [ C p * W ( N O ) H ] ( u - H ) 2 [ C p * W ( N O ) ( C H 2 S i M e 3 ) ] . T h e r e i s a g r e a t d e a l o f i n f o r m a t i o n t o be g a i n e d f r o m a d e t a i l e d a n a l y s i s o f t h e *H NMR s p e c t r u m o f t h i s c o mplex. T h i s s p e c t r u m i s d e f i n i t i v e a s t o t h e c o n s t i t u t i o n o f t h e compound, and p r o v i d e s much i n f o r m a t i o n a s t o i t s g e o m e t r y . The f u l l s p e c t r u m ( i n C D 3 N 0 2 ) i s shown i n F i g . 4-20. N i t r o m e t h a n e — d 3 was c h o s e n a s t h e s o l v e n t b e c a u s e t h e r e s i d u a l p r o t o n r e s o n a n c e s o f many o f t h e more common NMR s o l v e n t s (C^Dg, C D C 1 3 > C D 2 C 1 2 , ( 5 ) ( C D 3 ) 2 C 0 ) o v e r l a p w i t h p e a k s due t o t h e c o m p l e x . I n t e r e s t i n g l y enough, t h e compound i s much l e s s s o l u b l e i n C D 3 N 0 2 ( 68) t h a n i t i s i n C-D,-. The f i r s t t h i n g t h a t i s a p p a r e n t a b o u t D 6 t h e s p e c t r u m ( b o t h i n C D 3 N 0 2 a n d CgDg), i s t h a t t h e r e i s o n l y one i s o m e r , i n c o n t r a s t t o t h e [ C p ' W ( N O ) H ] 2 ( y - H ) 2 (Cp'=Cp o r Cp*) 205 H, H E CPA Cp*c B H C SiMe. Cp B ON-^W B : HE HA H B k J 1 / A / H D ^BorC C ~ SiMe3 W A ~ N O H c ° r B NcP* H A J V u V . -2 F i g . 4-20. -4 8 (ppm) The 400-MHz lH NMR spectrum o f [Cp*W(NO)H](v-H) 2[Cp*W(NO)(CH 2SiMe 3)] i n CD 3N0 2- f o r a f u l 1 d i s c u s s i o n and assignment. See t e x t c o m p l e x e s . A d d i t i o n a l l y , t h e r e i s no i n d i c a t i o n o f any f l u x i o n a l i t y f r o m t h e s p e c t r u m , a s e x t e n s i v e c o u p l i n g i s o b s e r v e d . A s s i g n m e n t o f some a s p e c t s o f t h i s s p e c t r u m a r e s t r a i g h t f o r w a r d . S h a r p s i n g l e t s a r e o b s e r v e d f o r t h e two i n e q u i v a l e n t Cp* l i g a n d s a n d t h e S i M e 3 g r o u p . One o f t h e Cp* r e s o n a n c e s ( C p * B ) i s e x a c t l y c o i n c i d e n t ( i n CgD^) w i t h t h e a n a l o g o u s peak i n t h e s p e c t r u m o f [ C p * w ( N O ) H ] 2 ( y - H ) 2 a n d so i s a s s i g n e d t o t h e 1 i g a n d on Wg. The two p r o t o n s on t h e a-C o f t h e C H 2 S i M e 3 g r o u p a r e a s s i g n e d (Hg a n d H c) on t h e b a s i s o f t h e 2 g e m i n a l c o u p l i n g c o n s t a n t ( J g C = 12.5 Hz) a n d t h e o b s e r v a t i o n o f 183 W s a t e l l i t e s w i t h s m a l l c o u p l i n g c o n s t a n t s s i m i l a r t o t h o s e s e e n f o r t h e r e l a t e d m o n o n u c l e a r t u n g s t e n compounds. The a s s i g n m e n t o f t h e t h r e e r e m a i n i n g s e t s o f r e s o n a n c e s i s c o n s i d e r a b l y more i n v o l v e d . P r o t o n s A t h r o u g h E ( F i g . 4-20) f o r m a f i r s t - o r d e r , f i v e s p i n s y s t e m and d e c o u p l i n g a t e a c h o f t h e i r p o s i t i o n s e s t a b l i s h e d t h e c o u p l i n g c o n s t a n t s g i v e n i n T a b l e 4-11. In a d d i t i o n t o t h e g e m i n a l c o u p l i n g n o t e d a b o v e , one o f t h e a-C p r o t o n s (Hg) i s c o u p l e d t o one o f t h e h y d r i d e n u c l e i , H A , w h i l e t h e t h r e e h y d r i d e n u c l e i show f u l l c o u p l i n g amongst t h e m s e l v e s . E x p a n s i o n s o f t h e r e s o n a n c e s due t o H^, H n a n d Ĥ - a r e shown i n 183 F i g . 4-21, a l o n g w i t h t h e i r s i m u l a t i o n s ( e x c l u d i n g t h e W s a t e l 1 1 t e s ) . v o : 7 ; The a s s i g n m e n t s o f H A , H n a n d H E a s h y d r i d e 183 l i g a n d s a r e b a s e d on t h e o b s e r v a t i o n o f l a r g e , one-bond w c o u p l i n g s , t y p i c a l f o r t h i s c l a s s o f compound ( s e e c h a p t e r s 2 and 207 H, H D H, -20 Hz. F i g . 4-21. E x p a n s i o n s o f t h e e x p e r i m e n t a l ( t o p ) a n d s i m u l a t e d ( b o t t o m ) p e a k s o f t h e h y d r i d e r e g i o n s o f t h e 400-MHz *H NMR s p e c t r u m o f [ C p * W ( N O ) H ] ( u - H ) 2 [ C p * W ( N O ) ( C H 2 S i M e 3 ) ] . See F i g . 4-20 f o r a s s i g n m e n t o f t h e r e s o n a n c e s . 208 183 3 ) . F u r t h e r m o r e , i n t e g r a t i o n o f t h e W s a t e l l i t e s shows t h a t t h e H A a n d H n r e s o n a n c e s a r e due t o b r i d g i n g h y d r i d e l i g a n d s ( s a t e l l i t e s ~25% o f t h e a r e a ) , w h i l e t h e H £ p e a k s a r e due t o a t e r m i n a l h y d r i d e ( s a t e l l i t e s ~157. o f t h e a r e a ) . T h i s i s g i v e n a d d i t i o n a l s u p p o r t by t h e d e t e c t i o n o f s h o u l d e r s on t h e main 183 r e s o n a n c e o f H £ t h a t c a n be a s s i g n e d t o two-bond W c o u p l i n g . A p a r t i c u l a r l y n o t e w o r t h y a s p e c t o f t h e s e a s s i g n m e n t s i s t h e r e l a t i v e c h e m i c a l s h i f t s e x h i b i t e d by t h e b r i d g i n g a n d t e r m i n a l h y d r i d e l i g a n d s ( F i g . 4 - 2 0 ). The b r i d g i n g h y d r i d e p e a k s a r e f a r a p a r t , s e p a r a t e d by a l m o s t 12 ppm, w h i l e t h e t e r m i n a l h y d r i d e r e s o n a n c e i s s e p a r a t e d f r o m t h a t o f a b r i d g i n g 1 i g a n d by l e s s t h a n 1.3 ppm. T h i s f u r t h e r i l l u s t r a t e s t h e p o i n t made i n c h a p t e r 3 t h a t t h e c h e m i c a l s h i f t o f a h y d r i d e 1 i g a n d i s n o t a good i n d i c a t o r o f i t s b r i d g i n g o r t e r m i n a l n a t u r e . I n d e e d , i n t h i s c o mplex, t h e i n t e r m i n g l i n g o f t h e p e a k s due t o p r o t o n s A-E w o u l d 183 h a v e made a s s i g n m e n t i m p o s s i b l e w i t h o u t b e n e f i t o f t h e W s a t e 11i t e s . A s s i g n m e n t o f H A a n d H n t o t h e p o s i t i o n s shown i n F i g . 4-20 ca n be made on t h e b a s i s o f a s e r i e s o f NOE d i f f e r e n c e e x p e r i m e n t s . Enhancements o f t h e p e a k s due t o H A a n d Ĥ . were o b s e r v e d upon i r r a d i a t i o n o f t h e H Q r e s o n a n c e , w h i l e o n l y Hp enhancement o c c u r r e d when e i t h e r t h e H A o r H E peak was i r r a d i a t e d . T h i s shows t h a t H Q i s c l o s e ( i n s p a c e ) t o b o t h H A a n d Hg., a n d i s t h e r e f o r e o r i e n t e d on t h e s i d e o f t h e W-W a x i s t o w a r d s Ĥ ., w h i l e H A a n d H^ a r e w e l l s e p a r a t e d . S uch a n 209 a s s i g n m e n t f u r t h e r p e r m i t s t h e a s s i g n m e n t o f " c i s " a n d " t r a n s " 2 J H H c o u p l i n g i n a n HW(y-H) 2W s y s t e m . I t c a n be s e e n t h a t " t r a n s " c o u p l i n g (-9.0 Hz h e r e ) i s g r e a t e r t h a n " c i s " c o u p l i n g (5.0 Hz h e r e ) a n d t h e a s s i g n m e n t g i v e n i n T a b l e s 2-1 I a n d 4-1 I f o r t h e [ C p ' W ( N 0 ) H ] 2 ( y - H ) 2 (Cp'=Cp o r Cp*) c o m p l e x e s r e f l e c t t h i s . I t i s i n t e r e s t i n g t o n o t e t h a t i n a l l t h e s y s t e m s e x p l o r e d 2 1 i n t h i s work, J H H c o u p l i n g s a r e g r e a t e r t h a n J H H c o u p l i n g s H a c r o s s t h e w=^=w i n t e r a c t i o n — t h e s e s m a l l ' ^ H H v a l u e s a r e H p r o b a b l y m a n i f e s t a t i o n s o f t h e H-H a n t i b o n d i n g i n t e r a c t i o n s t h a t c a l c u l a t i o n s have shown t o be p r e s e n t . * 6 4 * No n u c l e a r O v e r h a u s e r e f f e c t was o b s e r v e d f o r t h e p e a k s due t o Hg o r H^ when a n y o f t h e t h r e e h y d r i d e r e s o n a n c e s were i r r a d i a t e d . C o n s e q u e n t l y , i n d i v i d u a l a s s i g n m e n t o f Hg and H c p e a k s i s n o t p o s s i b l e . B e c a u s e t h i s m o l e c u l e c o n t a i n s two i n e q u i v a l e n t t u n g s t e n 183 c e n t r e s , c o u p l i n g s o f t h e h y d r i d e l i g a n d s t o a W n u c l e u s when t h e l a t t e r i s s i t u a t e d a t one m e t a l c e n t r e s h o u l d be d i f f e r e n t t h a n when i t i s a t t h e o t h e r . S i n c e W s a t e l l i t e s due t o t h e f s o t o p o m e r c o n t a i n i n g two W n u c l e i c a n n o t be s e e n , t h e s a t e l l i t e s o b s e r v e d a r e t h e r e s u l t o f t h e s u p e r i m p o s i t i o n o f t h e 183 183 s p e c t r u m o f t h e f s o t o p o m e r w i t h W a t WA ( W A) on t h e 183 183 s p e c t r u m o f t h e i s o t o p o m e r w i t h W a t W 0 ( W_). I n s p e c t i o n O a o f F i g . 4-21 shows t h a t t h e t u n g s t e n - 1 8 3 s a t e l l i t e s f o r t h e b r i d g i n g h y d r i d e p e a k s a r e n o t s i m p l y s m a l l e r v e r s i o n s o f t h e m a i n r e s o n a n c e , b u t a r e more complex, i n d i c a t i n g t h a t c o u p l i n g s 210 183 183 t o WA a n d Wg a r e s i m i l a r , b u t n o t i d e n t i c a l . S i n c e i s a 183 t e r m i n a l h y d r i d e , i t s one-bond W s a t e l l i t e s ( c o u p l i n g t o 183 Wg) have t h e same p a t t e r n a s t h e main p e a k s , w h i l e t h e two- 183 bond c o u p l i n g t o WA i s much s m a l l e r a n d o b s e r v e d a s s h o u l d e r s . C a r e f u l a n a l y s i s o f t h e s a t e l l i t e s o f t h e H. a n d H~ p e a k s a l l o w A D t h e c a l c u l a t i o n o f i n d i v i d u a l l J H W v a l u e s , b u t a t t h i s s t a g e , 183 183 t h e y c a n n o t be a s s i g n e d i n d i v i d u a l l y t o Ŵ  a n d Wg. The s o l u t i o n t o t h i s p r o b l e m l i e s w i t h a s e r i e s o f s p i n t i c k l i n g e x p e r i m e n t s . * 7 0 * A s i m p l i f i e d s p l i t t i n g d i a g r a m f o r 183 t h r e e o f t h e s p i n s ( H E , H A and Wg, where WQ i s a W n u c l e u s ) i n t h e [ C p * W ( N O ) H ] ( u - H ) 2 [ C p * W ( N O ) ( C H 2 S i M e 3 ) ] m o l e c u l e i s shown i n F i g . 4-22. U n d e r n e a t h t h e d i a g r a m a r e d e n o t e d t h e s p i n s t a t e s +1/2 o r -1/2) o f t h e i n d i v i d u a l n u c l e i t h a t g i v e r i s e t o t h e s p l i t t i n g s . The s i t u a t i o n i s d e p i c t e d f o r when a l l t h r e e J ' s a r e p o s i t i v e . (The d i a g r a m w o u l d be t h e same i f a l l t h e s i g n s were r e v e r s e d , w i t h t h e + a n d - s i g n s i n t e r c h a n g e d ) . T h i s s p l i t t i n g 183 d i a g r a m o n l y a p p l i e s , o f c o u r s e , t o t h e W s a t e l l i t e s a n d n o t t o t h e main r e s o n a n c e s o f t h e s p e c t r u m . As may be s e e n , t h e u p f i e l d , o r r i g h t , h a l f o f e a c h s e t o f b o t h t h e H £ a n d H A s i g n a l s a r i s e f r o m Wg b e i n g i n t h e same, +1/2, s p i n s t a t e . T h e r e f o r e , i r r a d i a t i o n o f t h e r i g h t h a l f o f t h e H A s p e c t r u m s h o u l d r e s u l t i n p e r t u r b a t i o n o f t h e r i g h t h a l f o f t h e H E s p e c t r u m , a n d v i c e v e r s a . T h i s d e p e n d s on t h e s i g n o f 1 J H ( A ) _ U ( B ) D e , n 9 "the same a s *^H(E)-W(B) — ' ^ t h e s e s i g n s were o p p o s i t e , t h e n i r r a d i a t i o n o f t h e r i g h t h a l f o f t h e H A s p e c t r u m w o u l d g i v e a n e f f e c t on t h e 21 1 l e f t h a l f o f t h e H £ s p e c t r u m . The same r e s u l t c a n be o b t a i n e d f r o m an a n a l y s i s o f t h e a n a l o g o u s h D ~ " H A ~ W B S P 1 ' ^ ' 1 " ^ d i a g r a m , a s w e l l , o f c o u r s e , a s o t h e r p o s s i b l e c o m b i n a t i o n s . T h i s a l l o w s us t o d e t e r m i n e n o t o n l y t h e r e l a t i v e s i g n s o f t h e c o u p l i n g s o f H , H N a n d t o a n d WQ b u t a l s o t o d e t e r m i n e w h i c h '«-lHw c o u p l i n g c o n s t a n t p e r t a i n s t o w h i c h t u n g s t e n c e n t r e . The r e l e v a n t p a r t s o f t h e s p e c t r a f r o m t h e e x p e r i m e n t s t o make t h e s e d e t e r m i n a t i o n s a r e shown i n F i g . 4-23. H, H U B H E H A - + u B - - F i g - 4-22. - + + + - + - + + + - + + - + A s i m p l i f i e d s p l i t t i n g d i a g r a m f o r c o u p l i n g s e x h i b i t e d by [ C p * W ( N O ) H ] ( y - H ) 2 [ C p » W ( N O ) ( C H 2 S 1 M e 3 ) ] . S p i n s t a t e s (+1/2 o r - 1 / 2 ) a r e d e n o t e d by + o r - s i g n s . The s i t u a t i o n d e p i c t e d i s t h a t w i t h a l l t h r e e J ' s p o s i t i v e . See t e x t f o r a c o m p l e t e d i s c u s s i o n . 212 183 F i g u r e 4-23a shows e x p a n s i o n s o f t h e W s a t e l l i t e s o f t h e r e s o n a n c e s due t o H^, H n a n d H A « The t o p p a r t o f t h e f i g u r e shows t h e e x p e r i m e n t a l s p e c t r a . D i r e c t l y u n d e r n e a t h a r e shown (69) t h e s u p e r p o s i t i o n o f t h e s i m u l a t e d s p e c t r a v ' due t o c o u p l i n g t o 1 8 3W A ( t h i c k l i n e ) and 1 8 3 W g ( t h i n l i n e ) . ( O f c o u r s e , t h e a s s i g n m e n t s shown i n F i g . 4-23 a r e b a s e d on t h e s p i n t i c k l i n g e x p e r i m e n t s a b o u t t o be d e s c r i b e d . ) The b o t t o m p a r t o f F i g . 4- 23a shows t h e s i m u l a t e d s p e c t r a a f t e r t h o s e due t o t h e i n d i v i d u a l i s o t o p o m e r s have been s u m m e d . I t i s t h e s e summed s i m u l a t i o n s t h a t a r e t o be compared w i t h t h e e x p e r i m e n t a l s p e c t r a a n d , a s c a n be s e e n , t h e a g r e e m e n t i s e x c e l l e n t . The o t h e r p a r t s o f F i g . 4- 23 a r e o r g a n i z e d i n t h e same f a s h i o n . F i g . 4 - 2 3 . ( n e x t two p a g e s ) S p i n t i c k l i n g e x p e r i m e n t on [ C p * w ( N O ) H ] ( w - H ) 2 [ C p « W ( N O ) ( C H 2 S i M e 3 ) ] . In e a c h s e c t i o n , t h e t o p i s t h e e x p e r i m e n t a l s p e c t r u m , t h e 183 m i d d l e a r e t h e s i m u l a t i o n s o f t h e i n d i v i d u a l W s a t e l l i t e s s u p e r i m p o s e d upon e a c h o t h e r : t h i c k l i n e — 183 183 c o u p l i n g t o WA; t h i n l i n e — c o u p l i n g t o Wg, b o t t o m shows t h e sum o f t h e s i m u l a t e d t u n g s t e n - 1 8 3 s a t e l l i t e s , a) s p e c t r u m w i t h no i r r a d i a t i o n ; b ) , c) and d) t i c k l i n g i r r a d i a t i o n c e n t r e d a t t h e a r r o w . See t e x t f o r c o m p l e t e d i s c u s s i o n . 213  T 1 1 —1 1 • 215 N o r m a l l y , when a s p i n t i c k l i n g e x p e r i m e n t i s p e r f o r m e d ( i n a c o n v e n t i o n a l o r g a n i c , lH o n l y s y s t e m ) , low i r r a d i a t i o n powers a r e u s e d i n o r d e r t o a v o i d s a t u r a t i n g t h e e n t i r e r e s o n a n c e . * 7 0 * However, i n o u r s y s t e m , b e c a u s e t h e l j H ^ ' s a r e l a r g e , t h e +1/2 s p i n s t a t e o f WQ c a n be i r r a d i a t e d w i t h f u l l , c o n v e n t i o n a l d e c o u p l i n g power w i t h o u t s a t u r a t i n g t h e -1/2 s p i n s t a t e , a l l o w i n g t h e s e t i c k l i n g e x p e r i m e n t s t o be i n t e r p r e t e d s i m i l a r l y t o c o n v e n t i o n a l d e c o u p l i n g e x p e r i m e n t s . F i g . 4-23b shows t h e r e s u l t s o f t h e i r r a d i a t i o n o f t h e i go u p f i e l d h a l f o f t h e W s a t e l l i t e s o f t h e H A s p e c t r u m ( i r r a d i a t i o n c e n t r e d a t t h e a r r o w ) . B e c a u s e t h e s a t e l l i t e s due t o w A and Wg o v e r l a p so much, no d i f f e r e n t i a t i o n between t h e c o u p l i n g s t o t h e s e m e t a l n u c l e i i s p o s s i b l e h e r e . However, a s c a n be s e e n , t h i s i r r a d i a t i o n r e s u l t s i n t h e d e c o u p l i n g o f t h e u p f i e l d h a l v e s o f t h e s a t e l l i t e s f o r b o t h H^ a n d H n . C o m p a r i s o n o f t h e s e u p f i e l d s e c t i o n s w i t h t h e r i g h t h a l f o f t h e s i m u l a t i o n s g i v e n b e n e a t h shows e x c e l l e n t a g r e e m e n t . (The s i m u l a t i o n computer programme do e s n o t a l l o w f o r d e c o u p l i n g o f o n l y h a l f o f a d o u b l e t a n d so t h e l e f t h a l f o f t h e s i m u l a t i o n s s h o u l d be i g n o r e d . ) F i g . 4-23c, s h o w i n g i r r a d i a t i o n o f t h e r i g h t h a l f o f t h e H n s p e c t r u m , y i e l d s t h e same r e s u l t . I t i s t h e i r r a d i a t i o n i l l u s t r a t e d i n F i g . 4-23d t h a t a l l o w s t h e a s s i g n m e n t o f t h e one-bond J H W c o u p l i n g s t o t h e i n d i v i d u a l WA and Wg c e n t r e s . I r r a d i a t i n g t h e u p f i e l d h a l f o f t h e one-bond 183 W s a t e l l i t e s i n t h e H^ s p e c t r u m r e s u l t s o n l y i n t h e d e c o u p l i n g 216 o f t h e p a r t o f t h e t u n g s t e n s a t e l l i t e s i n t h e H n a n d s p e c t r a 183 t h a t come f r o m t h e Wg i s o t o p o m e r . C o n s e q u e n t l y , t h e o b s e r v e d u p f i e l d h a l v e s o f t h e H Q a n d H E t u n g s t e n s a t e l l i t e s a r e t h e 183 s u p e r p o s i t i o n s o f t h e s p e c t r a due t o t h e u n p e r t u r b e d WA 183 i s o t o p o m e r and t h e p e r t u r b e d Wg i s o t o p o m e r , a s t h e s i m u l a t i o n s 183 i l l u s t r a t e . What i s f o u n d i s t h a t Wg c o u p l e s t o H A a n d H n w i t h a l m o s t t h e same c o u p l i n g c o n s t a n t (83.5 and 84.0 Hz 183 r e s p e c t i v e l y ) , w h i l e WA e x h i b i t m a r k e d l y d i f f e r e n t c o u p l i n g s t o t h e s e n u c l e i (78.5 and 93.5 Hz r e s p e c t i v e l y ) . Why t h i s s h o u l d be s o i s n o t c l e a r . As n o t e d a b o v e , t h e s e s p i n t i c k l i n g e x p e r i m e n t s a l l o w t h e a s s i g n m e n t s o f t h e r e l a t i v e s i g n s o f t h e h y d r i d e - m e t a l c o u p l i n g c o n s t a n t s . In a l l t h e s e e x p e r i m e n t s , i r r a d i a t i o n o f t h e u p f i e l d h a l f o f a t u n g s t e n - 1 8 3 s a t e l l i t e r e s u l t s i n t h e p e r t u r b a t i o n o f t h e u p f i e l d h a l f o f t h e o t h e r s a t e l l i t e s . T h i s means t h a t 1 * 1 , 1 , 1 , _ _ H J H ( A ) - W ( A ) ' ° H ( A ) - W ( B ) t ° H ( D ) - W ( A ) ' UH(D)-W(B) a n a 1 J L J / C . . I 1 / D x a l l have t h e same s i g n . In a n o t h e r e x p e r i m e n t , t h e H ( t ) —W (b ) 183 r i g h t h a l f o f t h e W s a t e l l i t e s due t o t h e two-bond c o u p l i n g o f H^ w i t h WA, w h i c h a p p e a r s a s a s h o u l d e r on t h e mai n r e s o n a n c e ( F i g . 4 - 2 3 a ) , i s i r r a d i a t e d . B e c a u s e t h i s c o u p l i n g i s s m a l l (11.5 H z ) , a low i r r a d i a t i o n power must be u s e d . A l t h o u g h t h e r e s u l t s a r e n o t a s unambiguous a s f o r t h e o t h e r s p i n t i c k l i n g s , t h e s p e c t r a a p p e a r t o a g a i n show p e r t u r b a t i o n s o f t h e u p f i e l d 2 h a l v e s o f t h e H n a n d Hg- s p e c t r a . T h i s means t h a t J H ( E ) - W ( A ) n a s t h e same s i g n a s t h e o t h e r c o u p l i n g s j u s t m e n t i o n e d . The o v e r a l l 217 r e s u l t o f t h i s i s t h a t , f o r t h i s s y s t e m , t h e s i g n s o f t h e o n e - 1 183 bond b r i d g i n g a n d t e r m i n a l h y d r i d e H- W c o u p l i n g s a n d t h e two- 1 183 bond t e r m i n a l h y d r i d e H- W c o u p l i n g s a r e t h e same. T h i s c o n f i r m s t h e a s s u m p t i o n on t h i s p o i n t made f o r t h e a n a l y s e s c a r r i e d o u t i n c h a p t e r 3. The s p i n - t i c k l i n g e x p e r i m e n t s r e p o r t e d h e r e do n o t a l l o w a s s i g n m e n t o f t h e a b s o l u t e s i g n o f t h e h y d r i d e - t u n g s t e n - 1 8 3 183 c o u p l i n g c o n s t a n t s . F o r t h i s t o be done, a c c e s s t o t h e W s p e c t r u m o f t h e complex i s n e c e s s a r y and a p p r o p r i a t e e q u i p m e n t i s n o t a v a i l a b l e . T h i s i s u n f o r t u n a t e , a s [ C p * W ( N O ) H ] ( y - H ) 2 [ C p * W ( N O ) ( C H 2 S i M e 3 ) ] i s u n i q u e l y s u i t e d t o do t h i s . Geminal c o u p l i n g s u c h a s t h a t e x h i b i t e d by t h e w-CH DH,,-Si (72) f r a g m e n t i s a l w a y s n e g a t i v e a n d s o i t w o u l d be a r e l a t i v e l y s i m p l e m a t t e r t o d e t e r m i n e t h e o t h e r a b s o l u t e s i g n s f o r t h e c o u p l e d n u c l e i i n t h i s s y s t e m . Few a b s o l u t e s i g n d e t e r m i n a t i o n s have been made f o r t r a n s i t i o n m e t a I - h y d r i d e c o u p l i n g * 7 3 * a n d , a s f a r a s we c a n t e l l , no s u c h d e t e r m i n a t i o n s have been made i n t u n g s t e n s y s t e m s . N. The Pathway f o r t h e F o r m a t i o n o f [Cp*W(NO) H] 2 (y-H) 2 arid [ C p * W ( N O ) H ] ( y - H ) 2 [ C p * W ( N O ) ( C H 2 S i M e 3 ) ] . The c o n c u r r e n t f o r m a t i o n o f t h e s e two compounds i s i n t r i g u i n g a n d a l i k e l y pathway l e a d i n g t o t h i s o c c u r r e n c e i s g i v e n i n Scheme 4-V. E x p e r i m e n t s done i n c o n n e c t i o n w i t h t h e p r e p a r a t i o n s o f t h e m o n o n u c l e a r a l k y l h y d r i d e c o m p l e x e s d i s c u s s e d 218 i n s e c t i o n C o f t h i s c h a p t e r p r o v i d e s u p p o r t f o r s t e p s a a n d b i n Scheme 4-V, l e a d i n g t o t h e f o r m a t i o n o f t h e 1 6 - e l e c t r o n W*RH f r a g m e n t . I t i s r e a s o n a b l e t o e x p e c t t h a t t h i s c a n u n d e r g o f u r t h e r h y d r o g e n o l y s i s v i a s t e p s c a n d d t o f o r m W*H2, t h e o t h e r f r a g m e n t n e c e s s a r y t o g i v e t h e o b s e r v e d compounds. I t i s e x p e c t e d t h a t s t e p c, l i k e s t e p a , woul d be r e l a t i v e l y s l o w compared t o t h e r a p i d r e d u c t i v e e l i m i n a t i o n s o f b a n d d. T h e s e f r a g m e n t s w o u l d t h e n u n d e r g o t h e c o u p l i n g r e a c t i o n s e, f a n d g t o g i v e t h e d i n u c l e a r m o l e c u l e s , RW*(y-H) 2W*R, HW*(u-H) 2W*R a n d HW*(u-H) 2W*H, o f w h i c h t h e l a t t e r two a r e t h e i s o l a t e d p r o d u c t s . In t h e r e a c t i o n done a t 920 p s i g , t h e mixed p r o d u c t , Hw*(y-H) 2W*R i s t h e m a j o r p r o d u c t a n d no RW*(y-H) 2W*R compound was o b s e r v e d . T h i s means t h a t t h e r e must be a d e l i c a t e b a l a n c e between t h e r a t e o f s t e p c a n d t h a t o f s t e p f i n o r d e r f o r some, b u t n o t a l l , o f t h e W*RH t o be c o n v e r t e d t o t h e W*H2 n e c e s s a r y f o r t h e f o r m a t i o n o f b o t h i s o l a t d d i n u c l e a r m a t e r i a l s . I t a l s o means t h a t W*H2 i s an e f f i c i e n t t r a p o f t h e W*RH f r a g m e n t , and t h a t t h e d i n u c l e a r a l k y l h y d r i d e complex i s o l a t e d i s a n a l o g o u s t o t h e m o n o n u c l e a r s p e c i e s d i s c u s s e d e a r l i e r , w i t h t h e p h o s p h i n e r e p l a c e d by t h e Cp*W(N0)H 2 g r o u p i n g . I t i s a l s o i n t e r e s t i n g t o n o t e t h a t t h e p r o d u c t d i s t r i b u t i o n between HW*(y-H) 2W*R a n d HW*(y-H) 2W*H i s n o t n o t i c e a b l y a l t e r e d when t h e r e a c t i o n t i m e ( a t 920 p s i g H 2 a n d i n he x a n e s ) i s c h a n g e d f r o m 20 min t o 24 h. T h i s s u g g e s t s t h a t HW(u-H) 2W*R doe s n o t d i s s o c i a t e i n t o m o n o n u c l e a r f r a g m e n t s i n s o l u t i o n , n o r i s i t l i a b l e t o h y d r o g e n a t i o n a s a d i n u c l e a r 219 s p e c i e s . Scheme 4-V H, - TMS w*R2 -r_w*R2H2] W*=Cp*W(NO) R=C H 2 S i M e 3 [W*RH] H, [ W » R H 3 ] - TMS [W*H 2] 2 [W*RH] R W * ( u - H ) 2 W » R [ W » H 2 ] + [W*RH] -HW*(y-H) 2W*R 9 2 [W*H 2] HW*(u-H)2W*H When t h i s h y d r o g e n o l y s i s i s done a t lower p r e s s u r e s ( s e c t i o n J ; 80 p s i g i n s t e a d o f 920 p s i g ) , among t h e numerous p e a k s p r e s e n t i n t h e lH NMR s p e c t r u m o f t h e c r u d e r e a c t i o n m i x t u r e a r e ones a t t r i b u t a b l e t o [Cp*W ( N O ) H ] ( y - H ) 2 [ C p * W ( N O ) ( C H 2 S i M e 3 ) ] a n d [ C p * W ( N O ) H ] 2 ( y - H ) 2 . In t h i s s y s t e m , t h e p r o p o r t i o n o f t h e f o r m e r t o t h e l a t t e r ( H W * ( y - H ) 2 W » R t o HW*(y-H) 2W*H) a p p e a r s t o be g r e a t e r t h a n i n t h e h i g h e r p r e s s u r e c a s e . T h i s i s a s wou l d be e x p e c t e d , s i n c e a lower H 2 p r e s s u r e s h o u l d n o t c o n v e r t a s much W*RH t o W*H 2. In a d d i t i o n t o t h e s e t s o f pe a k s a s s i g n a b l e t o H W * ( y - H ) 2 W « R and HW*(y-H) 2W*H i s a n o t h e r p r o m i n e n t s e t s i m i l a r t o 220 t h a t o f HW*(y-H) 2W*R. U n l i k e t h e f i v e s p i n s y s t e m ( e x c l u d i n g Cp* an d S i M e g r e s o n a n c e s ) o b s e r v e d f o r HW*(y-H) 2W*R ( s e e s e c t i o n M), t h i s o t h e r s e t c o n s i s t s o f a f o u r s p i n s y s t e m , l a c k i n g a t e r m i n a l h y d r i d e r e s o n a n c e . However, i t d o e s i n c l u d e two b r i d g i n g h y d r i d e p e a k s a t 6 * -7.8 (. l^ h V ) * 74 Hz) a n d » 6.0 ( ! J H w * 96 Hz) a n d two 2 g e m i n a l W-CH - S i p r o t o n s a t < * -0.3 a n d * -1.4 c o u p l e d w i t h J * 12 Hz, w i t h t h e s e c o n d o f t h e s e c o u p l e d t o t h e f i r s t b r i d g i n g 2 h y d r i d e w i t h » 3 Hz (NMR d a t a i n CgDg). C o m p a r i s o n o f t h e s e d a t a w i t h t h o s e g i v e n i n T a b l e 4-11 f o r [ C p * W ( N 0 ) H ] ( y - H ) 2 [ C p * W ( N 0 ) ( C H 2 S i M e 3 ) ] i n C 6 D 6 ( t h e c o u p l i n g c o n s t a n t s a r e g i v e n f o r t h e C D 3 N 0 2 s p e c t r u m ) shows a r e m a r k a b l e r e s e m b l a n c e . In a d d i t i o n , t h e i n t e g r a t i o n s f o r t h e g e m i n a l p r o t o n s i n t h i s f o u r s p i n s y s t e m i s t w i c e t h a t r e l a t i v e t o t h e h y d r i d e p e a k s t h a n i s t h e c a s e f o r t h e HW*(y-H) 2W*R compound. T a k e n t o g e t h e r , t h e s e d a t a s t r o n g l y s u g g e s t t h e p r e s e n c e o f t h e c e n t r o s y m m e t r i c d i m e r t h e p r o d u c t o f s t e p e i n Scheme 4-V. In t h e s e l o w e r p r e s s u r e r e a c t i o n s , t h i s m a t e r i a l i s p r e s e n t i n a p p r o x i m a t e l y t h e same q u a n t i t y a s t h e HW*(y-H) 2W*R c o m p l e x . U n f o r t u n a t e l y , t h e l a r g e number o f o t h e r p r o d u c t s f r o m c o m p e t i n g p a t h w a y s i n t h i s r e a c t i o n m i x t u r e has n o t y e t a l l o w e d t h e I s o l a t i o n o f t h i s compound. 221 The f a c t t h a t RW*(y-H) 2W*R p r o d u c t i o n a p p e a r s t o be d e c r e a s e d w h i l e f o r m a t i o n o f HW*(y-H) 2WR and HW*(u-H) 2W*H i n c r e a s e s a s t h e H 2 p r e s s u r e i s r a i s e d i s c o n s i s t e n t w i t h t h e pathway p r o p o s e d i n Scheme 4-V and w i t h s t e p c b e i n g somewhat r a t e d e t e r m i n i n g . T h e r e f o r e , f u r t h e r i n c r e a s e s i n H 2 p r e s s u r e s h o u l d i n c r e a s e t h e p r o p o r t i o n o f HW*(u-H) 2W*H f o r m e d . However, o u r a p p a r a t u s i s l i m i t e d t o a p r e s s u r e o f ~1400 p s i g , a nd an e x p e r i m e n t u s i n g 1290 i n s t e a d o f t h e 920 p s i g u s e d b e f o r e d i d n o t n o t i c e a b l y a l t e r t h e r a t i o o f [ C p * W ( N 0 ) H ] ( y - H ) 2 t o [ C p * W ( N 0 ) H ] ( y - H ) 2 [ C p * W ( N 0 ) ( C H 2 S i M e 3 ) ] . C o n s e q u e n t l y , i t i s p r o b a b l e t h a t a n o t h e r , o r d e r - o f - m a g n i t u d e , i n c r e a s e i n H 2 p r e s s u r e i s n e c e s s a r y t o g e t a s u b s t a n t i a l improvement i n [Cp * W ( N O ) H ] ( y - H ) 2 p r o d u c t i o n , a t l e a s t i n a room t e m p e r a t u r e , h e x a nes s o l v e n t r e a c t i o n . I t i s s u g g e s t e d t h e r e f o r e , t h a t t h e most p r o m i s i n g r o u t e t o t r y n e x t t o o b t a i n s i g n i f i c a n t amounts o f [ C p ' W ( N 0 ) H ] ( y - H ) 2 (Cp'=Cp o r C p * ) , w h i c h i n some s e n s e has been t h e m o t i v a t i n g f o r c e b e h i n d most o f t h e work d e s c r i b e d i n t h i s t h e s i s , i s t o c o n t i n u e h i g h - p r e s s u r e h y d r o g e n a t i o n s o f t h e Cp*W(N0)R 2 compounds and i n v e s t i g a t e t h e e f f e c t s o f v a r y i n g t h e t e m p e r a t u r e , s o l v e n t and R 1 i g a n d . 222 0. R e f e r e n c e s a n d N o t e s 1. L e g z d i n s , P.; R e t t i g , S . J . ; S a n c h e z , L.; B u r s t e n , B.E.; G a t t e r , M.G. J . Am. Chem. S o c . 1985, 107, 1411-1413. 2. L e g z d i n s , P.; R e t t i g , S . J . ; S a n c h e z , L. Q r g a n o m e t a l 1 i c s 1985, 4. 1470-1471. 3. L e g z d i n s , P.; S a n c h e z , L. Jk_ Am. Chem. 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The p r e p a r a t i o n o f Cp*W(C0) 2(NO) u s i n g C 5 M e 5 H a n d NaNH 2 i s n o t t h e optimum r o u t e f r o m W(CO)g a n d C^Me 5H. D r y d e n , N.H.; P h i l l i p s , E.C. p e r s o n a l c o m m u n i c a t i o n . 12. Hoyano, J.K.; L e g z d i n s , P.; M a l i t o , J.T. I n o r g . S y n t h . 223 1978, 18, 126-131. 13. Cp*W(NO)I 2 was f i r s t p r e p a r e d by C.R. Nu r s e o f t h i s l a b o r a t o r y ( N u r s e , C.R. Ph.D. D i s s e r t a t i o n , The U n i v e r s i t y o f B r i t i s h C o l u m b i a , 1983). The p r e p a r a t i o n d e s c r i b e d i n t h e p r e s e n t work i s s u p e r i o r . 14. M e 3 S i C H 2 M g C l i s s o l d a s a 1.0 M s o l u t i o n i n d i e t h y l e t h e r by t h e A l d r i c h C h e m i c a l Co. 15. I d e n t i f i e d by a n a l o g y t o C p W ( 0 ) 2 ( C H 2 S i M e 3 ) . 16. H u n t e r , A.D.; L e g z d i n s , P. Organometa 1 1i c s 1986, 5, 1001 — 1009. 17. 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S o c . , Da 1 t o n T r a n s . 1979, 1557-1562. c) B e r r y , M.; E l m i t t , K.; G r e e n , M.L.H. v K _ Chem. S o c . , 224 Da 1 t o n T r a n s . 1979, 1950-1958. 22. F i s c h e r , E.O.; F r a n k , A. Chem. B e r . 1978, 111, 3740-3744. 23. Yang, G.K.j Bergman, R.G. J_^ Am. Chem. S o c . 1983, 105, 6500-6501. 24. T h e r e was a s t a t i s t i c a l l y s i g n i f i c a n t peak i n t h e f i n a l d i f f e r e n c e F o u r i e r map o f C p R e ( C 0 ) 2 ( H ) ( C H 2 C 6 H 5 ) t h a t was (22) a s c r i b e d t o t h e h y d r i d e 1 i g a n d , ' b u t i t i s n o t i n a c h e m i c a l l y r e a s o n a b l e p o s i t i o n . 25. P a r s h a l 1 , G.W. "Homogeneous C a t a l y s i s " ; W i l e y : T o r o n t o , 1980. 26. a) Hal p e r n , J . A c c . Chem. Res. 1982, 15, 238-244. b) C o l 1 man, J.P.; Hegedus, L.S.; N o r t o n , J.R.; F i n k e , R.G. " P r i n c i p l e s a n d A p p l i c a t i o n s o f O r g a n o t r a n s i t i o n M e t a l C h e m i s t r y " ; U n i v e r s i t y S c i e n c e B ooks: M i l l V a l l e y , CA, 1987, p 100 a n d r e f e r e n c e s t h e r e i n . c ) C a l h o r d a , M.J.; D i a s , A.R.; Minas de P i e d a d e , M.E.; Salema, M.S.; M a r t i n h o S i m o e s , J.A. Q r g a n o m e t a l 1 i c s 1987, 6, 734-738 a n d r e f e r e n c e s t h e r e i n . 27. H a l p e r n , J . A c c . Chem. Res. 1982, 15, 332-338. 28. J o n a s , K.; W i l k e , G. Angew. Chem., I n t . E d . E n g l . 1969, 8, 519-520. 29. M i c h e l i n , R.A.; B e l l u c o , U.; Ros, R. I n o r g . Chim. A c t a 1976, 24, L33-L34. 30. A b i s , L.; S a n t i , R.; H a l p e r n , J . J_^ Q r g a n o m e t a l . Chem. 1981, 215, 263-267. 225 31. A b i s , L.; Sen, A.; H a l p e r n , J . J_j_ Am. Chem. S o c . 1978, 100, 2915-2916. 32. M i l s t e i n , D. A c c . Chem. 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PMePh 2 : 6p = -28 ppm (CgD^) by c o m p a r i s o n w i t h an a u t h e n t i c samp1e. 41. OPJlePh 2 : <5H = 1.53 ( d , 2 J H p = 13.2 H z ) , 6p = 25.0 (CgDg) by c o m p a r i s o n w i t h an a u t h e n t i c s a m p l e ; f o r p r e p a r a t i o n s e e r e f . 17. 42. C o l 1 man, J . P . ; Hegedus, L.S.; N o r t o n , J.R.; F i n k e , R.G. Op. C i t . , p 167 a n d r e f e r e n c e s t h e r e i n . 43. L e g z d i n s , P.; M a r t i n , D.T.; N u r s e , C R . I n o r g . Chem. 1980, 226 19, 1560-1564 a n d r e f e r e n c e s t h e r e i n . 44. C.R. N u r s e u n s u c c e s s f u l l y a t t e m p t e d t o i s o l a t e C p » W ( C 0 ) ( N O ) I 2 . ( 1 3 ) 45. D r y d e n , N.H. p e r s o n a l c o m m u n i c a t i o n . 46. J o n e s , R.H.; E i n s t e i n , F.W.B. p e r s o n a l c o m m u n i c a t i o n . 47. C p W ( N O ) ( C H ^ S i M e 3 ) 2 a l s o shows L e w i s b a s e p r o p e r t i e s : B r u n e t , N. p e r s o n a l c o m m u n i c a t i o n . 48. PMe 3 i s one o f t h e most s t r o n g l y d o n a t i n g o f t h e t e r t i a r y p h o s p h i n e s — s e e Tolman, C.A. Chem. Rev. 1977, 77, 313-348. 49. A f i v e - f o l d e x c e s s o f PMe 3 was u s e d i n o r d e r t o m a i n t a i n a s u f f i c i e n t c o n c e n t r a t i o n o f t h i s v o l a t i l e m a t e r i a l i n s o l u t i o n — s e e : Rosenbaum, E . J . ; S a n d b e r g , C.R. Am. Chem. S o c . 1940, 62. 1622-1623. 50. K l a h n - O l i v a , A.H.; S i n g e r , R.D.; S u t t o n , D. J_j_ Am. Chem. S o c . 1986, 108, 3107-3108. 51. A r o m a t i c C-C s t r e t c h i n g f r e q u e n c i e s o c c u r i n t h e 1500-1600 cm 1 r e g i o n o f t h e IR s p e c t r u m — s e e : M o r r i s o n , R.T.; Boyd, R.N. " O r g a n i c C h e m i s t r y " , 3 r d e d . ; A l l y n a n d B a c o n : B o s t o n , 1973, p 444. 52. a) C h e t c u t i , P.E.; Hawthorne, M.F. J_;_ Am. Chem. S o c . 1987, 109. 942-943. b) Werner, H.; Hohn, A.; O z i a l l a s , M. Angew. Chem., I n t . E d . E n g l . 1986, 25. 1090-1092. 53. One o f t h e t e c h n i q u e s u s e d by i n v e s t i g a t o r s o f a l k a n e C-H a c t i v a t i o n t o i d e n t i f y a nd i s o l a t e t h e p r o d u c t s o f t h e 227 r e a c t i o n has been t o t r e a t t h e r e s u l t i n g a l k y l h y d r i d e c omplex w i t h a h a l o g e n a t e d h y d r o c a r b o n . T h i s u s u a l l y r a p i d l y r e s u l t s i n a much more s t a b l e a l k y l halocompound t h a t c a n r e a d i l y be c h r o m a t o g r a p h e d , a n d t h u s s e p a r a t e d f r o m t h e o r i g i n a l r e a c t i o n b y - p r o d u c t s . U n f o r t u n a t e l y , t h i s r o u t e i s u n a v a i l a b l e t o u s , a s t r e a t m e n t o f t h e h y d r i d o a l k y l c o m p l e x e s d e s c r i b e d i n t h i s c h a p t e r w i t h C B r ^ i n C H 2 C 1 2 g i v e s no s i g n i f i c a n t r e a c t i o n e v e n a f t e r 24 h. As o u r compounds r e a c t w i t h a l l c h r o m a t o g r a p h y m e d i a t r i e d ( F l o r i s i l , S i l i c a g e l , Sephadex, A l u m i n a ( I ) and ( I I I ) ) e x c e p t A l u m i n a ( V ) ( w h i c h i s n o t u s e f u l f o r e f f e c t i n g s i g n i f i c a n t s e p a r a t i o n s ) , we have had no s u c c e s s i n e m p l o y i n g c h r o m a t o g r a p h y t o i s o l a t e s m a l l amounts o f a d e s i r e d p r o d u c t f r o m a v e r y d i r t y r e a c t i o n . 54. C p * w ( N O ) ( P M e 3 ) 2 was i d e n t i f i e d by i t s c h e m i c a l s h i f t a n d c h a r a c t e r i s t i c l a r g e *«-lp̂  i n t h e 3 1 P { * H ) NMR s p e c t r u m by c o m p a r i s o n w i t h an a u t h e n t i c sample ( s e e E x p e r i m e n t a l S e c t i o n ) . 55. I t s h o u l d be n o t e d t h a t C p * W ( N O ) ( P M e 3 ) 2 a p p e a r s t o p o s s e s s a v e r y e l e c t r o n - r i c h m e t a l , w i t h v K 1 „ ( C H 0 C l 0 ) = 1498 cm one NO 2 2 o f t h e l o w e s t f r e q u e n c i e s known f o r a ( p r e s u m a b l y ) l i n e a r NO g r o u p . * 5 6 * L i k e o t h e r C pM(NO)L 2 c o m p o u n d s , * 1 6 * t h i s complex i s v e r y a i r - s e n s i t i v e a n d c a n n o t t o l e r a t e e v e n b r i e f e x p o s u r e t o a i r . I n t e r e s t i n g l y , upon e x p o s u r e t o a i r , no c o l o u r c h a n g e f r o m i t s i n i t i a l o r a n g e i s o b s e r v e d , however 228 t h e e l e m e n t a l a n a l y s i s t h e n i s no l o n g e r c o r r e c t f o r t h e b i s - L compound and t h e V N Q d i s a p p e a r s i n i t s IR s p e c t r u m . 56. C h r i s t e n s e n , N.J.; H u n t e r , A.D.; L e g z d i n s , P.; S a n c h e z , L. 1norg. Chem. i n p r e s s . 57. S u s l i c k , K.S. Adv. Q r g a n o m e t a l . Chem. 1986, 25, 73-119. 58. R i c h t e r - A d d o , G.B. p e r s o n a l c o m m u n i c a t i o n . 59. R i c h t e i — A d d o , G.B.; Was s i n k , 8. p e r s o n a l c o m m u n i c a t i o n . 60. L e g z d i n s , P.; M a l i t o , J . T . I n o r g . Chem. 1975, 14, 1875. 61. M a b b o t t , G.A. Chem. Ed. 1983, 60, 687-702 and r e f e r e n c e s t h e r e i n. 62. T h e o r e t i c a l c u r v e s have been d e v e l o p e d f o r p l o t s o f i l\ pc' pa as a f u n c t i o n o f s c a n r a t e f o r a number o f s i t u a t i o n s i n v o l v i n g v a r i o u s c o m b i n a t i o n s o f charge t r a n s f e r c o u p l e d w i t h d i f f e r i n g t y p e s o f c h e m i c a l r e a c t i o n s . The shape o f t h e p l o t i s c h a r a c t e r i s t i c o f a p a r t i c u l a r c o m b i n a t i o n o f c h a r g e t r a n s f e r and c h e m i c a l r e a c t i o n — s e e : N i c h o l s o n , R.S.; S h a i n , I. A n a l . Chem. 1964, 36, 706-723. 63. a) K o c h i , J.K. " O r g a n o m e t a 1 1 i c Mechanisms and C a t a l y s i s " ; A c a d e m i c P r e s s : New Y o r k , 1978, pp 282-285, 350-354. b) T h e r m a l l y , p h o t o 1 y t i c a 1 1 y a n d o x i d a t i v e l y i n d u c e d e l i m i n a t i o n o f b e n z e n e has been o b s e r v e d f r o m C p 2 w ( P h ) ( H ) . No d e t a i l e d m e c h a n i s t i c s t u d i e s have been c a r r i e d o u t on t h e (21) t h e r m a l o r p h o t o c h e m i c a l r e a c t i o n s . The e l e c t r o c h e m i c a l l y i n d u c e d r e a c t i o n has been shown t o o c c u r n o t by s i m p l e r e d u c t i v e e l i m i n a t i o n , b u t r a t h e r t o i n v o l v e 229 s o l v e n t m o l e c u l e s — s e e : K l i n g l e r , R . J . ; Huffman, J .C.; K o c h i , J.K. J . Am. Chem. S o c . 1980, 102, 208-216. 64. Sherwood, D . E . , J r . ; H a l l , M.B. I n o r g . Chem. 1982, 21, 3458- 3464. 65. a) G e l l , K . J . ; S c h w a r t z , J . JL_ Am. Chem. S o c . 1978, 100, 3246-3248. b) J o r d a n , R.F.; B a j g u r , C.S.; D a s h e r , W.E.; R h e i n g o l d , A.E. O r g a n o m e t a l 1 i c s 1987, 6, 1041-1051. 66. O t h e r known h y d r i d o a l k y l c o m p l e x e s w i t h a t l e a s t one b r i dg i ng h y d r i de 1i gand i nc1ude: a) Cp*(Ph) I r ( y - H ) ( p - n 1 ~ n 3-a 1 1 y 1 ) I r C p * — M c G h e e , W.D.; Bergman, R.G. J_^ Am. Chem. S o c . 1986, 108, 5621-5622. b) { [ ( E t 3 P ) 2 P t P h ] ( u - H ) [ P t H ( P E t 3 ) 2 ] } + — B r a c h e r , G.; Gove, D.M.; V e n a n z i , L.M.; B a c h e c h i , F.; Mura, P.; Z a m b o n e l l i , L. Angew. Chem., I n t . Ed. E n g l . 1978, 17, 778-779. c) [ C p 2 H W ( u - H ) ( P E t 3 ) 2 ( P h ) ] + ( 6 7 ) d) { P t [ P ( C 6 H 1 1 ) 3 ] ( S i E t 3 ) ) 2 ( u - H ) 2 — C l r i a n o , M.; G r e e n , M; Howard, J.A.; P r o u d , J . ; S p e n c e r , J . L . ; S t o n e , F.G.A.; T s i p i s , C.A. J_j_ Chem. S o c . , Da 1 t o n T r a n s . 1978, 801-808. 67. A l b i n a t i , A.; N a e g e l i , R.; T o g n i , A.; V e n a n z i , L.M. Organometa11i c s 1983, 2, 926-928. 68. C H 3 N 0 2 , a l t h o u g h a q u i t e p o l a r s o l v e n t , i s known t o have po o r d o n a t i n g p r o p e r t i e s — s e e : Mayer, U.; Gutmann, V.; G e r g e r , W. Monatsh. Chem. 1975, 106, 1235-1257 and r e f e r e n c e s t h e r e i n . 230 69. S c h a t z , P.F. RACOON 2.0; Moore, J.W. d i r e c t o r ; P r o j e c t SERAPHIM; E a s t e r n M i c h i g a n U n i v e r s i t y : Y p s i l a n t i , MI, 48197, 1984. 70. B e c k e r , E.D. " H i g h R e s o l u t i o n NMR", 2nd e d . ; A c a d e m i c : T o r o n t o , 1980, pp 213-216. 71. The computer p r o g r a m t o sum RACOON 2.0 f i l e s was w r i t t e n by N e i l H. D r y d e n o f o u r r e s e a r c h g r o u p . 72. B e c k e r , H.D. Op. C i t . , p 95. 73. l j H P t has been f o u n d t o be p o s i t i v e i n t r a n s - [ ( E t ^ P ) 2 P t H C 1 ] — s e e : M c F a r l a n e , W. J_;_ Chem. S o c . , Chem. Commun. 1967, 772- 773. 74. B e c k e r , E.O. Op_ C i t . , pp 102-104 and r e f e r e n c e s t h e r e i n . 231 S p e c t r a 1 A p p e n d i x - S e l e c t e d IR and NMR s p e c t r a Compound P a9 e £ C p W ( N O ) I ] 2 ( i i - H ) 2 233 [ C p W ( N O ) H ] 2 ( y - H ) 2 233 [ C p W ( N O ) { P ( O P h ) 3 J ] 2 ( p - H ) 2 234 CpW(NO)H 2CP(OPh) 33 234 [ C p W ( N O ) B r 2 ] 2 235 Cp W ( N O ) B r H [ P ( O P h ) 3 ] 236 C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) [ P ( O P h ) 3 ] 238 C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e P h 2 ) 240 C p W ( N O ) ( H ) [ P ( O P h ) 2 ( O C 6 H 4 ) ] 242 C p * W ( N 0 ) I 2 244 C p * W ( N O ) ( C H 2 S i M e 3 ) 2 245 C p * W ( 0 ) 2 ( C H 2 S i M e 3 ) 246 C p * W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e 3 ) 247 C p * W ( N 0 ) ( H ) ( C 6 H 5 ) ( P M e 3 ) 250 C p * W ( N O ) ( P M e 3 ) 2 251 [ C p * W ( N O ) H ] 2 ( u - H ) 2 253 [ C p * W ( N O ) H ] ( u - H ) 2 [ C p * W ( N O ) ( C H 2 S i M e 3 ) ] 254 232 CCpW<NO>13 2 9 J - H >2 i n CH2C12 — O. 2 mm O Q I 1 233 ABSORBANCE ABSORBANCE ABSORBANCE ABSORBANCE C p W ( N O ) B r H [ P ( O P h ) 0 ] NMR i n C,D 300-MHz JH . JAUAJL I I I I I I I I I I | I M I I I I I I | I I I I I I I I I | I I I I I I I I I | I I I I I I I I I | I I I I I I I I I J I I I I I I I I I i I I I I I I I I I | I I I I I I I B . O 7 . 0 6 . 0 5 . 0 4 . 0 3 . 0 2 . 0 1 . 0 0 . 0 P P M 121.421-MHz 3 1P{*H} LU I i i i i | n n | i i i i | i—i i i—| i i—i—r-j—i—r~\—i—]—i—i—i—i—|—i—i—i—i—|—i—i—i—i—]—i i i—i—j 1 5 0 1 4 5 1 4 0 1 3 5 1 3 0 1 2 5 ' 1 2 0 1 1 5 1 1 0 1 0 5 P P M 1 0 0 237 % TRANSMITTANCE .00 20.00 40.00 60.00 80.00 100.00 2 1 .7 .5 A .3 .2 ABSORBANCE ABSORBANCE C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) [ P ( O P h ) 3 ] NMR i n CgDg 300-MHz lH J i l 11111111111111 121.421-MHz 3 1 P { J H } I i i i i | i i i i | i i i i | i i i i | i i i i | i i i i | i i i i | i i i i | i 4 2 0 - 2 P P M r r r 1 ' | II ' ' I ' i i i | i ' i i i i ' i i | i i i i | i i i i | i i i i | i i i i [ i i i i | i i i i i 1 7 0 1 6 0 1 5 0 1 4 0 1 3 0 P P M 1 2 0 ' 239 ABSORBANCE ABSORBANCE C p W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e P h 2 ) NMR i n CgDg 400-MHz JH b{ppm) 121.421-MHz 3 1 P { l H } i i i i i i i i ' i i i i i i i i i i i i i 2 0 1 0 3 0 I I I I | ! I I 1 j 1 I I I | I - 1 0 P P M 241 00 % TRANSMITTANCE 20.00 40.00 60.00 80.00 100.00 2 1 .7 .5 .4 .3 .2 .1 ABSORBANCE ABSORBANCE C p W ( N O ) ( H ) [ P ( O P h ) 2 ( O C 6 H 4 ) ] NMR i n CgDg 300-MHz *H Jill I 1 I I I I I I I I I I I I I I I I I 1 I I I I I I I I I I I I I I I I I I I I 1 I I I 1 I I I I I I 6 4 2 0 - 2 P P M 121.421-MHz 3 1 P { 1 H ) l i r-r-r-r 1 8 0 I i i i i I i i i i | i i i i | i i i i | 1 7 0 1 6 0 i l | l l l l | i 1 3 0 P P M TTT-| 1 2 0 1 5 0 i i i | i i i i | i i i i | i i 1 4 0 243 ABSORBANCE ABSORBANCE Cp»W CNDi CCH2SlMo3) 2 - N u j o l MICRONS 2.5 3 4 5 6 8 10 12 15 20 25 I I I I , . I . I . I. I I I i l l 1 . ! ! ' . 4600 3800 3000 2200 1800 1400 1000 800 600 400 WAVENUMBERS 4600 3800 3000 2200 1800 1400 WAVENUMBERS 1000 800 600 400 245 w of ru ro o U l " o o "0 "• ui n o v 0 * 1 £ 3 X O N ~- ro — o i i ro 3 n> U) 3 3) O D % TRANSMITTANCE .00 20.00 40.00 60.00 80.00 100.00 ABSORBANCE ABSORBANCE ABSORBANCE C p * W ( N O ) ( H ) ( C H 2 S i M e 3 ) ( P M e 3 ) NMR i n C 6 D 6 300-MHz *H L i —|—i—i—i—i—|—i—r - 1 —i—|—i—i—r - i—|—i—i—i—i—|—i—i—i—i—|—i—i—i—i—|—i—i—i—i—|—r 2 . 0 1 . 5 1 . 0 0 . 5 0 . 0 - 0 . 5 - 1 . 0 P P M - 1 . 5 121.421-MHz 3 1 P { J H ) T I I | i I I I | I i i i | i I I I | I I I I I I i i— i | i i — i — i — | — i — i — i — r - 2 0 - 2 5 - 3 0 - 3 5 P P M I ' 1 1 ' J - 5 -IC - 1 5 248 Cp»CND> <H> <CBH5> CPHa3) - Nujol MICRONS 2.5 3 4 5 6 8 10 12 15 20 25 4600 3800 3000 2200 1800 1400 1000 800 600 400 WAVENUMBERS 249 C p * W ( N O ) ( H ) ( C 6 H 5 ) ( P M e 3 ) NMR i n C 6 D 6 121.421-MHz 3 IP{*H} 1 |—i—i—i—i—r i—i—i—i—|—i—i—i—i—|—i—i—i—i—|—i—i—i—i—|—i—i—i—i—|—i—i—i—i—|—i—i—i—i— 0 - 5 -10 -15 -20 -25 -30 -35 PPM 250 ABSORBANCE % TRANSMITTANCE 00 20.00 40.00 60.00 80 00 100.00 2 1 .7 .5 .4 .3 .2 .1 ABSORBANCE C p * w ( N O ) ( P M e 3 ) 2 NMR i n C 6 D 6 300-MHz lH I I I I I I I I M i i i I i i i i i i i i i i i i i i i i i II i i i i i i i i i i i i i i i i i i i i I i i i i i i i i i I i i i i 2 . ' 4 2 . 2 2 . 0 1 . 6 1 . 6 1 . 4 1 . 2 P P M 121.421-MHz 3 1 P { * H ) I i i i i—r i—i—i—i— i— i—i—i—i— i— i—i—i—i— i— i—i—i—i— i— i—i—i— i— i— i— i— i—i— i— i— i— i— i— i 0 - 5 - 1 0 - 1 5 - 2 0 - 2 5 - 3 0 - 3 5 P P M - 4 0 252 % TRANSMITTANCE .00 20.00 40.00 60.00 80.00 100.00 2 1 .7 .5 .4 .3 .2 .1 ABSORBANCE ABSORBANCE ABSORBANCE

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