{"http:\/\/dx.doi.org\/10.14288\/1.0060388":{"http:\/\/vivoweb.org\/ontology\/core#departmentOrSchool":[{"value":"Science, Faculty of","type":"literal","lang":"en"},{"value":"Chemistry, Department of","type":"literal","lang":"en"}],"http:\/\/www.europeana.eu\/schemas\/edm\/dataProvider":[{"value":"DSpace","type":"literal","lang":"en"}],"https:\/\/open.library.ubc.ca\/terms#degreeCampus":[{"value":"UBCV","type":"literal","lang":"en"}],"http:\/\/purl.org\/dc\/terms\/creator":[{"value":"Martin, Jeffrey Thomas","type":"literal","lang":"en"}],"http:\/\/purl.org\/dc\/terms\/issued":[{"value":"2010-08-16T20:44:01Z","type":"literal","lang":"en"},{"value":"1987","type":"literal","lang":"en"}],"http:\/\/vivoweb.org\/ontology\/core#relatedDegree":[{"value":"Doctor of Philosophy - PhD","type":"literal","lang":"en"}],"https:\/\/open.library.ubc.ca\/terms#degreeGrantor":[{"value":"University of British Columbia","type":"literal","lang":"en"}],"http:\/\/purl.org\/dc\/terms\/description":[{"value":"Although hydrides of metal carbonyls are widely known, the number of hydrides in the related family of metal nitrosyls is extremely small. The preparation of a series of nitrosyl hydrides from the treatment of [CpW(NO)I\u2082]\u2082 (Cp=\u019e\u2075-C\u2085H\u2085) with Na[H\u2082Al(OCH\u2082CH\u2082OCH\u2083)\u2082] is described. The addition of one or two equivalents of the aluminum reagent results in the formation of [CpW(NO)IH]\u2082 or [CpW(NO)H\u2082]\u2082 respectively. The reaction of [CpW(NO)IH]\u2082 with a Lewis base (L=P(OPh)\u2083, P(OMe)\u2083, PPh\u2083 or PMe\u2083) gives the monometallic CpW(NO)IHL, while [CpW(NO)H\u2082]\u2082 reacts with P(OPh)\u2083 or P(OMe)\u2083 to yield [CpW(NO)HL]\u2082 which undergoes further reaction to give CpW(NO)H\u2082L. Proton NMR spectroscopy shows that all bimetallic species contain bridging hydride ligands and are therefore best, formulated as [CpW(NO)1]\u2082(\u00b5-H)\u2082, [CpW(NO)H]\u2082(\u00b5-H)\u2082 and [CpW(NO)L]\u2082(\u00b5-H)\u2082.\r\nThe \u00b9H NMR spectrum of [CpW(NO)H]\u2082(\u00b5-H)\u2082 shows that there is\r\nno hydride ligand exchange on the NMR time scale and that\r\n\u00b9jH(terminal)W \u2243 \u00b9jH(bridging)w > \u00b2jHW. From this finding, it is \r\npossible to develop new criteria for assessing the static or fluxional nature of hydride ligands for several families of organotungsten hydrides (Cp\u2082W, CpW(CO)\u2083, W(CO)\u2083 and CpW(NO)x (x=l or 2)). Within each family, the magnitude of \u00b9JHW strongly reflects the type of metal hydride bonding, i.e.\r\n[Formula Omitted]\r\nand suggests that bridge bonding involves all the atoms in the\r\nbridge and therefore the \"fused\" notation is introduced.\r\nTreatment of CpW(NO)(CH\u2082SiMe\u2083)\u2082 with low pressures of H\u2082\r\n(60-80 psig) in the presence of Lewis bases (L=P(0Ph)\u2083, PMePh\u2082)\r\ngives the unusually stable alkyl hydride compounds\r\nCpW(NO)(H)(CH\u2082SiMe\u2083)L. This chemistry is then extended to the Cp* (Cp*=\u019e\u2075 -C\u2085Me\u2085) analogues, including the preparation of the\r\nappropriate starting materials. Upon thermolysis of\r\nCp*W(NO)(H)(CH\u2082SiMe\u2083)(PMe\u2083) in C\u2086H\u2086, the intermolecular C-H\r\nactivation product Cp*W(N0)(H)(C\u2086H\u2085)(PMe\u2083) is cleanly formed.\r\nHowever, intermolecular activation of CH\u2084, C\u2086H\u2081\u2082 or n-C\u2086H\u2081\u2084 does\r\nnot occur under similar experimental conditions.\r\nHydrogenolysis of Cp*W(NO)(CH\u2082SiMe\u2083)\u2082 at high pressures (\u2243920 psig) with no Lewis base present results in the formation of isolable [Cp*W(NO)H]\u2082(\u00b5-H)\u2082 and\r\n[Cp*W(N0)H](\u00b5-H)\u2082[Cp*W(N0)(CH\u2082SiMe\u2083)]. The latter is a new example of the rare class of dinuclear alkyl hydride complexes. Proton NMR spin tickling experiments on this compound allow the complete assignment of all couplings in the spectrum and show\r\nthat \u00b9jH(terminal)W' \u00b9JH(bridging)W and \u00b2jHW have the same sign.","type":"literal","lang":"en"}],"http:\/\/www.europeana.eu\/schemas\/edm\/aggregatedCHO":[{"value":"https:\/\/circle.library.ubc.ca\/rest\/handle\/2429\/27449?expand=metadata","type":"literal","lang":"en"}],"http:\/\/www.w3.org\/2009\/08\/skos-reference\/skos.html#note":[{"value":"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 \u00a9 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\u201e]_ (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 , , . , \u00ab,, * J I J \u00ab 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 \u2014 j \u2014 M \u00ab W \u2014 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 \u201e, C^-H,\u201e 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 \u00a3 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\u00bbW(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 \u00a3 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\u201e i n C H \u201e 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\u00bbW(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 -\u00bb\u2022 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 \u2022* 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\u2014 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 \u00bb 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 \u2014 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 ) \u2022 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 \u00bb 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 \u2014 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\u00ab\u00bb(PMe 3) l r H 2 \u2022 Cp\u00bb(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 \u201e 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 \u00ab\u2022 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)\u201e *\u2022 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 \u2022 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 \u2022 [ ( 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 \u2014 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 \u2014 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 \u201e ( 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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O r g a n o m e t a l 1 l e s 1982, 1, 116-124. 48. 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 \u201e 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\u00b0C 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 \u00ab 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\u00b0C) 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 \u00b0 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\u00b0C) 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 \u00b0 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 \u2022P, \u00b0c (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\u00ab(\u00ab0)l 2(P\u00abe 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 \u00ab ( 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\u00ab(N0)IH) 2 174 14.74 14.75 1.47 1.50 3.44 3.49 1646 n.o. (Cp\u00ab(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\u00ab(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\u00ab(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\u00b06 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\u00b06 CP 5.43 ( d , 5, 3 J H P = 3) P(0\u00abe) 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\u00b06 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 \u00b0 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\u00ab(HO)lH[P(OBe)3] *H CDCIJ Vs 3 1 P('H) cfio6 CP P\u00abOBe)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\u00a5(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\u00b06 C P Pne3 \u00bb - 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\u00b06 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\u00ab(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 \u00b0 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 \u00b0 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(,\u20228, 5.31 (3, 10) -1.21 ( s , 2 ) d ( C P \u00ab ( 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 (\u2022\u2022 2, J H ( A ) H ( A , , \u2022 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 ' ) \u00ab 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)\u00ab = -5.94 ( t d , I . \\ M - % ) 5.23 ( s , 10) 7.01 (\u2022, 2) -1.90 (\u2022, 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 \u00ab ( H O ) ( P ( O P h ) 3 ) ] 2 ( M - H ) 2 C ' H C 0 C l 3 f 31 C6\u00b06 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 (\u2022 , 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\u00b06 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
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 \u201e 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 \u00ab 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 \u2014 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\u00b0 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\u00b0C 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 ] \u201e . 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\u00b0C) 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 \u2022 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\u201e]\u201e 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\u201eW->W(C0) c , 2 J 1 _ 1 1 . = 19.2 H z ( 2 3 ) \u2014 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 \u2014 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\u2014W =j=W^NO ON\u2014W =|=W^NO H A < '\"Cp \\\\f H M * \" H A Isomer A Isomer B (AA'XX1) (A2MX) C p v H I ON\u2014W=+=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 \u00bb 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 \u201e 5 v -C5H5 j -n -C5H5 O N \u2014 ^ W \u2014 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 \u2022 [ 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,,\u201e 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\u00b0 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\u00b0C) 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) \u2014 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 \u2014 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 \u00bb * 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\u00b0C) 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 \u20143 \u20145 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 \u2014 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 \u2014 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 \u2014 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 ) 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 \u2014 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 \u00b0 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 \u00bb 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 \u2014 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\u00b0). 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 \u00b0 , 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 \u00bb 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\u00ab 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 ) \u00b0 . 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\u00abW(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 \u2014 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 \u00b0 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 H^ - 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 \u00a3 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 \u00a3 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 H^ . 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 H^ ., 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 \u2014 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 W^ 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 \u00a3 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) \u2014 ' ^ 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 \u00a3 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 '\u00ab-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 \u00bb 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 \u00ab 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 \u00ab 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 \u2014 183 183 c o u p l i n g t o WA; t h i n l i n e \u2014 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 \u20141 1 \u2022 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 ) ' \u00b0 H ( A ) - W ( B ) t \u00b0 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 ) \u2014W (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 \u00bb R H 3 ] - TMS [W*H 2] 2 [W*RH] R W * ( u - H ) 2 W \u00bb R [ W \u00bb 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 \u00bb 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 \u00ab 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 \u00bb 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 \u00bb 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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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 \u2014 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 *\u00ab-lp^ 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 \u201e ( 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 \u2014 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 \u2014 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 \u2014 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 * \u2014 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 ] } + \u2014 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 \u2014 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 \u2014 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 ] \u2014 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 \u00a3 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