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Some chemistry of organometallic nitrosyl complexes of Cr, Mo and W Chin, Teen Teen 1989

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SOME CHEMISTRY OF ORGANOMETALLIC NITROSYL COMPLEXES C r , Mo and W By TEEN TEEN CHIN B . S c , The U n i v e r s i t y of New Brunswick, 1986 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE 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 January 1989 • Teen Teen C h i n , 1989 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 CH£MlST&y The University of British Columbia Vancouver, Canada Date 06/*'//9#9 DE-6 (2/88) i i A b s t r a c t While c a t i o n i c n i t r o s y l complexes c o n t a i n i n g the "Cp/M(NO)2" (Cp' = » 75- C5H5 (Cp) or r?5-C5Me5 (Cp*) ; M = C r , Mo and W) fragment are well-known, c a t i o n i c n i t r o s y l complexes c o n t a i n i n g the "Cp'MfNO)" fragment are r a r e l y encountered. The p r e p a r a t i o n of a s e r i e s of c a t i o n i c n i t r o s y l complexes c o n t a i n i n g the l a t t e r fragment r e s u l t i n g from the treatment of [Cp'M(NO)Xm]n (M= Mo or W; X = I , Br or CI; m = 2 ; n = 1 or 2 ; M = Cr; X = I; m = 1 ; n = 2 ) w i t h n i t r o s o n i u m , [ N 0 ] + , or s i l v e r ( I ) , [ A g ]+, s a l t s i n C H 3 C N i s d e s c r i b e d . Treatment of the Mo and W d i h a l o n i t r o s y l complexes, [Cp'M(NO)X2]n, with one e q u i v a l e n t of [ N 0 ] + or [ A g ]+ s a l t s i n C H 3 C N a f f o r d s the diamagnetic monocations [Cp'M(NO)X(NCCH3)2] + . I n a s p e c i a l c a s e , the treatment of Cp Mo(NO)I2 w i t h one e q u i v a l e n t of [ N 0 ] + i n C H 3 C N a f f o r d s the unprecedented d i c a t i o n [ C p * M o ( N O ) ( N C C H 3 )3]2 +. These diamagnetic c a t i o n s have been c h a r a c t e r i z e d by t h e i r elemental a n a l y s e s , IR and NMR data and s i n g l e - c r y s t a l X-ray s t r u c t u r a l d e t e r m i n a t i o n s of [ C p M o ( N O ) C l ( N C C H 3 ) 2 ] [ B F 4 ] and [ C p * M o ( N O ) ( N C C H 3 ) 3 ] [ P F 6 ] 2 . E x t e n s i o n of t h i s chemistry t o [CpCr(NO)I]2 r e s u l t s i n the i s o l a t i o n of a new paramagnetic c a t i o n i c complex, [CpCr(NO) ( N C C H3)2] [ P F6] . The chromium complex ( a l s o i s o l a t e d as i t s BPh4~ s a l t ) i s c h a r a c t e r i z e d by i t s elemental a n a l y s i s , IR and ESR data as w e l l as a s i n g l e c r y s t a l X-ray s t r u c t u r e i i i d e t e r m i n a t i o n . Upon treatment of [CpCr(NO)(NCCH3)2][PF6] with -NaOMe, the b i m e t a l l i c [CpCr(NO)(OMe)]2 complex i s o b t a i n e d . The s y n t h e s i s and c h a r a c t e r i z a t i o n o f t h e d i n i t r o s y l dimers [Cp*M(NO)2]2 (M = C r , Mo) i s d e s c r i b e d . They a r e prepared i n moderate y i e l d s by the r e d u c t i o n o f Cp*M(NO)2Cl (M = C r , Mo) w i t h z i n c amalgam i n THF. The molybdenum dimer [Cp*Mo(NO)2]2> r e a c t s w i t h S n C l2 t o form the c h l o r o complex, Cp*Mo(NO)2Cl. i v T able of Contents A b s t r a c t i i T a b l e o f Contents i v L i s t s o f T a b l e s v i i L i s t s o f F i g u r e s ' v i i i L i s t s o f Schemes i x L i s t s o f A b b r e v i a t i o n s x Acknowledgements x i i Chapter One - General I n t r o d u c t i o n 1 References 9 Chapter Two - New O r g a n o m e t a l l i c C a t i o n i c N i t r o s y l Complexes of Cr, Mo and W 10 I n t r o d u c t i o n 11 Experimental S e c t i o n 13 R e s u l t s and D i s c u s s i o n 29 (I) The Syntheses and C h a r a c t e r i z a t i o n of the Diamagnetic C a t i o n i c Complexes 1 - 8 (I-A) [Cp*Mo(NO)(NCCH3)3][PF6]2, Complex 1 31 (I-B) [Cp*Mo(NO)X(NCCH3)2][PF6] (X = C I , Br, I ) , Complexes 2, 4 and 6 39 (I-C) [CpMo(NO)X(NCCH3)2][BF4] (X = B r , C I ) , Complexes 3 and 5 41 (I-D) [Cp'W(NO)I(NCCH3)2][Y] (Y = BF4 o r P F6) , Complexes 7 and 8 48 V (I-E) Probable M o l e c u l a r S t r u c t u r e of the Monocationic Complexes 50 (I-F) S y n t h e t i c Routes Used f o r the P r e p a r a t i o n o f the Complexes 1 - 8 51 (I-G) Proposed Mechanism f o r the R e a c t i o n o f Cp/M(NO)X2 w i t h [NO] + 52 (I-H) R e a c t i o n s o f Cp*Mo(NO)I2 and (HB(Me2pyz)3}Mo(NO)I2 w i t h [Ag]PF6 54 (I-I) S i g n i f i c a n c e o f Complexes 1 - 8 55 (II) S y n t h e s i s , C h a r a c t e r i z a t i o n and Chemical R e a c t i v i t y o f [CpCr(NO)(NCCH3)2]PF6 9 57 (II-A) [CpCr(NO)(NCCH3)2]PF6 9 57 (II-B) R e a c t i o n o f [CpCr(NO)I]2 w i t h [Ag]PF6 i n CH2C12 65 (II-C) Some Chemical R e a c t i v i t y of Complex 9 66 Summary 69 References and Notes 70 Chapter Three - S y n t h e s i s and C h a r a c t e r i z a t i o n o f the D i n i t r o s y l Dimers [Cp*M(NO)2] (M = C r , Mo) I n t r o d u c t i o n E xperimental S e c t i o n R e s u l t s and D i s c u s s i o n 73 74 76 v i (I) P r e p a r a t i o n of the Cp*M(NO)2Cl (M = C r , Mo) Complexes 82 (II) The [Cp?M(NO)2]2 (M - C r , Mo) Complexes 82 (II-A) P r e p a r a t i o n o f the [Cp*M(NO)2]2 (M = C r , Mo) Complexes 82 (II-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 the [Cp*M(NO)2]2 (M = C r , Mo) Complexes 85 (II-C) R e a c t i o n o f [Cp*Mo(NO)2]2 w i t h S n C l2 88 (II-D) A Comparison of the [Cp*M(NO)2]2 (M = C r, Mo) and the [Cp'M(CO)2]2 (M = Fe, Ru) Compounds 88 Summary 92 References and Notes 93 S p e c t r a l Appendix 95 v i i L i s t s o f Tables T a b l e 2 .1 P h y s i c a l and A n a l y t i c a l Data f o r t h e Complexes 1 - 9 25 T a b l e 2.2 I n f r a r e d Data f o r t h e Complexes 1 - 9 26 T a b l e 2.3 XH and 1 3C{1H) NMR Data f o r the Complexes 1 - 8 27 Tabl e 2.4 S e l e c t e d Bond Lengths (A) f o r [Cp*Mo(NO)(NCCH3)3][PF6]2 Complex 1 37 T a b l e 2.5 S e l e c t e d Bond Angles (deg) f o r [Cp*Mo(NO)(NCCH3)3][PF6]2 Complex 1 38 T a b l e 2.6 S e l e c t e d Bond Lengths (A) f o r [CpMo(NO)Cl(NCCH3)2][BF4] Complex 5 4 6 Table 2.7 S e l e c t e d Bond Angles (deg) f o r [CpMo(NO)Cl(NCCH3)2][BF4] Complex 5 47 Tabl e 2.8 S e l e c t e d Bond Lengths (A) f o r [CpCr(NO)(NCCH3)2][PF6] Complex 9 62 T a b l e 2.9 S e l e c t e d Bond Angles (deg) f o r [CpCr(NO)(NCCH3)2][PF6] Complex 9 63 L i s t o f F i g u r e s F i g u r e 2.1 F i g u r e 2.2 F i g u r e 2.3 F i g u r e 2.4 F i g u r e 2.5 F i g u r e 3.1 F i g u r e 3.2 F i g u r e 3.3 S o l i d - s t a t e m o l e c u l a r s t r u c t u r e o f [Cp*Mo(NO)(NCCH3)3][PF6]2 Complex 1 S o l i d - s t a t e m o l e c u l a r s t r u c t u r e of [CpMo(NO)Cl(NCCH3)2][BF4] Complex Proposed s t r u c t u r e o f t h e [Cp/M(NO)X(NCCH3)2]+ Complexes ESR spectrum of Complex 9 i n DMF S o l i d - s t a t e m o l e c u l a r s t r u c t u r e o f [CpCr(NO)(NCCH3)2][PF6] Complex 9 Probable M o l e c u l a r S t r u c t u r e s o f [C p * C r ( N O )2]2 Probable M o l e c u l a r S t r u c t u r e s o f [Cp*Mo(NO)2]2 S t r u c t u r e of the Group 8 Carbonyl Complexes i x Scheme 2.1 Scheme 2.2 L i s t o f Schemes X L i s t s o f A b b r e v i a t i o n s A - angstrom cm~^ - w a v e n u m b e r b p y - 2 , 2 ' - b i p y r i d i n e C p - t 7 5 - c y c l o p e n t a d i e n y l C p * - T 7 5 - p e n t a m e t h y l c y c l o p e n t a d i e n y l c a l c d - c a l c u l a t e d D M F - N j N ' - d i m e t h y l f o r m a m i d e d e g - d e g r e e e . s . d . - e s t i m a t e d s t a n d a r d d e v i a t i o n g - g r a m h - h o u r [ H B ( M e 2 p y z ) 3 ] ~ - t r i s ( 3 , 5 - d i m e t h y l p y r a z o l y l ) b o r a t e M e - C H 3 , m e t h y l P h - C 6 H 5 ' P n e n v l p h e n - 1 , 1 0 - p h e n a n t h r o l i n e E S R - e l e c t r o n s p i n r e s o n a n c e I R - i n f r a r e d N M R - n u c l e a r m a g n e t i c r e s o n a n c e [ N 0 ] + - n i t r o s o n i u m i o n T H F - t e t r a h y d r o f u r a n X - I , B r o r C I l i g a n d x i V J J Q - n i t r o s y l stretching frequency VCQ - carbonyl stretching frequency ppm - parts per m i l l i o n 1 3C{ 1H) - proton-decoupled carbon 13 E / i - mass-to-charge r a t i o (in the mass spectrum) [ P ] + - parent molecular ion (in the mass spectrum) x i i Acknowledgements I would f i r s t l i k e to thank my s u p e r v i s o r , P r o f e s s o r P e t e r L e g z d i n s , whose guidance, f r i e n d s h i p , optimism and c o n s t a n t encouragement has made the completion of t h i s work p o s s i b l e . I a l s o want to thank the members of the 319/325 group, both past and p r e s e n t , f o r p r o v i d i n g a wonderful (minus t h e i r abuse) r e s e a r c h environment. I am t r u l y indebted t o my ver y d i l i g e n t p r o o f r e a d e r s , Nancy ( i n p a r t i c u l a r ) , E v e r e t t , N e i l , J u l i u s and P e t e r . My thanks a l s o go t o George f o r very h e l p f u l d i s c u s s i o n s d u r i n g t h i s work. I would a l s o l i k e t o thank E v e r e t t a g a i n f o r o b t a i n i n g some 1 3C NMR s p e c t r a and N e i l a g a i n f o r i n v a l u a b l e 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 V i v i e n f o r s o l v i n g the X-ray s t r u c t u r e s . I am a l s o g r a t e f u l t o the e x c e l l e n t t e c h n i c a l s t a f f of the Chemistry department f o r t h e i r a s s i s t a n c e d u r i n g the course of t h i s work. In p a r t i c u l a r , the s e r v i c e s of Mr. Steve Rak, Mr. P e t e r Borda, Mrs. M a r i e t t a A u s t r i a and Mr. M a r s h a l l Lapawa were f u l l y a p p r e c i a t e d . L a s t l y , I want to express my g r a t i t u d e to my parents f o r t h e i r support throughout t h i s work. 1 Chapter 1 General I n t r o d u c t i o n 2 C o o r d i n a t i o n of s m a l l molecules t o t r a n s i t i o n metals has always been o f i n t e r e s t t o o r g a n o m e t a l l i c c h e m i s t s . The i n c o r p o r a t i o n o f the gaseous molecules i n t o t r a n s i t i o n - m e t a l complexes may a l t e r t h e c h e m i s t r y o f the bound s m a l l molecule from t h a t o f the f r e e s p e c i e s . T h i s a l l o w s t h e r e a c t i v i t y of the c o o r d i n a t e d molecules t o be e x p l o i t e d . One o f the most important s m a l l molecules t o be e x p l o i t e d t o date i s carbon monoxide, CO , and volumes of i n f o r m a t i o n have been p u b l i s h e d on the chemistry of t r a n s i t i o n - m e t a l c a r b o n y l complexes.1 The c h e m i s t r y of t r a n s i t i o n - m e t a l n i t r o s y l complexes (compounds c o n t a i n i n g the NO l i g a n d ) , however, i s l e s s w e l l developed. But, w i t h the i n t e r e s t i n the s y n t h e s i s and r e a c t i v i t y of n i t r o s y l complexes over the l a s t two decades, i t i s c l e a r t h a t the extent of chemistry e x h i b i t e d by these n i t r o s y l complexes may be as broad as t h a t d i s p l a y e d by t h e i r carbonyl c o u n t e r p a r t s . A major t h r u s t i n the i n v e s t i g a t i o n s o f t r a n s i t i o n -metal n i t r o s y l complexes d e r i v e s from the c o n s i d e r a b l e i n t e r e s t i n :3'4 ( i ) the c o n v e r s i o n of NO gas, a major p o l l u t a n t e m i t t e d from the combustion of f o s s i l f u e l s , t o l e s s harmful p r o d u c t s such as N2 and "NI^. The f i r s t s t e p i s t o t r a p the NO on a t r a n s i t i o n - m e t a l c e n t e r t o form a n i t r o s y l complex. Once 3 t h i s i s obtained, the r e a c t i v i t y of the coordinated NO ligand can be exploited to a t t a i n the desired objective. ( i i ) the u t i l i z a t i o n of transition-metal n i t r o s y l complexes i n organic synthesis; e.g. to study the transformations and reactions of the coordinated NO ligand with various organic substrates to y i e l d N-bonded organic compounds. The e l e c t r o n i c structures of NO and CO are very s i m i l a r except that NO has one more electron which occupies the «•* o r b i t a l . The presence of t h i s extra electron allows the NO ligand to behave i n a fashion unobserved for a carbonyl group, i . e . to form a bent M-N-0 bond. Thus, the d i f f e r e n t bonding modes of the NO group may be described as follows : 5 ' 6 a) terminal, l i n e a r M-NO , b) terminal, bent M-NO , and c) bridging. a) Terminal. Linear M-NO Bond The terminal, l i n e a r bonding mode of n i t r o s y l ligands i s the most common, e s p e c i a l l y f o r organometallic compounds. In i t s terminal, l i n e a r form, as i l l u s t r a t e d by the resonance structures below, the n i t r o s y l ligand 4 functions as a three-electron donor. The i d e a l i z e d MNO angle i s 180°, but this angle i s usually between 165° to 180°. The bonding involves a synergic combination of c-donation from the nitrosyl ligand and Mr-NO** bacfcdonation. The degree of the metal ^-donation i s dependent on the electron richness of the metal center. Traditionally, the linear nitrosyl ligand i s considered to be bound formally as N0+, which i s i s o e l e c t r o n i c to CO. b) Terminal. Bent M-NO Bond The terminal, bent bonding mode of NO i s not as common as the terminal, l i n e a r bonding mode in organometallic compounds. This type of bonding i s often observed for l a t e transition-metal n i t r o s y l coordination complexes, but i s rare i n organometallic n i t r o s y l complexes. In t h i s form, the n i t r o s y l ligand functions as a one-electron donor (formally NO"), i . e . Although the idealized MNO angle i s 120°, the observed MNO 5 angles can range between 120° to 140°, depending on the extent of the i n t e r a c t i o n of the nitrogen lone p a i r with the metal. Bent n i t r o s y l groups are generally found at the a p i c a l p o s i t i o n of square pyramidal complexes. An i d e a l example of a transition-metal n i t r o s y l complex representing the two types of M-NO coordination geometries ( l i n e a r M-NO and bent M-NO) described e a r l i e r i s shown i n Figure 1.1.7 The Ru-NO bond angle of the a x i a l NO ligand i s much smaller than that of the basal NO ligand. Also, the Ru-N bond distance i n the bent NO ligand i s longer than i n the l i n e a r NO ligand. These s t r u c t u r a l features are consistent with the simple bonding description described i n the preceding paragraphs. c) B r i d g i n g NO group Ru Figure 1.1 Structure of [Ru(NO) 2(PPh 3) 2(Cl)] + 6 Complexes containing the bridging NO ligand are known although they are much l e s s common than the terminal NO d e r i v a t i v e s . Both doubly and t r i p l y bridging NO groups are known. An example of a complex containing the doubly and t r i p l y bridging forms i s shown i n Figure 1.2.8 In the doubly bridging mode, the NO ligand donates two electrons to one metal and one electron to the other metal. The t r i p l y bridged NO ligand i s considered to be a one-electron donor to each metal centre. (T7 5-C5H5) N 0 Figure 1.2 Structure of Cp3Mn 3(NO) 4 One of the most d i s t i n c t i v e physical properties of the NO ligand i s the i n f r a r e d W J J 0 band. Terminal NO complexes ex h i b i t strong v0^ bands ranging from 1900 cm"1 (in c a t i o n i c 7 complexes) t o as low as 1455 cm"1 ( i n a n i o n i c complexes). The a s s i g n i n g s t r u c t u r e s . B r i d g i n g NO groups g e n e r a l l y e x h i b i t s p e c t r a . The major o b j e c t i v e a t the o u t s e t o f t h i s r e s e a r c h was t o determine the e f f e c t o f NO l i g a n d s on the c h a r a c t e r i s t i c c hemistry o f o r g a n o m e t a l l i c n i t r o s y l complexes. S p e c i f i c a l l y , the work presented i n t h i s t h e s i s d e a l s p r i m a r i l y w i t h the s y n t h e s i s and r e a c t i v i t y o f some Group 6 o r g a n o m e t a l l i c n i t r o s y l complexes c o n t a i n i n g the Cp'M(NO) or Cp'M(NO)2 fragments (Cp' = i75-C5H5 (Cp) o r rj5-C5Me5 (Cp*) ; M = C r , Mo or W), i . e . t^O frequencies of bent MNO groups are usually lower than the V J J Q frequencies of l i n e a r MNO groups but t h e i r ranges overlap such that the t ^0 frequency i s not a r e l i a b l e c r i t e r i o n f o r lower V J J 0 frequencies than terminal NO groups i n t h e i r IR I I M M I o a (M« Cr. Mo or W; R - H or Me) 8 The complexes t h a t c o n t a i n these fragments possess piano s t o o l m o l e c u l a r s t r u c t u r e s and the M-NO l i n k a g e s are e s s e n t i a l l y l i n e a r . In t h i s c o n n e c t i o n , Chapter 2 of t h i s t h e s i s d e s c r i b e s the r e a c t i o n s of the complexes, [Cp'M(NO)X2]n (M = Mo or W; n = 1 or 2; X = C l , Br or I) and [ C p C r ( N O ) I ]2, with [ A g ]+ or [N0]+ s a l t s i n a c e t o n i t r i l e . T h i s study has l e d t o the syntheses of a s e r i e s o f novel diamagnetic c a t i o n i c complexes [Cp'M(NO)X(NCCH3)2]+ (M = Mo or W; X = C l , Br or I) and [Cp*Mo(NO)(NCCH3)3]2 +. A l s o , the s y n t h e s i s , c h a r a c t e r i z a t i o n and r e a c t i v i t y of a paramagnetic r a d i c a l c a t i o n [CpCr(NO)(NCCH3)2]*+ are p r e s e n t e d . Chapter Three d e a l s w i t h the r e d u c t i o n chemistry of the d i n i t r o s y l compounds Cp*M(NO)2Cl (M = C r , Mo, W). T h i s study has l e d t o the i s o l a t i o n of the new d i n i t r o s y l dimers [Cp*M(NO)2]2 (M = Cr and Mo). The p r e p a r a t i o n and chemical p r o p e r t i e s of these dimers i s d e s c r i b e d and compared with t h e i r v a l e n c e i s o e l e c t r o n i c c a r b o n y l analogues [Cp'M(CO) 2]2 (Cp' = Cp or Cp*; M = Fe, Ru). 9 References 1. Collman, J . P.; Hegedus, L. S.; Norton, J . R.; F i n k e , R. G. P r i n c i p l e s and A p p l i c a t i o n s of O r a a n o t r a n s i t i o n Metal  Chemistry; U n i v e r s i t y S c i e n c e Books: M i l l V a l l e y , CA, 1987, Chapter 3. 2. (a) G r i f f i t h , W. P. Adv. Oraanomet. Chem. 1968, 2, 211. ( b ) C o n n e l l y , N. G. I n o r a . Chim. Acta Rev. 1972, £ , 47. (c) Enemark, J . H.; Feltham, R. D. Coord. Chem. Rev. 1974, 13, 339. (d) L e g z d i n s , P.; Richter-Addo, G. B. Chem. Rev. 1988, 88., 991-3. M c C l e v e r t y , J . A. Chem. Rev. 1979, 79, 53. 4. Pandey, K. K.; Roesky, H. W. Adv. I n o r q . Chem. Radiochem. 1983, 2_6, 337. 5. C o t t o n , F. A.; W i l k i n s o n , G. "Advanced I n o r g a n i c  Chemistry"; 4th Ed.; Wiley I n t e r s c i e n c e : T o r o n t o , 1980, Chapter 3. 6. Lukehart, C. M. "Fundamental T r a n s i t i o n Metal  Organoroetallic Chemistry"; Brooks/Cole: Belmont, 1985, Chapter 6. 7. P i e r p o n t , C. G.; Van Derveer, D. G.; Durland, W.; E i s e n b e r g , R. J . Am. Chem. Soc. 1970, 9_2, 4760. 8. E l d e r , R. C. Inorg..Chem. 1974, 13, 1037. 10 Chapter 2 New Organometallic Cationic N i t r o s y l Complexes Cr, Mo and W 11 I n t r o d u c t i o n An e l e c t r o c h e m i c a l s t u d y on t h e s e r i e s o f d i h a l o n i t r o s y l c o m p l e x e s , [ C p ' M o ( N O ) X 2 ] n [ C p ' = Cp o r C p * ; X = I , Br o r C I ; n = 1 o r 2 ] , was i n i t i a t e d i n o u r l a b o r a t o r y b y G. B . R i c h t e r - A d d o a few y e a r s a g o . * I n g e n e r a l , t h e s e complexes u n d e r g o r e v e r s i b l e o n e - e l e c t r o n r e d u c t i o n s (by c y c l i c v o l t a m m e t r y ) . The e l e c t r o c h e m i c a l l y o b s e r v e d r e d u c t i o n s can be e f f e c t e d on a p r e p a r a t i v e s c a l e by e m p l o y i n g C p 2 C o as t h e c h e m i c a l r e d u c t a n t , i . e . Cp'Mo(NO )X 2 + C p 2 C o • [Cp'Mo(NO)X 2 ] * ~ [ C p 2 C o ] + (2.1) These u n u s u a l r a d i c a l a n i o n i c complexes a r e i s o l a b l e i n good y i e l d s and have been f u l l y c h a r a c t e r i z e d . 2 I n t h i s c o n n e c t i o n , i t has a l s o been o b s e r v e d t h a t t h e s e d i h a l o n i t r o s y l complexes e x h i b i t i r r e v e r s i b l e o x i d a t i o n b e h a v i o u r . A c c o r d i n g l y , t h e c h e m i c a l b e h a v i o u r o f t h e Cp'Mo(NO)X 2 complexes u n d e r o x i d i z i n g c o n d i t i o n s becomes o f i n t e r e s t . I n t h i s c h a p t e r , t h e r e a c t i o n s o f t h e s e n i t r o s y l c o m p l e x e s w i t h two d i f f e r e n t c h e m i c a l o x i d a n t s ( [ N O ] P F 6 and [Ag]Y (Y = B F 4 o r P F 6 ) ) i n CH 3 CN a r e p r e s e n t e d . T h i s s t u d y has a l s o been e x t e n d e d t o encompass t h e d i i o d o complexes o f 12 t u n g s t e n , [Cp'W(NO)I2]n (n. = 1 or 2 ) , and the r e l a t e d monoiodo chromium complex, [ C p C r ( N O ) I ]2» T h i s i n v e s t i g a t i o n has l e d t o t h e s y n t h e s i s o f a new s e r i e s o f diamagnetic monocationic n i t r o s y l complexes [Cp/M(NO)X(NCCH3)2][Y] (Cp' - Cp o r Cp*; M= Mo o r W; X - I , Br or C l ; Y = BF4 or PF6) and a d i c a t i o n i c complex [Cp*Mo(NO)(NCCH3)3][PF6]2. E x t e n s i o n o f t h i s i n v e s t i g a t i o n t o the r e l a t e d chromium complex, [ C p C r ( N O ) I ]2, has r e s u l t e d i n t h e i s o l a t i o n o f a no v e l paramagnetic c a t i o n i c complex [C p C r ( N O ) ( N C C H3)2] [ P F6] . In t h i s c h a p t e r , the s y n t h e s i s and c h a r a c t e r i z a t i o n of these c a t i o n i c complexes i s p r e s e n t e d . Some r e a c t i v i t y o f the paramagnetic c a t i o n i c chromium complex [CpCr(NO)(NCCH3)2][PF6] i s a l s o d e s c r i b e d . 13 Experimental Section A l l reactions and subsequent manipulations were performed under anaerobic and anhydrous conditions using conventional Schlenk techniques 3 or i n a Vacuum Atmospheres Corp. Dri-Lab Model He-43-2 drybox. The halo n i t r o s y l reagents, [CpMo(NO)Br 2] 2 4, Cp*W(NO)I 2 5 and [CpCr(NO)I] 2 6, were prepared by published procedures. The permethylated •Cp*Mo(NO)X2 (X= Br, I) analogues were prepared by t r e a t i n g Cp*Mo(CO)2(NO) and X 2 i n a manner s i m i l a r to that employed for the preparation of t h e i r Cp analogues. Both [Cp /Mo(NO)Cl 2] 2 (Cp' = Cp or Cp*) 7 complexes were prepared by tr e a t i n g the corresponding Cp'Mo(CO)2(NO) species with an equimolar amount of PC1 5 i n E t 2 0 . The [Cp'Mo(NO)Cl 2] 2 complexes that p r e c i p i t a t e d from E t 2 0 were i s o l a t e d by f i l t r a t i o n of the reaction mixture and subsequently dried i n vacuo. The purity of the halo n i t r o s y l complexes was ascertained by elemental analyses and conventional spectroscopic techniques. A l l other reagents used were of reagent grade or of comparable purity and were purchased from commercial suppliers. A c e t o n i t r i l e , hexanes, and d i e t h y l ether were dried with CaH 2, nitromethane with CaS0 4, THF with sodium/benzophenone k e t y l , toluene and benzene with sodium, and CH 2C1 2 with P 20 5. The solvents were d i s t i l l e d from t h e i r respective drying agents and purged with 14 dry N2 p r i o r t o use. A l l r e a c t i o n s d e s c r i b e d below were performed a t ambient temperatures. I n f r a r e d s p e c t r a were obt a i n e d w i t h a N i c o l e t 5DX FT-IR instrument ( i n t e r n a l l y c a l i b r a t e d w i t h a He/Ne l a s e r ) . Proton NMR s p e c t r a were obtained on a Bruker WP-80 or V a r i a n XL-300 spectrometer w i t h r e f e r e n c e t o the r e s i d u a l proton s i g n a l of the deuterated s o l v e n t employed, and are r e p o r t e d i n ppm d o w n f i e l d from M e4S i . Carbon-13 NMR s p e c t r a were recorded on a V a r i a n XL-3 00^ spectrometer operated by the s t a f f o f the departmental NMR l a b o r a t o r y headed by Dr. S.O. Chan. The ESR s p e c t r a were recorded u s i n g a spectrometer and i n t e r f a c e d ft computer system operated by Dr. F.G. H e r r i n g . Low r e s o l u t i o n mass s p e c t r a were recorded with a Kratos MS50 instrument, at 7 0 eV, by the s t a f f of the mass-spectrometry l a b o r a t o r y headed by Dr. G.K. E i g e n d o r f . Elemental analyses were performed by Mr. P. Borda. • P r e p a r a t i o n of [Cp*Mo(NO)(NCCH3)3][PF6]2, 1. A s t i r r e d s o l u t i o n o f Cp*Mo(NO)I2 (1.18 g, 2.29 mmol) i n CH3CN (60 mL) was t r e a t e d dropwise at room temperature with a s o l u t i o n of [N0]PF6 (0.401 g, 2.29 mmol) i n CH3CN (15 mL). The r e a c t i o n mixture was allowed t o s t i r f o r 40 min d u r i n g which time the c o l o u r of the s o l u t i o n changed from dark reddish-brown t o l i g h t brown. The prog r e s s of the r e a c t i o n 15 was monitored by IR spectroscopy which r e v e a l e d t h a t the i n t e n s i t y o f the t > N 0 of Cp*Mo(NO)I2 (1660 cm- 1) g r a d u a l l y decreased w i t h the concomitant growth o f a new n i t r o s y l band at 1680 cm- 1. The volume of the s o l v e n t i n the f i n a l r e a c t i o n mixture was then reduced t o 1 0 mL i n vacuo. A d d i t i o n o f d i e t h y l e t h e r (120 mL) p r e c i p i t a t e d [Cp*Mo(NO)(NCCH3)3][PF6]2, complex 1 , as an a i r - s t a b l e , y e l l o w , m i c r o c r y s t a l l i n e s o l i d (0.617 g, 0.915 mmol, 40% y i e l d ) . The a n a l y t i c a l , IR and N M R data f o r t h i s compound and the other new compounds s y n t h e s i z e d i n t h i s work are c o l l e c t e d i n Tables 2.1, 2.2 and 2.3 presented on pages 25, 26, and 27, r e s p e c t i v e l y . The d i c a t i o n i c complex 1 c o u l d a l s o be obtained i n s i m i l a r y i e l d by t r e a t i n g Cp*Mo(N0)I2 with two e q u i v a l e n t s of [Ag]PF6 i n CH3CN. The f i n a l r e a c t i o n mixture was f i l t e r e d through a column ( 2 x 2 cm) of C e l i t e supported on a f r i t . Workup of the r e s u l t i n g y e l l o w f i l t r a t e was as d e s c r i b e d above. Large o v a l shaped c r y s t a l s of [Cp*Mo(N0)(NCCH3)3][PF6]2 1 s u i t a b l e f o r X-ray c r y s t a l l o g r a p h i c a n a l y s i s were grown by m a i n t a i n i n g a s a t u r a t e d CH3CN/Et20 s o l u t i o n o f complex 1 a t 0°C f o r 7 days. P r e p a r a t i o n o f [Cp*Mo(NO)I(NCCH3)2]PP6, 2. S o l i d [Ag]PF6 (0.256 g, 1.01 mmol) was added t o a s t i r r e d CH3CN 16 s o l u t i o n (20 mL) of Cp*Mo(N0)I 2 (0.520 g, 1.01 mmol). The colour of the reaction mixture changed from dark reddish-brown to dark yellow and a yellow-white p r e c i p i t a t e formed. A f t e r 30 min, a IR spectrum of the supernatant s o l u t i o n revealed the complete consumption of the s t a r t i n g organometallic complex (VJJQ 1660 cm"1) and the formation of a new nitr o s y l - c o n t a i n i n g compound (vjj0 1684 cm" 1). The f i n a l reaction mixture was f i l t e r e d through a column ( 2 x 3 cm) of C e l i t e supported on a medium porosity glass f r i t . The r e s u l t i n g dark yellow f i l t r a t e was concentrated to 5 mL, layered with E t 2 0 (40 mL) and cooled to 0°C f o r 12 h. The mic r o c r y s t a l l i n e s o l i d that deposited was c o l l e c t e d and dried i n vacuo (5 x 10" 3 mm) for 5-6 h. This procedure afforded 0.21 g (0.34 mmol, 34% yield) of [Cp*Mo(NO)I(NCCH 3) 2]PF 6, complex 2 , as an a n a l y t i c a l l y pure, dark yellow mi c r o c r y s t a l l i n e s o l i d . Preparation of [CpMo(N0)Br(NCCH 3) 2]BF 4, 3. To a s t i r r e d CH3CN s o l u t i o n (40 mL) of CpMo(NO)Br2 (1.22 g, 3.47 mmol) was added s o l i d [Ag]BF 4 (0.67, g, 3 .4 mmol). The colour of the so l u t i o n instantaneously changed from l i g h t brown to dark orange and a creamy, l i g h t yellow s o l i d p r e c i p i t a t e d . A f t e r 30 min, an IR spectrum of the supernatant solu t i o n revealed the complete consumption of CpMo(N0)Br2 (V^Q 1686 cm"1) and the formation of a new product (V^Q 1709 cm" 1). 17 Subsequent workup of the reaction mixture was as described for the preparation of the c a t i o n i c complex 2. This procedure afforded 0.92 g (2.1 mmol, 61% yield) of [CpMo(NO)Br(NCCH 3) 2]BF 4, complex 3, as a l i g h t brown, m i c r o c r y s t a l l i n e s o l i d . [CpMo(N0)Br(NCCH 3 ) 2 ] P F 6 could also be synthesized by treatment of CpMo(N0)Br2 with an equimolar amount of [N0]PF 6 i n CH3CN but the transformation did not proceed cleanly and the f i n a l c a t i o n i c product was obtained i n very low isola t e d y i e l d (5%). Preparation of [Cp*Mo(N0)Br(NCCH 3) 2]PF 6, 4. A s t i r r e d CH3CN solution (40 mL) of Cp*Mo(N0)Br2 (0.26 g, 0.62 mmol) was treated dropwise with a solution of [NO]PF6 (0.107 g, 0.611 mmol) i n CH3CN (10 mL), and the progress of the reaction was monitored by IR spectroscopy. The in t e n s i t y of the n i t r o s y l band due to Cp*Mo(N0)Br2 (V^Q 1659 cm""1) slowly decreased with an increase i n the in t e n s i t y of a new n i t r o s y l band at 1684 cm"1. After 2 h, the reaction mixture was treated i n a manner s i m i l a r to that described f o r the preparation of complex 1. By t h i s procedure, the complex 4, [Cp*Mo(NO)Br(NCCH 3) 2]PF6» was is o l a t e d as a dark yellow m i c r o c r y s t a l l i n e s o l i d i n 68% y i e l d (0.24 g, 0.42 mmol). 18 Preparation of [CpMo(NO)Cl(NCCH 3) 2]BF 4, 5 . S o l i d [Ag]BF 4 (0.280 g, 1.44 mmol) was added to a s t i r r e d CH3CN sol u t i o n (30 mL) of CpMo(NO)Cl 2 (0.38 g, 1.4 mmol). The colour of the reaction mixture changed from dark orange-brown to dark yellow and a white s o l i d p r e c i p i t a t e d . A f t e r 30 min, an IR spectrum of the solution mixture revealed the complete consumption of CpMo(N0)Cl 2 (I^Q 1680 cm"1) and the formation of a new product (I^Q 1707 cm" 1). Subsequent workup of the reaction mixture was as described above f o r the preparation of complex 2. By t h i s method, 0.22 g (0.56 mmol, 38% yield) of a n a l y t i c a l l y pure, yellow-orange c r y s t a l s of [CpMo(NO)Cl(NCCH3) 2]BF 4, complex 5, were obtained. [CpMo(NO)Cl(NCCH3) 2]PF 6 could also be obtained by the treatment of CpMo(N0)Cl 2 with [N0]PF 6 i n CH3CN but t h i s route afforded the cation i n very low is o l a t e d y i e l d (5%). Large c r y s t a l s of [CpMo(NO)Cl(NCCH3) 2]BF 4 suitable for X-ray crystallographic analysis were obtained by maintaining a CH3CN/Et 20 solution of the s a l t at -25°C for 7 days. Preparation of [Cp*Mo(NO)Cl(NCCH 3) 2]PF 6, 6. A CH3CN sol u t i o n (10 mL) of [N0]PF 6 (0.208 g, 1.19 mmol) was added dropwise to a s t i r r e d solution of Cp*Mo(N0)Cl 2 (0.380 g, 1.24 mmol) i n CH3CN (30 mL). The colour of the reaction 19 mixture gradually changed from l i g h t brown to a l i g h t e r brown. The progress of the reaction was monitored by IR spectroscopy which revealed that the i n t e n s i t y of the V^Q of Cp*Mo(NO)Cl2 (1652 cm"1) gradually decreased with the concomitant growth of a new n i t r o s y l band at 1680 cm"1. A f t e r 2.5 h, the re s u l t i n g reaction mixture was treated as described e a r l i e r f o r the preparation of complex 1. This method afforded a n a l y t i c a l l y pure, l i g h t brown-orange c r y s t a l s of [Cp*Mo(N0)CI(NCCH 3) 2 ]PF 6 , complex 6, (0.11 g, 0.22 mmol, 20% y i e l d ) . Preparation of [CpW(NO)I(NCCH 3) 2]PF 6, 7 . A s t i r r e d CH3CN solution (60 mL) of CpW(N0)I2 (0.67 g, 1.26 mmol) was treated dropwise at room temperature with a solution of [ N O ] P F 6 (0.21 g, 1.20 mmol) i n CH3CN (15 mL). The reaction mixture was allowed to s t i r for 6 h during which time the colour of the solution changed from l i g h t brownish-orange to l i g h t brownish-green. Subsequent workup of the reaction mixture was as described for the preparation of complex 1. This procedure afforded 0.12 g (0.20 mmol, 15% yield) of a n a l y t i c a l l y pure yellowish-green c r y s t a l s of [CpW(NO)I(NCCH 3) 2]PF 6, 7 . Preparation of [Cp*W(NO)X(NCCH3) 2]BF 4, 8. To a s t i r r e d CH3CN solution (30 mL) of Cp*W(NO)I2 (0.750 g, 1.24 20 mmol) was added [ A g ) B F 4 (0.242 g, 1.24 mmol). The colour of the s o l u t i o n immediately changed from dark orange-red to dark yellow with the concomitant formation of a creamy yellow p r e c i p i t a t e . A f t e r 30 min, an IR spectrum of the supernatant so l u t i o n revealed the complete consumption of Cp*W(NO)I2 (V^Q 1638 cm"1) and the formation of a new product (V^Q 1661 cm" 1). The reaction mixture was f i l t e r e d through a column ( 2 x 2 cm) of C e l i t e supported on a f r i t , and the f i l t r a t e was concentrated to 10 mL. Addition of E t 2 0 (40 mL) resulted i n the p r e c i p i t a t i o n of a dark yellow s o l i d which was coll e c t e d and washed with E t 2 0 (2 x 10 mL). The dark yellow s o l i d was then dried i n vacuo f o r 5-6 h. This procedure produced 0.58 g (0.89 mmol, 72% yield) of [Cp*W(NO)I(NCCH 3) 2 ]BF 4 , 8. Preparation of [CpCr(NO)(NCCH 3) 2]PF 6, 9. To a s t i r r e d s o l u t i o n containing [CpCr(N0)I) 2 (0.780 g, 1.42 mmol) i n a c e t o n i t r i l e (30 mL) was added [ A g ] P F 6 (0.720 g, 2.80 mmol). The colour of the solution immediately changed from dark o l i v e green to bright green, a change that was accompanied by the formation of a yellow-white p r e c i p i t a t e . A f t e r the reaction mixture had been s t i r r e d f o r 30 min at room temperature, an ZR spectrum of the soluti o n indicated the complete consumption of the s t a r t i n g organometallic reactant (VJJO 1680(s) cm"1) and the formation of a new n i t r o s y l -21 containing compound (UJJQ 1710(S) cm" 1). The reaction mixture was f i l t e r e d through a column of C e l i t e ( 2 x 2 cm) supported on a medium porosity glass f r i t . The br i g h t green f i l t r a t e was concentrated to approximately 5 mL i n vacuo. Addition of d i e t h y l ether (20 mL) afforded a green m i c r o c r y s t a l l i n e s o l i d that was c o l l e c t e d by f i l t r a t i o n and washed with d i e t h y l ether ( 2 x 2 0 mL). The bright green s o l i d was dried i n vacuo (5 x 10~ 3 mm) at room temperature f o r 12 hours. This procedure -afforded [CpCr(NO)(NCCH 3) 2]PF 6, complex 9, (0.50 g, 1.40 mmol, 49% yield) as an elementally pure, m i c r o c r y s t a l l i n e green s o l i d . Large c r y s t a l s of [CpCr(NO)(NCCH3)23 P F6' c o m P l e x 9» suitable for X-ray crystallographic analysis were obtained by maintaining a CH 3CN/Et 20 solution of complex 9 at -25°C for 2 weeks. A DMF solution of complex 9 used f o r ESR measurement was prepared as follows. The DMF solvent was f i r s t dried over anhydrous BaO f o r 24 h, f i l t e r e d through C e l i t e and then purged with N2. In a glove box, a weighed amount of complex 9 was dissolved i n enough DMF to make up a 5 x 10" 5 M solution. A small portion of the r e s u l t i n g green s o l u t i o n was then trans f e r r e d i n t o a melting point c a p i l l a r y tube v i a a disposable syringe. The c a p i l l a r y tube was then sealed with Dow-Corning High Vacuum grease. 22 R e a c t i o n o f [CpCr(NO)I] 2 w i t h [Ag]BF 4 i n CE 2C1 2. A s t i r r e d CH 2C1 2 s o l u t i o n (20 mL) of [CpCr(N0)I] 2 (0.400 g, 0.730 m m o l ) w a s t r e a t e d w i t h s o l i d [Ag]BF 4 (0.285 g, 1.46 mmol). The colour o f the reaction mixture changed from dark green to darker o l i v e green and a creamy white s o l i d p r e c i p i t a t e d . A f t e r 30 min, an IR spectrum of the supernatant solut i o n indicated the complete consumption of the s t a r t i n g organometallic reactant ( v N 0 1676(s) cm" 1), and two new strong n i t r o s y l absorptions had grown i n at 1842 and 1740 cm"1. The f i n a l reaction mixture was f i l t e r e d through a column of C e l i t e ( 2 x 3 cm) supported on a medium porosity glass f r i t . The o l i v e green f i l t r a t e was treated dropwise with a CH 2C1 2 s o l u t i o n of [(Ph 3P) 2N]Cl u n t i l the l a t t e r absorptions i n i t s IR spectrum were completely replaced by bands at 1819(s) and 1713(vs) cm"1. The r e s u l t i n g green brown solut i o n was f i l t e r e d through a short F l o r i s i l column ( 2 x 4 cm) supported on a f r i t . The golden-brown f i l t r a t e was concentrated to 5 mL and addition of hexanes (50 mL) afforded CpCr(NO) 2Cl (0.020 g, 13% y i e l d ) which was c o l l e c t e d and dried i n vacuo. The organometallic compound was r e a d i l y i d e n t i f i e d by i t s c h a r a c t e r i s t i c s p ectral p r o p e r t i e s . 9 : IR (CH 2C1 2) t ^ 0 1819(s), 1713(s) c m " 1 ; 2H NMR (C 6D 6) 6 4.77 ( s , 5H) ; low 23 r e s o l u t i o n mass spectrum (probe temperature 150°C) , m/j_ 212 [ P + ] . Some R e a c t i v i t y of [ C p C r ( N O ) ( N C C H 3 ) 2 ] P F 6 , 9. a ) R e a c t i o n of . C p C r ( N O ) ( N C C H 3 ) 2 ] P F 6 w i t h N a [ B P h 4 ] , To a CH2C12 s o l u t i o n (20 mL) o f [CpCr(NO)(NCCH3)2]PF6 (0.10 g, 0.27 mmol) was added s o l i d Na[BPh4] (0.090 g, 0.27 mmol). The r e s u l t i n g mixture was s t i r r e d a t room temperature f o r 1 h, d u r i n g which time the c o l o r o f the s o l u t i o n changed from b r i g h t green t o a s l i g h t l y d arker green, and a white s o l i d p r e c i p i t a t e d . An IR spectrum o f the s o l u t i o n e x h i b i t e d o n l y one s t r o n g n i t r o s y l band a t 1718(s) cm- 1. The f i n a l mixture was f i l t e r e d through a column o f C e l i t e (2 x 2 cm) supported on a g l a s s f r i t , and the green f i l t r a t e was taken t o dryness i n vacuo. The r e s u l t i n g green s o l i d was r e d i s s o l v e d i n CH3CN (5 mL) and l a y e r e d with E t20 (30 mL). T h i s mixture was co o l e d t o -25°C o v e r n i g h t . T h i s procedure a f f o r d e d [CpCr(NO)(NCCH3)2]BPh4.l/2CH3CN (0.0300 g, 20.3% y i e l d ) as an a n a l y t i c a l l y pure m i c r o c r y s t a l l i n e green s o l i d . A n a l . C a l c d . f o r C 3 3 H3 1N3O B C r : C , 71.77; H , 5.72; N, 8.62. Found: C , 71.30; H , 5.70; N, 8.35. IR (Nujol mull) V J J Q 1696(s) cm"1; «C N 2320(w), 2292(w), 2253(vw) cm"1. 24 b) Reaction of [CpCr(NO)(NCCH 3) 2]PF 6 with NaOMe. Excess NaOMe (0.080 g, 1.5 mmol) was added to a s t i r r e d CH 2C1 2 s o l u t i o n (20*mL) of [CpCr(NO)(NCCH 3) 2]PF 6 (0.10 g, 0.27 mmol). The colour of the reaction mixture gradually changed from b r i g h t green to dark o l i v e green over the course of 30 min and a white p r e c i p i t a t e was observed. An IR spectrum of the supernatant s o l u t i o n displayed a new n i t r o s y l band at 1661(s) cm"1, and the n i t r o s y l band of the s t a r t i n g organometallic reactant (v^0 1715 cm"1) had completely disappeared. The f i n a l mixture was f i l t e r e d through a F l o r i s i l column ( 2 x 4 cm), and the column was washed with CH 2C1 2/THF (1:1) u n t i l the washings were colourless. The r e s u l t i n g o l i v e green f i l t r a t e was taken to dryness i n vacuo. The green s o l i d was redissolved i n CH 2C1 2 (5 mL), layered with hexanes (15 mL) and cooled to -25°C overnight. This procedure yielded [CpCr(NO)(OMe)] 2 (0.012 g, 25% yield) which was re a d i l y i d e n t i f i e d by i t s c h a r a c t e r i s t i c spectroscopic p r o p e r t i e s . 6 IR(CH 2C1 2) WJJO 1661 (s) cm"1. Mass spectrum (probe temperature 150°C) 326 [P - N0] +. 2 5 T a M » 2.1. Physical and A n a l y t i c a l . D a t a( a ) f o r the Complexes 1 - 9 . Complex Y i e l d ( % ) C H N [Cp*Ho(NO)(NCCH3)3][PF6]2 1 4 0 2 8 . . 7 5 ( 2 9 . 2 6 ) 3 . 5 3 ( 3 . 6 6 ) 8 . 3 0 ( 8 . 5 4 ) [Cp*Mo(NO)I(NCCH3)2]PF6 2 3 4 2 6 , . 8 9 ( 2 7 . . 3 2 ) 3 . 3 4 ( 3 . . 4 1 ) 6 . 4 2 ( 6 . 8 3 ) [CpMo(NO)Br(NCCH3)2]BF4 3 6 1 2 4 . .8 6 ( 2 4 . . 5 4 ) 2 . 6 0 ( 2 . • 2 7 ) 9 . 2 5 ( 9 . 5 4 ) [Cp*Ho(NO)Br(NCCH3)2]PF6 4 6 8 2 9 . 7 5 ( 2 9 . . 5 8 ) 3 . , 7 9 ( 3 . . 7 0 ) 7 . 3 6 ( 7 . 3 9 ) [CpMo(NO)Cl(NCCH3)2]BF4 5 3 8 2 7 . 2 2 ( 2 7 . • 3 1 ) 2 . . 9 1 ( 2 , . 7 8 ) 1 0 . 62 ( 1 0 . 6 2 ) [Cp*Mo(NO)Cl(NCCH3)2]PF6 6 2 0 3 2 • 2 5 ( 3 2 , . 0 9 ) 4 . . 0 6 ( « . 0 1 ) 8 . 2 0 ( 8 . 0 2 ) [CpW(NO)I(NCCH3)2]PF6 7 1 5 1 7 . 0 7 ( 1 7 . . 0 6 ) 2 . . 1 1 ( 1 . 7 4 ) 6 . 8 2 ( 6 . 6 3 ) [Cp*W(NO)I(NCCH3)2]BF4 e 7 2 2 6 . 4 1 ( 2 6 . • 0 5 ) 3 . . 3 2 ( 3 , . 2 6 ) 6 . 8 1 ( 6 . 5 1 ) [CpCr(NO)(NCCH3)2]PF6 9 4 8 2 8 . 8 8 ( 2 8 , . 8 8 ) 2 . . 9 4 ( 2 . 9 3 ) 1 1 . 2 3 ( 1 1 . 1 3 ) (a) C a l c u l a t e d values i n parentheses. 2 6 T a b l e 2.2. Infrared Data f o r the Complexes l-».<a> Nujol » u l l In CH3CN Nujol mull Complex "NO (cn- 1) (cm- 1) [Cp*Mo(NO)(NCCH3)3][PF6]2 1 1718 (1645) 1680 (1660) 2320, 2292(u) [Cp*Mo(NO)I(NCCH3)2]PF6 2 1686 (1645) 1684 (1660) 2326, 2295(v) [CpMo(NO)Br(NCCH3)2]BF4 3 1701 (1668) 1709 (1686) 2326, 2297(v) [Cp*Mo(NO)Br(NCCH3)2]PF6 4 1678 (1649) 1684 (1659^ 2322 , 2295(w) [CpMo(NO)Cl(NCCH3)2]BF4 5 1705 (1659) 1707 (1680) 2328 , 2299(w) [Cp*Mo(NO)Cl(NCCH3)2]PF6 6 1668 (1648) 1680 (1652) 2326, 2297(v) [CpW(NO)I(NCCH3)2)PF6 7 1686 (1640) 1676 (1657) 2328 , 2299(w) [Cp*W(NO) I (NCCH-,) 2] B F4 8 1653 (1627) 1661 (1638) 232 4 , 2293(w) [CpCr(NO)(NCCH3)2]PF6 9 17 09 (1663) 1710 (1680) 2326, 2297(w) Nitroeyl »tretcfaln9 f requer>cie» o f the neutral precux»or» are given in parentheses. 27 T a i l * 1 . 9 . _ a H NMR and 1 3 C ( l H ) KKR d a t a f o r t h a Coaplaxaa 1 - a . *H KXR(f) " C l ^ ) KXR(f) [ C p * M o ( N O ) ( N C C H 3 ) 3 ] [ P F 6 ] 2 X [Cp Mo(NO)I(NCCM 3 ) 2 ]PF 6 2 [CpMo(NO)Br(NCCH 3 ) 2 ]BF 4 S [Cp*Mo(NO)Br(NCCH 3 ) 2 ]PF 6 4 2.74 («,»H,CH 3CN) 2.18 ( « , 1 5 H , C 5 ( C H 3 ) 5 ) 2.65 (a,6H,CH 3 CK) 2.09 ( . , ^ , 0 5 ( 0 1 3 ) 5 ) 6.52 ( s , 5 H , C 5 H 5 ) 2.56 (»,6H,CT 3 CN) 2.67 (»,6H,CH 3 CN) 2.08 (S, 1 5 H , C 5 ( C H 3 ) 5 ) 140.30 125.03 10.61 4.84 140.89 122.63 11.20 4.89 139.10 112.20 4.63 n.o. (B,CH3£N) ( a , C 5 ( C H 3 ) 5 ) ( • , C 5 ( C H 3 ) 5 ) ( • , ^ 0 1 ) («,CH 3CN) ( • , £ 5 ( 0 1 3 ) 5 ) ( • , C 5 ( £ H 3 ) 5 ) (8 ,£H 3CN) (8 ,CH 3CN) ( » , C 5 H 5 ) («,£H 3CN) (CpMo(NO)C l (NCCB 3 ) 2 ] B r 4 S 6 .51 ( a , 5 B , C 5 R 5 ) 2.54 (a,6H,CH 3 CN) 137.63 <»,CH3£N) 112.52 ( a , £ 5 H 5 ) 4 .46 (a,£H 3CN) 28 T a b l e 2.9 (Cont 'd) tCp*«o(HO)CI(«CCH3)2lPr6 [CpW(NO)I(NCCH 3 ) 2 )PF 6 < b > • 2 .65 (•,6H,CH 3 CH) 2.07 < » , 1 5 H , C 5 ( C H 3 ) 5 ) 7 6.45 ( s , 5 H , C 5 H 5 ) 1.96 (s,6H,CH 3 CN) 137.11 <»,CH3£N) 1 2 3 . J 3 (•,C5(CH3)5) 10.68 ( • , C 5 ( C H 3 ) 5 ) 4 .48 (»,£H 3CN) n.o. [Cp*W(NO)I(NCCH 3 ) 2 )BF 4 • 2.74 (•,6H,CH 3CN) 139.93 (s,CH 3 £N) 2.21 ( « , 1 5 H , C 5 ( C H 3 ) 5 ) 118.37 ( » , C 5 ( C H 3 ) 5 ) 10.76 (S ,C 5(CH 3) 5) 5.16 (S,£H3CN) NKR s p e c t r a a r c recorded i n C 0 3 N 0 2 . ( b ) NKR spectrum i s recorded i n CD 3 CN. n . o . • not o b t a i n e d . 29 Results and Discussion The preparation and characterization of the diamagnetic complexes 1 - 8 w i l l be discussed i n Part ( I ) . The preparation, characterization and subsequent chemical r e a c t i v i t y of the paramagnetic complex 9 w i l l be considered i n Part ( I I ) . (I) The Syntheses and Characterization of the  Diamagnetic Cationic Complexes 1 - 8 . The c a t i o n i c complexes 1 - 8 obtained during t h i s work were prepared by the treatment of the Cp'M(NO)X2 complexes with e i t h e r [N0] + or [Ag] + s a l t s i n CH3CN. The transformations involved are summarized i n Scheme 2.1. The progress of the reactions was conveniently monitored by IR spectroscopy. A l l the complexes 1 - 8 were p u r i f i e d by 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 from t h e i r respective CH 3CN/Et 20 solutions. The physical data (yields, elemental analyses, IR, *H NMR and 1 3C{ 1H) NMR spectra) of complexes 1 - 8 are c o l l e c t e d i n Tables 2.1 - 2.3. The preparations and physical properties of each of these c a t i o n i c complexes w i l l now be considered i n turn. Cp'M(NO)X2 ICp'M(NO)X(HCCH3)2]+ Scheme 2.1 31 (I-A) [Cp*Mo(NO)(NCCH3)3)[PF6]2, complex 1. Treatment o f Cp*Mo(NO)I2 w i t h one e q u i v a l e n t o f [NO]PF6 i n CH3CN a f f o r d s [Cp*Mo(NO)(NCCH3)3][PF6]2 1 (as i n eq 2.2) i n moderate y i e l d . The same complex i s o b t a i n e d r e g a r d l e s s whether one o r two e q u i v a l e n t s o f [NO]PF6 are used. In eq 2.2, the s t o i c h i o m e t r i c r a t i o o f Cp*Mo(NO)I2 t o [NO)PF6 i s w r i t t e n as 1 : 2 f o r the sake o f b a l a n c i n g the e q u a t i o n . Cp*Mo(NO)I2 + 2 [NO]PF6 • [Cp*Mo(NO)(NCCH3)3][PF6]2 + "2IN0" (2.2) complex 1 In o r d e r t o o b t a i n uncontaminated [Cp*Mo(NO)(NCCH3)3][PF6]2 i n r e s p e c t a b l e y i e l d , i t i s important t h a t the [NO]PF6 reagent ( d i s s o l v e d i n CH3CN) be added s l o w l y i n a dropwise manner t o the Cp*Mo(NO)I2 complex, otherwise the r e a c t i o n i s o f t e n accompanied by the formation o f many n i t r o s y l - c o n t a i n i n g b y p r o d u c t s , a f e a t u r e which lowers the i s o l a t e d y i e l d o f the d e s i r e d product s u b s t a n t i a l l y . A l t e r n a t i v e l y , the d i c a t i o n i c complex 1 can a l s o be s y n t h e s i z e d by t r e a t i n g Cp*Mo(NO)I2 w i t h two e q u i v a l e n t s of [Ag]PF6 i n CH3CN, i . e . , Cp*Mo(NO)I2 + 2 [Ag]PF6 • [Cp*Mo(NO) (NCCH3)3] [ P F6]2 + 2 [Ag)I (2.3) 32 Pure [Cp*Mo(NO)(NCCH 3) 3][PF 6] 2 i s a yellow m i c r o c r y s t a l l i n e s o l i d which i s thermally stable at room temperature i n the s o l i d state under N 2 f o r several months. As a s o l i d , i t can be handled i n a i r f o r several hours without any noticeable decomposition. The complex i s sparingly soluble i n THF and quite soluble i n acetone, a c e t o n i t r i l e and nitromethane to y i e l d a i r - s e n s i t i v e yellow solutions. The i n f r a r e d spectra of [Cp*Mo(NO)(NCCH 3) 3][PF 6] 2, complex 1, e i t h e r as a Nujol mull or as a CH3CN solution, e x h i b i t strong absorptions a t t r i b u t a b l e to the terminal n i t r o s y l ligand. The n i t r o s y l - s t r e t c h i n g frequency of complex 1 (1718 cm - 1 as a Nujol mull) occurs at a much higher frequency than that of i t s neutral precursor Cp*Mo(NO)I2 (1645 cm""1) i n d i c a t i v e of a substantial decrease i n backbonding to the n i t r o s y l ligand. In addition to the n i t r o s y l - s t r e t c h i n g frequency, the IR spectrum (Nujol mull) of complex 1 also exhibit two weak bands at 2320 and 2292 cm"1 a t t r i b u t a b l e to the t>CN of the coordinated a c e t o n i t r i l e l i g a n d s . 1 0 These observed t>CN bands are comparable to those observed f o r the d i c a t i o n i c complex [Cp 2T i ( N C C H 3) 2] [ P F 6] 2 ( v ^ 2325 and 2288 cm" 1). 1 1 The -^H NMR spectrum o f complex 1 i n CD 3N0 2 exhibits a s i n g l e t at 6 2.74 corresponding to the three equivalent 33 CH3CN ligands as well as a s i n g l e t due to the Cp* ligand at S 2.18. The proton resonance of the CH3CN ligands i s s h i f t e d 0.74 ppm downfield to that of free CH3CN (5 2.00 i n CD 3N0 2). The downfield s h i f t which accompanies the coordination of the CH3CN to the metal centre has also been observed i n other c a t i o n i c m e t a l - a c e t o n i t r i l e complexes. 1 1' 1 2 The three CH3CN ligands i n complex 1 show considerable l a b i l i t y i n solution at 25°C as demonstrated by 1H NMR spectroscopy. Thus, the 1H NMR spectrum of a freshly prepared solution of [Cp*Mo(N0)(NCCH 3) 3][BF 4] 2 i n CD3CN exhibits a resonance at 6 1.93 due to the protons of free CH3CN along with another peak at 6 2.58 for the coordinated CH3CN. When the sample i s l e f t standing at room temperature f o r several hours, the signal at S 2.58 disappears completely together with an increase i n the in t e n s i t y of the resonance at 1.93 ppm. These observations are i n d i c a t i v e of an exchange between the coordinated CH3CN and free CD3CN molecules, i . e . , [Cp*Mo(N0) (NCCH 3) 3] [ B F 4 ] 2 + 3 CD3CN 1 » [Cp*Mo(N0)(NCCD 3) 3][BF 4] 2 + 3 CH3CN (2.4) This i s c e r t a i n l y an important feature since i t has been previously demonstrated that the a b i l i t y of some c a t i o n i c t r a n s i t i o n metal n i t r o s y l complexes (with coordinated 34 a c e t o n i t r i l e ligands) to catalyze the oligomerization and polymerization of o l e f i n s i s due to the e l e c t r o p h i l i c nature of the cation as well as to the l a b i l i t y of the a c e t o n i t r i l e ligands i n s o l u t i o n . This feature w i l l be discussed i n more d e t a i l l a t e r i n t h i s chapter. In order to remove any possible ambiguities about the true nature of [Cp*Mo(NO)(NCCH 3) 3][PF 6] 2, the structure of t h i s complex has been determined c r y s t a l l o g r a p h i c a l l y . (The X-ray analyses discussed i n t h i s work were done by Ms. Vivien Yee and Dr. James Trotter of t h i s department. Details of the data c o l l e c t i o n and refinement w i l l be reported elsewhere). The s o l i d state molecular structure of [Cp*Mo(NO)(NCCH3)3][PF 6] 2 i s shown i n Figure 2.1. L i s t s of selected bond lengths and bond angles are presented i n Tables 2.4 and 2.5 respectively. The c r y s t a l structure of [Cp*Mo(NO)(NCCH3)3][PF 6] 2 consists of di s c r e t e [Cp*Mo(NO)(NCCH3)3] 2 + cations and PF 6~ anions. As may be observed, the molybdenum atom i s coordinated to a Cp* rin g , to a n i t r o s y l ligand and to the nitrogen of the three a c e t o n i t r i l e ligands. The coordination geometry about the cen t r a l Mo atom i s that of a four-legged piano s t o o l . A comparison of the s t r u c t u r a l parameters between complex 1 and other c a t i o n i c complexes containing the "Cp*Mo(N0)M fragment cannot be made since reports on the s t r u c t u r a l determinations 35 of c a t i o n i c complexes containing t h i s p a r t i c u l a r unit are lacking i n the chemical l i t e r a t u r e . Nevertheless, the s t r u c t u r a l features i n complex 1 can be compared to the c l o s e l y r e l a t e d c a t i o n i c complex, t{(C 5H 7N 2) 3BH}Mo(NO)(NCCH 3) 2]PF 6, 1 3 as well as the neutral carbonyl complex, Cp*Mo(CO) 3H, 1 4 and they are discussed i n more d e t a i l below. The distance of the Mo atom to the plane of the Cp* r i n g i n complex 1 i s 2.027 A, which i s i n reasonable agreement to that found for Cp*Mo(CO)3H (2.016 A). The MoNO angle i n complex 1 i s e s s e n t i a l l y l i n e a r , although s l i g h t l y more bent than i n [{(C 5H 7N 2) 3BH)Mo(N0)(NCCH 3) 2]PF 6 (170.5(6)° vs. 173.4(8)°). The Mo-NO bond (1.803 A) i s longer and the N-0 bond (1.16 A) i s shorter compared to the respective bond lengths i n [{(C 5H ?N 2) 3BH)Mo(NO)(NCCH 3) 2]PF 6. The three a c e t o n i t r i l e ligands are N-bonded to the Mo centre i n a l i n e a r fashion and the Mo-N bond lengths (2.173(5) A, 2.142(6) A and 2.131(6) A) are i n reasonable agreement to that found f o r [{(C 5H 7N 2) 3BH}Mo(N0)(NCCH 3) 2]PF 6 (2.139(9) A and 2.145(9) A) . The a c e t o n i t r i l e ligand which i s trans to the n i t r o s y l ligand exhibits a longer Mo-N bond (2.173(5) A) compared to the other two a c e t o n i t r i l e ligands, a feature which i s i n accord with i t s l e s s successful competition f o r the a v a i l a b l e electrons on the metal centre being trans to the strongly electron-withdrawing NO ligand. 36 Figure 2.1. S o l i d - s t a t e molecular structure of [Cp*Mo(NO)(NCCH 3) 3][PF 6 ] 2 complex 1. 37 Table 2.4. Selected Bond Lengths (A) f o r [Cp*Mo(NO)(NCCH 3) 3][PF 6] 2» Complex 1. Bond Length< a) Mo - Cp* 2.027(3) Mo - Nl 1.803(5) Mo - N2 2.173(5) Mo - N3 2.142(6) Mo - N4 2.131(6) 0 - Nl 1.161(7) N2 - C l l 1.122(7) N3 - C13 1.121(8) N4 - C15 1.121(9) C l l - C12 1.451(8) C13 - C14 1.462(11) C15 - C16 1.481(11) (a) E.s.d .'s are i n parentheses. 38 Table 2.5. Selected Bond Angles (deg) f o r [Cp*Mo(NO)(NCCH 3) 3][PF 6]2, Complex 1. Bond Angle Nl - Mo - Cp 121.3(2 N2 - Mo - _ * Cp 126.81(17 N3 - Mo - Cp 103.32(17 N4 - Mo - Cp 104.40(17 Mo - Nl - 0 170.5(6 Mo - N2 - C l l 175.7(6 Mo - N3 - C13 174.2 (6 Mo - N4 - C15 177.8(6 Nl - MO - N2 111.9(2 Nl - MO - N3 87.0(2 Nl - MO - N4 85.6(2 N2 - MO - N3 78.1(2 N2 - Mo - N4 78.8(2 N2 - C l l - C12 178.2(7 N3 - C13 - C14 178.9(8 N4 — C15 - C16 177.9(9 (a) E.s.d.'s are i n parentheses. 3 9 (I-B) The Complexes [Cp*MokNO)X(NCCH3)2][PFg] (Z = I , B r , C I ) , Complexes 2, 4 and 6. I n t e r e s t i n g l y enough, treatment o f t h e bromo and c h l o r o analogues Cp*Mo(NO)X2 (X = B r , CI) w i t h one e q u i v a l e n t o f [NO]PF6 i n CH3CN under t h e same c o n d i t i o n s as f o r the iodo complex does not a f f o r d a d i c a t i o n i c compound. I n s t e a d , these r e a c t i o n s a f f o r d o r g a n o m e t a l l i c monocationic complexes i . e . , Cp*Mo(NO)X2 + [NO]PF6 • [Cp*Mo(NO)X(NCCH3)2]PF6 X = Br, complex 4 (2.5) X = C I , complex 6 However, the iodo analogue, [ C p * M o ( N O ) I ( N C C H 3 )2] P F6, cannot be prepared by t h i s r o u t e . Rather, t h i s complex can be prepared by the treatment of Cp*Mo(NO)I2 w i t h one e q u i v a l e n t of [Ag]PF6 i n C H 3 C N (eq 2.6). Cp*Mo(NO)I2 + [Ag]PF6 • [Cp*M(NO)I(NCCH3)2]PF6 + [Ag]I complex 2 (2.6) In t h e i r pure form, these t h r e e c a t i o n i c complexes are t h e r m a l l y s t a b l e dark y e l l o w t o orange s o l i d s t h a t can be handled i n a i r f o r s h o r t p e r i o d s of time w i t h no n o t i c e a b l e decomposition o c c u r r i n g . I f they are obtained i n an impure 40 form, they are prone to undergo decomposition to l i g h t brown o i l s when exposed to a i r . The complexes are soluble i n polar organic solvents (similar s o l u b i l i t y properties as complex 1) to give a i r - s e n s i t i v e l i g h t orange solutions. Their I R spectra (as Nujol mulls) display VJIQ 'S i n the region 1668-1686 cm"1 (Table 2.2), a t t r i b u t a b l e to the terminal n i t r o s y l ligands. Again, these V^Q values are s h i f t e d to a higher frequency as compared to t h e i r neutral dihalo n i t r o s y l precursors i n d i c a t i v e of reduced backbonding from the metal centre to the NO ligand i n the c a t i o n i c complexes. An i n t e r e s t i n g feature that can be observed i n t h i s s e r i e s [Cp*Mo(NO)X(NCCH 3) 2] +, i s that the n i t r o s y l stretching frequencies (in the s o l i d state) decreases i n the order I > Br > C l . An increase i n V^Q i s usually attributed to a decrease i n electron density at the metal centre thereby permitting l e s s backbonding into the NO *•* o r b i t a l . Since the e l e c t r o n e g a t i v i t y of the halide group decreases i n the order Cl > Br > I, one would anticipate the electron density a v a i l a b l e f o r backbonding to decrease i n the order Cl > Br > I as w e l l . However, the observed increase i n the V^Q values i s opposite to expectations (based on e l e c t r o n e g a t i v i t y arguments). The exact reason f o r the observation of t h i s opposite trend i s not clear. This trend i s also observed i n the s e r i e s CpW(N0)2X (X - I, Br, C l ) . 1 5 In addition to the NO 41 bands, weak absorptions att r i b u t a b l e to the coordinated CH3CN ligands (t>cjj) a r e observable i n the region 2322-2295 cm"1 i n t h e i r IR spectra. By analogy to the s t r u c t u r a l l y characterized complex 1 already discussed i n the preceding paragraphs, the CH3CN ligands are probably coordinated to the metal centre v i a the N atom i n a l i n e a r fashion. The *H NMR spectra of these complexes exhibit the expected resonances for the coordinated CH3CN as well as the Cp* ligands. The positions of the Cp* resonances i n the NMR spectra are i n close agreement to that observed f o r the better known [Cp*Mo(CO) 2L 2]PF 6 (L = n i t r i l e s or phosphines) complexes. 1 6 Unlike the positions of the V^Q frequencies i n the IR spectra, the positions of the Cp* resonances i n the NMR spectra do not exh i b i t any trends with respect to the ele c t r o n e g a t i v i t y differences of the halide group. Complexes 2, 4 and 6 probably possess the f a m i l i a r four-legged piano st o o l molecular structures. However, further discussion on t h e i r molecular geometries w i l l be deferred u n t i l the properties of several r e l a t e d complexes are discussed. (I-C) [CpMo(NO)X(NCCH 3) 2][BF 4] (X s Br, C l ) , Complexes 3 a n d 5. I t has been observed 1 that the treatment of CpMo(NO)I2 with [NO]PF 6 i n CH3CN affords 42 [CpMo(NO)I(NCCH 3) 2]PF 6*CH 3CN, a s summarized i n eq. 2.7, i n good y i e l d . CH3CN CpMo(NO)I2 + [NO]PF 6 • [CpMo(N0)I(NCCH3)2]PF6.CH3CN (2.7) However the treatment of the bromo and chloro analogues, CpMo(NO)X2 (X - Br, CI), with [NO]PF 6 i n C H 3 C N under the same conditions y i e l d s the corresponding [CpMo(NO)X(NCCH 3) 2]PF 6 complexes i n extremely low y i e l d s ( 5 % ) . These low is o l a t e d y i e l d s are probably due to several factors. F i r s t l y , the long reaction times involved (4 to 5 h) may allow the thermal decomposition of the c a t i o n i c products to occur. Secondly, i n addition to the products of in t e r e s t , many other n i t r o s y l -containing byproducts (observable i n the IR spectra during the course of the reaction) are also formed during the reaction thus making the f i n a l i s o l a t i o n of the c a t i o n i c complexes d i f f i c u l t . Thirdly, the f i n a l c a t i o n i c products are often contaminated with unreacted s t a r t i n g materials thus requiring repeated f r a c t i o n a l c r y s t a l l i z a t i o n s i n the p u r i f i c a t i o n procedure which lowers the is o l a t e d y i e l d s . Although the [CpMo(NO)X(NCCH 3) 2]PF 6 (X «= Br, CI) complexes can be obtained by the treatment of CpMo(NO)X2 with [ N 0 ] + i n CH3CN, the low is o l a t e d y i e l d s do not allow t h e i r c h a r a c t e r i s t i c chemistry to be studied conveniently. To 43 obtain these c a t i o n i c complexes i n better y i e l d s , I next attempted the reaction of CpMo(NO)X2 with [Ag]BF 4 i n CH3CN. Indeed, the treatment of the CpMo(NO)X2 (X « Br, Cl) complexes with one equivalent of the [Ag] + s a l t i n CH3CN affords the cations i n much higher y i e l d s (as i n eq 2.8). CpMo (NO) X 2 + [Ag]BF 4 • [CpMo(NO)X(NCCH 3) 2]BF 4 + [Ag]X (2.8) X = Br, complex 3 X = C l , complex 5 The physical properties of the new complexes 3 and 5 are quite s i m i l a r to those of t h e i r Cp* analogues. Their IR spectra e x h i b i t n i t r o s y l absorptions i n the region 1705-1709 cm"1, which are approximately 20-35 cm"1 higher i n energy than those exhibited by t h e i r Cp* analogues. This i s simply a r e f l e c t i o n of the better electron-donating a b i l i t i e s of the Cp* ligand as compared to the Cp ligand. In addition, the t>CN bands which are due to the coordinated CH3CN ligands are observable i n the region 2299-2326 cm"1. The s o l i d - s t a t e molecular structure of complex 5 i s shown i n Figure 2.2. L i s t s of selected bond lengths and bond angles are presented i n Tables 2.6 and 2.7, respectively. The c r y s t a l structure of complex 5 consists of discrete [CpMo(NO)Cl(NCCH 3) 2] + cations and BF 4~ anions. As may be 44 observed, 5 also possesses the f a m i l i a r four-legged piano s t o o l molecular geometry. The o v e r a l l s t r u c t u r a l parameters about the Mo atom exhi b i t normal values and some comparisons can be made with the corresponding values observed f o r related c a t i o n i c Mo complexes. The average distance of the Mo atom to the plane of the Cp ri n g (2.032 A) i n 5 i s s l i g h t l y longer than that observed for [Cp 2MoI(NCCH 3)]PF 6 1 7 (1.986 A and 1.965 A) . The Mo-Cl distance (2.415 A) i n 5 i s s l i g h t l y shorter than the corresponding distance observed i n Cp 2MoCl(C 2H 5) 1 8 (2.502 A) . The Mo-NO bond (1.790 A) i s shorter and the N-0 bond (1.183 A) i s longer than the respective bond lengths i n complex 1. The MoNO group (169.8°) i s also e s s e n t i a l l y l i n e a r although i t i s j u s t s l i g h t l y more bent than that i n complex 1. The two CH3CN ligands (in a trans o r i e n t a t i o n to each other) are also N-bonded to the Mo center i n a l i n e a r fashion and the Mo-N bond lengths (2.160 A and 2.141 A) are i n reasonable agreement with the corresponding bond lengths observed i n complex 1. By comparison, the c l o s e l y related [CpMo(NO)I(PMe 3) 2] + complex has been formulated as having trans PMe3 l i g a n d s . 1 9 45 Figure 2 . 2 . S o l i d - s t a t e molecular structure of [CpMo(NO)Cl(NCCH 3 ) 2 ]BF 4 complex 5 46 Table 2.6. Selected Bond Lengths (A) f o r tCpMo(NO)Cl(NCCH 3) 2][BF 4] Complex 5. Bond Length Mo - Cp 2.032(5) Mo - Nl 1.790(12) Mo - N2 2.160(3) Mo - N3 2.141(3) 0 - Nl 1.183(5) Mo - CI 2.415(12) N2 - C6 1.119(5) N3 - C8 1.129(5) C6 - C7 1.448(6) C8 - C9 1.448(6) ( a) E.s.d.'s are i n parentheses. 47 Table 2.7. Selected Bond Angles (deg) for [CpMo(N0)Cl(NCCH3)2HBF4] Complex 8. Bond Angle ( a ) Cl — Mo — Nl 110.31(14) Cl - Mo - N2 78.73(11) Cl - Mo - N3 78.55(10) Cl - Mo - Cp 129.43(14) Nl - Mo - N2 87.75(15) Nl - Mo - N3 87.58(15) Nl - Mo - Cp 120.23(19) N2 - Mo - N3 153.54(14) N2 - Mo - CP 103.75(17) N2 - Mo - Cp 101.09(18) MO - Nl - 0 169.8(4) Mo - N2 - C6 175.6(4) MO - M3 - C8 177.6(4) (*) E.s.d.'s are i n parentheses. 48 (I-D) [Cp'W(NO)I(NCCH3)][Y] (Y = PF 6 or B F 4 ) , Complexes 7 and 8. I t has been previously observed 2 0 that under cert a i n reducing conditions, the Cp'W(NO)I2 complexes e x h i b i t d i f f e r e n t chemical behaviour compared to the molybdenum analogues, Cp /Mo(NO)I 2. Therefore, i t i s of i n t e r e s t to determine i f the dihalo n i t r o s y l complexes of tungsten w i l l behave d i f f e r e n t l y than the corresponding molybdenum complexes under the ox i d i z i n g conditions studied i n t h i s work. Thus, the reactions of the Cp /W(NO)I 2 complexes with [NO]PF 6 and [Ag]PF6 i n C H 3 C N have also been investigated. Treatment of CpW(NO)I2 with one equivalent of [NO]PF6 i n CH3CN affords the analogous [CpW(NO)I(NCCH 3) 2]PF 6, complex 7, i . e . CpW(NO)I2 + [NO]PF 6 •[CpW(NO)I(NCCH 3) 2]PF 6 complex 7 (2.9) Unfortunately, extending reaction 2.9 to the Cp* analogue, Cp*W(NO)I2, r e s u l t s i n the formation of a mixture of several n i t r o s y l - c o n t a i n i n g products (observable i n the IR spectrum during the course of the reaction). To obtain the Cp* analogue of complex 7, the reaction between Cp*W(NO)I2 and tAg]BF4 was next attempted. Indeed, t h i s reaction (eq 2.10) affords the complex [Cp*W(NO)I(NCCH3)2]BF4, 8 i n good y i e l d . 49 Cp*W(NO)I2 + [Ag]BF 4 [ Cp*W (NO) I (NCCH3) 2 ] BF 4 + [Ag]I complex 8 (2.10) In t h e i r pure form, these two compounds 7 and 8 are s l i g h t l y more a i r - s e n s i t i v e than t h e i r molybdenum congeners but can s t i l l be handled i n a i r for short periods of time with no noticeable decomposition occurring. Their s o l u b i l i t y properties are s i m i l a r to those of t h e i r Mo analogues although the tungsten c a t i o n i c complexes are more a i r - s e n s i t i v e i n soluti o n . As anticipated, the IR spectra of complexes 7 and 8 e x h i b i t V^Q'S -*-n ^ n e region 1653-1686 cm - 1 a t t r i b u t a b l e to the terminal n i t r o s y l ligands and weak t ^ ' s i n the region 2299-2324 cm - 1 due to the coordinated a c e t o n i t r i l e ligands. A comparison of the n i t r o s y l stretching frequencies of [C p * W ( N O ) I ( N C C H 3 ) 2 3 + a n a i t s corresponding Mo congener reveals that the t>N0 of the W complex i s approximately 30 cm - 1 lower i n energy than that of the Mo complex. This trend i s i n accord with that previously observed for the [CpM(NO)I(PMe 3) 2] + complexes (M = Mo, u N Q 1668 cm"1; M = W, u N C 1645 c m - 1 ) . 1 9 The 1H NMR spectra (Table 2.3) of complexes 7 and 8 e x h i b i t the expected resonances for the coordinated CH3CN ligands as well as the Cp or Cp* rings. 50 (I-E) Probable Molecular Structures of the Monocationic Complexes. By analogy to complex 5, the r e s t of the c a t i o n i c complexes [Cp'M(NO)X(NCCH 3) 2] + described i n t h i s work can be proposed t o possess the four-legged piano s t o o l molecular geometries i n the s o l i d state with the CH3CN ligands trans to each other (Figure 2.3). This proposal i s based on the s i m i l a r i t i e s i n t h e i r spectroscopic properties to those of the s t r u c t u r a l l y characterized complex 5. Figure 2.3 Proposed Structure of the [Cp'M(NO)X(NCCH 3) 2] + Complexes. 51 (I-F) S y n t h e t i c Routes Used f o r the P r e p a r a t i o n o f the Complexes 1 - 8 . Two p r i n c i p a l s y n t h e t i c r o u t e s t o the c a t i o n i c n i t r o s y l complexes 1 - 8 have been developed d u r i n g t h i s work. By the r e a c t i o n of [ N 0 ] + or [ A g ]+ s a l t s w i t h the n e u t r a l p r e c u r s o r s Cp/M(NO)X2 i n CH3CN, I have been a b l e t o generate the c a t i o n i c complexes 1 - 8 through an exchange of the h a l i d e group wi t h the l e s s c o o r d i n a t i n g PF6~ o r BF4~ groups. Concomitant s o l v e n t i n c o r p o r a t i o n (CH3CN) i n t o the metal's c o o r d i n a t i o n sphere a l s o o c c u r s . When [ N 0 ] + s a l t s are used, i t i s important t h a t the [ N 0 ] + reagent ( d i s s o l v e d i n CH3CN) be added s l o w l y i n a dropwise manner t o the o r g a n o m e t a l l i c r e a c t a n t . Otherwise, the r e a c t i o n s do not proceed c l e a n l y , and the c a t i o n i c product complexes are subsequently d i f f i c u l t t o i s o l a t e i n a pure form. When [ A g ]+ s a l t s are added t o s o l u t i o n s o f the d i h a l o n i t r o s y l complexes, the t r a n s f o r m a t i o n s are r a p i d , s t r a i g h t f o r w a r d and proceed with the immediate p r e c i p i t a t i o n o f the [Ag]X (X = I , Br or Cl) s a l t s . The p r e c i p i t a t e d [Ag]X s a l t s can then be removed by f i l t r a t i o n . T h e r e f o r e , Ag(I) s a l t s are the reagents o f c h o i c e f o r the s y n t h e s i s o f these c a t i o n i c p r o d u c t s . In a l l the above t r a n s f o r m a t i o n s , (as i n Scheme 2.1), p r o c e e d i n g from the n e u t r a l d i h a l o n i t r o s y l Cp/M(NO)X2 complexes t o the c a t i o n i c [Cp'M(NO)X(NCCH3)2]+ complexes or 52 the d i c a t i o n [Cp*Mo(NO)(NCCH 3) 3] 2 +, DQ change i n the formal oxidation state of the metal centre has taken place. (1-6) Proposed Mechanism for the Reaction of Cp/M(NO)Z2 vith [N0]+. The mechanism by which the monocationic [Cp'Mo(NO)X(NCCH 3) 2] + complexes originate i n the reactions of [ N 0 ] + with Cp/Mo(NO)X2 complexes remains to be investigated. Nevertheless, a possible reaction pathway shown i n Scheme 2 . 2 can be proposed. [Cp /M(NO)X 2(CH 3CN)] [N0] + [Cp /M(NO)X 2(CH 3CN)]' + + NO' - x-H[Cp'M(NO)X(CH 3CN)] +" CH3CN - "XNO" [Cp'M(NO)X(NCCH 3) 2] + Scheme 2.2 53 In the reactions of [ N 0 ] + with t r a n s i t i o n metals, there i s evidence i n the chemical l i t e r a t u r e that [ N 0 ] + may sometimes behave as a n i t r o s y l a t i n g a g e n t 2 1 or as a one-electron o x i d a n t . 2 2 The dihalo n i t r o s y l complexes Cp'Mo(NO)X2 are assumed to be monomeric i n CH3CN, s t a b i l i z e d by the coordination of a CH3CN molecule to the Mo centre. As summarized by Scheme 2.2, the i n i t i a l step of the reaction may involve the oxidation of the 18-electron Cp'Mo(NO) X 2 (NCCH3) complex to the 17-electron r a d i c a l cation, [Cp'M(NO)X 2(CH 3CN)]* +, by [ N 0 ] + , while [ N 0 ] + i s i t s e l f being reduced to NO. The postulated r a d i c a l cation intermediate i s consistent with the observations that the reactions of the perhydro complexes, CpMo(NO)X2, with [ N 0 ] + require a longer reaction time to go to completion than the permethylated analogues, since the ease of oxidation of a t r a n s i t i o n metal complex generally increases with the increase i n electron density on the metal centre. The formation of the 17-electron metal centre may l a b i l i z e the halide ligand which could then r e s u l t i n the loss of " X * " which may then be trapped by "NO*" to form XNO ( n i t r o s y l halides are well known inorganic compounds). 2 3 The r e s u l t i n g 16-electron intermediate [Cp'Mo(NO)X(NCCH3)] + could then be further s t a b i l i z e d by 54 another molecule o f C H 3 C N t o y i e l d the 1 8 - e l e c t r o n p r o d u c t , [Cp/Mo(NO)X(NCCH3)2]+. (1-6) Reactions of Cp*Mo(NO)X2 and {HB(Me 2pyz) 3}Mo(NO)I 2 with [Ag]PF6. An i n t e r e s t i n g comparison can be made between Cp*Mo(NO)I2 and the c l o s e l y r e l a t e d (HB(Me2pyz)3)Mo(NO)I2 with r e s p e c t t o t h e i r r e a c t i v i t y w i t h [Ag]PF6 i n CH3CN. When ^HB(Me2pyz)3)Mo(NO)I2 i s t r e a t e d w i t h one e q u i v a l e n t o f [Ag]PF6 i n CH3CN (as i n eq 2.11), a paramagnetic product [{HB(Me2pyz)3)Mo(NO)(NCCH3)2]PF6, i s o b t a i n e d .1 3 The same product i s a l s o o b t a i n e d when two e q u i v a l e n t s o f [Ag]PF6 are used. {HB(Me2pyz)3)Mo(NO)I2 + n[Ag]PF6 • [{HB(Me2pyz)3)Mo(NO)(NCCH3)2]PF6 + n[Ag]I (2.11) (n= 1, 2) In c o n t r a s t , when Cp*Mo(NO)I2 i s t r e a t e d w i t h one e q u i v a l e n t o f [Ag]PF6 i n CH3CN, the diamagnetic complex 2 i s o b t a i n e d . However, when two e q u i v a l e n t s o f (Ag]PF6 a r e used, t h e d i c a t i o n i c complex 1 i s formed, i . e . , 55 Cp*Mo(NO)I2 + n[Ag]PF6 (I-H) S i g n i f i c a n c e o f Complexes 1 - 8 . Although c a t i o n i c o r g a n o m e t a l l i c complexes c o n t a i n i n g the d i n i t r o s y l fragment MCp'M(NO)2" a r e f r e q u e n t l y encountered i n Group 6 n i t r o s y l c h e m i s t r y , c a t i o n i c complexes c o n t a i n i n g the m o n o n i t r o s y l fragment "Cp'M(NO)" are not as common. Complexes 1 - 8 can be viewed as " o r g a n o m e t a l l i c Lewis a c i d s " , [Cp'M(NO)X]+ or [Cp*Mo(NO) ]2 +, s t a b i l i z e d by the c o o r d i n a t i o n of weakly b a s i c CH3CN l i g a n d s . These c a t i o n i c complexes c o n s t i t u t e a s m a l l c l a s s o f i s o l a b l e Group 6 e l e c t r o p h i l i c t r a n s i t i o n metal n i t r o s y l complexes c o n t a i n i n g the "Cp'MfNO)" fragment. The o n l y o t h e r complexes bel o n g i n g t o t h i s c l a s s r e p o r t e d i n the chemical l i t e r a t u r e are the [CpMo(NO)I(L)2]+ (L = phosphines) compounds.1 9'2 4 T h e r e f o r e , w h i l e t h e monocationic complexes 2 - 8 d e s c r i b e d i n t h i s work may have some precedence i n t h e chemical l i t e r a t u r e , no d i c a t i o n i c compound c o n t a i n i n g t h e "Cp*Mo(NO)'• fragment has been r e p o r t e d t o d a t e . I n o t h e r words, complex 1, [Cp*Mo(NO)(NCCH3)3][PF6]2, i s an unprecedented o r g a n o m e t a l l i c n i t r o s y l complex. [Cp Mo(NO)I(NCCH3)2]PF6 (2.12) [Cp*Mo(NO)(NCCH3)3][PF6]2 56 There have been s e v e r a l r e p o r t s i n the l i t e r a t u r e on the f o r m a t i o n and s y n t h e t i c a p p l i c a t i o n s o f t r a n s i t i o n - m e t a l a c e t o n i t r i l e c o m p l e x e s .2 5'2 6 For example, Sen and co-w o r k e r s2 5 1 3 have shown t h a t the complexes [M(NO)2(NCCH3)4]2 + (M = Mo, W) and [ P d ( N C C H3)4]2 + can induce the o l i g o m e r i z a t i o n of a wide range of o l e f i n s under m i l d c o n d i t i o n s . T h i s a c t i v i t y i s a t t r i b u t e d t o the l a b i l i t y o f the CH3CN l i g a n d s i n s o l u t i o n thus a l l o w i n g easy s o l v e n t - s u b s t r a t e exchange i n the metal's c o o r d i n a t i o n sphere and f u r t h e r s u b s t r a t e a c t i v a t i o n which i s induced by the presence of the c a t i o n i c charge. In a d d i t i o n , the e x t e n s i v e chemistry e x h i b i t e d by the c a t i o n i c c a r b o n y l complexes [ (rj5-C5R5)Mo (CO) 2 (NCCH3) 2 ]+ and [ ( r?5- C5R5) M ( C O )3_n( N C C H3)n]+ (R = H, Me; M = Fe, Ru; n = 1, 2) i s w e l l documented.2 6 A l s o , the c o u n t e r i o n s PF6~ or BF4~ i n the complexes 1 - 8 are n o n - c o o r d i n a t i n g (or a t most weakly c o o r d i n a t i n g ) which means t h a t they can be r e p l a c e d by other l i g a n d s under m i l d c o n d i t i o n s . In view of the e x t e n s i v e c h e m i s t r y e x h i b i t e d by ot h e r c a t i o n i c t r a n s i t i o n - m e t a l a c e t o n i t r i l e complexes, t h i s suggests t h a t the c a t i o n i c n i t r o s y l complexes 1 - 8 can, i n p r i n c i p l e , be u t i l i z e d i n o r g a n i c s y n t h e s i s and t o serve as u s e f u l p r e c u r s o r s t o a v a r i e t y o f new n i t r o s y l complexes. The c h a r a c t e r i s t i c c h e m i s t r y of these c a t i o n i c complexes remains t o be i n v e s t i g a t e d . 57 (II) Synthesis, Characterization and Chemical Reactivity of rCpCr(NO) (NCCH 3) 21 rpF g1 . 9^ . (II-A) [CpCr(NO)(NCCH 3) 2]PF 6 / 9 1 9 I t has been p r e v i o u s l y observed t h a t under r e d u c i n g c o n d i t i o n s i n the presence o f Lewis bases [CpCr(NO)I]2 and the [CpM(NO)X2]2 (M = Mo or W) compounds y i e l d the n e u t r a l complexes having the g e n e r a l formula CpM(NO)L2 (M = C r , Mo and W; L = Lewis b a s e s ) . As d e s c r i b e d i n P a r t (I) e a r l i e r , treatment of the Cp/M(NO)X2 (M = Mo or W) compounds w i t h a s i l v e r ( I ) s a l t i n CH3CN y i e l d s the diamagnetic c a t i o n s having the ge n e r a l formula [ C p/M ( N O ) X ( N C C H3)2]+« In c o n t r a s t , the product r e s u l t i n g from the treatment o f [CpCr(NO)I]2 with a s i l v e r ( I ) s a l t i n CH3CN does not resemble those produced by the Mo and W d i h a l o n i t r o s y l complexes. More i n t e r e s t i n g l y , treatment of the o l i v e green a c e t o n i t r i l e s o l u t i o n of [CpCr(NO)I]2 w i t h two e q u i v a l e n t s of [Ag]PF6 r e s u l t s i n the formation o f a b r i g h t green s o l u t i o n w i t h the concomitant p r e c i p i t a t i o n o f A g l . T h i s t r a n s f o r m a t i o n i s represented by eq 2.13. CH3CN [CpCr(NO)I]2 + 2 [Ag]PFg • [CpCr(NO)(NCCH3)2][PF6] + 2 A g l (2.13) 58 F i l t r a t i o n o f the mixture f o l l o w e d by a d d i t i o n o f d i e t h y l e t h e r t o the green f i l t r a t e r e s u l t s i n the p r e c i p i t a t i o n of the new complex 9, [ C p C r ( N O ) ( N C C H 3 )2] P Fg. The new complex 9 i s a paramagnetic green s o l i d t h a t can be handled i n a i r f o r s e v e r a l hours without any n o t i c e a b l e d e c o m p o s i t i o n . I t i s s o l u b l e i n CH3CN, C H 3 N 0 2 , and THF, and i s s p a r i n g l y s o l u b l e i n C H 2 C 1 2 t o y i e l d b r i g h t green a i r - and m o i s t u r e - s e n s i t i v e s o l u t i o n s . The IR spectrum (Table 2.2) of [CpCr(NO)(NCCH3)2]PF6 i n the s o l i d s t a t e e x h i b i t s a s t r o n g a b s o r p t i o n a t 17 09 cm- 1 a t t r i b u t a b l e t o the t e r m i n a l NO l i g a n d . In a d d i t i o n t o the NO band, two weak bands at 2326 and 22 97 cm- 1 i n the t>C N r e g i o n are a l s o observed due t o the c o o r d i n a t e d a c e t o n i t r i l e l i g a n d s . T h i s n i t r o s y l s t r e t c h i n g frequency o f 9 i s s h i f t e d 46 cm- 1 h i g h e r than i t s n e u t r a l p r e c u r s o r , [ C p C r ( N O ) I ]2, which i s c o n s i s t e n t w i t h the e x i s t e n c e o f decreased backbonding t o the n i t r o s y l l i g a n d i n the c a t i o n i c p r o d u c t . The uN 0 of 9 may a l s o be compared t o the c o r r e s p o n d i n g frequency i n (rj5-C1 3Hg) Cr (CO) 2 (NO) 2 7 ( uN Q 1713 cm"1). The near c o i n c i d e n c e o f the n i t r o s y l s t r e t c h i n g frequency between complex 9 and the d i c a r b o n y l complex i s presumably due t o the h i g h e r formal o x i d a t i o n s t a t e of the metal ( C r ( I ) ) and poor JT a c c e p t o r a b i l i t i e s o f the CH3CN l i g a n d s i n 9 v e r s u s the lower formal o x i d a t i o n s t a t e (Cr(0)) 59 and good * acceptor a b i l i t i e s of the CO ligands i n the neutral carbonyl complex. The ESR spectrum of complex 9 as a DMF s o l u t i o n at room temperature shows a three l i n e pattern (g«= 1.984) with approximately equal peak i n t e n s i t i e s (Figure 2.4). This pattern r e s u l t s from the hyperfine coupling of the unpaired electron with 1 4 N (1=1) of the NO ligand. The observed coupling constant to 1 4 N i s 5.21 G. a ( » N ) i — r Figure 2.4. ESR spectrum of complex 9 i n DMF. 60 There i s a p o s s i b i l i t y that the 17 -electron cor.plex 9 may be dimeric, e s p e c i a l l y i n the s o l i d state. To examine t h i s p o s s i b i l i t y , as well as to determine the mode of coordination of the a c e t o n i t r i l e ligands to the Cr centre an X-ray structure of complex 9 has been obtained. The s o l i d - s t a t e molecular structure of complex 9 i s shown i n Figure 2.5. Selected bond lengths and bond angles are given i n Tables 2.8 and 2.9, respectively. As shown i n Figure 2.5, complex 9 i s a monomer with a three-legged piano s t o o l molecular geometry. The distance of the Cr centre to the plane of the Cp ri n g i n complex 9 i s 1.857 A. which i s shorter than that of (f? 5-C 1 3H 9) Cr (CO) 2 (NO) at 1.884 A. Within the CrNO moiety of complex 9, the Cr-N distance (1.686 A) and the N-0 distance (1.168 A) are i n very close agreement to the corresponding bond lengths observed f o r (»? 5-C 1 3H g) Cr (CO) 2 ( N O ) (1.687 A and 1.169 A) . The CrNO bond angle i n complex 9 (170.4°) i s e s s e n t i a l l y l i n e a r although i t i s more bent than i n (r? 5-C 1 3H 9)Cr(CO) 2(NO) (178.9°). The two a c e t o n i t r i l e ligands are N-bonded ( i n a l i n e a r fashion) to the Cr centre i n 9. The Cr-N bond lengths are i n reasonable agreement with the previously determined structures of c a t i o n i c Cr complexes with N-bonded a c e t o n i t r i l e l i g a n d s . 2 8 61 Figure 2.5. Solid-state molecular structure of [ C p C r ( N O ) ( N C C H 3 ) 2 ] [ P F 6 ] , complex 9 62 Table 2.8. Selected Bond Lengths (A) f o r [CpCr(NO) (NCCH 3) 2][I ,F 6] f Complex 9 . Bond Length<a> Cr - Cp 1.857(9) Cr - Nl 1.686(6) Cr - N2 2.02(2) Cr - N3 2.011(12) 0 - Nl 1.168(8) N2 - C6 1.140(2) N3 - C8 1.10(2) C6 - C7 1.40(3) C8 - C9 1.49(3) ( a) E.s.d.'s are i n parentheses. 63 Table 2 . 9 . S e l e c t e d B o n d A n g l e s ( d e g ) f o r [ C p C r ( N O ) ( N C C H 3 ) 2 ] [ P F 6 ] , C o m p l e x 9 . Bond Angle<a> Nl — c r — N2 97.1(6) Nl - Cr - N3 98.6(7) Nl - Cr - Cp 122.4(4) N2 - Cr - N3 91.0(2) N2 - Cr - Cp 118.3(6) N3 - Cr - Cp 122.3(6) Cr - Nl - 0 170.4(11) Cr - N2 - C6 175.7(15) Cr - N3 - C8 176.7(15) N2 - C6 - C7 173(2) N3 - C8 - C9 176(2) ( a ) E . s . d . ' s a r e i n p a r e n t h e s e s . 64 There are very few examples of 17-electron neutral or c a t i o n i c organometallic chromium n i t r o s y l complexes reported i n the chemical l i t e r a t u r e t o date. The only other known example of a 17-electron cation belonging t o t h i s class of compounds i s [CpCr(NO)(L-L)] + ((L-L) « phen or b p y ) . 2 9 This complex i s prepared by the thermal s u b s t i t u t i o n reaction presented i n eg 2.14 [CpCr (N0) 2 (NCCH3) ]PF 6 + L-L • [CpCr(NO) (L-L) ]PF 6 + NO + CH3CN (2.14) This synthetic route (eq 2.14) to the r a d i c a l cation i s li m i t e d to strongly donating bidentate ligands since the reaction benefits thermodynamically from the "chelate e f f e c t " . Also, the f i n a l products must be stable at high temperatures since the reaction only proceeds i n ref l u x i n g CH 3N0 2. In comparison, reaction 2.13 proceeds at room temperature, and the reaction i s driven by the p r e c i p i t a t i o n of the s i l v e r h alide s a l t . Also, the CH3CN ligands i n 9 are weaker N-donors than the bpy or phen ligands. This can be observed by comparing the IR spectrum of 9 with that of the [CpCr(NO)(L-L ) ] + complexes. In CH 3 N 0 2 , the IR spectrum of [CpCr(NO)(NCCH 3) 2]PF6 exhibits a strong n i t r o s y l absorption at 1709 cm - 1. The p o s i t i o n of t h i s band i s at a higher frequency when compared to [CpCr(NO)(L-L)]PF 6 ((L-L) = phen or bpy; v N 0 65 1690 cm"1) s u g g e s t i n g t h a t t h e r e i s more e l e c t r o n d e n s i t y on the metal c e n t r e i n t h e l a t t e r complexes t o backdonate t o the NO ** l i g a n d t h u s i n d i c a t i n g t h e weaker d o n a t i n g a b i l i t y o f t h e CH3CN l i g a n d s compared t o the b i d e n t a t e N-donor l i g a n d s . (II-B) R e a c t i o n o f [CpCr(NO)I]2 v i t h [Ag]PF6 i n CH2C12. S i n c e i o d i d e a b s t r a c t i o n from [CpC r ( N O ) I ]2 i n a c o o r d i n a t i n g s o l v e n t ( C H 3 C N ) l e a d s t o the f o r m a t i o n o f {CpCr(NO)(NCCH3)2]PF6, I next attempted r e a c t i o n 2.13 i n a n o n - c o o r d i n a t i n g s o l v e n t ( i e . CH2C12) t o see i f the c o r r e s p o n d i n g [ C p C r ( N O ) ( C H2C 12)2)+ complex can be generated s i n c e the l o o s e l y bound s o l v e n t molecules i n t h i s c a t i o n w i l l r e nder the c a t i o n more r e a c t i v e . When the r e a c t i o n between [ C p C r ( N 0 ) I ]2 and [Ag]PF6 i s c a r r i e d out i n CH2C12, the t r a n s f o r m a t i o n t h a t occurs i s q u i t e complex. U l t i m a t e l y , a "CpCr(NO)2+" c o n t a i n i n g s p e c i e s i s o b t a i n e d as i n d i c a t e d by the IR spectrum o f the r e a c t i o n mixture ( V J J0 a t 1842 (s) and 1740(s) cm"1). However, attempts t o i s o l a t e t h i s complex only l e a d t o extremely a i r - s e n s i t i v e g r e e n i s h - b l u e o i l s . N e v e r t h e l e s s , i t can be d e r i v a t i z e d t o the known c h l o r i d e complex, C p C r ( N O )2C l , by a d d i t i o n o f [PPN)C1 ( B i s ( t r i p h e n y l p h o s p h i n e i m i n i u m c h l o r i d e ) ) t o t h e r e a c t i o n m i x t u r e . 66 (II-C) Some Chemical Reactivity of complex 9 . When [CpCr(NO)(NCCH3)2]PF6 i s treated with one equivalent of NaBPh4 in CH2C12 s o l u t i o n , a metathesis of the PFg~ anion f o r the BPh4~ group occurs, i . e . , [CpCr(NO)(NCCH3)2]PF6 + Na[BPh4] • CpCr(NO)(NCCH3)2]BPh4 + NaPFg (2.15) The c a t i o n , as i t s BPh4" s a l t , i s i s o l a t e d o n l y i n 20% y i e l d . The low y i e l d o f [CpCr(NO)(NCCH3)2]BPh4 i s o l a t e d i s somewhat s u r p r i s i n g s i n c e the chemical t r a n s f o r m a t i o n i n v o l v e d (eq. 2.15) i s o n l y a simple metathesis r e a c t i o n . Probably another s i d e r e a c t i o n which may occur b e f o r e or a f t e r the metathesis r e a c t i o n i s t h a t i n CH2C12 one o f the CH3CN l i g a n d s i s s u f f i c i e n t l y l a b i l e t o y i e l d the e l e c t r o p h i l i c "CpCr(NO)(NCCH3)+" i n t e r m e d i a t e which can a b s t r a c t a phenyl group from t h e BPh4~ counterion to g i v e an a r y l complex CpCr(NO)(NCCH3)Ph, i . e . , [CpCr(NO) (NCCH3)2)PF6 + NaBPh4 •CpCr(NO) (NCCh*3)Ph + NaPFg + CH3CN + BPh3 (2.16) 67 The neutral 17-electron a r y l complex i s probably thermally unstable at room temperature, a f a c t that would lead to i t s decomposition.' The mode of r e a c t i v i t y f o r the organoboron complex c i t e d i n eg 2.16 i s not without precedent since i t has previously been observed that treatment of [CpW(NO) 2]BF 4 with Na[BPh 4] under s i m i l a r conditions y i e l d s the a r y l complex, CpW(NO) 2Ph. 3 0 When complex 9 i s treated with excess NaOMe i n CH 2 C 1 2 , the b i m e t a l l i c complex [CpCr(NO)(OMe)] 2 i s obtained, i . e . , eq 2.17. The product i s o l a t e d from t h i s 2[CpCr ( N 0 )(NCCH 3) 2]PF 6 + xs NaOMe • [CpCr(NO)(OMe)] 2 + 2 N a P F 6 + 2CH 3CN (2.17) reaction i s rather unexpected. One would anticipate the attack of the methoxide group to occur e i t h e r at the NO or at the CH3CN group since both ligands are known to engage i n such reactions, e s p e c i a l l y when present i n a c a t i o n i c complex. 3 1 I t can be proposed that the OMe" group here f i r s t replaces the PF 6~ group to y i e l d the 19-electron complex CpCr(NO)(OMe)(NCCH 3) 2 which then loses i t s CH3CN ligands and dimerizes to [CpCr(NO)(OMe)] 2. The propensity f o r the monomeric Cr complex to dimerize and form the b i m e t a l l i c compound i s not re a d i l y explicable. Similar tendencies are 68 also r e f l e c t e d i n the unsuccessful attempts to make the 18-electron [CpCr(NO)I 2] 2 which r e a d i l y converts to [CpCr(NO)l] 2 i n CH 2C1 2. 6 In contrast, the [CpM(NO)I 2] 2 (M «= Mo,W) compounds can be made i n good y i e l d s and do not r e a d i l y convert t o the corresponding monohalo dimers, [CpM(NO)I] 2. Several attempts were made to synthesize the neutral analogue of the r a d i c a l cation, i . e . CpCr(NO)(NCCH 3) 2. Reduction of [CpCr(NO)(NCCH 3) 2]PF 6 with Na/Hg i n THF only ieads to a non-nitrosyl containing brown s o l u t i o n . A less potent reducing agent such as zinc dust leads to the formation of an extremely a i r - s e n s i t i v e bright purple s o l i d which i s often contaminated with the r a d i c a l cation. Attempts to pu r i f y the purple s o l i d did not meet with success. 69 Summary This work has demonstrated that the treatment of the dihalo n i t r o s y l complexes of molybdenum and tungsten, Cp'M(NO)X2, with [ N 0 ] + and [Ag] + s a l t s , i n CH3CN affords a se r i e s of new diamagnetic c a t i o n i c n i t r o s y l complexes, [Cp /M(NO)X(NCCH 3) 2] + and [Cp*Mo(NO)(NCCH 3) 3] 2 +. The physical and spectroscopic properties of these c a t i o n i c complexes are consistent with t h e i r possessing the conventional four-legged piano s t o o l molecular geometry. In addition, treatment of [CpCr(NO)I] 2 with a [Ag] + s a l t i n CH3CN leads to the successful i s o l a t i o n of the novel paramagnetic chromium cation, [CpCr(NO)(NCCH 3) 2] +. The complex i s monomeric i n the s o l i d state possessing the f a m i l i a r three-legged piano stool molecular geometry. A solution ESR measurement shows that the unpaired electron i s delocalized on the nitrogen atom of the n i t r o s y l ligand. Taking into account the l a b i l i t y of the CH3CN ligands i n so l u t i o n and the "non-coordinating" c h a r a c t e r i s t i c s of the counterion (PF 6 or BF 4) i n the new organometallic complexes prepared i n t h i s work, t h i s suggests that the organometallic cations may i n p r i n c i p l e serve as convenient precursors t o novel n i t r o s y l complexes of Cr, Mo and W. 70 References and Notes 1. Richter-Addo, G. B. Ph.D. D i s s e r t a t i o n , U n i v e r s i t y of B r i t i s h Columbia, B r i t i s h Columbia, 1988. 2. L e g z d i n s , P.; Richter-Addo, G. B. submitted t o O r g a n o m e t a l l i c s . 3. S h r i v e r , D. F.; Drezdzon, M. A. The M a n i p u l a t i o n o f A i r - s e n s i t i v e Compounds, 2nd ed.; W i l e y - I n t e r s c i e n c e : Toronto, 1986. 4. Seddon, D.; K i t a , W. G.; Bray, J . ; M c C l e v e r t y , J . A. Tn o r g . Synth. 1976, 16, 24. 5. Dryden, N. H.; L e g z d i n s , P.; E i n s t e i n , F. W. B.; Jones, R . H. Can. J . Chem. 1988, 2100. 6. L e g z d i n s , P.; Nurse, C. R. I n o r q . Chem. 1985. 24, 327. 7. Dryden, N. H.; Le g z d i n s , P.; unpublished o b s e r v a t i o n s . 8. P h i l l i p s , P. S.; H e r r i n g , F. G. J . Macrn. Reson. 1984, 57, 43. 9. Hoyano, J . K.; L e g z d i n s , P.; M a l i t o , J . T. I n o r q . Synth. 1978, 18, 129. 10. S t o r h o f f , B. N.; Huntley, C. L . J r . Coord. Chem. Rev. 197 7, 23, 1. 11. Bruce, M. R. M.; T y l e r , D. R. O r g a n o m e t a l l i c s 1985, 4, 528. 12. Sen, A.; Thomas, R. R. Or g a n o m e t a l l i c s 1982, 1, 1251. 13. D e n t i , G.; G h e d i n i , M.; McCleverty, J . A. and Adams, H.; B a i l e y , N. A. T r a n s i t i o n Met. Chem. 1982, 7, 222-224. 14. L e o n i , P.; G r i l l i , E.; P a s q u a l i , M.; T o m a s s i n i , M. J . Chem. Soc. Dalton T r a n s . 1986, 1041. 15. Stewart, R. P.; Moore, G. T. I n o r q . Chem. 1975, 14/ 2699. 16. L a p i n t e , C.; Asdar, A.; Tudoret, M. J . J . Organomet. Chem. 1988, 349, 353. 71 17. C a l h o r d a , M. J . ; D i a s , A. R.; Domingos, A. M. T.; Duarte, M. T. L. S.; G a r c i a , M. H.; Ramao, C. C. J . Orqanomet.  Chem. 1987, 320, 63. 18. P r o u t , C. K. e t a l . A c t a C r v s t . 1974, B30, 2290. 19. C h r i s t e n s e n , N. J . ; Hunter, A. D.; L e g z d i n s , P.; Sanchez, L. Inorq• Chem. 1987, 26. 3344. 20. Reduction o f [CpMo(NO)1^]2 w i t n Na/Hg, i n THF, i n the presence o f a c y c l i c conjugated d i e n e s , y i e l d s novel [CpMo(NO) (>74-diene) ] . However, the congeneric W diene complex cannot be made by the same r o u t e . 21. Crooks, G. R.; Johnson, B. F. G. J . Chem. Soc. (A). 1 9 7 0 , 1662 . 22. C o n n e l l y , N. G.; Johnson, G. A. J . Orqanomet. Chem. 1974, 77, 341. 23. C o t t o n , F. A.; W i l k i n s o n , G. "Advanced I n o r g a n i c  Chemistry" Wiley I n t e r s c i e n c e , F i f t h E d i t i o n , 1988, p 332. 24. (a) M c C l e v e r t y , J . A.; Seddon, D. J . Chem. Soc. Dalton  T r a n s . 1972, 2526. (b) McCleverty, J . A.; Hunt, M. M.; K i t a , W. G. J . Chem. Soc.. D a l t o n . T r a n s . 1978, 474. (c) Mc C l e v e r t y , J . A.; James, T. A. J . Chem. Soc. (A). 1 9 7 1 , 1596. 25. (a) J o r d a n , R. F.; E c h o l s , S. F. I n o r g . Chem. 1987, 26, 383 and r e f e r e n c e s t h e r e i n . (b) Sen, A.; L a i , T. W. Or q a n o m e t a l l i c s 1982, 1, 415. 26. (a) B o t t r i l l , M.; Green, M. J . Chem. S o c , Dalton T r a n s . 1977, 2365. (b) C a t h e l i n e , D.; A s t r u c , D. Or q a n o m e t a l l i c s 1984, 3, 1094. 27. Atwood, J. - L . ; Herberhold, M. J . Orqanomet. Chem. 1979, 165. 65. 28. W i l k i n s o n , G.; S a l t , J . E.; Hurthouse, M. B.; M o t e v a l l i , M. J . Chem. S o c . Dalton T r a n s . 1986, 1141. 29. W o j c i c k i , A.; Regina, R. F. I n o r q . Chem. 1980, 19, 3803. 30. L e g z d i n s , P.; M a r t i n , D. T. O r q a n o m e t a l l i c s . 1983, 2, 1785. 72 Bottomley, F. Ace. Chem. Res. 1978, 11, 158 and r e f e r e n c e s c i t e d t h e r e i n . 7 3 Chapter 3 Synthesis and Characterization of the D i n i t r o s y l Dimers [Cp*M (NO) 2 ] 2 (Cp* - ij 5-C 5Me 5; M - Cr, Mo). 74 I n t r o d u c t i o n The compound [CpCr(NO)2]2 w a s f i r s t r e p o r t e d by King and B i s n e t t e i n 1964.1 I t was f i r s t o b t a i n e d i n o n l y 5% y i e l d v i a t he r e d u c t i o n of CpCr(NO)2Cl with NaBH4 i n a two-phase water-benzene system. However, our r e s e a r c h group subsequently d i s c o v e r e d t h a t i t i s be s t prepared i n much h i g h e r y i e l d s by the r e d u c t i o n o f CpCr(NO)2Cl w i t h e i t h e r Zn/Hg i n THF2 ( i . e . eq 3.1) or Na/Hg i n benzene3. The hig h y i e l d s y n t h e s i s o f t h i s dimer enabled an e x t e n s i v e Zn/Hg CpCr(NO)2Cl • [ C p C r ( N O )2]2 (3.1) THF, RT study o f i t s p h y s i c a l and chemical p r o p e r t i e s t o be undertaken. In view o f the e x t e n s i v e and v a r i e d chemistry o f [CpCr(NO)2]2 t h a t our r e s e a r c h group has d e v e l o p e d ,4 - 7 the p r e p a r a t i o n o f the Mo and W analogues f o r comparative purposes i s undoubtedly one of our prime o b j e c t i v e s . U n f o r t u n a t e l y , when the CpM(NO)2Cl (M = Mo, W) complexes are s u b j e c t e d t o the experimental c o n d i t i o n s i n d i c a t e d i n eq. 3.1, o n l y i n t r a c t a b l e p roducts are o b t a i n e d . To da t e , the Mo and W dimers, 75 [CpM(NO) 2] 2, have yet to be i s o l a t e d even though they have been the object of much synthetic e f f o r t . 8 I t has been shown that pentamethylcyclopentadienyl (Cp*)-containing compounds often ex h i b i t dramatically d i f f e r e n t chemistry from that shown by t h e i r unsubstituted cyclopentadienyl analogues. 9 I t was thought that perhaps the reduction of the respective chloro complexes of Cr, Mo and W containing the i75-C5Me5 ligand ( i . e . Cp*M(NO)2Cl) under the same conditions as those i n eq. 3.1 should y i e l d the respective d i n i t r o s y l dimers [Cp*M(NO) 2) 2. Indeed t h i s expectation has been r e a l i z e d , and i n t h i s chapter the syntheses and characterization of the new dimers [Cp*M(NO) 2] 2 (M = Cr, Mo) are described. Furthermore, the physical and chemical properties of these dimers are compared and contrasted to t h e i r valence i s o e l e c t r o n i c carbonyl analogues [Cp'M(CO) 2] 2 (Cp' = Cp or Cp*; M = Fe, Ru), as well as t h e i r congeneric Cp analogue,. [CpCr(NO) 2] 2. 76 Experimental Section A l l reactions and subsequent manipulations were performed under anaerobic and anhydrous conditions. General experimental procedures employed i n t h i s study were s i m i l a r to those described i n the preceding chapter. Cp*W(NO) 2Cl 1 0 and Cp*Cr(CO) 2(NO) 1 1 were prepared by published procedures. The pur i t y of a l l the complexes prepared was ascertained by elemental analyses and conventional spectroscopic techniques. Preparation of Cp*M(N0) 2Cl (M = Cr, Mo). Both of the Cp*M(NO) 2Cl complexes were prepared i n a s i m i l a r manner, but to achieve optimum y i e l d s the reactions were performed at -78°C. The preparation of the Mo complex i s described here as a representative example. A s t i r r e d solution of Cp*Mo(CO)2(NO) (7.00 g, 22.1 mmol) i n CH 2C1 2 (50 mL) was treated dropwise with a CH 2C1 2 s o l u t i o n of n i t r o s y l c h l o r i d e . 1 2 (The C1N0 sol u t i o n t y p i c a l l y consisted of approximately 50 mmol of C1N0 i n 30 mL of CH 2C1 2). Gas evolution occurred, and the colour of the solu t i o n changed from orange to o l i v e green. The progress of the reaction was monitored by IR spectroscopy, and the n i t r o s y l chloride solution was added u n t i l the carbonyl absorptions of the s t a r t i n g organometallic reactant ( u c o 2004(s), 1923(vs) cm"1) had disappeared and new n i t r o s y l bands 77 had appeared at 1728(s) and 1641(vs) cm"1. The f i n a l reaction mixture was concentrated i n vacuo to approximately 20 mL and was f i l t e r e d through a short ( 2 x 4 cm) F l o r i s i l column supported on a f r i t . The column was washed with CH 2C1 2 u n t i l the washings vere colourless, and the f i l t r a t e was concentrated i n vacuo to approximately 20 mL. Addition of hexanes (100 - 150 mL) resulted i n the p r e c i p i t a t i o n of an o l i v e green m i c r o c r y s t a l l i n e s o l i d . The o l i v e green s o l i d was c o l l e c t e d by f i l t r a t i o n , washed with 2x10 mL of cold (0°C) hexanes and dried i n vacuo. This procedure afforded 5.75 g (17.6 mmol, 80% yield) of a n a l y t i c a l l y pure Cp*Mo(NO)2C1. Anal. Calcd. f o r C 1 0H 1 5N 20 2ClMo : C, 36.81; H, 4.60; N, 8.59. Found : C, 36.63; H, 4.71; N, 8.50. IR (Nujol mull) u N 0 1717 (S) , 1642(VS) cm"1; (CH 2C1 2) t^Q 1728(s), 1641(vs) cm"1. 1H NMR (CDCl-j) 6 1.89 (C 5(CH. 3) 5). Low resolution mass spectrum (probe temperature 120°C) m/z. 326 [P] + . The chromium analogue was obtained s i m i l a r l y as a dark reddish-brown m i c r o c r y s t a l l i n e s o l i d i n 60% y i e l d . Anal. Calcd. f o r C 1 0 H 1 5 N 2 0 2 C l C r : C, 42.55; H, 5.32; N, 9.93. Found : C, 42.34; H, 5.40; N, 9.86. IR (Nujol mull) WJJQ 1763(s), 1681(VS) cm"1; (CH 2C1 2) 1782(s), 1682(vs) cm"1. XH NMR (C 6D 6) 6 1.34 ( C 5 ( C H 3 ) 5 ) . Low r e s o l u t i o n mass spectrum (probe temperature 120°C) m/a 282 [ P ] + . 78 Preparation o f [Cp*Cr(NO) 2] 2. A zinc amalgam was prepared by s t i r r i n g zinc dust (0.46 g) with mercury (10 g) f o r 1 h. This amalgam was then s t i r r e d with a s o l u t i o n of Cp*Cr(NO) 2Cl (0.20 g, 0.71 mmol) i n THF (30 mL) at room temperature. The progress of the reaction was monitored by IR spectroscopy. The reaction was allowed to proceed u n t i l the n i t r o s y l absorptions of the s t a r t i n g chloro complex (V^Q 1777(s), 1677(s) cm - 1) had completely disappeared and had been replaced by a band at 1638(s) cm"1 a t t r i b u t a b l e to the [Cp*Cr(NO) 2]2 complex. During t h i s time, the colour of the reaction mixture changed from reddish-brown to dark red-v i o l e t . The reaction mixture was f i l t e r e d through a column of C e l i t e ( 1 x 2 cm) supported on a f r i t , and the f i l t r a t e was taken to dryness i n vacuo. The r e s u l t i n g residue was redissolved i n benzene (10 mL) and chromatographed on an alumina column (Woelm, Basic, a c t i v i t y 3) with benzene as eluant. The single dark purple band that developed was c o l l e c t e d and taken to dryness i n vacuo to y i e l d 0.080 g (45% yi e l d ) of dark purple, a n a l y t i c a l l y pure [Cp*Cr(NO) 2) 2. Anal. Calcd. f o r C 2 0 H 3 0 N 4 0 4 C r 2 : C, 48.58; H, 6.07; N, 11.34. Found : C, 48.58; H, 5.96; N, 11.18. IR (KBr p e l l e t ) U J J Q 1630(s), 1487(w) cm"1. XH NMR (CDC13) 6 1 ' 5 0 a n d 1.65 ( C 5 ( C H 3 ) 5 ) . 1 3 C ( 1 H ) NMR (C f iD 6) S 8.71 ( C 5 ( C H 3 ) 5 ) , 109.32 ( C 5 ( C H 3 ) 5 ) . Low resolution mass spectrum (probe temperature 120°C) E / £ 494 [ P ] + . 79 Preparation of [Cp*Mo(NO) 2] 2. Cp*Mo(NO) 2Cl (0.30 g, 0.92 mmol) was s t i r r e d with Zn amalgam (0.17 g of zinc dust i n 10 g of mercury) i n THF (60 mL). The progress of the reaction was again monitored by IR spectroscopy. A f t e r 15h, an IR spectrum of the supernatant s o l u t i o n revealed the consumption of the s t a r t i n g chloro complex (V^Q 1723(s), 1638(s) cm"1) and the formation of a new nitro s y l - c o n t a i n i n g compound (v^Q 1591(s) cm" 1). The THF soluti o n was f i l t e r cannulated away from the mercury-containing residues. The f i l t r a t e was taken to dryness i n vacuo to y i e l d a dark red-v i o l e t s o l i d . This s o l i d was extracted with hexanes (4 x 10 mL); the hexanes extracts were combined and taken to dryness. The dark purple residue was dissolved i n CH 2C1 2 (10 mL) and cooled t o 0°C for 24h. The bright purple, m i c r o c r y s t a l l i n e s o l i d that deposited was colle c t e d and dried i n vacuo for 24h t o y i e l d elementally pure [Cp*Mo(NO)2]2 (0.060 g, 23% y i e l d ) . Anal. Calcd. for C 2 0H 3 0N 4O 4Mo 2 : C, 41.20; H, 5.15; N, 9.62. Found : C, 41.50; H, 5.31; N, 9.54. IR (KBr pell e t ) v$0 1692(s), 1585(vs, br) cm"1. XH NMR (C f iD 6) 6 1.47 ( C 5 ( C H 3 ) 5 ) . 1 3C{ 1H) NMR (C 6D 6) 6 9.39 <C 5 ( £ H 3 ) 5 ) , 111.34 ( C 5 ( C H 3 ) 5 ) . Low resolution mass spectrum (probe temperature 120°C) m/z 582 [ P ] + . 80 Attempted Syntheses of [Cp*W(NO)2]2* (i) A THF s o l u t i o n (60 mL) of Cp*W(N0) 2Cl (0.20 g, 0.48 mmol) was s t i r r e d with zinc amalgam (0.20 g of Zn dust i n 10 g of Hg) f o r 1 h. During t h i s time the colour of the reaction mixture changed from green t o greenish-brown. Monitoring the progress of the reaction by IR spectroscopy indicated the decrease i n i n t e n s i t y of the NO bands of the chloro complex ( I ^ Q 1702(s), 1623(vs) cm"1) but no new n i t r o s y l absorptions were observed. Prolonged s t i r r i n g of the reaction mixture eventually l e d to the consumption of the s t a r t i n g chloro complex. ( i i ) A THF s o l u t i o n (60 mL) of Cp*W(N0) 2Cl (0.20 g, 0.48 mmol) was s t i r r e d with a stoichiometric amount of Na/Hg at room temperature. After 15 min, the IR spectrum of the so l u t i o n revealed the complete consumption of the s t a r t i n g organometallic reactant (v^0 1702(s), 1623(vs) cm"1) and the formation of a new nitrosyl-containing complex (I^Q 1672(m), 1591(m) cm - 1). During t h i s time, the colour of the reaction mixture changed from green to l i g h t brown. The f i n a l mixture was f i l t e r e d through a short column ( 2 x 2 cm) of C e l i t e supported on a f r i t ; the f i l t r a t e was taken to dryness to y i e l d a small amount of a brown, o i l y s o l i d . This o i l y residue was redissolved i n CH 2C1 2 (10 mL), layered with E t 2 0 (20 mL) and cooled at 0°C f o r 24 h. This procedure afforded a small amount of an a i r - s e n s i t i v e yellow p r e c i p i t a t e which was 81 c o l l e c t e d and d r i e d i n vacuo f o r s e v e r a l h o u r s . Elemental a n a l y s e s o f t h i s y e l l o w s o l i d prepared on two s e p a r a t e o c c a s i o n s showed i t t o be q u i t e v a r i a b l e i n C, H and N c o n t e n t s : C, 32.07; H, 4.22; N, 5.16 and C, 35.57; H, 4.83; N, 4.30. R e a c t i o n o f [Cp*Mo(NO)2]2 v i t h 8 n C l2. To a s t i r r e d THF s o l u t i o n (20 mL) of [Cp*Mo(N0)2)2 (0.050 g, 0.086 mmol) at room temperature was added S n C l2 (0.050 g, 0.26 mmol). The r e a c t i o n mixture was s t i r r e d f o r 1 h d u r i n g which time the c o l o u r o f the s o l u t i o n changed from p u r p l e t o green-brown. An IR spectrum of the s o l u t i o n e x h i b i t e d two new n i t r o s y l bands at 1723 and 1638 cm- 1. The s o l u t i o n was taken t o dryness i n vacuo, and the r e s i d u e was r e d i s s o l v e d i n CH2C12. T h i s CH2C12 s o l u t i o n was then chromatographed on a F l o r i s i l column with CH2C12 as the e l u a n t . The green band t h a t separated was c o l l e c t e d , and the s o l v e n t was removed from th e e l u a t e i n vacuo. The o l i v e green r e s i d u e was found t o be Cp*Mo(N0)2Cl by comparison o f i t s s p e c t r o s c o p i c p r o p e r t i e s t o t h a t o f an a u t h e n t i c sample: IR (Nujol mull) V^Q 1717(s), 1642(vs) cm"1; XH NMR (CDC13) 6 1.89 ( s , C 5 ( C f i 3 ) 5 ) . 82 Results and Discussion ( I ) Preparation of the Cp*M(N0)2Cl (M = Cr, Mo) Complexes. Treatment of the Cp*M(CO)2(NO) complexes with C1N0 i n CH 2C1 2, according to eg. 3.2., r e s u l t s i n the formation of the d i n i t r o s y l chloride complexes, Cp*M(NO) 2Cl, in good y i e l d s . The transformation in eq. 3.2 i s s i m i l a r to that Cp*M(CO)2(NO) + C1N0 • Cp*M(NO) 2Cl + 2CO (M = Cr, Mo) (3.2) observed f o r the corresponding Cp-containing complexes. 1 3 The Cp*Cr(NO) 2Cl complex i s a dark reddish-brown c r y s t a l l i n e s o l i d that i s sparingly soluble i n hexanes and E t 2 0 but very soluble i n CH 2C1 2, THF and toluene. The Mo analogue i s a green c r y s t a l l i n e s o l i d with s i m i l a r s o l u b i l i t y properties. In t h e i r pure form, both complexes can be stored under N 2 at room temperature for extended periods of time and may be handled i n a i r f o r short periods of time without noticeable decomposition. ( I I ) The [Cp*M(NO) 2] 2 (M = Cr, Mo) Complexes ( I I - A ) Preparation of the £Cp*M(NO) 2] 2 (M = Cr, Mo) Complexes. Treatment of the Cp*M(N0)2Cl (M «= Cr, Mo) complexes with zinc amalgam i n THF according to the general equation 3.3 83 a f f o r d s the co r r e s p o n d i n g d i n i t r o s y l dimer complexes, [Cp*M(NO)2]2, i ° moderate y i e l d s . The p r o g r e s s o f the r e a c t i o n can be c o n v e n i e n t l y monitored by IR s p e c t r o s c o p y . Zn/Hg 2Cp*M(N0)2Cl • [Cp*M(NO)2]2 (3.3) THF, RT [ C p * C r ( N O )2]2 i s b e s t p u r i f i e d by column chromatography of the crude complex as a benzene s o l u t i o n on an alumina column. Pure [ C p * C r ( N O )2]2 i s a dark p u r p l e s o l i d which i s t h e r m a l l y s t a b l e at room temperature under N2 f o r s e v e r a l months. As a s o l i d , i t i s a i r s e n s i t i v e but may be handled q u i c k l y i n a i r without n o t i c e a b l e decomposition. The complex i s v e r y s o l u b l e i n T H F , C H2C 12 and benzene, but o n l y s p a r i n g l y s o l u b l e i n E t20 and hexanes t o y i e l d dark p u r p l e s o l u t i o n s which are a i r - and m o i s t u r e - s e n s i t i v e . During the s y n t h e s i s o f [Cp*Mo(NO)2]2, once the s t a r t i n g m a t e r i a l i s consumed, i t i s important t h a t the s o l u t i o n be separated from the amalgam. Prolonged s t i r r i n g of the r e a c t i o n mixture beyond t h i s time r e s u l t s i n much lower y i e l d s o f t h e d e s i r e d p r o d u c t . While [ C p * C r ( N O )2]2 can be p u r i f i e d by column chromatography, a benzene s o l u t i o n o f [Cp*Mo(NO)2]2 decomposes immediately on an alumina column. Attempts t o chromatograph a s o l u t i o n o f crude [Cp*Mo(NO)2]2 on 84 a F l o r i s i l column or an alumina column (Woelm, Basic, a c t i v i t y 2, 3 or 4) employing benzene, toluene or CH 2C1 2 as eluant only lead to the decomposition of the Mo dimer. The crude Mo dimer can be p u r i f i e d by r e p e t i t i v e extraction of the crude product with hexanes, taking the combined extracts to dryness, and re d i s s o l v i n g the residue i n CH 2C1 2. Pure [Cp*Mo(NO) 2] 2 can be is o l a t e d by c r y s t a l l i z a t i o n from the CH 2C1 2 s o l u t i o n at 0°C. Pure [Cp*Mo(NO)2]2 i s a bright purple s o l i d and i s much more a i r - and moisture-sensitive than i t s Cr analogue i n the s o l i d state. I f obtained i n an impure form, the Mo dimer undergoes decomposition both i n solution and i n the s o l i d state to a brown i n t r a c t a b l e s o l i d even when stored under N 2. The s o l u b i l i t y properties of [Cp*Mo(NO)2] 2 are s i m i l a r to that of i t s Cr congener. I t s solutions are extremely a i r - and moisture-sensitive and decomposition of the complex 1 4 occurs r e a d i l y even under N 2 i f the solvent i s not rigorously dry. Even when i t i s a n a l y t i c a l l y pure, the Mo dimer does not p e r s i s t i n so l u t i o n for more than 4-5 days at low temperatures. I t should be noted that i n c e r t a i n solvents, a slow reaction between [Cp*Mo(NO) 2] 2 and the solvent occurs. For example, i n CC1 4 there i s a slow conversion of the Mo dimer to the chloro complex, Cp*Mo(NO)2C1, over a period of 8-10 days. This tranformation i s accelerated by u l t r a v i o l e t i r r a d i a t i o n of the reaction s o l u t i o n . 1 5 85 Regrettably, when Cp*W(NO)2Cl i s treated with zinc amalgam under the same experimental conditions as i n eg 3.3, the corresponding [Cp*W(NO) 2] 2 * s n o t obtained. Using a more potent reducing agent, Na/Hg, also does not a f f o r d the W dimer. (II-B) Spectroscopic Properties of the [Cp*M(NO) 2] 2 (M = Cr, Mo) Complexes. The low resolution mass spectra of [Cp*Cr(NO) 2] 2 and [Cp*Mo(NO) 2] 2 both display peaks at t r i b u t a b l e to t h e i r corresponding parent ions and ions corresponding to the loss of the n i t r o s y l ligands and other groups (e.g. fragmentation of the Cp* r i n g s ) . Unfortunately, the overlapping of some medium and strong i n t e n s i t y peaks i n the lower mass range makes any d e f i n i t e further assignments d i f f i c u l t . Several possible molecular structures of [Cp*Cr(NO) 2] 2 having d i f f e r e n t combinations of bridging and terminal n i t r o s y l ligands can be envisaged. By analogy to the s t r u c t u r a l l y characterized [ C p C r ( N O ) 2 ] 2 , 1 6 the molecular structure of [Cp*Cr(NO) 2] 2 can be proposed to be the trans n i t r o s y l - bridged structure i n the s o l i d state (Figure 3.1-B). This proposal i s based on the s i m i l a r i t y i n the NMR and IR sp e c t r a l properties between [Cp*Cr(NO) 2] 2 and i t s well known perhydro analogue. The proton NMR spectrum of [Cp*Cr(NO) 2] 2 86 i n C D C I 3 e x h i b i t s two s i n g l e t s at 1.50 and 1.65 ppm with an i n t e n s i t y r a t i o of 21:1. By analogy t o the [CpCr(NO) 2]2 system, the high and low f i e l d s i n g l e t s i n the NMR spectrum of [Cp*Cr(NO) 2] 2 can be assigned to the c i s and trans bridged isomers, r e s p e c t i v e l y (Figure 3.1-A and -B). The IR spectrum of [Cp*Cr(NO) 2] 2 i n the s o l i d state (KBr p e l l e t ) e x h i b i t s a strong n i t r o s y l band at 1630 cm"1 suggesting a terminal NO ligand and a weak band at 1487 cm"1 suggesting a bridging NO ligand. By comparison, the IR spectrum of the perhydro analogue [CpCr(NO) 2] 2 i n the s o l i d state also e x h i b i t s two n i t r o s y l bands at 1662 and 1504 cm"1 a t t r i b u t a b l e to the terminal and bridging NO groups r e s p e c t i v e l y . 1 7 The n i t r o s y l s tretching frequencies f o r the Cp* compound are s h i f t e d to a lower wavenumber than the Cp analogue; s i m i l a r e f f e c t s have been previously observed and are attr i b u t e d to the greater electron donating a b i l i t y of the Cp* ligand as compared to the Cp l i g a n d . 1 8 Figure 3.1. Probable Molecular Structures of [Cp*Cr(N0) 2] 87 Intere s t i n g l y enough, the IR spec-rum of [Cp*Mo(N0) 2]2 i n t h e s o l i d state exhibits two n i t r o s y l bands i n the terminal n i t r o s y l region (I^Q 1692(B), 1585(VS, br)) but appears to lack any bands at t r i b u t a b l e to a bridging m e t a l - n i t r o s y l linkage. I n f a c t , i t resembles the IR spectrum of i t s monomeric precursor Cp*Mo(NO) 2Cl (v 0^ 1721(s), 1644(vs, b r ) . So, i n the s o l i d state, the Mo dimer can be s i m p l i s t i c a l l y viewed as two equivalent Cp*Mo(NO)2 moieties linked by a Mo-Mo bond with no bridging n i t r o s y l groups (Figure 3.2). In i t s proton NMR spectrum, [Cp*Mo(NO) 2] 2 e x h i b i t s a s i n g l e t proton resonance at 1.47 ppm i n C 6D 6 which i s a t t r i b u t a b l e to the equivalent methyl protons on each of the Cp* ligands. (M « Mo; L - NO) Figure 3.2. Probable Molecular Structures of [Cp*Mo(NO) 2] 2 88 (II-C) Reaction of [Cp*Mo(NO) 2] 2 v i t h 5 n C l 2 ? Treatment of [Cp*Mo(N0) 2] 2 with excess S n C l 2 i n THF leads t o the formation of Cp*Mo(NO) 2Cl (as i n eg. 3 . 4 ) . [Cp*Mo(NO) 2] 2 + S n C l 2 • 2Cp*Mo(N0)2C1 + Sn (3.4) The progress of the reaction can be conveniently monitored by IR spectroscopy since the absorptions due to the n i t r o s y l groups of the reactant [Cp*Mo(NO) 2] 2 occur at 1591 cm"1 whereas those due to the product Gp*Mo(NO)2Cl occur at 1723 and 1638 cm"1. The molybdenum chloro complex can be separated from the reaction mixture by column chromatography techniques. The propensity of the Mo dimer to abstract the chlorine ligands from S n C l 2 i s reminiscent of that observed f o r [CpCr(NO)232*^ I N V I E W O F T H E F A C T T H A T T H E C c P C r ( N ° ) 2 3 2 complex has been shown to s e l e c t i v e l y remove halogen from c e r t a i n organic subtrates,' t h i s suggests that the new Mo dimer i s also capable of t h i s mode of r e a c t i v i t y towards organic substrates, perhaps with altered s e l e c t i v i t i e s . (II-D) A comparison of the [Cp*M(NO) 2] 2 ((M = Cr, Mo) and the [Cp'M(CO) 2] 2 (M = Fe, Ru) compounds. Having now synthesized the [Cp*M(NO) 2] 2 (M «* Cr, Mo) compounds, i t i s i n t e r e s t i n g to compare t h e i r properties to 89 those exhibited by t h e i r valence i s o e l e c t r o n i c carbonyl analogues [Cp'M(CO) 2] 2 (Cp' - Cp or Cp*; M - Fe, Ru) as well as the known [CpCr(NO) 2] 2. Like the [Cp*M(NO) 2] 2 compounds, [CpCr(NO) 2] 2 also e x i s t s as a purple s o l i d . I t i s , however, l e s s soluble than the corresponding [Cp*Cr(NO) 2] 2 compound. In i t s mass spectra, [CpCr(NO) 2] 2 also e x h i b i t s a highest peak a t t r i b u t a b l e to the parent ion as well as peaks corresponding to the sequential loss of the n i t r o s y l ligands. As mentioned e a r l i e r , [CpCr(NO) 2] 2 has been shown to possess a trans NO bridged structure i n the s o l i d state, but i t e x i s t s as a mixture of c i s and trans bridged isomers i n s o l u t i o n . The Cp* analogue, [Cp*Cr(NO) 2) 2, i s apparently s i m i l a r . The carbonyl compound, [Cp*Fe(CO) 2] 2, was f i r s t reported by King and co-workers some time ago. 1 9 I t i s a red-v i o l e t s o l i d and i s sparingly soluble i n non-polar organic solvents but very soluble i n polar organic solvents. I t s molecular structure has been proposed to e x i s t exclusively as the trans carbonyl bridged isomer (Figure 3.3) i n s o l u t i o n (cyclohexane). F i g u r e 3.3 Structure of the Group 8 Carbonyl Complexes 90 By c o m p a r i s o n , t h e c o n g e n e r i c Ru c a r b o n y l d i m e r , [ C p * R u ( C O ) 2 ] 2 , a p p a r e n t l y a l s o e x i s t s as t h e t r a n s b r i d g e d c a r b o n y l i s o m e r . I n r e l a t i o n t o t h i s , 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 a r b o n y l complex [ ( C 5 M e 4 E t ) R u ( C O ) 2 ] 2 has been shown t o p o s s e s s the t r a n s c a r b o n y l b r i d g e d s t r u c t u r e as w e l l ( F i g u r e 3 . 3 ) .2 0 The UV i r r a d i a t i o n o f [ C p * R u ( C 0 ) 2 ] 2 i n c h l o r i n a t e d s o l v e n t s ( e . g . C H 2 C 1 2 ) l e a d s t o t h e f o r m a t i o n o f t h e c o r r e s p o n d i n g c h l o r o complex C p * R u ( C 0 ) 2 C 1 2 1 , i . e . , h u [ C p * R u ( C O ) 2 ] 2 • 2 C p * R u ( C O ) 2 C l ( 3 . 5 ) C H 2 C 1 2 Upon t r e a t m e n t w i t h S n C l 2 , t h e Ru c a r b o n y l d i m e r , [ C p R u ( C O ) 2 ] 2 , undergoes an o x i d a t i v e a d d i t i o n r e a c t i o n w i t h S n C l 2 t o y i e l d a p r o d u c t which c o n t a i n s a Ru-Sn b o n d 2 2 i . e . e g . 3.6. C l . C l [ C p R u ( C O ) 2 ] 2 + S n C l 2 • [ C p ( C O ) 2 R u R u ( C O ) 2 C p ] (3.6) 91 By way of contrast, [Cp*Mo(NO) 2] 2 apparently exists as a non-nitrosyl bridged dimer i n the s o l i d s tate. However, the behaviour of [Cp*Mo(NO)2] 2 i n chlorinated solvents i s quite s i m i l a r to the carbonyl complex, ( C p * R u ( C O )2]2. Thus, the UV i r r a d i a t i o n of [Cp*Mo(NO)2] 2 i n chlorinated solvents (e.g. CC1 4) also y i e l d s the corresponding molybdenum chloro complex, i . e . , hv [Cp*Mo(NO) 2] 2 • 2 Cp*Mo(NO) 2Cl (3.7) c c i 4 On the other hand, the chemical r e a c t i v i t y of [Cp*Mo(NO) 2] 2 with SnCl 2 i s quite d i f f e r e n t when compared to the Ru carbonyl complex. Instead of forming a Mo-Sn bond, the Mo dimer abstracts the chloro ligands from Sn C l 2 to y i e l d Cp*Mo(NO)2Cl (as shown i n eq. 3.4). In view of the extensive chemistry that has been performed on [Cp Ru(CO) 2] 2 A , t h i s observation suggests that [Cp*Mo(NO) 2] 2 should exh i b i t a varied and r i c h chemistry although i t s c h a r a c t e r i s t i c r e a c t i v i t y has not been explored i n d e t a i l yet. 92 S u m m a r y T h i s w o r k d e s c r i b e s t h e s y n t h e s i s o f [ C p * M ( N O ) 2 3 2 ( M m c r , M o ) b y t h e t r e a t m e n t o f C p * M ( N O ) 2 C l ( M - C r , M o ) w i t h z i n c a m a l g a m i n T H F . B o t h t h e c o m p l e x e s e x i s t a s r e l a t i v e l y t h e r m a l l y s t a b l e , a i r - a n d m o i s t u r e - s e n s i t i v e d i a m a g n e t i c p u r p l e s o l i d s . I n t h e s o l i d s t a t e , t h e C r d i m e r i s p r o p o s e d t o p o s s e s s t h e t r a n s NO b r i d g e d s t r u c t u r e w h i l e t h e M o d i m e r a p p a r e n t l y p o s s e s s t h e n o n N O b r i d g e d s t r u c t u r e . T h e [ C p * M o ( N O ) 2 ] 2 d i m e r r e a c t s w i t h S n C l 2 i n T H F t o y i e l d C p * M o ( N O ) 2 C l . T h e p r e p a r a t i o n o f t h e s e d i m e r s p r o v i d e s a c c e s s t o a r e l a t i v e l y u n e x p l o r e d a r e a o f G r o u p 6 o r g a n o m e t a l l i c n i t r o s y l c o m p l e x e s . 93 References 1. King, R. B.; Bisnette, M. B. Inorq. Chem. 1964, 3_, 791. 2. Hoyano, J . K.; Legzdins, P.; Malito, J . T. J . Chem. Soc.. Dalton Trans. 1975, 1022. 3. Kolthammer, B. W. S.; Legzdins, P.; Malito, J . T. Inorq.  Svnth. 1979, 1£, 208. 4. Kolthammer, B. W. S.; Legzdins, P. J . Chem. Soc.. Dalton Trans t 1978, 31. 5. Legzdins, P.; Wassink, B. Orqanometallics 1984, 2, 1811. .6. Hames, B. W.; Legzdins, P.; B a l l , R. G.; Trotter, J . Inorq. Chem. 1980, 19_, 3626. 7. Kolthammer, B. W. S.; Legzdins, P.; Martin, D. T. Tetrahedron Lett. 1978, 323. 8. Hames, B. W.; Legzdins, P. Orqanometallics 1982, 1, 116 and references therein. 9. Calabro, D. C.; Hubbard, J . L.; Blevins, C. H.; Campbell, A. C.; Lichtenberger, D. L. J . Am. Chem. Soc.. 1961, 101. 6839 and references therein. 10. Legzdins, P.; Martin, D. T. Orqanometallics 1983, 2, 1785. 11. Atwood, J . L.; Malito, J . T.; Shakir, R. J . Chem. Soc.. Dalton Trans. 1980, 1253. 12. Malito, J . T. Ph.D. Dissertation, University of B r i t i s h Columbia, B r i t i s h Columbia, 1976. 13. Hoyano, J . K.; Legzdins, P.; Malito, J . T. Inorq. Svn.. 1978, 18, 126. 14. In THF, E t 2 0 and benzene, the Mo dimer decomposes to an orange complex whose i d e n t i t y remains to be ascertained. The IR spectra (Nujol mull) of the orange complex exhibits 2 n i t r o s y l bands at 1693(B) and 1612(B) cm"1. I t s low res o l u t i o n mass spectrum exhibits a highest peak at 526. 94 15. I r r a d i a t i o n was done i n photoreactor using a medium-pressure mercury lamp (Hanovia L-450 W) housed i n a water cooled Pyrex immersion v e i l . 16. Calderon, J . L.; Fontana, S.; Frauendorfer, E.; Day, V. W. J . Oraanomet. Chem. 1974, §±, CIO. 17. Kirchner, R. M.; Marks, T. J.» K r i s t o f f , J . S.j Ibers, J . A. J . Am. Chem. Soc. 1973, 95. 6602. 18. King, R. B. Coord. Chem. Rev. 1976, 2&, 155. 19. King, R. B.; Bisnette, M. B. J . Oraanomet. Chem. 1967, 8., 287. 20. Bailey, N. A.; Radford, S. L.; Sanderson, J.A.; Tabatabaian, K.; White, C.; Worthington, J . M. J . Oraanomet. Chem. 1978, 154. 343. 21. Stasunik, A.; Malisch, W. J . Oraanomet. Chem. 1984, 270. C56. 22. Albers, M. O.; Robinson, D. J.? Singleton, E. Coord. Chem.  Rev. 1987, 2 2 , 1. 95 S p e c t r a l Appendix S e l e c t e d I n f r a r e d and NMR S p e c t r a o f Compounds. 96 IR spectrum o f [Cp*Mo(NO)(NCCH3)3][PF6]2, 1 as a N u j o l m u l l . N V A V E M U » M * E R S <CM-l) 97 I R spectrum of [ C p * M o ( N O ) I ( N C C H 3 ) 2 ] P F 6 , 2 as a N u j o l m u l l . N »aoo. © a2oa .o sesa.o ssoco 170s. o »4oa .o 1100.0 100.00 sco. 00 MAVCMUMSBM CCM-4> 98 99 I R s p e c t r u m o f [ C p * M o ( N O ) B r ( N C C H 3 ) 2 ] P F 6 , 4 a s a N u j o l m u l l . V A V S M U M « C * S C C M - : > 100 IR spectrum o f [CpMo(NO)Cl(NCCH3)2]BF4, 5 as a N u j o l m u l l . V AYt£U-UM#«£«8 CwM-1 > 101 IR spectrum o f [Cp*Mo(NO)Cl(NCCH3)2]PF6, 6 as a N u j o l m u l l . S •9 102 IR spectrum o f [CpW(NO)I(NCCH3)2]PF6, 7 as a N u j o l m u l l . 103 IR spectrum o f [Cp*W(N0)I(NCCH3)2]BF4, 8 as a N u j o l m u l l . 8 i IS o 4 . . O S . O « a » . 0 SOOO.O - 7 0 0 . 0 1 4 0 0 . 0 U O O . O . 0 0 . 0 0 •OO. VAVOtUMCCRS <CM-1> 104 IR spectrum o f [CpCr(NO)(NCCH3)2]PF6, 9 as a N u j o l m u l l . N W A V E N U M S C f t B C C M - 1 J 105 IR spectrum o f [CpCr(NO)(NCCH3)2]BPh4.l/ 2 C H 3 C N as a N u j o l m u l l . • *4 O c a 106 IR spectrum o f [CpCr(NO)2]BF4 as a CH2C12 s o l u t i o n . o VAVENUMBERS <CM-1> 107 ! H NMR s p e c t r u m o f [ C p * M o ( N O ) I ( N C C H 3 ) 2 ) [ P F g ] , 2 i n C D 3N0 2, C 5 W 5 CB3CM J A • i 1 , J 7 b f ] 1 • • 11111 • • 1 )i , a. I o rr>* 1 3 C ( 1 H ) NMR s p e c t r u m o f [ C p * M o ( N O ) I ( N C C H 3 ) 2 ] [ P F 6 ] , 2 i n C D 3N0 2. C 5 ( £ H 3 ) 5 CH3EH I CH3CN ISO >b0 i » o ">° m i | ) J. ' I i 1 go fro 40 1° ° 108 % NMR Bpectrum of [ C p M o ( N O ) C l ( N C C H 3 )2] [ B F4] , 5 i n C D 3 N 0 2 . C5H5 CB,CH ' . 1 1 7 • | I I I U I I I I j H M | I M I | l S t 3 o fPt* 1 3C{1H) NMR spectrum of [CpMo(NO)Cl(NCCH3)2][BF4], 5 i n C D 3 N 0 2 . CHjfiN « M J . i7j7777|Ti'i_n H I | I I M | >V>"i j _ ' • n " • U " ' I I ,t,o mo n o 8-D t*° " 1 0 9 110 

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