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UBC Theses and Dissertations

New organomtallic nitrosyl derivatives of the group 6B elements Martin, David Timothy 1979

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NEW ORGANOMETALLIC NITROSYL DERIVATIVES OF THE GROUP 6B ELEMENTS by DAVID TIMOTHY MARTIN .Sc., The University of B r i t i s h Columbia, 1977 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 thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA July 1979 (c) David Timothy Martin, 1979 I n p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e a n d s t u d y . I f u r t h e r a g r e e t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e Head o f my D e p a r t m e n t o r by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . D e p a r t m e n t nf CHEMISTRY The U n i v e r s i t y o f B r i t i s h C o l u m b i a 2075 W e s b r o o k P l a c e V a n c o u v e r , C a n a d a V6T 1W5 AUGUST 15, 1979 DE-6 B P 75-51 1 E ABSTRACT The complexes CpM(NO) 2Cl (M=Cr, Mo or W) can be reduced using Na[A1H 2(OCH 2CH 2OCH 3) 2] to y i e l d [CpCr(NO) 2] 2 and CpM(NO)2H (M=Mo or W), respectively. A study of the chemis-try of CpW(NO)2H shows that i t acts as a source of the hy-dride ion i n polar solvents. For example, CpW(NO)2H reacts with anhydrous p-toluenesulfonic acid to form CpW(NO)2S03-CJEJ. The complex also undergoes loss of H with Ph 3CBF 4. This novel r e a c t i v i t y i s compared with that exhibited by carbonylhydride complexes of the t r a n s i t i o n metals. The molybdenum congener, CpMo(NO)2H, i s unstable i n the s o l i d state but can be characterized i n solution. No d i r e c t phys-i c a l evidence can be found for the existence of CpCr(NO) 2H. The reaction of I 2 with CpW(CO)2NO results i n the i s o -l a t i o n o'f a completely decarbonylated product, [CpW(NO)I 2] 2. CpW(CO)2NO + I 2 > 1/2[CpW(NO)I ] 2 This dimeric compound reacts with a variety of reagents to form monomeric products. [CpW(NO)I 2] 2 + 2L ^2CpW(N0)(I) 2L .L=Group 5 donor ligand T e r a a l l y l t i n , 'Sn (C'3H[i) 4 , reacts with [CpW (NO).'12] 2 to form CpW(NO) ( n 3-C.jHg)I. An X-ray crystallographic analysis of t h i s complex shows that the a l l y l group exhibits consider-able a , ir d i s t o r t i o n . This asymmetry i s also evident i n solu-t i o n at ambient temperature. This f a c t allows straightforward analysis of the 1E and 1 3C magnetic resonance spectra. The previously reported molybdenum analogue, CpMo(NO)(n3-C^H^)I, can be prepared by a l l y l a t i o n of [CpMo (NO) ~L^) 2 w ;"- t h S n ^ C 3 H 5 ^ 4 -- i v -ACKNOWLEDGEMENTS I wish to thank the technical s t a f f , as well as the faculty, of the Chemistry department for t h e i r assistance-throughout my studies. I also wish to thank the fellow grad-uate students with whom I shared a laboratory, e s p e c i a l l y B.W. Hames and C.R. Nurse. I am indebted to Margaret Wiens for typing t h i s thesis. F i n a l l y , there are two people for whom a written acknowledgement hardly does j u s t i c e . Without the guidance and encouragement of Dr. Brian Kolthammer and Prof. Peter Legzdins, t h i s work could not even have been attempted. - v -TABLE OF CONTENTS Page ABSTRACT i i ACKNOWLEDGEMENTS i v TABLE OF CONTENTS v LIST OF TABLES . . v i LIST OF FIGURES v i i ABBREVIATIONS AND COMMON NAMES v i i i CHAPTER I INTRODUCTION 1 CHAPTER II PREPARATION AND CHARACTERIZATION OF (n5-CYCLOPENTADIENYL)HYDRIDODINI-: -TROSYLTUNGSTEN 6 Experimental Section 7 Results and Discussion 16 CHAPTER III SYNTHESIS AND CHARACTERIZATION OF BIS[ (n5-CYCLOPENTADIENYL)DIIODONI-TROSYLTUNGSTEN] 26 Experimental Section 27 Results and Discussion 33 CHAPTER IV PREPARATION OF (n3-ALLYL) (n5-CYCLO-PENTADIENYL)IODONITROSYL -TUNGSTEN AND -MOLYBENUM .. 44 Experimental Section 45 .-Results and Discussion>, 47 REFERENCES 61 - v i -LIST OF TABLES Table Page I Spectral Properties of CpW(NO)2H and Related Complexes 18 II Physical Properties of the Complexes CpW(NO) (I) 9 L (L=PPh-., P(OPh),, SbPh-, or CO) .... T . 7 29 III Mass Spectral Data for CpW(CO)(NO)P(OPh) 31 IV Mass Spectral Data for [CpW(NO)I 2l 2 35 V Mass Spectral Data for CpW(NO)(I) 2P(OPh) 3 37 VI Mass Spectral Data for (C 5H 5) 2W(NO)I .... 41 VII Mass Spectral Data for CpW(NO)(n 3-C 3H 5)I 49 VIII :H and 1 3 C NMR Spectral Data for the Ehdo Isomer of CpW(NO) ( n 3-C 3H 5)I 55 IX Mass Spectral Data for CpMo (NO) ( n 3-C3H[-) I 57 - v i i -LIST OF FIGURES Figure Page 1. The c h a r a c t e r i s t i c chemistry of CpW(NO)2H 23 2. Molecular structure of CpW(NO)(n3-C,H C)I 50 3 D 3. 27 0 MHz 1K FT-NMR spectrum i n the a l l y l region of CpW (NO) (n 3-C-H_)I i n CDC13 .... . . 53 4. 270 MHz }E FT-NMR spectrum i n the a l l y l region of CpMo(NO) (n 3 -C^H c.)I i n CDC13 7. . . . 58 - v i i i -ABBREVIATIONS AND COMMON NAMES The abbreviations used i n t h i s thesis are those recommended i n the Handbook for Authors of Papers i n  American Chemical Society Publications (AGS 1978). o A Angstrom atm atmospheres calcd calculated cm 1 wave numbers i n re c i p r o c a l centimetres Cp pentahapto-cyclopentadienyl d days dec decomposes Et ethyl h hours Hz Hertz IR infrared J magnetic resonance coupling constant m/z mass-to-charge r a t i o Me methyl min minutes mm millimetres of mercury mmol millimoles mp melting point NMR nuclear magnetic resonance RT room temperature THF terahydrofuran 6 NMR chemical s h i f t n 3,n 5 trihapto, pentahapto v IR stretching frequency - 1 -CHAPTER I INTRODUCTION A feature c h a r a c t e r i s t i c of the d-block t r a n s i t i o n metals i s the a b i l i t y to form complexes with neutral molecules such as isocyanides, phosphines, carbon monoxide and nitrogen monoxide. These ligands possess vacant -rr-orbitals that allow them to s t a b i l i z e low formal oxidation states of metals. The most important iT-acceptor ligand i s carbon monoxide and studies of the preparation of t r a n s i t i o n metal carbonyls as well as t h e i r chemistry are well documented.1 The chemistry of t r a n s i t i o n metal nitrogen monoxide compounds i s less well developed. P o t e n t i a l l y , the extent of the chemistry that may be exhibited by n i t r o s y l complexes i s as broad as that of carbonyl complexes. Although nitrogen monoxide and carbon monoxide are known to bond to t r a n s i t i o n metals i n a sim i l a r fashion, the NO ligand contains one more electron which occupies a TT* o r b i t a l . The presence of t h i s extra electron allows a v a r i a t i o n i n the nature of the M-N-0 bond which i s unknown for the carbonyl ligand. There are two d i f f e r e n t bonding modes which may be described as follows: (1) Linear The nitrosonium ion, N0 +, i s is o e l e c t r o n i c with carbon monoxide and, thus, i t has three bonding electron - 2 -pairs between the atoms and a lone electron pair on both the nitrogen and oxygen. Both atoms are sp hybridized and both are p o t e n t i a l donors. However, the nitrogen coordinates p r e f e r e n t i a l l y , thereby avoiding a large formal charge on the more electronegative element. The nitrosonium-ion can be considered as a a-donor and the re s u l t i n g M-N=0 i s li n e a r . Occupied metal dir o r b i t a l s provide some degree of MTT ) NOu* overlap establishing a syn e r g i s t i c bonding relationship. (Alternatively, the li n e a r group may be considered as nitrogen monoxide and a metal containing an, empty o- o r b i t a l and a h a l f - f i l l e d u - o r b i t a l which interacts with the TT* electron of the NO). When bonding i n thi s way, the n i t r o s y l ligand i s a formal three-electron donor. (2) Bent A bent n i t r o s y l ligand i s an analogue of an organic nitroso group or the NO group i n C1N0. The M-N-0 linkage consists of a doubly bonded NO group, a single a-bond between the nitrogen and the metal, and a lone pair of electrons on the nitrogen atom. The nitrogen atom in t h i s case i s sp 2 hybridized and the r e s u l t i n g M-N-0 system i s bent. When bonding i n t h i s way, the n i t r o s y l ligand i s a formal one-electron donor. Competition between line a r and bent bonding modes of the ligand i s resolved when the electron p a i r i s forced to reside either i n an atomic o r b i t a l on the nitrogen atom or i n a low-lying molecular o r b i t a l . Both of these types of bonding are present i n the - 3 -molecular structure of [Ru(NO),(PPh,) 0 c 1 i , shown below. A perspective drawing of the inner coordination geometry of [ R U C 1 ( N O M P ( C , H S ) > ) J ] + . The estimated standard deviations for the bond lengths shown are: Ru -N, 0.016; Ru-P, 0.005; Ru-Cl , 0.005; N - O . 0 .016A . The basal n i t r o s y l ligand forms a lin e a r M-N-0 l i n k with a r e l a t i v e l y short M-N bond. In contrast, the a x i a l n i t r o s y l ligand coordinates with a Ru-N-0 bond angle of 136° and a longer Ru-N distance. Although the ide a l bond angle for the bent system i s 120°, d i f f e r i n g amounts of inte r a c t i o n between the lone pair on the ligand and the metal o r b i t a l s produce M-N-0 groups with bond angles ranging from 120°-180°. 2 In fact, tautomerism between the two possible forms can convert a coordinately saturated compound to an unsaturated species without the customary requirement of the d i s s o c i a t i o n of a ligand. I t i s therefore reasonable to expect that n i t r o s y l complexes should exhibit d i f f e r e n t chemical properties from t h e i r i s o e l e c t r o n i c carbonyl analogues. A recent example of thi s unique chemistry has been - 4 -shown by a comparison of the chemistry of the well-known [ C p F e ( C O ) w i t h i t s i s o e l e c t r o n i c n i t r o s y l analogue [CpCr(NO) 2]2• 3 T n e n i t r o s y l complex reacts e f f i c i e n t l y and s e l e c t i v e l y with halogen-containing organic substrates. For example, i t performs se l e c t i v e v i c i n a l halogen abstraction from v i c - d i h a l o a l k y l halides leaving the t h i r d halogen unper-turbed, e. g. trans-dibromide of cholesteryl bromide The chemical transformations performed by [CpCr(NO) 2] 2 cannot be duplicated by the carbonyl analogue. At the outset of t h i s research there were.two general objectives, namely 1) the preparation of new organometallic n i t r o s y l complexes, and 2) the study of t h e i r c h a r a c t e r i s t i c physical and chemical properties. To this end, the Group 6B metals were chosen for specifie-study. Chapter II describes t h e - f i r s t detailed study of an organometallic hydridonitrosyl complex. Chapter III describes the preparation and c h a r a c t e r i s t i c - 5 -chemistry of [CpW (NO) T_2] 2 . F i n a l l y , Chapter IV describes the preparation and novel physical properties of the asymmetric complex CpW(NO)(n 3-C 3H 5)I. - 6 -CHAPTER II PREPARATION AND CHARACTERIZATION OF (n 5-CYCLOPENTADIENYL)- HYDRIDODINITROSYLTUNGSTEN AND ITS GROUP VIB CONGENERS The general methods for the synthesis of t r a n s i t i o n metal hydrides f a l l into six categories, namely: 1) Reactions with molecular hydrogen, e.g. , Os(CO) 5 + H 2 i o 0 h a t m > H 2Os(CO) 4 + CO (1) 2) Reactions of metal complexes with complex hydrides, e.g., 5 [CpM(CO) + NaBH. » CpM (CO) ?H + CO (2) M = Mo,W 3) Hydrogen transfer from solvent or coordinated group, e.g., 6 C p 2 T i C l 2 £2^2£L+ [ C p 2 T i H ] 2 ( 3 ) 4) Hydrolyses and dehydrohalogenation, e.g., 7 (C 9H )_N [CpRe(CO) 2NO] + a c ^ J / w a t e r ^ C PRe(CO )(NO)H (4) 5) Protonation, e.g., 0 Cp2WH2 + HBr : > [Cp 2WH 3] +Br~ (5) 6) Oxidative addition of hydrogen or hydrogen halides - 7-to ca t i o n i c metal complexes, e.g., 9 [ I r ( C O ) L 4 ] + + H 2 ^ p ( C H 3 ) 2 p h ) [ H 2 I r ( C O ) L 3 ] + (6) Since well developed preparative routes to halo-n i t r o s y l complexes e x i s t , 1 0 ' 1 1 i t seemed reasonable that attempted reduction of these complexes could be the best route to hydridonitrosyl species. This chapter describes the attempts to convert some of these precursors, s p e c i f i c a l l y the complexes CpM(NO) 2Cl (M=Cr, Mo, W) 1 2 to the desired hydridonitrosyIs. EXPERIMENTAL SECTION A l l chemicals used were of reagent grade or comparable purity and were either purchased from commercial suppliers or prepared according to reported procedures. Their pu r i t y was ascertained from elemental analyses and/or melting point determinations. A l l melting points are uncorrected and were taken i n c a p i l l a r i e s under pr e p u r i f i e d nitrogen using a Gallenkamp Melting Point Apparatus. A l l solvents were dried according to standard procedures 1 3 and thoroughly purged with prepurified nitrogen p r i o r to use. A l l manipulations, unless otherwise stated, were performed on the bench using conventional techniques for the manipulation of a i r sensitive compounds 1 4 or i n a Vacuum Atmospheres Corporation Dri-Lab model HE-43-2 dry box f i l l e d with prepurified nitrogen. Infrared spectra were recorded on Perkin Elmer 457 - 8 -or 710A spectrophotometers and calibr a t e d with the 1601 cm"1 absorption band of polystyrene f i l m . Routine proton magnetic resonance spectra were recorded on Varian Associates T-60 or XL-100 spectrometers using tetramethylsilane as an i n t e r n a l standard. High resolution *H FT-NMR spectra were recorded at 270 MHz by Mrs. M.M. Tracey on a departmental spectrometer em-ploying an Oxford Instruments superconducting magnet and Nicolet Instrument Corporation hardware. Tetramethylsilane was again used as an i n t e r n a l standard. Carbon-13 NMR spectra were re-corded on a Varian Associates CFT-20 spectrometer with reference to the solvent used. A l l chemical s h i f t s are reported i n ppm downfield from Me^Si. The mass spectra were recorded at 7 0 eV on an Atlas CH4B spectrometer with the assistance of Mr. J.W. Nip. Elemental analyses were performed by Mr. P. Borda, and the x-ray s t r u c t u r a l determination was carr i e d out by Dr. T.J. Greenhough. Reaction of CpW(NO)2Cl with Ka. [A1H2 (OCH2CH2OCH3) 2 ] . To a green solution of CpW(NO) 2Cl 1 2 (3.00 g, 8.71 mmol) i n t o l -uene (75 mL) at -7 8°C was added dropwise with s t i r r i n g a solu-tion of Na[A1H 2(OCH 2CH 2OCH 3) 2] 1 5 (2.49 mL, 8.71 mmol) di l u t e d to 20 mL with toluene. The reaction mixture changed immedi-ately to dark green, and a brown s o l i d p r e c ipitated. A f t e r a l l the aluminum reagent had been added, the reaction mix-ture was s t i r r e d for an additional 0.5 h to ensure complete reaction. Without being allowed to warm to room temperature, the mixture was quickly f i l t e r e d through a short (3x5 cm) c o l -- 9 -umn of F l o r i s i l supported on a medium porosity f r i t t e . The bright green f i l t r a t e was taken to dryness i n vacuo, and the residue was dissolved i n 10 mL of dichloromethane. The. res u l t i n g solution was transferred onto a 2x6 cm F l o r i s i l column. Elution of the column with dichloromethane resulted i n the develop-ment of a single bright green band which was col l e c t e d and taken to dryness under reduced pressure. Sublimation of the residue at ambient temperature (5x10 3 mm) onto a dry-ice-cooled probe yielded a n a l y t i c a l l y pure CpW(NO)2H (1.65 g, 61% y i e l d ) . Anal. Calcd for C cH,WN„0„: C, 19.37; H, 1.95; N, 9.04. D O 2. 2. Found: C, 19.58; H, 1.83; N, 8.91. IR (CH2C1,2) : v (NO) 1718, 1632 cm"1. Mp 52°C. Reaction of CpW(NO)2Cl with NaBH^. The reaction of CpW(NO)2Cl (1.00 g, 2.91 mmol) i n THF (25 mL) with s o l i d NaBH^ (0.11 g, 2.9 mmol) at ambient temperature for 1 h proceeded completely analogously to the preceeding trans-formation. The reaction mixture was taken to dryness i n vacuo. The residue was treated as described above to y i e l d 0.12 g (13% yield) of CpW(N0)2H. Reaction of [CpW(NO)2CO]PFgWJth NaBD^. To a s t i r r e d green suspension of [CpW(NO) 2(CO)]PF g 1 6 (2.40 g, 4.98 mmol) in THF (60 mL) was added s o l i d NaBD^ (0.21 g, 5.02 mmol). The reaction mixture was s t i r r e d vigorously for 1 h during which time i t became red-brown. The solvent was then removed i n vacuo, and the r e s u l t i n g residue was extracted with ca. 10 mL - 10 -of dichloromethane. Chromatography of the dark green extracts on a 2x6 cm F l o r i s i l column with dichloromethane as eluant resulted i n the development of a single bright green band that was eluted and col l e c t e d . The eluate was taken to dryness i n vacuo to obtain CpW(NO)2D (0.36 g, 23% yield) which was i d e n t i f i e d by i t s infrared and mass spectra. Reaction of CpMo. (NO) ^ C l with Na [A1H2 (OCH2CH2OCH3) 2] . To a s t i r r e d green solution of CpMo(NO) 2C1 1 2 (1.00 g, 3.89 mmol) i n toluene (25 mL) at -78°C was added dropwise a solution of Na[A1H 2(OCH 2CH 2OCH 3) 2J (1.11 mL, 3.89 mmol) dil u t e d to 10 mL with toluene. Immediately the reaction mixture developed a dark green colouration, and a red-brown pr e c i p i t a t e formed. After a l l the aluminum reagent had been added, the mixture was s t i r r e d for an additional 0.5 h. I t was then quickly f i l t e r e d while cold through a short (3x5 cm) column of F l o r i s i l supported on a medium-porosity f r i t t e . The green f i l t r a t e was permitted to warm to room temperature and was t i t r a t e d with a toluene solution of I 2 (ca. 0.2 M) u n t i l the c h a r a c t e r i s t i c colour of I 2 persisted. V o l a t i l e species were removed under reduced pressure, and the remain-ing residue was dissolved i n ca. 5 mL of dichloromethane. Chromatography of thi s solution on a 2x6 cm F l o r i s i l column with dichloromethane as eluant resulted i n the development of a single green band which was col l e c t e d . The eluate was taken to dryness i n vacuo to obtain green CpMo(N0) 2I (0.29 g, 21% y i e l d overall) which was 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 - 11 -physical p r o p e r t i e s . 1 6 Reaction of CpCr(NO) 2Cl with Na[A1H2(OCHgCHgOCH,)2]. A solution of Na[A1H 2(OCH 2CH 2OCH 3) 2] (1.35 mL, 4.72 mmol) di l u t e d to 10 mL with toluene was added dropwise at room temperature to a s t i r r e d , golden solution of CpCr(NO) 2C1 1 2 (0.80 g, 4.72 mmol) in toluene (25 ml) . The reaction mixture became red, and a brown s o l i d precipitated. After being s t i r r e d for an additional 0.5 h, the mixture was f i l t e r e d through a F l o r i s i l column (3x4 cm) supported on a medium porosity f r i t t e . The f i l t r a t e was concentrated i n vacuo to ca. 5 mL and was syringed onto a 3x4 cm column of alumina (Woelm neutral, a c t i v i t y grade 1). Elution with benzene developed a single red band which was c o l l e c t e d and taken to dryness under reduced pressure to obtain red-purple, micro-c r y s t a l l i n e [CpCr(NO) 2] 2 (0.15 g, 22% y i e l d ) , r e a d i l y ident-i f i a b l e by i t s d i s t i n c t i v e physical p r o p e r t i e s . 1 7 Reactions of CpW(NO)2H with I 2 and B r 2 . To a green solution of CpW(NO)2H (0.30 g, 0.97 mmol) i n dichloromethane (25 mL) at room temperature was added dropwise with s t i r r i n g a purple solution of I 2 (1.23 g, 0.49 mmol) i n dichloromethane (15 mL). At once the reaction mixture turned dark green. The f i n a l solution was concentrated i n vacuo to ca. 5 mL and was syringed onto a 2x6 cm F l o r i s i l column. Elution with dichloromethane resulted i n the development of a single green band which was c o l l e c t e d . Solvent was removed from the eluate i n vacuo to obtain CpW(NO)2I (0.20 g, 47% yield) which was - 12 -.1 6 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 physical properties A s i m i l a r experiment performed by using Br,, afforded the analogous CpW(NO) 2Br 1 6 i n 48% y i e l d . Reaction of CpW(NO)2H with ^-CF^CgH^SC^H. To a s t i r r e d green solution of CpW(NO)2H (0.31 g, 1.0 mmol) in THF (30 mL) at room temperature was added s o l i d , anhydrous p-toluene-sul f o n i c acid (0.17 g, 1.0 mmol). The reaction mixture darkened while being s t i r r e d for 0.5 h before being taken to dryness i n vacuo. The residue was dissolved i n dichloro-methane (30 mL) to obtain a blue-green solution. Addition of hexanes (60 mL) to t h i s solution induced the deposition of a red-brown s o l i d which was removed by f i l t r a t i o n . Slow concentration of the f i l t r a t e under reduced pressure resulted i n the c r y s t a l l i z a t i o n of a n a l y t i c a l l y pure, green CpW(NO)20-S0 2C 6H 4CH 3 (0.35 g, 73% y i e l d ) . Anal. Calcd for C^H-^WN^S: C, 30.01; H, 2.52; N, 5.84 Found: C, 29.75; H, 2.51; N, 5.66. IR (CH 2C1 2): v(NO) 1737, 1650 cm 1. Mp 120°C dec. Mass spectrum: most intense parent ion m/z 4 80. Reaction of CpW(NO)2H with Ph 3CBF 4. A yellow solution of Ph 3CBF 4 1 8 (0.33 g, 1.0 mmol) i n a c e t o n i t r i l e (5 mL) was added dropwise to a s t i r r e d solution of CpW(NO)2H (0.31 g, 1.0 mmol) i n a c e t o n i t r i l e (30 mL) at -10°C. After complete mixing of the two solutions, an infrared spectrum of the r e s u l t i n g blue-green solution indicated [CpW(NO) 2(CH 3CN)] + to be the only ;nitros.yl-containing species present. 1 6 Upon - 13 -addition of Nal (0.15 g, 1.0 mmol), the reaction mixture immediately became olive-green. The reaction mixture was taken to dryness in vacuo, and the residue was dissolved i n a minimum of dichloromethane (5 mL). Chromatography of t h i s solution on F l o r i s i l with dichloromethane as eluant (vide supra) provided a green eluate which was concentrated i n vacuo to 2 0 ml. The addition of hexanes (20 mL) and continued slow concentration of the solution resulted i n the p r e c i p i t a t i o n of olive-green crystals of CpW(NO)2I (0.25 g, 57% y i e l d based on CpW(NO)2H) which were co l l e c t e d by..-filtration. The f i l t r a t e was taken to dryness in vacuo to leave a l i g h t green residue. This s o l i d was dissolved i n a minimum of benzene, and the solution was transferred to the top of a 3x4 cm column of alumina ( a c t i v i t y grade 1). The column was washed with 100 mL of benzene to obtain a colour-less eluate. Removal of solvent from the eluate under reduced pressure provided Ph^CH (0.15 g, 61% yield) which was i d e n t i f i e d by comparison of i t s physical properties with those of an authentic sample. The above experiment was repeated by using CpW(N0)2D to obtain a comparable y i e l d of Ph^CD which was i d e n t i f i e d mass spectrometrically. Reaction of CpW(NO)2H with HCoCCO)^. To a pale yellow solution of HCo(CO) 4 [prepared from Co 2(CO)g (0.34 gf I.Q mmol) i n THF (50 mL) 1 9] cooled to -78°C was added dropwise with s t i r r i n g a solution of CpW(NO)2H (0.62 g, 2.0 mmol) i n THF - 14 -(50 mL) . After the addition was complete, the reaction mix-ture was permitted to warm slowly to room temperature where-upon i t s colour changed gradually to red-brown. The mixture was s t i r r e d at ambient temperature for an additional 16 h to ensure complete reaction, and i t was then f i l t e r e d through a short (3x4 cm) column of C e l i t e . Concentration of the f i l t r a t e under reduced pressure resulted i n the removal of solvent and an orange-red, v o l a t i l e compound which was not i s o l a t e d but was i d e n t i f i e d as Co(CO)3NO by a solution infrared spectrum. 2 0 After removal of a l l v o l a t i l e species, the remaining orange-brown residue was sublimed at room temperature (5x10 3 mm) onto a dry-ice-cooled probe to obtain CpW(CO) 2N0 1 2 (0.25 g, 37% y i e l d based on W) . Reaction of CpW(NO)2H with CpW(CO)3H. To a green solution of CpW(NO)2H (0.31 g, 1.0 mmol) i n THF (30 mL) was added s o l i d , yellow CpW(CO) 3H 2 1 (0.33 g, 1.0 mmol), and the r e s u l t i n g solution was s t i r r e d at room temperature for 48 h. During t h i s time, the reaction mixture became red, and a considerable amount of brown p r e c i p i t a t e formed. The solvent was removed from the mixture i n vacuo, and the residue was extracted into dichloromethane. (5 mL) . The red solution was then chromatographed on a 2x5 cm F l o r i s i l column with dichloromethane as eluant to obtain a single red band which was col l e c t e d and taken to dryness i n vacuo. Sublimation of the residue at room temperature onto a dry - 15 -ice-cooled probe afforded orange CpW(CO) 2N0 1 2 (0.14 g, 0.42 mmol). The red s o l i d remaining i n the sublimer was found to be [CpW(CO) 3] 2 2 2 (0.09 g, 0.14 mmol). Both products were i d e n t i f i e d by t h e i r c h a r a c t e r i s t i c physical properties. Treatment of C p W ( N O ) w i t h HPhCCHBr. A small amount of CpW(NO)2H (0.10 g, 0.32 mmol) i n THF (10 mL) was treated with an excess of neat bromostyrene (0.10 mL, 0.14 g, 0.7 8 mmol). The mixture was allowed to s t i r at room temperature for 3 6 h during which time a large amount of red-brown s o l i d deposited. The pr e c i p i t a t e was removed by f i l t r a t i o n and the solvent was removed from the green f i l t r a t e under reduced pressure. The residue was found to contain only unreacted s t a r t i n g materials. Treatment of CpW(NO)2H with Fe(CO) 5- To THF (20..mL) . and CpW(NO)2H (0.10 g, 0.32 mmol) was added neat Fe(CO) 5 (0.05 mL, 0.07 g, 0.36 mmol). The s t i r r e d reaction mixture was refluxed for 18 h. At the end of that time a solution infrared spectrum showed CpW(N0)2H to be the only nitrosyl-containing species present. Treatment of CpW(NO)2H with CCl^. A small amount of CpW(NO)2H (0.10 g, 0.32 mmol) was dissolved i n CC1 4 (50 mL) and the reaction mixture was s t i r r e d at room temperature for 2 4 h. During that time there was no conversion to CpW(N0) 2Cl, as evidenced by solution infrared spectra, and CpW(NO)„H was -recovered quantitatively. - 16 -Results and Discussion Reduction of CpM(NO) 2Cl (M=Cr, Mo or W) Complexes. King and Bisnette f i r s t reported i n 1963 that the reduction of CpCr(NO) 2Cl with NaBH^ i n a two phase water-benzene system affords [CpCr(NO) 2l 2 i n 5% y i e l d . 2 3 A plausible f i r s t step of t h i s reaction may well involve the formation of the therm-a l l y unstable hydridochromium complex CpCr(NO) 2H, which subsequently dimerizes to the observed product with concomitant expulsion of hydrogen. 2 1* However, there have been no reports since that time concerning the i s o l a t i o n of t h i s hydride or i t s molybdenum and tungsten analogues. The complexes CpM(NO)2H (M=Mo or W) can best be prepared by treatment of the respective CpM(NO) 2Cl precursors with the reducing agent sodium dihydridobis(2-methoxyethoxy)-aluminate 1 5 i n toluene at -78°C . C PM(N0) 2C1 giu e n e , -78°C > CPM(NO)2H (7) M=Mo or W [Al]=Na[H 2Al(OCH 2CH 2OCH 3) 2] Monitoring of the progress of reaction 7 by i n f r a r e d spectroscopy indicates that the optimum stoichiometric r a t i o of the reactants i s 1:1. I t also shows that an aluminohydride adduct with CpM(NO)2 i s not formed, 2 5 but the exact nature of the aluminum byproduct remains to be ascertained The thermally stable complex CpW(NO)2H can be'; r e a d i l y obtained i n 61% y i e l d from reaction 1, but the molybdenum - 17 -congener has so far defied a l l attempts at i s o l a t i o n . Bright green toluene solutions containing CpMo (NO) 2H slowly deposit a red-brown s o l i d when s t i r r e d at ambient temperature inr.a p r e p u r i f i e d nitrogen atmospheres the decomposition being complete in ^ 3 days. The rate of decomposition of the hydrido complex i s markedly enhanced by removal of the solvent in vacuo, a procedure which affords only the red-brown s o l i d . This s o l i d does not dissolve i n common organic solvents, and i t s infrared spectrum (Nujol mull) i s devoid of any absorp-tions attributable to a coordinated n i t r o s y l group. Never-theless, spectroscopic (Table I) and chemical (vide infra) properties of the green toluene solutions are completely consistent with the presence of CpMo(NO)2H. Not s u r p r i s i n g l y , reduction of CpCr(NO) 2C1 with Na[A1H 2(OCH 2CH 2OCH 3) 2] i n toluene at room temperature does produce [CpCr(NO) 2l 2 i n 22% y i e l d . C PCr(NO) 2Cl » [C PCr(NO) 2] 2 (8) Reaction 8 does not occur at -78°C. No d i r e c t physical evidence.for the existence of the elusive CpCr(NO) 2H could be found at either temperature. However, by analogy with the tungsten and molybdenum systems, i t i s probable that reaction 8 does proceed v i a thi s hydridochromium complex which must be very thermally unstable. The observed increase i n thermal s t a b i l i t y of the CpM(NO)pH compounds from the f i r s t - 18 -Table I. Spectral Properties of CpW(NO)„H and Related Complexes Inf r a r e d , a cm 1 Proton NMR,b <S Complex v (NO) other C 5H 5 other CpW(NO)2H 1718 1632 1900 v (W-H) 5.05b 2.77 CpW(NO)2D 1718 1632 1372 v (W-D) 5.05b CpW(NO) 2S0 3C 7H 7 1737 1650 6.15C 2.70 s 7.41 m [CpW(NO) 2(CH 3CN)]BF 4 1770 1690 CpMo(NO)2H 1732 1642 a a In CH 2C1 2 unless otherwise indicated. b In C,D,-. 6 6 3H 4H c In CDC1 ' In toluene. - 19 -to the th i r d t r a n s i t i o n series p a r a l l e l s the observed behaviour of the analogous complexes, CpM(CO)3H, for which the thermal and oxidative s t a b i l i t i e s also increase i n the order Cr<Mo <W.2I+ Conversions'7 and 8 can also be effected i n tetrahydro-furan with NaBH^, but the yi e l d s of the desired products are much lower. For instance, CpW(NO)2H i s obtainable i n only 13% y i e l d i n t h i s manner. However, i t has been found that t h i s hydrido product can be formed, a l b e i t i n only 23% y i e l d , by reaction 9. When NaBD^ i s employed as the reducing agent, [CpW(NO)2(CO) ]PF 6 |§|^4 » CpW(NO)2H (9) reaction 9 represents a convenient route to the deuteride, CpW(NO)2D. Physical Properties of CpW(NO)2H. (n 5-Cyclopentadienyl)-hydridodinitrosyltungsten i s a bright green, diamagnetic s o l i d which can be handled i n a i r for short periods of time without the occurence of noticeable decomposition. I t i s f r e e l y s o l -uble i n common organic solvents, but only sparingly soluble i n p a r a f f i n hydrocarbons, to give a i r - s e n s i t i v e green solu-tions, and i t sublimes r e a d i l y at room temperature (5x10 3 mm) onto a dry ice-cooled probe. Its spectral properties (Table I) are consistent with the compound having the molecu-l a r structure shown below. Thus, an infrared spectrum of a dichloromethane solution of the complex exhibits two strong - 20 -O N ' 1 >H N 0 absorptions at 1718 and 1632 cm 1 attributable to the terminal n i t r o s y l ligands. These bands are at frequencies s l i g h t l y lower than the corresponding absorptions of the CpW(NO)2Cl p r e c u r s o r 1 0 which has recently been found to adopt a s i m i l a r "piano s t o o l " geometry i n the s o l i d s t a t e . 2 6 Furthermore, there i s a broad, weak band at 1900 cm 1 assignable as the terminally bonded W-H stretching absorption. In accord with t h i s assignment i s the f a c t that the infrared spectrum of CpW(NO)2D i n CH 2C1 2 does not exhibit t h i s band but does show a weak absorption at 1372 cm 1 assignable to a terminal W-D group. As expected, the observed s h i f t , v(MH)/v(MD), equals 1.38 since v(MH) and v (NO) are not appreciably mixed i n the hydrido derivative. The XH NMR spectrum of CpW(NO)2H i n CgDg consists of a sharp resonance at 6 5.05 and a s l i g h t l y broader resonance at 62.77 of r e l a t i v e i n t e n s i t y 5:1. The former signal i s c h a r a c t e r i s t i c of a pentahapto cyclopentadienyl r i n g . The l a t t e r i s assigned to a hydrogen atom bonded d i r e c t l y to the - 21 -tungsten centre since i t does not appear i n the 1E MNR spectrum of CpW(NO)2D recorded under i d e n t i c a l conditions (Table I ) . However, 183W-1H coupling i s not observed even though such coupling has been measured for the related CpW(CO)^H complex. 2 7 The occurrence of the hydride resonance at r e l a t i v e l y low f i e l d i s somewhat anomalous since these resonances are usually observed at high f i e l d s , t y p i c a l l y i n the range 6-5 to -20. 2 8 For example, CpRe(CO)(NO)H displays a broad signal at 6-8.2 due to the hydride l i g a n d . 7 A low f i e l d resonance i s not unknown for t r a n s i t i o n metal hydrides, but to date i t has been c h a r a c t e r i s t i c only of some bis(cyclopentadienyl)hydrido complexes of titanium, zirconium 2 9 and niobium* 3 0 The mass spectrum of CpW(N0)2H exhibits a fragmentation pattern s i m i l a r to that displayed by CpW(NO)2CH^31 under i d e n t i c a l conditions. Peaks attributable to the parent ion and ions corresponding to the stepwise loss of n i t r o s y l ligands are observable i n both cases, but ions r e s u l t i n g from cleavage and rearrangement of the cyclopentadienyl ring appear to be much more abundant i n the spectrum of CpW(NO)2H. Unfortunately, overlapping of some medium to strong i n t e n s i t y peaks i n the lower mass range makes unambiguous assignments d i f f i c u l t , e s p e c i a l l y i n l i g h t of the polyisotopic nature of tungsten. The Chemical Reactivity of CpM(NO)2H [M=Mo or W]. When compared with metal carbonyl hydrides to which they are - 22 -formally related, the CpM(NO)2H complexes display both s i m i l a r i t i e s and very s t r i k i n g differences i n t h e i r chemical r e a c t i v i t y (Figure 1). For instance, even though carbonyl hydrides of general formula CpM(CO) H [X=3, M=Cr, Mo orV/W24; X=2, M=Fe 3 2 or Ru 3 3] can a l l be decomposed thermally or oxidatively to y i e l d the corresponding dimers, [CpM(CO) x] 2, the green CpM(NO)2H species only decomposes to red-brown n i t r o s y l - f r e e s o l i d s when subjected to the same experimental conditions. Moreover, CpW(NO)2H does not react with halo-carbons such as CHC13 or CC1 4 at ambient temperature although such a reaction i s often employed to establish the presence of a metal-hydrogen bond. 2 8 However, l i k e numerous carbonyl hydrides, CpW(NO)2H does react d i r e c t l y with halogens to afford the respective halo derivatives i n reasonable y i e l d s . A sim i l a r conversion allows the chemical i d e n t i -f i c a t i o n of CpMo(NO)2H as the product formed i n reaction 7 above, i . e . CpMo(NO)2H (not i s o l a t e d ) — t o l u e n e ? CpMo (NO) 2 * •• ( 1 0 ) The most s i g n i f i c a n t difference between CpW(NO)2H and most carbonyl hydrides i s evident i n i t s acid-base behaviour. Many neutral hydridocarbonyls are Lowry-Br0nsted acids i n polar s o l v e n t s , 2 8 but the hydridotungsten complex acts as a source of H~ under these conditions. This f a c t i s c l e a r l y demonstrated by i t s reaction with anhydrous p-toluenesulfonic no reaction CpW(NO) ? X [X= Br or I ] t no reaction hexanes,5days x 2 CH 2 Cl 2 CHCt3dr CCl 4 , 24 h CpW(C0)2(N0) + [cPw(coy2 (h) (a) (bl £ E = £ _ C p ^ ( N 0 ) 2 H : ; C H S S ° - H . C p W ( N q 2 0 S 0 2 C 5 H 4 C H : (c) THF ( f ) Ke) (d? to HCo (CO)4 THF THF reflux, 24 h Fe(COL CpW(CO)2(NO) + C o (CO) (NO) 3 no reaction (C 6H 5) 3CBF 4 CH 3CN ^ [CpW(NO)2(CH3CN)]+ CpW(NO)2I Figure 1. The c h a r a c t e r i s t i c chemistry of CpW(NO)2H. - 2.4 -acid to y i e l d the new p-toluenesulfonato complex under conditions which leave CpW(CO)3H unaltered. Consistent with t h i s view of W(S + )-H(6 ) bond p o l a r i t y i s the f a i l u r e of CpW(NO)2H to react with (C 2H 5) 3N and i t s reaction with the well-known hydride abstractor triphenylcarbenium t e t r a f l u o r o -borate i n a c e t o n i t r i l e to afford [CpW(NO)2(CH^CN)]BF^ and Ph3CH. The organic product can be i s o l a t e d i n 61% y i e l d , but the organometallic complex i s obtained as an o i l which cannot be r e a d i l y p u r i f i e d . However, i t can be i d e n t i f i e d by comparison of i t s infrared spectrum (v(NO) at 1770 and 1690 cm - 1 i n CH3CN) with that exhibited by [CpW(NO) 2(CH 3CN)]PF g and by i t s reaction with Nal to form CpW(NO) 2I. 1 6 As expected, similar treatment of CpW(NO)2D with Ph 3CBF 4 provides Ph3CD i n comparable y i e l d s . The hydridic character of the tungsten hydride i s surprising since i t i s generally believed that the presence of electron-withdrawing ligands on the metal centre enhances the a c i d i c character oS;: M-H bonds. 2 8 Nevertheless, the chemistry pf CpW(N0)2H resembles that t y p i c a l l y exhibited by transition-metal t e r t i a r y phosphine hydride complexes which are also not a c i d i c i n solution and w i l l not form sodium s a l t s analagous to those"of theicarbonyl hydrides. Direct nucleo-p h i l i c transfer of hydride from a hydridocarbonyl complex to e l e c t r o p h i l i c centres has been observed r e c e n t l y . 3 4 However, the complex involved, [CpV(CO)3H] , i s anionic and therefore probably contains a large amount of electron density - 25 -at the metal. I t thus appears that the n i t r o s y l ligands i n CpW(NO) 2H are not p a r t i c u l a r l y e f f e c t i v e as ir-acids i n removing electron density from tungsten. Consistent with t h i s view i s the f a c t that several cations of the type [CpW(NO)2L] + (L=neutral Lewis base) are known, 1 6 but the anion [CpW(NO)2] has yet to be characterized (cf. reaction (h)). In l i g h t of the observed hydridic behaviour of CpW(NO)2H, i t i s not unreasonable to expect that i t w i l l react with a c i d i c hydridocarbonyls to form b i m e t a l l i c carbonylnitrosyl complexes. However, these types of products have yet to be is o l a t e d from such reactions., Thus,-when CpW(NO)2H i s treated with equimolar amounts of HCo(CO) 4 or CpW(CO)3H, the only carbonyl- and nitrosyl-containing products i s o l a t e d r e s u l t from the scrambling of the two ligands among the metal centres, possibly v i a a b i m e t a l l i c intermediate. A si m i l a r r e d i s t r i b u t i o n of ligands has been observed recently to occur during reactions of Ni(NO)(PPh 3) 2X (X=Cl,Br or I) with carbonylmetallates such as CpMo(CO)3 , 3 5 F i n a l l y , i t i s known that strong hydride donors attack electrophiles such as metal carbonyls to produce formyl com-p l e x e s . 3 6 However, CpW(NO)2H i s not s u f f i c i e n t l y hydridic to react with Fe(CO) 5 i n refluxing tetrahydrofuran. Unlike the M-H linkages of many a c i d i c t r a n s i t i o n metal h y d r i d e s , 2 8 the W-H bond i n the n i t r o s y l hydride does not undergo simple addition reactions with unsymmetrical alkenes such as bromo-styrene. The CpW(NO)2H i s consumed during the reaction, but no new organometallic n i t r o s y l products are formed. CHAPTER III SYNTHESIS AND CHARACTERIZATION OF BIS[(n5-CYCLOPENTADIENYL)  DIIODONITROSYLTUNGSTEN] Since an investigation of the chemistry of CpW(NO)2H produced some surprising r e s u l t s (Chapter I I ) , i t became apparent that i t was necessary to f u l l y evaluate the function of the NO groups i n that complex. A convenient way to do t h i s would be to determine the e f f e c t of varying the other ligands attached to the metal on the physical and chemical properties of hydridonitrosyl complexes of tungsten. However, a survey of the chemical l i t e r a t u r e reveals that very few convenient starting materials have been reported. Fortunately, considerably more work has been done on molybdenum complexes. For example, i t has been reported that CpMo(CO)2NO reacts readily with the halogens (X 2; X=C1 3 7, Br o r . I 3 8 ) . CpMo(CO)2NO + X 2 ^ 2 — 2 — » 1/2 [CpMo(NO)X2] 2 (11) These complexes, i n turn, provide convenient pre-cursors to many ha l o n i t r o s y l complexes of molybdenum, e.g. 3 7~ l t c [CpMo(NO)X2] 2 + 2L :—*2CpMo(N0) (X) 2 L L=Group V donor ligand (12) - 27 -[CpMo (NO) I ] 2 + 2T1(C 5H 5). * 2 (C.-H,-) 2^0 (NO) I . (13) This chapter reports the r e s u l t s of attempts to prepare some tungsten congeners of these molybdenum complexes. EXPERIMENTAL A l l experimental procedures described here were performed under the same general conditions outlined i n Chapter I I . Reaction of CpW(CO)2NO with ~L^. To a s t i r r e d , orange solution of CpW(CO) 2N0 1 2 (5.00 g, 14.93 mmol) i n CH 2C1 2 (100 mL) was added s o l i d iodine (3.79 g, 14.93 mmol). Vigorous gas evolution immediately occurred and the reaction mixture turned red-violet. The reaction mixture was allowed to s t i r at room temperature f o r 30 min before being taken to dryness in vacuo. The red-brown residue was c r y s t a l l i z e d from CH 2C1 2/ hexanes to y i e l d dark brown, mic r o c r y s t a l l i n e [CpW(NO)I 2] 2 (7.52 g, 94% y i e l d ) . Anal. Cald for C - ^ t ^ ^ I ^ V ^ : C, 11.27; H, 0.95; N, 2.63. Found: C, 11.26; H, 0.88; N, 2.53. IR (CH 2C1 2): v(N0) 1652 cm"1. 1U NMR (CDC1 3): 66.15. Mp 120°C dec. Reactions of [CpW(NO)I 2] 2 with Donor Ligands(L). These experiments were a l l performed s i m i l a r l y and the L=P(OPh) 3 reaction i s described as an example. A stoichiometric amount of neat triphenyl phosphite (0.26 mL, 0.31 g, 1.00 mmol) was added to a s t i r r e d solution of [CpW (NO') I 23 2 (°- 53 g, 0.50 mmol) in CH 2C1 2 (50 mL) . The - 2 8 -solution immediately turned deep red. Hexanes (50 mL) were added and the reaction mixture was slowly concentrated under reduced pressure. This resulted i n the c r y s t a l l i z a t i o n of brown, a n a l y t i c a l l y pure CpW(NO)(I) 2P(OPh) 3 (0.68 g, 81% y i e l d ) . ^COH} NMR (CDC13) : 101.36 {s, C ^ } , 121. 03 {d, J ( 1 3 C - 3 1 P ) 3.3 Hz, C,HC-C0} 126.01 {s, C, Hc-C.}, 129.79 {s, C,HC-C-.}, 150.79 {d, J ( 1 3 C - 3 1 P ) 12.3 Hz, C ^ - C ^ . The other complexes ( s i m i l a r l y coloured) were obtained i n y i e l d s of 78-80% (Table I I ) . Treatment of [CpW(NO)I 2] 2 with PhCCPh. A stoichiometric amount of diphenylethyne (0.18 g, 1.0 mmol) was added to a s t i r r e d solution of [CpW(NO)I 2l 2 (0.53 g, 0.5 mmol) i n CH 2C1 2 (50 mL). The reaction mixture was s t i r r e d at room temperature for 18 h. At the end of that time a solution infrared spectrum did not indicate any consumption of the nitrosyl-containing reactant. Reaction of [CpW (NO) I,,] 2 with CO. Carbon monoxide was gently bubbled through a solution of [CpW(NO)I 2] 2 (0.53 g, 0.50 mmol) i n CH 2C1 2 (25 mL) for 30 min. At the end of that time a solution infrared spectrum indicated ca. 90% conversion to CpW(NO)(I) 2(CO). Continued reaction with CO did not appear to consume any more of the s t a r t i n g material. The reaction mixture was taken to dryness i n vacuo to quantitatively recover [CpW(NO)I 2] 2. Reaction of [CpW (NO) I,,] 2 with NO. Prepurified nitrogen monoxide was gently bubbled through a solution of [CpW(N0)I 9] 9 Table I I . Physical Properties of the Complexes CpW(NO)(I)2L [L= PPh 3, P(OPh) 3, SbPh 3 or CO] Mp Analysis: Calcd (Found) IR,v_(NO) C H N (cm l) Cp lE NMR other CpW(NO)(I) 2P(OPh) 3 140° dec 32.77 2.40 1.66 (32.73) (2.33) (1.58) 1651 a 5.90 j ( l H _ 3 1 p ) 3.0 Hz 7.19 (15H, b) CpW(NO)(I) 2PPh 3 158° dec 34.74 2.54 1.76 (34.79) (2.48) (1.79) 1633 5.91 J( 1H- 3 1P) 1.2 Hz 7. 54 (15H, b) CpW(NO)(I) 2SbPh 3 141° dec 31.16 1.58 2.26 (31.09) (1.60) (2.26) 1640' 6.00 7 .50 (15H, b) CpW(CO) (NO) (I) 16941 a In Nujol mull b In CDC13 solution ° In CH 2Cl 2, v(CO): 2040 cm 1 - 30 -(0.53 g, 0.50 mmol) i n CH 2C1 2 (25 mL) f o r 15 min. A large amount of brown s o l i d p r e c i p i t a t e d during the course of the reaction. At the end of that time a solution infrared spectrum revealed that a l l of the reactant was consumed. The reaction mixture was concentrated under reduced pressure to ca. 5 mL. This solution was transferred to the top of a short F l o r i s i l column (3x5 cm). Elution with CH 2C1 2 resulted i n the development of a single o l i v e green band which was co l l e c t e d . The eluate was taken to dryness i n vacuo to y i e l d 0.12 g (28% y i e l d based on W) of CpW(NO)2I, as 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 physical p r o p e r t i e s . 1 6 Reaction of CpW(CO)2NO with P(OPh) 3. A toluene (40 mL) solution containing CpW(CO)2NO (1.43 g, 4.30 mmol) and t r i -phenyl phosphite (1.13 mL, 1.33 g, 4.30 mmol) was s t i r r e d at reflux for 16 h. At the end of that time, the reaction mix-ture was f i l t e r e d through a short (3x5 cm) column of alumina supported on a medium porosity f r i t t e . The f i l t r a t e was taken to dryness under reduced pressure to leave an orange s o l i d . A small amount of unreacted CpW(CO)2NO was removed by sublim-ation at 60°C (5x10 3 mm) onto a water-cooled probe. The sub-limation residue was r e c r y s t a l l i z e d from CH 2Cl 2/hexanes to y i e l d orange-yellow CpW(CO)(NO)P(OPh)3 (1.32 g, 49% y i e l d ) . Anal. Calcd for C 2 4H 2 QN0 5PW: C, 46.70; H, 3.27; N, 2.27. Found: C, 46.99; H, 3.25; N, 2.29. IR (CR"2C12) : v (NO) 1625, v(C0) 1938 cm - 1. lE NMR (CDCl 3): 64.80 (s, 5H), 7.15 (b, 15H). Mp 138°C dec. Mass spectrum summarized i n Table I I I . - 31 -Table I I I . Mass Spectral Data for CpW(CO)(NO)P(OPh) Q a m/z Rel abund Assignment 617 100 CpW(CO)(NO)P(OPh)3+ 589 45 CpW(NO)P(OPh)3+ 524 10 CpW(CO)(NO)P(OPh)2+ 496 22 CpW(NO)P(OPh)2+ 310 11 P(OPh) 3 + 217 44 P!(0Ph) 2 + The assignments involve the most abundant naturally occurring isotope i n each fragment. Mass spectral data includes a l l fragments containing W. The spectrum also included peaks corresponding to further fragmentation of P(OPh) 3. - 32 -Reaction of CpW(CO)(NO)P(OPh)3 with I,,. To a s t i r r e d , orange solution of CpW(CO)(NO)P(OPh)3 (0.62 g, 1.0 mmol) i n CH 2C1 2 (35 mL) was added s o l i d iodine (0.25 g, 1.0 mmol). The reaction mixture immediately began to turn a dark red colour but was s t i r r e d at room temperature for 30 min to ensure complete reaction. Addition of hexanes (35 mL), followed by slow concentration under reduced pressure, resulted i n the c r y s t a l l i z a t i o n of a n a l y t i c a l l y pure CpW(NO)(I) 2P(OPh) 3 (o.67 g, 79% y i e l d ) . Reaction of [CpW(NO)I2J2 with T1(C 5H 5). To a s t i r r e d , green solution of [CpW(NO)I 2] 2 (0.42 g. 0.39 mmol) i n THF (40 mL) was added s o l i d Tl(C 5H 5) (0.21 g, 0.79 mmol). The reaction mixture gradually darkened to give a deep red colour and a yellow s o l i d p r e c ipitated. The mixture was s t i r r e d at room temperature for 1 h before being taken to dryness i n vacuo. The res u l t i n g residue was extracted into dichloro-methane (40 mL) and the extracts were.filtered through a short (3x3 cm) column of C e l i t e supported on a medium porosity " f r i t t e . The f i l t r a t e .was concentrated under reduced pressure to ca. 5 mL. Addition of hexanes (60 mL) resulted i n the p r e c i p i t a t i o n of golden-brown microcrys-t a l l i n e (C 5H 5) 2W(NO)I (0.22 g, 60% y i e l d ) . Anal. Calcd for C-^H-^INOW: C, 25.48; H, 2.12; I, 26.96; N, 2.97. Found: C, 25.13; H, 2.01; I, 27.00; N, 3.13. IR(CH 2C1 2) : v (NO) 1622 cm"1. 1E NMR (CDC1 3): 66.16 (s) . Mp 127f>°C dec. - 33 -Results and Discussion At room temperature i n dichloromethane solution, CpW^O^NO reacts quickly and quantitatively with iodine. Monitoring of the reaction by infrared spectroscopy shows a disappearance of the absorptions due to the reactant (v(CO) 2010, 1925; v(NO) 1655 cm 1) and the appearance of a new set of absorp-tions i n the carbonyl and n i t r o s y l regions (v(CO) 2040, v(NO) 1694 cm l ) . These observations are consistent with the replacement of one carbonyl ligand with two iodo ligands. The r e s u l t i n g carbonyldiiodonitrosyl complex i s unisolable. It decarbonylates and oligimerizes slowly under ambient conditions and rapidly under vacuum. The f i n a l product i s [CpW(NO)I 2] 2 (v(NO) 1652 cm" 1). Therefore, the o v e r a l l reaction can be summarized: CpW(CO)2N0 + I 2 CpW(NO)(I)2(CO) The thermal i n s t a b i l i t y of the product formed i n Equation 14 i s not unusual. In fact, the l a b i l i t y of carbonyl ligands appears to be an i n t r i n s i c property of t r a n s i t i o n metal c a r b o n y l n i t r o s y l h a l i d e s . 1 1 The complex b i s [ ( n 5 - c y c l o p e n t a d i e n y l ) d i i o d o n i t r o s y l -tungsten] i s a red-brown, diamagnetic s o l i d that i s f r e e l y soluble i n tetrahydrofuran and acetone, less soluble i n ben-zene, dichloromethane and chloroform and completely insoluble C H 2 C 1 2 * CpW(NO) (I) 2(CO) + CO (14) _CH 2— 2—» 1/2 [CpW(NO) I 2] 2 + CO (15) - 34 -in hexanes. Solutions are a i r - s e n s i t i v e but the s o l i d can e a s i l y be handled i n a i r for short periods of time. The IR spectrum (THF or CH 2C1 2) displays a single n i t r o s y l - s t r e t c h -ing absorption i n the terminal NO region. The complex i s best formulated as an iodo-bridged dimer (shown below) since a monomeric formulation would require a tungsten atom with two electrons less than the favoured eighteen-electron configura-ti o n . The dimeric nature i s also suggested by i n d i r e c t physical evidence. The mass spectrum of [CpW(NO)I 2] 2 (Table IV) does not display a parent ion peak (m/z=1066). However, peaks indicating s i g n i f i c a n t quantities of ions containing two tungsten atoms ( i . e . Cp 2W 2(NO) 2 I2 + a n d C p 2 W 2 ^ N 0 ^ 2 I 2 + ^ are consistent with a dimeric molecule. Nonetheless, the r e l a t i v e abundance of the ions CpW(NO)I 2 + and CpWI 2 + indicate that the dimer i s r e a d i l y cleaved on vapourization or electron impact. The f a c i l e cleavage of the halogen bridges of the dimeric [CpW(NO)I 2] 2 i s also shown by i t s ready reaction with a variety of Lewis bases (Equation 16) to y i e l d the monomeric [CpW(NO)I 2] 2 + 2L — — 2 — 2 — > 2CpW(N0) (I) 2 L (16) L=P(C 6H 5) 3, P(OC 6H 5) 3 or S b (C 6H 5) 3 - 35 -Table IV. Mass Spectral Data for [CpW(NO) 1 9] m/z Rel Abund Assignment 812 2 Cp 2W 2(NO) 2I 2 + 782 2 Cp 2W 2(NO)I 2 + 533 98 CpW(NO)I 2 + 503 100 CpWI 2 + 438 10 w i 2 + 406 15 CpW(NO)I+ 376 79 CpWI + 350 34 (C 3H 3)WI + 311 3 WI + 279 3 CpW(NO)+ 249 25 CpW+ 184 12 w+ a Assignments based on most abundant naturally occurring isotopes i n each fragment. Massaspectral data includes only fragments containing W. - 3 6 -complexes CpW(NO)(I) 2L. These complexes are orange-brown solids which are sparingly soluble i n chloroform and dichloro-methane but even less soluble i n benzene, tetrahydrofuran or acetone. The IR spectra display single n i t r o s y l - s t r e t c h i n g absorptions i n the range 1633-1659 cm 1 which are 30-60 cm 1 lower than that exhibited by the CpW(NO)(I)2(CO) complex i n solution. The w(NO) decrease as L varies i n the order C 0 > P ( O P h ) 3 > P 0 3 has been previously observed i n other systems; 4 1 and i s consistent with the replacement of a carbonyl ligand by better electron donating ligands and the reported v a r i a t i o n in electron donating and accepting a b i l i t i e s . The mass spectrum of CpW(NO)(I) 2P(OPh) 3 (Table V) does not display a parent ion peak but does reveal a fragmentation pattern attributable to CpW(NO)(I) 2 + and P(OPh) 3 +. Attempts to obtain mass spectra of the CpW(NO) U ) 2 L (L=PPh3 or SbPh3) complexes led to ambiguous r e s u l t s . The spectra contained peaks at high values of m/z (400-800) but they did not display the c h a r a c t e r i s t i c isotope pattern of tungsten. Apparently these complexes do not possess s u f f i c i e n t v o l a t i l i t y to be analyzed by conventional electron-impact techniques. Assuming a "four-legged piano s t o o l " geometry for the complexes CpW(NO)(I) 2L, there exists the p o s s i b i l i t y of two isomers i n which the iodo ligands are either c i s or trans to each other. Spectral properties suggest that only one isomer of each complex i s formed. The 1E NMR spectra (Table II) - 37 " Table V. Mass Spectral Data for CpW(NO)(I) 2P(OPh) 3 a m/z Rel abund Assignment 533 21 CpW(NO)I2 503 19 CpWI 2 + 376 17 CpWI+ 350 10 (C 3H 3)WI + 310 37 P(OPh) 3 + 217 100 P(OPh) 2 + + a The assignments involve the most abundant naturally occurring isotopes i n each fragment. Mass spectral data includes a l l fragments containing W. The spectrum also included peaks corresponding to further fragmentation of P(OPh),. - 38 -trans display a single broad resonance due to the phenyl protons and a single resonance i n the cyclopentadienyl region. In those cases where the L ligand contains a phosphorous atom the cyclopentadienyl protons are coupled to the 3 1 £ nucleus. In order to f i n d a more sensitive determination of the number of isomers i n solution, the proton-decoupled carbon-13 magnetic resonance spectrum of CpW(NO)(I)^ (OPh)^ was recorded (see Experimental Section). The assignments of the cyclopentadienyl and triphenylphosphite ligands are based on previously reported results and the expected chemical s h i f t s of these two l i g a n d s . 4 2 The i n d i r e c t coupling constants, J ( 1 3 C - 3 1P) and J ( 1 3 C - 3 1 P ) , are based on an 1 2 examination of the spectrum of the free ligand. Most importantly, the 1 3C NMR spectrum of the .complex indicates the presence of only one isomer i n solution. However, which isomer that i s remains unknown at present. The complexes, CpW(NO)(I) 9L can be synthesized by - 39 -another route. For example, CpW(NO)(I) 2P(OPh) 3 can be prepared by the consecutive reactions CpW(CO)2N0 + P(OPh) ii ^ — ) CpW (CO) (NO) P (OPh) -j + CO (17) 2 — 2-* CpW (NO) (I) 2P (OPh) 3 + CO (18) CpW (CO) (NO) P (OPh) 3 + I 2 The CpW(CO)(NO)P(OPh)3 reagent can be read i l y prepared by a route analogous to that described previously for the triphenyl phosphine d e r i v a t i v e . 4 3 Reaction (18) could conceivably proceed by two routes (Scheme). The iodine could displace the carbonyl ligand to y i e l d CpW(NO)(I) 2P(OPh)3 d i r e c t l y . A l t e r n a t i v e l y , the iodine could displace the triphenyl phosphite ligand to generate CpW(NO)(I)2C0. This i n turn could react with the liberated triphenyl phosphite with the loss of the carbonyl ligand. The iodo bridges of [CpW(NO)I 2] 2 can also be cleaved by carbon monoxide. CpW(CO)(NO)P(OPh)3 CpW(NO)(I) 2P(OPh) 3 Scheme [CpW(NO)I 2l 2 + 2C0 —££2£i-2-» 2CpW (NO) (I) 2C0 (19) - 40 -The product has the same properties as those exhibited by the product of reaction 14. Monitoring of the reaction by solution IR spectroscopy indicates that the maximum conver-sion i s only 90%. However, i t i s possible that conversion i s complete, but decarbonylation occurs when a sample i s removed from a carbon monoxide atmosphere and placed i n a solution * infrared c e l l . Nitrogen monoxide also.reacts r e a d i l y with solutions of [CpVJ (NO) I 2] 2 as shown i n reaction 20. Only one N O [CpW(NO)I 2] 2 CH 2C1 2 } C P W ( N 0 ) 2 I ( 2 0 ) nitrosyl-containing species i s formed. Attempts to synthesize complexes CpW(NO)(I) 2L (L= alkene or alkyne) have not been successful. For example, treatment of [CpW(NO)I 2] 2 with diphenylethyne under the same conditions as s p e c i f i e d for the formation of the triphenyl phosphite derivative does not lead to the formation of any new nitrosyl-containing species. Thallium cyclopentadienide reacts with one-half the equimolar quantity of [CpWCNO)^^ i n a manner analogous to that reported for [CpMo(NO)I^]2'^ ° T h e P r o d u c t , (C 5H 5) 2W(NO)I, i s a brown, diamagnetic s o l i d that i s soluble i n polar organic solvents. In dichloromethane solution, the compound exhibits a single sharp absorption (1625 cm 1) i n the region expected for a l i n e a r , terminal n i t r o s y l group. The mass spectrum (Table VI) displays a parent-ion peak and a fragmentation - 41 -Table VI. Mass Spectral Data for (C^H-) 0W(NO)l a m/z Rel abund Assignment 471 18 (C 5H 5) 2W(NO)I 441 92 (C 5H 5) 2WI + 376 11 (C 5H 5)WI + 314 100 (C 5H 5) 2W + + The assignments involve the most abundant naturally occurring isotopes i n each fragment and include a l l fragments containing W. - 42 -pattern i n d i c a t i v e of a stepwise loss of ligands from the metal centre. The proton magnetic resonance spectrum of (C 5H 5) 2W(NO)I suggests that the two C,-Hj- groups are equiva-lent at room temperature i n solution since only a single resonance i s observed. This raises an interesting problem. If the complex i s to adhere to the the usual rare-gas con-f i g u r a t i o n , then the two C,.H rings must donate a t o t a l of -1 5 eight electrons. However, t h i s does not necessarily require that each of the organic ligands donates four electrons to the metal centre. Regardless of the bonding configuration in the s o l i d state, role exchange i s expected at room tem-perature i n solution. This process would make the two C^H^ groups r e s u l t i n only a single resonance i n the NMR spectrum. In the case of the molybdenum analogue, there have been several attempts to describe the r e l a t i v e contribution of each cyclopentadienyl group. O r i g i n a l l y i t was proposed that one of the rings was bonded i n a pentahapto manner and the other t r i h a p t o . 4 0 The equivalence of the two rings at • room temperature was attributed to rapid exchange. However, spectra recorded at temperatures as low as -120°C f a i l e d to indicate any inequivalence of the two C^H^ l i g a n d s . 4 4 This led to the suggestion that both rings were indeed bonded i n a n 4 fashion. More recently, investigators have proposed that the complex i s coordinatively unsaturated i n solution and that rapid exchange occurs between a pentahapto and a monohapto cyclopentadienyl r i n g . 4 5 Obviously, more work must - 43 -be done to deduce the configurations of the cyclopentadienyl groups in (CVH-) 9W (NO) I. CHAPTER IV PREPARATION OF (n3-ALLYL)(n5-CYCLOPENTADIENYL)IODONITROSYL- TUNGSTEN AND-MOLYBDENUM Very few a l l y l n i t r o s y l complexes are known. However, those that are known display some fascinating chemical proper t i e s . For example, the well-studied (n 3-C 3H 5) Fe (CO) 2 N C ) l t 6 has been found to be an e f f i c i e n t c a t a l y s t for the dimer-i z a t i o n of butadiene and iso p r e n e . 4 7 Dimerization of buta-diene with 1% by weight of (n 3-C 3H 5)Fe(CO) 2N0 y i e l d s a nearly quantitative conversion to 4-vinylcyclohex-l-ene. Another a l l y l n i t r o s y l complex, Ru(NO)(n 3-C 3H^)(PPh 3) 2 i s reported to be one of the few known cases where f a c i l e conversion of a l i n e a r to a bent n i t r o s y l ligand can o c c u r . 4 8 Furthermore, the c a t i o n i c complex [CpMo(CO) (NO) ( n C-^H^)] displays remark able s t e r e o s e l e c t i v i t y i n reactions with n u c l e o p h i l e s . 4 9 Nucleophilic attack occurs at the coordinated a l l y l ligand at the point determined by the position of lowest electron density. This control of regiochemistry i s believed to be exerted by an electronic e f f e c t a r i s i n g from the d i f f e r e n t e f f e c t i v e e l e c t r o n e g a t i v i t i e s of the carbonyl and n i t r o s y l ligands. The c a t i o n i c complex mentioned above ( and other a l l y l derivatives) has been reported twice i n the l i t e r a t u r e . The - 45 -f i r s t report b r i e f l y mentioned the syntheses of [CpMo(CO)(NO)-( n 3 - C 3 H 5 ) ] + and the neutral derivative CpMo(NO)(n 3-C 3H 5)I. 5 0 + CpMo(CO)2NO + C 3H 5X ^2 » [CpMo (CO) (NO) (n 3-C 3H 5)] I" (21) •4/ CpMo(NO)(n 3-C 3H 5)I However, no experimental d e t a i l s and no physical data were supplied. A more recent report described the preparation of [CpMo(CO)(NO)(n 3-C 3H 5)] + from CpMo(CO) 2(n 3-C 3H 5), i . e . , 4 9 CpMo(CO) ( n 3-C 3H 5) + NOPFg — 3 C N . ) ."(22) [CpMo(CO) (NO) (n 3~C 3H 5)]PF 6 . Similar tungsten complexes are desirable because of the i n -teresting chemistry displayed by a l l y l n i t r o s y l complexes i n general and as a l l y l analogues to CpW(NO)2X (X=C1, Br, I or H) i n p a r t i c u l a r . A possible route to such complexes may involve d i r e c t a l l y l a t i o n of [CpW(NO) 2 * EXPERIMENTAL SECTION A l l experimental procedures described here were perform-ed under the same general conditions outlined i n Chapter I I . Reaction of [CpW (NO) I.,],, with SnCC.^)^. To a s t i r r e d solution of [CpW(NO)I 2l 2 (1.07 g, 1.0 mmol) i n THF (30 mL) at room temperature was added neat Sn(C,H,-) . (0.25 mL, 1.0 mmol). - 46 -The o r i g i n a l green solution gradually acquired a red colour-ation while being s t i r r e d f or 12 h. The f i n a l reaction mixture was taken to dryness i n vacuo, the residue was dissolved i n C H 2 C I 2 (20 mL), and the res u l t i n g solution was f i l t e r e d through a short (3x5 cm) column of F l o r i s i l . An equal volume of hexanes was added to the f i l t r a t e , and the mixture was slowly concentrated under reduced pressure to induce the c r y s t a l l i z a t i o n of orange-brown CpW(NO)(n3-C3H,-)I (0.62 g, 70% y i e l d ) . Anal. Calcd for CgH-^NIOW: C, 21.50; H, 2.26; N, 3.13. Found: C, 21.46; H, 2.21; N, 3.11. IR (CH 2Cl 2): v(NO) 1636 cm"1. Mp 165°C dec. The molybdenum congener was obtained by reacting S n ( C 3 H 5 ) 4 with [CpMo(NO)I 2] 2 3 8 under the same conditions. Anal Calcd for CgH^NIMoO: C, 26.76; H, 2.81; N, 3.90. Found: C, 26.73; H, 2.78; N, 3.88. IR (CH 2C1 2): v(NO) 1658 cm"1. Mp 171°C dec. Y i e l d 88%. Reaction of [CpW(CO)(NO) ( n 3-C 3H 5)]PF £ with NaT. To a pale yellow solution of CpW(CO) 2(n 3-C 3H 5) 5 1 (0.70 g, 2.0 mmol) in CH3CN (50 mL) was added s o l i d NOPF^ (0.35 g, 2.0 mmol). The solution was s t i r r e d at room temperature for 2 h during which time i t gradually changed colour to orange. At the end of that time? .. s o l i d Nal (0.30 g, 2.0 mmol) was added to the reaction mixture. The solution was s t i r r e d at room temperature for an additional 18 h before being taken to dryness i n vacuo. Work up as described above yielded 0.51 g - 47 -(63% yield) of CpW(NO) ( n 3-C 3H 5)I as characterized by i t s d i s t i n c t i v e physical properties. Treatment of CpW(NO)(n 3-C 3H 5)I with PPh 3. A benzene solution (30 mL) containing CpW (NO) .(fi 3-C3H^) I (0.45 g, 1.0 mmol) and PPh 3 (0.26 g, 1.0 mmol) was s t i r r e d at reflux for one week. At the end of that time almost a l l of the CpW(NO)(n 3-C 3H 5)I was recovered unaltered (there was a small amount of decomposition) and no new n i t r o s y l containing species were detected. Treatment of CpW(NO)(n 3~C 3H 5)I with L i ( H B E t 3 ) . To an orange solution of CpW(NO)(n 3-C 3H 5)I (0.34 g, 0.76 mmol) i n THF (25 mL) at -78°C was added 0.80 mL of 1M s o l u t i o n 5 2 of Li(HBEt 3) i n THF. The reaction mixture was allowed to s t i r for 15 min. At the end of that time a solution IR spectrum showed that the n i t r o s y l absorptions due to the reactant had disappeared but there was no ind i c a t i o n of a new n i t r o s y l -containing species. The solvent was removed from the reaction mixture i n vacuo to leave a brown o i l . This was dissolved in CH 2C1 2 to give a solution that did not exhibit any absorptions i n the n i t r o s y l region of the IR spectrum. A simi l a r experiment using Na[A1H 2(OCH 2CH 2OCH 3) 2] proceeded with the same re s u l t s . Results and Discussion The new organometallic complex CpW(NO) ( n 3 _C 3H,_)I can be conviently prepared i n 7 0% y i e l d by the treatment of - 48 -[CpW (NO) 1 2 w :"- t h a n equimolar amount of SnfC^Hj-^ i n t e t r a -hydrofuran at ambient temperature, i . e . [CpW(NO)I 2] 2- |g|£-3%U—* 2CpW(NO) ( n 3 - C 3 H 5 ) I . (23) The complex i s an orange-brown, diamagnetic s o l i d which dissolves i n polar organic solvents to give reasonably a i r -stable solutions. Its IR spectrum (in CH 2C1 2) exhibits a strong absorption at 163 6 cm 1 a t t r i b u t a b l e to a terminal n i t r o s y l ligand. Its low-resolution mass spectrum (Table VII) displays a parent-ion peak and a fragmentation pattern corresponding to sequential loss of ligands from the metal centre. The complex has been characterized by s i n g l e - c r y s t a l X-ray d i f f r a c t i o n . 5 3 The gross stereochemical features (Figure 2) are not unusual. The molecule adopts a "piano-s t o o l " geometry and the a l l y l ligand i s i n the endo confor-mation r e l a t i v e to the rest of the molecule. The most chemi-c a l l y i n t e r e s t i n g feature of the molecular structure i s the marked asymmetry of the a l l y l ligand. The C(l)-C(2) length o of 1.43(1) A i s i n d i c a t i v e of p r i n c i p a l l y a single bond between the two atoms whereas the C(2)-C(3) distance of o 2.244(7) A f a l l s i n the range expected for single W-C a-bonds whereas the W-C(2) and W-C(3) bond lengths are somewhat longer. The geometries of the cyclopentadienyl and n i t r o s y l ligands are completely consistent with t h e i r - 49 -Table VII. Mass Spectral Data for CpW (NO) (n 3—C,H_)l a -5 5 m/z Rel abund Assignment 447 417 389 350 100 83 40 26 CpW(NO)(n 3-C QH c)I + CpW(n 3-C 3H 5)i + (C 3H 3) 2WI (C 3H 3)Wl" + The assignments involve the most abundant naturally occurring isotopes i n each fragment and include a l l fragments containing W. - 50 -Figure 2. Molecular structure of CpW(NO)(n 3-C 3H 5)I. Selected bond lengths (A): C(1)-C (2), 1.43(1); C(2)-C(3), 1.34(1); W-C(l), 2.244(7); W-C(2), 2.329(8); <W-C(3), 2.411(7). - 51 -functioning as five-and three- electron donors, respectively, to the metal centre. Consequently, to account for the diamag-netism of the complex and to provide the metal atom with the favoured eighteen-electron configuration, the tungsten-allyl linkage i s best represented as: As anticipated, the C-C bond of the a l l y l ligand which has more double bond character (C(2)-C(3)) i s situated trans to the NO group which i s acknowledged to be the better ir-acceptor ligand. The asymmetry of the tungsten-allyl linkage.persists i n solution, as evidenced by the lE and 1 3C NMR spectra of the complex (Figure 3 and Table V I I I ) . The 1 3 C NMR spectrum exhibits resonances due to three inequivalent a l l y l carbon atoms which can be assigned on the basis of t h e i r chemical s h i f t s . The/resonance attributable to C(l) has a chemical s h i f t which resembles those c h a r a c t e r i s t i c of ca. sp 3-hybridized carbon atoms i n transition-metal a l k y l s , while the - 52 -C(2) and C(3) resonances occur at lower f i e l d i n the region-expected for ca. sp 2 carbon atoms bonded to t r a n s i t i o n m e t a l s . 4 2 Consistent with the tungsten-allyl bonding depicted on page 51, the lE NMR spectrum confirms that the hydrogen' atoms bonded to C(l) and C(3) are i n d i f f e r e n t environments, the chemical s h i f t s of the l a t t e r r e f l e c t i n g t h e i r predominantly v i n y l i c character. The observed AGMRX pattern for the a l l y l ligand contrasts with the A 2M 2X pattern displayed by the symmetric n 3-C^H^ group of CpW (CO) 2 (n 3-C3H,-) . 55 Assignments of the resonances to in d i v i d u a l protons have been made on the basis of coupling constants and on the assumption that the endo conformer i s the p r i n c i p a l species i n solution. The indicated assignments and coupling constants have been sup-. ported by a series of homonuclear decoupling experiments. The lE and 1 3 C NMR spectra also indicate the presence i n solution of another isomer of CpW(NO)(n3-C3H,-)I, presumably the exo conformer, but the resonances are not s u f f i c i e n t l y well re-solved to permit detailed assignments. The observed r a t i o of endo/exo conformers i s c.a. 7/1. I t i s possible to prepare CpW (NO) (n3-C3H,-)I by another route. The treatment of CpW(CO) 2(n 3-C 3H 5) with NOPFg f o l -lowed by Nal re s u l t s i n the i s o l a t i o n of CpW(NO)(n 3-C3H,_) I. This sequence of reactions probably proceeds through the previously unknown cation [CpW(CO) (NO) (n C-^H^)] , i . e . , CpW(CO) 2 (n 3-C 3H 5) + NOPFg £H 3CN > (24) - 53 -Figure 3. 270 MHz 1E FT-NMR spectrum i n the a l l y l region of CpW(NO) (n3-C^H,-) I i n CDC1-. Table VIII. lE and 1 3C NMR Spectral Data for the Endo Isomer of CpW(NO) (n3-C-.H[_) I . a 1E NMR Data b Cp H l l H12 H21 H31 H32 65.96 62.08 62.90 65.44 63.92 64.53 J(l l - 2 1 ) 10.1 J(12-21) 6.6 J(31-21) 14.3 J(32-21) 7.3 J(l l - 1 2 ) 2.6 J(12-32) 3.8 J(31-ll) 1.8 J ( 3 2 - l l ) 1.0 J(31-32) 1.0 1 3C NMR Data Gp _^1 S S 699.84 637.52 6111.13 676.47 3i The solvent was CDCl^, and the chemical s h i f t s are accurate to + 0.01 ppm. k Coupling constants are i n Hz; those involving are accurate to + 0.1 Hz, whereas the other havererrors of ca, + 0.5 Hz. - 56 -[CpW(CO)(NO) ( n 3-C 0H c)]PF^ + CO [CpW(CO) (NO) (n 3-C 3H 5) ]PF g + Nal ™3CM » (25) CpW(NO) ( n 3-C 3H 5)I + NaPFg. During the course of reaction (24) the IR absorptions due to the reactant (v(CO) 1934, 1844 cm"1) are replaced by a new set of carbonyl and n i t r o s y l absorptions (v(CO) 2135, v(NO) 1714 cm" 1). These i n turn are slowly replaced during reaction (25) by a single absorption i n the n i t r o s y l region (v(NO): 1636 cm" 1). After the completion of t h i s work, i t was learned that a similar scheme has been used to prepare the series of complexes CpMo(NO)(n 3-allyl)X [X=NCO, CN or I; a l l y l = C 3 H 5 or C ^ ] . 5 6 CpMo (NO) (n 3-C3H<-) I can be prepared by a route s i m i l a r to reaction (22) u t i l i z i n g [CpMo (NO) I 2] 2 -k i . e . , [CpMo(NO)I 2] 2 | g^3-5U > 2CpMo(N0) ( n 3 - C 3 H 5 ) I . (26) The physical properties of CpMo (NO) (n 3-C3Hj.) I are similar to those displayed by the tungsten analogue. The orange-brown diamagnetic s o l i d dissolves i n polar solvents to give solutions that decompose only slowly i n a i r . The solution IR spectrum (CH 2C1 2) displays the expected strong terminal n i t r o s y l absorption (1658 cm" 1). The mass spectrum (Table IX) consists of peaks assignable to sequential loss of ligands from the parent ion. Its lE (Figure 4) and 1 3 C NMR spectra - 57 -Table IX. Mass Spectral Data for CpMo (NO) (n 3-C3Hc.) i a m/z Rel abund Assignment 361 100 CpMo(NO)( n 3-C 3H 331 55 CpMo (ji2-C,H_) I + 290 64 CpMoI+ 264 18 (C 3H 3)MoI + 234 21 CpMo(NO) ( n 3-C 3H 163 24 CpMo+ The assignments involve the most abundant naturally occurring isotopes i n each fragment and include a l l fragments containing Mo. - 58 -Figure 4. 27 0 MHz 1H FT-NMR spectrum i n the a l l y l region of CpMo (NO) (n3-C,H,-) I i n CDC1,. - 59 -- .60 -indicate that the a l l y l ligand i n t h i s complex also exhibits, a s i g n i f i c a n t O-TT d i s t o r t i o n . The 1 3C spectrum (in CDCl^) exhibits a single resonance due to the cyclopentadienyl carbon atoms (101.29) and a separate resonance (112.14, 81.24 and 45.29) for each of the a l l y l carbon atoms (C(2), C(3) and C(l) r e s p e c t i v e l y ) . The asymmetry of the a l l y l ligand has been confirmed by a s t r u c t u r a l determination and f u l l analysis of the proton magnetic resonance spectrum. 5 6 The recently reported 1H NMR spectra of the complexes CpMo(n3-a l l y l ester)(CO)(PPh^) also indicate d i s t o r t i o n of the a l l y l l i g a n d s . 5 7 I t thus appears that d i s t o r t i o n s may well be a general feature of a l l y l ligands attached to metal centres having el e c t r o n i c asymmetry. Attempts to reduce the W-I bond of CpW(NO)(n 3-C 3H 5)I have so f a r been unsuccessful. Treatment of the compound with either Li(HBEt^) or Na[H 2A1(OCH 2CH 2OCH 3) 2] at -78°C does not r e s u l t i n the formation of any new n i t r o s y l containing species. A possible reason i s that the hydride reagents p r e f e r e n t i a l l y attack a portion of the molecule other than the W-I bond. Recently, reduction of n i t r o s y l ligands by these reagents have been observed. 5 8 F i n a l l y , conversion of the a l l y l ligand of CpW(NO)(n 3-C 3H 5)I to an n 1 configuration does not appear to be a f a c i l e process as evidenced by the lack of a reaction with PPh 3 i n refluxing benzene. - 61 -REFERENCES (1) For example see Pino, P.; Wender, I. "Organic Synthesis v i a Metal Carbonyls", Vol. I; Wiley: New York, 1968; Vol. II; Wiley: New York, 1977. (2) a) Pierpoint, C.G.; Van Derveer, D.G.; Durland, W.; Eisenberg, R. J. Am Chem. Soc. 1970, 92, 4760. b) G r i f f i t h s , W.P. Adv. Organomet. Chem. 19 68, 7, 211. (3) Kolthammer, B.W.S. Ph.D. Thesis, University of B r i t i s h Columbia, 1979. (4) L'Eplattenier, F.; Calderazzo, F. Inorg. Chem. 19 67, 6j_ 2092. (5) T r e i c h e l , P.M.; Shubkin, R.L. Inorg. Chem. 1967, 6, 1328. (6) Brintzinger, H. J. Am. Chem. Soc. 1966, 88, 4305. (7) Stewart, R.P.,Jr.; Okamoto, N.; Graham, W.A.G. J.  Organomet. Chem. 1972, 42, C32. (8) Green,-M.L.H.; McCleverty, J.A.; Pratt, L.; Wilkinson, G. J. Chem. Soc. 1961, 4854. (9) Deeming, A.G.; Shaw, B.L. J . Chem. Soc. A. 197 0, 3356. (10) Legzdins, P.; Malito, J.T. Inorg. Chem. 197 5, 14, 1875. (11) Kolthammer, B.W.S.; Legzdins, P.; Malito, J.T. Inorg.  Chem. 1977, 16, 3173. (12) Hoyano, J.K.; Legzdins, P.; Malito, J.T. Inorg.  Synth. 1978, 18, 126. (13) Perrin, D.D.; Aremego, W.L.F.; Perrin, D.R. " P u r i f i -cation of Laboratory Chemicals"; Pergammon Press: Oxford, 1966. (14) Shriver, D.F. "The Manipulation of Air-S e n s i t i v e Compounds"; McGraw-Hill: New York, 1969. (15) Purchased from the Al d r i c h Chemical Co. as a 70% - 62 -benzene solution under the trade name Red-al. (16) Stewart, R.P.,Jr.; Moore, G.T. Inorg. Chem. 1975, 14, 2699. (17) Kolthammer, B.W.S.; Legzdins, P.; Malito, J.T. Inorg. Synth. 1979, 19, 208. (18) Olah, G.A.; Svoboda, J.J.; Olah, J.A. Synthesis 1972, 544. (19) a) Gilmont, P.; Blanchard, A.A. Inorg. Synth. 1946, 2,238. (b) Edgell, W.F.; Lyford, J. Inorg. Chem. 1970, 9, 1932. (20) King, R.B. "Organometallic Syntheses"; Academic Press: New York, 1965; Vol. 1, 168-9. (21) Ibid, 156-8. (22) Barnett, K.W.; Slocum, D.W. J . Organomet. Chem. 197 2,  44, 1.' • / (23) King, R.B.; Bisnette, M.B. J. Am. Chem. Soc. 1963,  85, 2527; Inorg. Chem. 1964, 3, 791. (24) Cf. the thermal dimerization of CpCr(CO) 3H: Piper, T.S.; Wilkinson, G. J. Inorg. Nucl. Chem. 1956, 3_j_ 104. (25) For the f i r s t such adduct to be characterized see: McNeese, T.J.; Wieford, S.S.; Foxman, B.M. J. Chem.  Soc. Chem. Commun. 197 8, 500,.' (26) Greenhough, T.J.; Kolthammer, B.W.S.; Legzdins, P.; Trotter, J. Inorg. Chem., submitted for publication. (27) F a l l e r , J.W.; Anderson, A.S.; Chen, C.C. J. Chem.  Soc. D. 1969, 719. (28) ... See for example, (a) Kaesz, H.D.; S a i l l a n t , R.B. Chem. Rev. 197 2, 72, 231 and references therein; (b) Shunn, R.A. i n "The Hydrogen Series", Vol. 1, Muetterties, E.L. Ed., Marcel Dekker, Inc., New York, 1971, 203-69. (29) Bercaw, J.E. Adv. Chem. Ser. 1978, 167, 136 and references therein. (30) Labinger, J.A. Adv. Chem. Ser. 1978, 167, 11. - 63 -(31) Hoyano, J.K.; Legzdins, P.; Malito, J.T. J. Chem.  S o c , Dalton Trans. 1975, 1022. (32) Green, M.L.H.; Street, C.N.; Wilkinson, G. Z. Natur- forsch. 1959, 14b, 1595. (33) Davison, A.; McCleverty, J.A.; Wilkinson, G. J. Chem.  Soc. 1963, 1133. (34) Kinney, R.J.; Jones, W.W.; Bergman, R.G. J. Am. Chem.  Soc. 1978, 100, 7902. (35) Braunstein, P.; Dehand, J.; Munehenbach, B. J.. Organ- omet. Chem. 1977, 124, 71. (36) Casey, CP.; Andrews, M.A. ; Rinz, J.E. J. Am. Chem.  Soc. 1979, 101, 7 41 and references therein. (37) McCleverty, J.A.; Seddon, D. J. Chem. Soc., Dalton  Trans., 197 2, 2526. (38) King, R.B. Inorg. Chem. 19 67, 6, 30. (39) James, T.A.; McCleverty, J.A. J. Chem. Soc. (A),  1971, 1596. (40) King, R.B. Inorg. Chem. 1968, 7, 90. 141) Tolman, CA. J. Am. Chem. Soc. 1970, 92, 2953. (42) Mann, B.E. Adv. Organomet. Chem. 1974, 12, 135. (43) Brunner, H. J. Organomet. Chem. 1969, 16, 119. (44) .-Calderon., J.L. ;. Cotton, F.A. J. Organomet. Ghent. 1971, 30, 377. (45) a) Hunt, M.M.; Kita, G.W.; Mann, B.E.; McCleverty, J.A. J. Chem. S o c , Dalton Trans. 1978, 467 . b) Hunt, M.M. ; Kita, W.G.; McCleverty, J.A. J. Chem. S o c , Dalton  Trans.1978, 474. c) Hunt, M.M.; McCleverty,J.A. J.  Chem. S o c , Dalton Trans. 1978, 480. (46) King, R.B. In "The Organic Chemistry of Iron"; Koerner von Gustorf, E.A.; Grevels, F.W.; F i s c h l e r , I., Ed.; Academic Press: New York, 1978, 482-5. (47) Candlin, J.P.; Janes, W.H. J. Chem. Soc. (C) 1968, 1856. - 64 -(48) a) Schoonover, M.W.; Eisenberg, R. J. Am. Chem. Soc.  1977, 99, 8371. (b) Schoonover, M.W. ; Kubiak, CP.; Eisenberg, R. Inorg. Chem. 1978, 17, 3050. (49) a) F a l l e r , J.W.; Rosan, A.M.: J.Am. Chem. Soc. 1976,  98, 3388. b) Adams, R.D.; Chodosh, D.F.; F a l l e r , J.W.; Rosan, A.M. J. Am. Chem. Soc. 1979, 101, 2570. (50) Bailey, N.A.; Kita, W.G.; McCleverty, J.A.; Murray, A.J.; Mann, B.E.; Walker, N.W.J. J. Chem. S o c , Chem.  Commun. 1974, 592. (51) Cousins, M.; Green, M.L.H. J. Chem. Soc. 1963, 889. (52) Purchased from the A l d r i c h Chemical Co. under the trade name Super-Hydride. (53) Greenhough, T.J.; Legzdins, P.; Martin, D.T.; Trotter, J. Inorg. Chem., submitted for publication. (54) Pauling, L. "The Nature of the Chemical Bond", 3rd ed.; Cornell University Press: Ithaca, N.Y., 1960; 232-9. (55) F a l l e r , J.W.; Chen, C.C.; Mattina, M.J.; Jakubowski, A. J. Organomet. Chem. 1973, 52, 361. (56) F a l l e r , J.W. personal communication. (57) C o l l i n , J.; Charrier, C ; Pouet, M.J.; Cadiot, P.; Roustan, J.L. J. Organomet. Chem. 1979, 168, 321. (58) Hames, B.W.; Legzdins, P. unpublished observations. 

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