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Studies on transition metal nitrosyl chemistry Malito, John T. 1976

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STUDIES ON TRANSITION METAL NITROSYL CHEMISTRY by JOHN T. MALITO B.Sc. (Hons.) Univers i ty of B r i t i s h Columbia, 1972. A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in the Department of Chemistry We accept th is thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA August, 1976 (3 John T. Mal i to , 1976 In p r e s e n t i n g t h i s t h e s i s in p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s f o r an advanced degree at 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 , I a g r e e that the 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 and s t u d y . I f u r t h e r agree 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 the Head o f my Department o r by h i s r e p r e s e n t a t i v e s . It i s u n d e r s t o o d tha 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 not 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 . Department o f The U n i v e r s i t y o f B r i t i s h Co lumbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 6 - i i -ABSTRACT The react ions of .n i t rosy l ch lor ide with a var ie ty of anionic and neutral metal carbonyl and n 5-cyclopentadienylmetal carbonyl compounds of Cr , Mo, W, Mn, Re, Fe and Co are descr ibed. In most cases n i t rosy l -con ta in ing complexes are formed in reasonable y i e l d s . The advantages and l im i ta t ions of n i t rosy l ch lor ide as a general synthet ic reagent fo r the preparation of t rans i t i on metal n i t rosy l complexes are discussed. The high y i e l d syntheses of CpM(C0)2(N0) (M = Cr , Mo or W) from NaCCpMCCO)^] and Diazald are de ta i l ed . Subsequent react ion of the d icarbony ln i t rosy l species with n i t rosy l ch lor ide affords the corresponding CpM(N0)2Cl complexes in exce l lent y i e l d s . The CpM(N0)2R (M = Cr or Mo; R = Me, E t , i-Bu or Ph: M = W; R = Me or-Ph) complexes are obtained in the react ions of CpM(N0)2Cl with a l k y l - or arylaluminum reagents. Some fur ther der ivat ives of the CpM(N0)2Cl complexes and the high y i e l d preparation of [CpCr(N0) 2 ] 2 are also descr ibed. Previously unreported compounds are character ized by in f rared and nuclear magnetic resonance spectroscopy and by mass spectrometry. ACKNOWLEDGEMENT I wish to thank the technical s ta f f and facu l ty of t h i s department for the i r assistance and support. In p a r t i c u l a r , I am indebted to Dr. B.R. James, Dr. R. Stewart and Dr. A. Storr who read th is thesis and made suggestions for improvement. A l s o , the aid and thoughtful d iscussion offered by Dr. A . E . Crease and Mr. B.W.S. Kolthammer are great ly appreciated. I a lso thank Miss L. Hon who typed th is t hes i s . I extend my grat i tude to Dr. P. Legzdins, whose unshakable optimism, sp i r i t ed humor and companionship provided both encouragement and guidance. - i v -TABLE OF CONTENTS Page ABSTRACT i i ACKNOWLEDGEMENTS i i i TABLE OF CONTENTS i v LIST OF TABLES vi i i LIST OF FIGURES i x ABBREVIATIONS AND COMMON NAMES x CHAPTER I, GENERAL INTRODUCTION 1 CHAPTER I I , THE REACTION OF NITROSYL CHLORIDE WITH SOME TRANSITION METAL CARBONYL ANIONS 4 2.1 INTRODUCTION 4 2.2 EXPERIMENTAL 5 2.2a Preparation of n i t rosy l ch lor ide 6 2.2b Preparation of bis(tr iphenylphosphine)iminium ch lo r i de , bromide and iod ide , (PPh 3) 2NX (X = C l , Br or I) 8 2.2c Preparation of bis(tr iphenylphosphine)iminium pentacarbonylhalotungstates, (PPh-)9NW(CO)r-X (X = C l , Br or I) f . t 11 2.2d Reactions of n i t rosy l ch lor ide with some anionic and neutral complexex of manganese, rhenium and i ron 13 2.2e Reactions of n i t rosy l ch lor ide with t r i ca rbony l -(n 5-cyclopentadienyl) anions of chromium, molybdenum and tungsten, [CpM(C0)o]~ (M = Cr , Mo or W) 15 2.2f Reaction of sodium n i t r i t e and ace t i c ac id with sodium t r icarbony l (n 5 -cyc lopentad ieny l ) tungsta te , Na[CpW(C0)3] 15 - v -Page 2.2g Reactions of n i t rosy l ch lor ide with b i s ( t r i pheny l -phosphine)iminium pentacarbonylhalotungstates, (PPh3)2NW(C0)5X (X = C l , Br or I ) , and with t e t r a -ethylammonium pentacarbonylchloro(or methyl) tungstate, Et4NW(C0)5X (X = Cl or Me) 16 2.2h Reactions of te t racarbonylhaloni t rosy l tungstens, W(C0)4(N0)X (X = Cl or Br) ,wi th tetrahydrofuran . . . 16 2.3 RESULTS AND DISCUSSION 18 2.3a Bis(tr iphenylphosphine)iminium ch lo r i de , bromide or iod ide , (PPh 3) 2NX (X = C l , Br or I) 18 2.3b Bis(triphenylphosphine)irninium pentacarbonylhalo-tungstates, (PPh 3) 2NW(C0) 5X (X = C l , Br or I) 20 2.3c Reactions of n i t rosy l ch lor ide with metal carbonyl anions 22 2.3d Reactions of te t racarbonylhaloni t rosy l tungstens, W(C0)4(N0)X (X = Cl or B r ) , with tet rahydrofuran. . 30 CHAPTER I I I , REACTIONS OF NITROSYL CHLORIDE WITH NEUTRAL METAL CARBONYL COMPLEXES - 32 3.1 INTRODUCTION 32 3.2 EXPERIMENTAL 35 Reactions of n i t rosy l ch lor ide with neutral complexes of i ron and cobalt 35 3.3 RESULTS AND DISCUSSION 37 3.3a Reactions of n i t rosy l ch lor ide with pentacarbonyl-i r o n , Fe(C0) 5 37 3.3b Reaction of n i t rosy l ch lor ide with b is [d icarbony l -(n 5 -cyc lopentad ieny l ) i ron ] , [CpFe(C0) 2 ] 2 39. 3.3c Reactions of n i t rosy l ch lor ide with t r i ca rbony l -n i t r osy l coba l t , Co(C0)3(N0), and d ica rbony l (n 5 -cyc lopentadienyl )cobal t , CpCo(C0) 9 40 - vi -Page CHAPTER IV, CYCLOPENTADIENYLNITROSYL COMPLEXES OF CHROMIUM, MOLYBDENUM AND TUNGSTEN 42 4.1 INTRODUCTION 42 4.2 EXPERIMENTAL 46 4.2a Preparation of d icarbony l (n 5 -cyc lopentad ieny l ) -n i t rosy l complexes of chromium, molybdenum and tungsten, CpM(CO)2(NO) (M.= C r , Mo or W) 46 4.2b Preparation of ch lo ro (n 5 - cyc lopen tad ieny l )d in i t r osy l complexes of chromium, molybdenum and tungsten, CpM(N0)2Cl (M = C r , Mo or w) 48 4.2c Preparation of (n 5 -cyc lopentad ieny l ) iodod in i t rosy l complexes of chromium, molybdenum and tungsten, CpM(N0)2I (M = Cr , Mo or W) 50 4.2d Preparation of b is [ (n 5 -cyc lopentadienyl )ethoxo-nitrosylchromium], [CpCr(NO)(0Et)] 2 50 4.2e Preparation of b is [ch lo ro (n 5 -cyc lopentad ieny l ) -ni trosylchromium], [CpCr(N0)Cl] 2 51 4.2f Preparation of a l k y l - and a ry l - (n 5 - cyc lopen tad ieny l ) -d i n i t r osy l complexes of chromium, molybdenum and tungsten, CpM(N0)9R (M = C r , Mo or W; R = a lky l or a ry l ) 52 4.2g Preparation of b i s [ (n 5 - cyc lopen tad ieny l )d in i t r osy l -chromium], [CpCr(N0) 2 ] 2 55 4.3 RESULTS AND DISCUSSION 58 4.3a The d icarbony l (n 5 -cyc lopentad ieny l )n i t rosy l complexes of chromium, molybdenum and tungsten, CpM(C0)~(N0) (M = Cr , Mo and W) 7 58 4.3b The ch loro (n 5 -cyc lopentad ieny l )d in i t rosy l complexes of chromium, molybdenum and tunqsten, CpM(N0)9Cl (M = C r , Mo or W) 7 59 4.3c Bis[(n 5-cyclopentadienyl )ethoxonitrosylchromium, [CpCr(NO)(0Et)]2, and b is [ch lo ro (n 5 -cyc lopentad ieny l ) -nitrosylchromium, [CpCr(N0)Cl] 9 66 - v i i -Page 4.3d The a l k y l - and a ry l - (n 5 - cyc lopen tad ieny l )d in i t rosy l complexes of chromium, molybdenum and tungsten, CpM(N0)2R (M = Cr , Mo or W; R = a lky l or a ry l ) 70 4.3e Bis [ (n 5 -cyc lopentadieny l )d in i t rosy lchromium, [CpCr(N0) 2 ] 2 78 CHAPTER V, CONCLUSION 83 - vi i i -LIST OF TABLES Table Page I Elemental Analyses and Physical Propert ies of (PPh 3) 2NW(C0) 5X (X = C l , Br or I) 12 II Reactions of Ni t rosy l Chlor ide with some Complexes of Rhenium and Iron 14 III Reactions of Ni t rosy l Chlor ide with (PPh3)2NW(C0)rX (X = C l , Br or I) and Et4NW(C0) 5X (X = Cl or C H 3 r . . . 17 IV Reactions of Ni t rosy l Chlor ide with some Neutral Complexes of Iron and Cobalt 36 V Elemental Analyses and Physical Propert ies of CpM(N0)2X (M = Cr , Mo or W; X = Cl or I) 49 VI Reaction Condit ions and Pu r i f i ca t i on Methods for CpM(N0)2R 53 VII Elemental Analyses and Physical Propert ies of CpM(N0)2R 56 VIII IR and ] H NMR Data for CpM(N0)2R Complexes 57 IX High Resolut ion Mass Spectral Data for CpCr(N0) 2Cl 63 X Low Resolut ion Mass Soectral Data fo r CpM(N0)9Cl (M = Mo or W) 7 64 XI Low Resolution Mass Spectral Data for [CpCr(N0)X] 2 •• 69 XII Mass Spectra Fragmentation Data for CpM(N0)2R 74 XIII Low Resolution Mass Spectral Data for [CpCr(NO),], . . 81 - i x -LIST OF FIGURES F l > r e Page 1. Apparatus for Pur i fy ing N i t rosy l Chlor ide 7 2. ] H NMR of (n 5 -C 5 H 5 )Mo(N0) 2 CH 2 CH 3 72 - X -ABBREVIATIONS AND COMMON NAMES The fol lowing abbreviat ions and common names, some of which are presently used in the s c i e n t i f i c l i t e r a t u r e , are employed throughout th is t hes i s . o A A1R 3 Amt. Bu n-Bu 20 ca lcd . cm compd. Cp dec. Diazald diglyme DME Et EtpO EtOAc EtOH h Hz IR J 3 ,4 - lu t i d ine m Me m/e min. mm Angstrom t r i a l k y l ( o r aryl)aluminum amount butyl d i -n-buty l ether cal culated wave numbers in rec iproca l centimeters compound pentahapto-cyclopentadienyl, n 5-CgHg decomposes N-methyl-N-nitroso-p-toluenesulfonami de bis(2-methoxyethyl)ether 1,2-dimethoxyethane ethyl d ie thy l ether ethyl acetate ethanol hour(s) Herz, cycles per second in f rared magnetic resonance coupling constant in cyc les per second 3,4-dimethyl pyr id ine medium methyl mass to charge ra t i o minute(s) mi l l imeters of mercury - x i -abbreviat ions and common names (cont 'd) NMR : nuclear magnetic resonance 4 -p ico l ine : 4-methylpyridine Ph : phenyl PPh.j : tr iphenylphosphine pz - : pyrazoyl R : a l ky l or aryl R.p : perf luoroal kyl s : strong Temp. : temperature THF : tetrahydrofuran w : weak n 3 : t r ihap to-n 5 : pentahapto-v : s t retching frequency T : NMR chemical sh i f t in parts per m i l l i on - 1 -CHAPTER I GENERAL INTRODUCTION Numerous t rans i t i on metal n i t rosy l compounds are known and the development of the i r chemistry, which has been the subject of several reviews (1, 2, 3 ) , has c lose ly para l le led that of the metal carbonyl complexes. Consequently, i t has been recognized for some time that n i t r i c oxide can bond to metals in a manner quite d i f f e ren t from carbon monoxide. The structuresof a number of n i t rosy l compounds (4) s t r i k i n g l y demonstrate the var iab le nature of the meta l -n i t rosy l bond, which has a lso received considerable at tent ion from a theore t ica l point of view (5). In pa r t i cu l a r , two bonding modes have been observed which are best represented by the Lewis structures I and I I . Structure I i s character ized by a l i near M-N-0 bond and an M-N bond distance which M = N = 0 M - _ N i n strongly suggests the existence of mul t ip le bond character . In th is instance the n i t r i c oxide l igand formal ly behaves as a three-electron donor. This type of bonding i s by far the most common among the complexes studied to date. In structure II the n i t rosy l group formal ly acts as - 2 -a one-electron donor and the M-N-0 bond angle i s 120°. Although the M-N bond i s longer than in the l i nea r bonding mode, i t i s s t i l l somewhat shorter than the expected s ing le M-N a-bond d is tance. While both of these l im i t i ng structures have been observed, most of the complexes have M-N-0 bond angles which range from 120° to 180°. The use of metal n i t rosy l complexes as. spec i f i c homogeneous ca ta lys ts has generated much recent i n te res t . For example, Fe(C0) 2 (N0) 2 c a t a l y t i c a l l y dimerizes butadiene to 4 -v iny lcyc lohex- l -ene , and isoprene to a mixture of 1 ,4-d imethy l -4-v iny l - and 1,5-d imethyl -5-v iny lcyclohex-1-ene (6). In te res t ing ly , both of these dimerizat ions occur even in the presence of other o l e f i n s , Lewis ac i ds , or Lewis bases. Furthermore, the Rh(NO)(PPh^)^ complex has been found to c a t a l y t i c a l l y hydrogenate both terminal and c y c l i c o le f i ns under ambient condit ions (7). I f t h i s hydrogenation i s performed in the absence of peroxides or 0 2 , accompanying o l e f i n isomerizat ion does not occur and the ca ta lys t may be recovered unchanged. Metal n i t rosy l complexes f ind the i r greatest app l ica t ion in the f i e l d of o l e f i n d i s p r o p o r t i o n a t e (8). Most commonly used are the M(N0) 2 X 2 L 2 (M = Mo or W; X = C l , Br or I; L = phosphines, phosphites, arsines and amines) complexes in conjunction with an organoaluminum cocata lyst such as M e 3 A l 2 C l 3 or A l C l 3 . Bearing in mind the in te res t ing bonding, s t r u c t u r a l , c a t a l y t i c and r e a c t i v i t y propert ies of metal n i t rosy l complexes, the development of new synthet ic routes to these compounds must surely be welcomed. A - 3 -perusal of a review a r t i c l e (9) which deals exc lus ive ly with the preparation of metal n i t rosy l compounds reveals the obvious lack of a general preparative route. This fac t in i t s e l f i s not surpr is ing since a large var ie ty of metals i s encompassed. Unfortunately, many of the ex is t i ng synthet ic routes produce the desired product in low y i e l d and/or with much expenditure of e f f o r t . The work in th i s thes is i s presented in the s p i r i t of developing new synthet ic techniques which, in addi t ion to y i e ld ing ex is t ing compounds more convenient ly , may also be appl ied to the synthesis of new metal n i t rosy l complexes. The studies presented in Chapter II and III are exploratory in nature. For instance, the scope of the react ion of n i t rosy l ch lor ide with a var ie ty of anionic and neutral organometal1ic complexes i s ou t l i ned . Chapter IV describes in de ta i l the successful app l i c t ion of th is and other synthet ic methods during the preparation of a var ie ty of ha lo - , a l k y l -and a ry l - (n 5 - cyc lopen tad ieny l )n i t rosy l complexes of chromium, molybdenum and tungsten. - 4 -CHAPTER II THE REACTION OF NITROSYL CHLORIDE WITH SOME TRANSITION METAL CARBONYL ANIONS 2.1 Introduction The f i r s t and only reported react ion of n i t rosy l ch lor ide with a t rans i t i on metal carbonyl anion involves the synthesis of (RB(pz) 3 )M(C0) 2 (N0) from [ (RB(pz) 3 )M(C0) 3 ]~ (RB(pz)3= t r i s (py razoy l ) -borate; R = H or pz; M = Cr , Mo or W) (10). In sp i te of the large number of read i l y obtainable metal carbonyl anions (11), th i s type of react ion has been completely ignored. A study to determine the extent to which n i t rosy l ch lor ide can be employed as a general reagent for the synthesis of neutral n i t rosy l complexes, from the corresponding carbonyl anions, was therefore undertaken. The genera l i ty of t h i s synthet ic approach as well as i t s l i m i t a t i o n s , are herein c l e a r l y de l ineated. In many instances, th is new route affords the desired n i t rosy l complexes more conveniently and in higher y i e l ds than was previously poss ib le . Furthermore, the need for organometal l ic anions which are soluble in non-donor solvents has l e d , during the course of th i s work, to the e f f i c i e n t and high y i e l d synthesis of (PPh 3) 2NX and (PPh 3) 2NW(C0) 5X (X = C l , Br or I ) . - 5 -S p e c i f i c a l l y , th is chapter describes the react ions of n i t rosy l ch lor ide with the fo l lowing species: (PPh 3 ) 2 NMn(C0) 5 , Na[Re(C0) 5 ] , Ph 3 SnRe(C0) 5 , Na 2 [Fe(C0) 4 ] , Na[CpFe(C0) 2 ] , CpFe(CO) 2SnPh 3 , Na[CpM(C0)3] (M = Cr , Mo or W) and A[W(C0)5X] (A = (PPh 3 ) 2 N; X = C l , Br or I: A = Et^N; X = Cl or Me). The chemical and physical propert ies of the products in the above react ions are considered where appropr iate. 2.2 Experimental A l l chemicals used were of reagent grade or comparable pur i ty and were e i ther purchased from commercial suppl iers or prepared according to reported procedures. Their pur i ty was ascertained from elemental analyses and/or melting point determinations. The uncorrected melting points were taken in c a p i l l a r i e s in a i r or under prepur i f ied nitrogen using a Gallenkamp Melt ing Point Apparatus. A l l solvents were dr ied according to known methods (12) and thoroughly purged with prepur i f ied nitrogen pr io r to use. A l l manipulat ions, unless otherwise s ta ted , were performed on the bench (using conventional techniques for handling a i r sens i t i ve compounds (13)) or in a Vacuum Atmospheres Corporation Dri-Lab model HE-43-2 dry box f i l l e d with prepur i f ied ni t rogen. Infrared spectra were recorded on Perkin Elmer 457 or 71 OA spectrophotometers and ca l ib ra ted with the 1601 cm" 1 absorption band of a polystyrene f i l m . Proton magnetic resonance spectra were recorded on a Varian Associates T-60 spectrometer using tetramethylsi 1ane as an - 6 -in ternal standard. The low-resolut ion mass spectra were taken at 70 eV on an At las CH4B spectrometer and the h igh-reso lu t ion mass spectrum was obtained on an Associated E l e c t r i c a l Industr ies MS902 spectro-meter with the assistance of Dr. G. Eigendorf and Mr. G. Gunn. Elemental analyses were performed by Mr. P. Borda of th i s Department. Two reagents used frequent ly throughout th is work were n i t rosy l ch lor ide (C1N0) and the bis(tr iphenylphosphine)iminium hal ides ((PPhg^NX; X = C l , Br or I ) . Their syntheses are described below. 2.2a Preparation of n i t rosy l ch lor ide. N i t rosy l ch lor ide was prepared in the fo l lowing manner, the procedure employed being a modi f icat ion of an e a r l i e r report (14). A 100 ml three-necked f l ask was equipped with a nitrogen i n l e t , a dropping funnel and a drying tower (2 x 20 cm) packed from top to bottom with equal volumes of anhydrous CaClp, KCI and NaN02- The top of the tower was f i t t e d with a 5 ml graduated cold trap equipped with a stopcock on the trap i n l e t , as shown in Figure 1 [ClNO is a highly corros ive substance which necessi tates the use of apparatus constructed exc lus ive ly from g l a s s ] . The trap out le t was connected to a 100 ml two-necked f lask equipped with a nitrogen i n l e t secured with a s i l i c a -gel drying tube. Af ter f lushing the ent i re apparatus with n i t rogen, the react ion f lask was charged with concentrated aqueous HC1 (32 ml). An aqueous so lu t ion (10 ml) of NaNOp (5.54 g) was added dropwise to the rap id ly s t i r r e d ac id so lu t ion at room temperature. The gaseous C1N0 which formed ins tan t l y was car r ied by a slow stream of N 7 (ca. 20 ml min ) FIG 1 A P P A R A T U S FOR P U R I F Y I N G N I T R O S Y L C H L O R I D E - 8 -into the cold trap held at -78°C. In th is manner, 2.5 ml (50 mmol) of ClNO were generated. This was d i s t i l l e d under vacuum in to the 100 ml f lask and 50 ml of CH 2 CT 2 , THF or Et^O were added to the cold ClNO to y i e l d deep red solut ions which were found to be thermally stable at 20°C. The chemical and physical propert ies of C1N0 have been extensively described (15). A l l subsequent react ions invo lv ing C1N0 were performed by the dropwise addi t ion of one of these solut ions to the appropriate react ion mixture while monitoring the course of the react ion by in f rared spectroscopy. 2.2b Preparation of bis(tr iphenylphosphine)iminium ch lo r i de , bromide  and iod ide , ( P P h J J l X (X = C l , Br or I ) . The compounds ( P P h ^ N X (X = C l , Br or I) were synthesized according to a modi f icat ion of a published procedure (16). 2.2bl Preparation of (PPhJpNCl. A three-necked 300 ml f lask was equipped with a nitrogen i n l e t , a gas i n l e t , a magnetic s t i r r e r and a Dry- ice re f lux condenser secured with a s i l i c a gel drying tube. The f lask was charged with PPh 3 (76.8 g, 293 mmol; Matheson Coleman and Be l l ) and 1 ,1 ,2 ,2 - te t ra -chloroethane (100 ml ; Fisher reagent). The resul tant so lut ion was cooled to -78° in a Dry- ice- isopropanol bath and ch lor ine (14.2 g , 200 mmol; Matheson of Canada) was bubbled through the react ion mixture _ 9 -over a period of 10 min. The gas i n l e t was replaced with a stopper and the Dry- ice condenser with a water-cooled re f lux condenser. NHpOH-HCl (6.9 g , 100 mmol; Mal l inckrodt ana ly t i ca l reagent grade) was added and the mixture was allowed to warm to room temperature. F i n a l l y , the react ion mixture was heated under re f lux un t i l the evolut ion of HCl(g) ceased (about 6 h) and then was allowed to cool to room temperature. [Subsequent manipulations were performed in a i r . ] The orange solut ion was poured into EtOAc (400 ml) whereupon a large quanti ty of tan c rys ta ls formed over a period of 18 h. The c rys ta l s were co l lec ted by suction f i l t r a t i o n , recrys ta l1 ized from bo i l ing water and dried in a vacuum des iccator . The s o l i d was d issolved in CH 2 C1 2 (260 ml) and E t 2 0 (500 ml) was added, thereby producing the white c r y s t a l l i n e product which was co l lec ted by suct ion f i l t r a t i o n . Final drying in vacuo (5 x 10 mm) at 125°C for 70 h afforded 49.1 g (85.5 mmol, 85% y ie l d ) of (PPh 3 ) 2 NCl . Ana l . Calcd. for [P (C 6 H 5 ) 3 ] 2 NC1: C, 75.32; H, 5.27; N, 2.44. Found: C, 75.56; H, 5.42; N, 2.22. m.p. (under N 2 ) : 275.5-276.5°C. Proton NMR, r ( i n CDC1 3), - C ^ : 2.33(m). 2.2b2 Preparation of (PPh-J^NBr. The (PPh 3) 2NBr was prepared in a manner comparable to that described above for (PPh ) 2NC1. The required amount of bromine (Fisher reagent grade) was d issolved in CHC12CHC12 (20 ml) and added dropwise, over a period of 1 h, to the vigorously s t i r r e d react ion mixture cooled in an ice-water bath. The i n i t i a l crude product was - 10-obtained by pouring the cooled react ion mixture into Et 2 0 (600 ml) and was r e c r y s t a l l i z e d from bo i l i ng water (750 ml). The product was f i n a l l y r ec r ys ta l ! i zed by the addi t ion of EtOAc (500 ml) to a CH^Clg so lut ion (150 ml) of the s a l t . Drying in vacuo (5 x 10 mm) for 70 h at 125°C produced 51.0 g (83 mmol, 83% y ie l d ) of the a n a l y t i c a l l y pure (PPh 3) 2NBr. Anal . Calcd. for [P (C 5H 5 ) 3 ] 2 NBr : C, 69.91; H, 4.89; N, 2.26. Found: C, 69.69; H, 4.92; N, 2.58. m.p. (under N 2 ) : 251.0-252.5°C. Proton NMR, x( in CDC1 3), - C gH 5: 2.52(m). 2.2b3 Preparation of (PPhJoNI. [The fo l lowing manipulations were performed in a i r . ] To a so lu t ion of (PPh 3 ) 2 NCl (18.8 g , 32.8 mmol) in EtOH (200 ml , "100%" not fur ther pur i f ied) was added f i n e l y pulver ized Nal (15.0 g, 100 mmol; Mal l inckrodt ana ly t i ca l reagent). The mixture was s t i r r e d rap id ly for 1 h at room temperature and then taken to dryness i_n_ vacuo. The product was extracted into a to ta l of 200 ml of CH 2 C1 2 and the extract was reduced to ca_. 100 ml in vacuo. The addi t ion of E t 2 0 (300 ml) produced the white c r y s t a l l i n e product which was co l lec ted by suct ion f i l t r a t i o n and dr ied at 125°C (5 x 10 mm) for 70 h. This procedure produced 20.6 g (31.0 mmol, 95% y ie l d ) of a n a l y t i c a l l y pure ( p p h 3 ) 2 N I • Anal . Calcd. for [P(CgH 5) 33 2 NI : C, 64.97; H, 4 .53; N, 2.10. Found: C, 65.09; H, 4.67; N, 2.17. m.p. (under N 2) 251.0-252.3°C. Proton NMR, i-( in CDC1 3), - C gH 5: 2.50(m). _ n _ The (PPh 3) 2NX (X = C l , Br or I) compounds are white so l i ds which are soluble in CH 2 C1 2 , CHC^CHC^, EtOH and bo i l i ng water, but insoluble in EtOAc, E t 2 0 , THF, benzene and hexanes. Although stable in dry a i r i n d e f i n i t e l y , these compounds are hygroscopic and are therefore best stored in a des iccator . 2.2c Preparation of bis(tr iphenylphosphine)iminium pentacarbonylhalo- tungstates, (PPh 3) 2NW(C0) 5X (X = C l , Br or I). These complexes were conveniently prepared by the react ion of W(C0)6 with the appropriate (PPh 3) 2NX s a l t . The experimental procedure, using the iodide complex as a representat ive example, was as fo l lows. A DME (90 ml) so lut ion containing W(C0)6 (7.39 g, 21.0 mmol; Pressure Chemical Co.) and (PPh 3 ) 2 NI (13.3 g , 20.0 mmol) was heated under re f lux for 6 h. The resul tant c lear yel low so lut ion was allowed to cool to room temperature and the volume reduced in vacuo un t i l the f i r s t traces of c rys ta l s appeared. Slow addi t ion of hexanes (120 ml) produced yel low c rys ta l s which were co l lec ted by suct ion f i l t r a t i o n and washed with hexanes (2 x 40 ml). The product was dr ied at 60°C (5 x 10 mm) for 18 h. A quant i ta t ive y i e l d of a n a l y t i c a l l y pure (PPh 3) 2NW(C0) 5I was thus obtained (Table I ) . The (PPh 3) 2NW(C0) 5X (X = Cl or Br) complexes were s i m i l a r l y obtained in greater than 95% y ie lds and the i r elemental analyses and physical propert ies are compiled in Table I. Table I. Elemental Analyses and Physical Propert ies of (PPh 3) 2NW(C0) 5X (X = C l , Br or I ) . Compound Color Mp. ,°C (under N 2) Analyses, % C H I Proton NMR, T ( i n C D C l J " C 6 H 5 -1 v (C0) , cm (in CH 2C1 2) (PPh 3) 2NW(C0) 5Cl Yellow 145(dec) Calcd: 54.84 3.37 1.56 2.52(m) Found: 54.44 3.51 1.38 2065(w), 1915(s), 1837(m) (PPh 3) 2NW(C0) 5Br Yellow 150(dec) (PPh 3) 2NW(C0) 5I Yellow 178(dec) Calcd: 52.25 3.21 1.49 Found: 52.04 3.31 1.33 Calcd: 49.77 3.06 1.42 Found: 49.74 3.20 1.22 2.50(m) 2065(w), 1915(s), 1842(m) 2.51(m) 2063(w), 1918(s), 1850(m) r o i - 13 -A l l three complexes are yel low so l ids which may be exposed to a i r for several days without not iceable decomposition but are best stored under n i t rogen. They are very soluble in C r ^ C ^ , diglyme and DME, less soluble in Et^O, THF and EtOAc and insoluble in hexanes. The s o l u b i l i t y increases markedly with increasing atomic weight of the halogen. 2.2d Reactions of n i t rosy l ch lor ide with some anionic and neutral  complexes of manganese, rhenium and i r on . Reaction with  bi s (tr iphenylphosphine)imini um pentacarbonylmanganate, (PPh,,),,NMn (CO) To a l i g h t yel low so lut ion of (PPh 3) 2NMn(C0) 5 (17) (0.81 g , 1.1 mmol) in CH 2 C1 2 (30 ml) was added dropwise with s t i r r i n g at room temperature a so lut ion of ClNO in CH 2 C1 2 . Immediately, the react ion so lu t ion became deep red and gas was evolved. Af ter the addi t ion of ClNO was complete, the solut ion was s t i r r e d for an addi t ional 10 min. D i s t i l l a t i o n in vacuo y ie lded a CH^Cl^ so lu t ion containing only Mn(C0)4(N0) which was i den t i f i ed by i t s in f rared spectrum (18). The y i e l d was estimated to be 70% from the re la t i ve i n tens i t i es of the carbonyl absorptions in the reactant and product in f rared spectra. The react ions of C1N0 with some organometall ic complexes of rhenium and i ron were performed s i m i l a r l y and the experimental procedures are summarized in Table I I . Table I I . Reaction of Ni t rosy l Chloride with some Complexes of Rhenium and Iron. Amt. of Transi t ion metal compd. C1N0 Solvent (mmol) (mmol) (ml) Temp, and Products(yields) react ion time Isolat ion and Ident i f i ca t ion Na[Re(C0) I ; ] 1 9 (4.0) 4.0 THF(50) 0 ° , 15 min. R e 2 ( C 0 ) 1 Q Sublimation at 40-60° (5xlO"Jmm); infrared spectrum 9 Ph3SnRe(C0)5°(1.5) 2.0 CH 2C1 2(10) 20°, 15 min. Re(C0) 5 SnCl x Ph 3 _ x Sublimation at 60° (5xl0 - , jmm): (x = 0,1,2,3) infrared spectrum*3 N a 2 [ F e ( C 0 ) 4 ] 2 1 ' 2 2 ( 1 0 ) 20 Et 90(150) -78° , 30 min. Fe(C0) 9(N0) 9(30%) Vacuum d i s t i l l a t i o n ; in f rared 23 spectrum ,24 Na[CpFe(C0) 2 ] " (14) 14 THF(50) 0°, . 20 min. [ C p F e ( C 0) 2] 2M0%) Iden t i f i ca t ion in so lut ion by infrared spectroscopy 9 24, CpFe(C0) 2SnPh 3 (2.0). 3.0 CrLCl ? (15) 20°, 15 min. CpFe(C0) 9-S n C 1 x P h 3 - x (x = 0,1,2,3) THF ex t rac ts ; in f rared . 25 spectrum a. By comparison with the in f rared spectrum of the authentic compound. b. Inferred from the characters t ic sh i f t of the carbonyl absorptions to higher wave numbers. - 15 -2.2e Reactions of n i t rosy l ch lor ide with t r i carbony l (n 5 -cyc lopenta-dienyl ) anions of chromium, molybdenum and tungsten, [CpM(C0) 3]~ (M = Cr , Mo or W). A THF solut ion of C1N0 was added dropwise, with rapid s t i r r i n g at room temperature to Na[CpCr(C0) 3] (27) (4.89 g , 22.0 mmol) in THF (120 ml) . Gas was evolved and a dark s o l i d prec ip i ta ted during the course of the reac t ion . The addi t ion of C1N0 was continued un t i l the s ta r t i ng anion was completely consumed. The in f rared spectrum of the f i na l react ion mixture revealed the presence of CpCr(C0) 2(N0) (1) and [CpCr(C0) 3 ] 2 (28) as the major carbonyl-containing compounds. The mixture was taken to dryness in vacuo and sublimation of the residue at 60° (5 x 10 mm) onto a water-cooled probe produced 1.01 g (5.0 mmol, 23% y i e l d ) of CpCr(C0) 2(N0) which was. i den t i f i ed by i t s in f rared spectrum. The react ions of the molybdenum and tungsten containing anions proceeded s i m i l a r l y . I f an excess of C1N0 was employed in the above syntheses, s i gn i f i can t amounts of CpM(N0)2Cl and attendant decomposition products were formed. The physical and chemical propert ies of the CpM(C0)2(N0) complexes have been previously described (28). 2.2f Reaction of sodium n i t r i t e and acet ic ac id with sodium t r i ca rbony l - (n 5 -cyc!opentadienyl ) tungstate, Na[CpW(C0)3]. To a solut ion of Na[CpW(C0)3] (27) (1.80 g, 5.1 mmol) and NaN02 (0.35 g , 5.1 mmol) in ni trogen-saturated water (30 ml) was added dropwise with s t i r r i n g an aqueous so lut ion (10 ml) of ace t i c ac id (5 mmol). Immediately, gas was evolved and a dark yel low so l i d formed. The react ion - 16 -mixture was fur ther s t i r r ed for 0.5 h and then f i l t e r e d . The resu l tant so l i d was dr ied in vacuo and sublimed at 60°C (5 x 10 mm) onto a water-cooled probe producing 1.01 g of a mixture of CpW(C0)2(N0) and CpW(C0)3H which were i den t i f i ed by t he i r in f rared spectra (1, 27, 29). 2.2g Reactions of n i t rosy l ch lor ide with bis(tr iphenylphosphine)iminium  pentacarbonylhalotungstates, (PPh 3) 2NW(C0) 5X (X = C l , Br or I ) ,  and with tetraethylammonium pentacarbonylchloro (or methyl)  tungstate, Et4NW(C0)5X (X = Cl or Me). A C h ^ C ^ so lut ion of C1N0 was added dropwise with s t i r r i n g to (PPh 3) 2NW(C0) 5Br (5.5 g, 5.8 mmol) in CH 2 C1 2 (50 ml) at -78°C. Gas was evolved and the addi t ion of C1N0 was continued un t i l the carbonyl in f rared absorptions due to the s ta r t ing material disappeared. The mixture was taken to dryness in vacuo. Sublimation of the residue at 45°C (5 x 10 mm) onto a water-cooled probe produced 0.82 g (2.0 mmol, 35% y ie l d ) of W(C0)4(N0)Br which was i den t i f i ed by i t s in f rared spectrum (30). The react ions of ClNO with the remaining tungsten complexes were performed s i m i l a r l y and the experimental de ta i l s are presented in Table I I I . 2.2h Reactions of te t racarbonylhaloni t rosy l tungstens, W(C0)4(N0)X  (X = Cl or Br), with tetrahydrofuran. A THF solut ion (20 ml) containing W(C0)4(N0)C1 (0.50 g, 1.4 mmol) was s t i r r ed at room temperature un t i l the in f rared absorptions Table I I I . Reactions of N i t rosy l Chloride with (PPh 3) 2NW(C0) 5X (X = C l , Br or I) and Et4NW(C0) X (X = Cl or Me). Metal Complex (mmol) Solvent (ml) Reaction temp. Products(yields) Iso lat ion and Ident i f i ca t ion (PPh 3) 2NW(C0) 5Cl(5.1) CH 2C1 2(50) -78° W(C0)4(N0)C1(25%) A (PPh 3) 2NW(C0) 5BY(5.8) CH 2C1 2(50) -78° W(C0)4(N0)Br(35%) A (PPh 3) 2NW(C0) 5I(9.O) CH 2C1 2(50) -78° W(CO)4(NO)I(2535) A E t 4 NW(C0) 5 Cl 3 1 (7.7) THF(75) or CH 2C1 2(100) -78° 25° W(C0)g and W(C0)4(N0)C1 (<v8%) i A Et 4 NW(C0) 5 CH 3 2 (3.6) CH 2C1 2(50) -78° or 25° W(C0) 6, W(C0)4(N0)C1, Et 4NW(C0) 5Cl B A Sublimation at 45°C (5x10" mm), in f rared spectrum. B Iden t i f i ca t ion in so lut ion by inf rared spectroscopy. - 18 -due to the i n i t i a l reactant disappeared (ca. 24 h). The so lu t ion was taken to dryness in vacuo (5 x 10 mm) to give a quant i ta t ive y i e l d of an orange complex i den t i f i ed as •[W(C0) 2(N0)(THF)C1] 2. Ana l . Calcd. for W(C0) 2(N0)C1(C 4Hg0): C, 19.10; H, 2.12; N, 3.71; C l , 9.39. Found: C, 19.20; H, 2 .11; N, 3.56; C l , 9.64. v(C0) cm" 1 ( in THF): 2020(s); 1907(s). v(N0) cm" 1 ( in THF): 1636(s). Proton NMR, T ( i n CgDg), THF: 5.60(m); 7.85(m). S i m i l a r l y , W(C0)4(N0)Br was quant i ta t i ve ly converted to [W(C0) 2(NO)(THF)Br] 2 as evidenced by the s i m i l a r i t y of i t s in f rared spectrum with that of [W(C0) 2(N0)(THF)C1] 2. v(C0) cm" 1 ( in THF): 2010(s); 1905(s). v(N0) cm" 1 ( in THF): 1635(s). The [W(C0) 2(N0)(THF)X] 2 (X = C l o r B r ) complexes are yel low-orange so l ids which are stable in a i r for at least 10 h but are best stored under n i t rogen. They are soluble in THF, CH 2 C1 2 and benzene and insoluble in hexanes. However, solut ions containing these compounds decompose rap id ly upon exposure to a i r . 2.3 Results and Discussion 2.3a Bis(tr iphenylphosphine)iminium ch lo r ide , bromide and iod ide , (PPhJ 2 NX (X = C l , Br or I). The (PPh 3) 2NX (X = Cl or Br) compounds can best be prepared in high y ie lds according to eq. 1. - 19 -3PPh 3 + 2X 2 + NH20H-HC1 ° - ( P P h ^ N X + Ph3PO + HC1 + 3HX 1. This synthesis has been previously u t i l i z e d only in the preparation of (PPh 3 ) 2 NCl (16), but we have subsequently found that the above react ion can also be d i r e c t l y appl ied to the high y i e l d synthesis of ( P P h ^ N B r . This method, however, f a i l s for the preparation of (PPh 3 ) 2 NI . The l a t t e r compound i s conveniently obtained quant i ta t i ve ly by the d isproport ionat ion react ion between (PPh 3 ) 2 NCl and Nal in ethanol according to the equation (PPh 3 ) 2 NCl + Na + + I" 3^- (PPh 3 ) 2 NI + NaCl(s) 2. in which the equi l ibr ium l i e s well to the side of ( P P h ^ N I by v i r tue of the low s o l u b i l i t y of NaCl in ethanol . The syntheses of (PPh 3) 2NX (X = Br or I) have been previously reported although a cumbersome and i n e f f i c i e n t method was used (16). The (PPh 3) 2NX compounds are stable i n d e f i n i t e l y in a i r and water. However, contrary to a previous report (16), we f ind them to be quite hygroscopic as shown by elemental analyses and proton NMR spectroscopic inves t iga t ions . Consequently, i f the presence of water i s detrimental in subsequent react ions invo lv ing these s a l t s , they must be stored in a des iccator . The compounds are thermally stable even at t he i r r e l a t i v e l y high melting points which are in excess of 250°C. Their chemical and physical propert ies are not unl ike those of t e t rae thy l -ammonium sa l t s except that , su rp r i s i ng l y , the (PPh 3) 2NX compounds are very soluble in chlor inated solvents. The geometric and e lec t ron ic - 20 -structures of the [ ( P P h 3 ) 2 N ] T cat ion have been the subjects of considerable study and both a bent and l i nea r arrangement of P-N-P atoms have been found (33, 34). The use of [ ( P P h 3 ) 2 N ] + as a counterion in the i so l a t i on of t rans i t i on metal carbonyl anions i s of immense value. Not only are c r y s t a l l i n e samples of the carbonyl anions read i l y obta inable, but these sa l t s are often a i r stable in the s o l i d state for many hours. A l so , unl ike the a l k a l i metal sa l t s of carbonyl anions, the [ ( P P h 3 ) 2 N ] + der ivat ives are very soluble and stable in chlor inated so lvents . In f ac t , th is enhanced s t a b i l i t y has been highly benef ic ia l in the x-ray s t ruc tura l determinations of many in te res t ing mono- and poly-nuclear metal carbonyl complexes (33). 2.3b Bis(tr iphenylphosphine)iminium pentacarbonylhalotungstates,  (PPh 3) 2NW(C0) 5X (X = C l , Br or I ) . The (PPh 3) 2NX (X = C l , Br or I) sa l t s react with W(C0)g in re f lux ing DME with the evolut ion of gas to give v i r t u a l l y quant i ta t ive y i e l ds of the (PPh 3) 2NW(C0) gX complexes, as in eq. 3. (PPh 3) 2NX + W(C0)6 (PPh 3) 2NW(C0) 5X + CO 3. These syntheses are comparable to those reported for the preparation of the Et4NW(C0)5X complexes in diglyme at 120°C (31). However, the react ions reported here are performed with great f a c i l i t y at 85°C and are complete in s i x hours. The lower react ion temperature and the shorter react ion _ 21 _ time serve to el iminate any accompanying decomposition products which may ar ise from the pyro lys is of the desired mater ia ls . Unl ike the Et4NW(C0)5X compounds, the [ ( P P h 3 ) 2 N ] + der iva t ives are not pho to l y t i ca l l y decomposed by ordinary l i g h t i n g , and they are also more stable toward atmospheric ox idat ion . In f a c t , as so l ids they are stable in a i r fo r several days and the i r solut ions may be exposed to a i r fo r a short period of time without not iceable decomposition. In cont ras t , the [Et^N]"1" containing compounds are so unstable in so lut ion that the acqu is i t i on of cons is tent ly accurate in f rared data i s d i f f i c u l t . The so lut ion in f rared spectra of the (PPh 3) 2NW(C0) 5X complexes d isp lay the expected three-band pattern s im i l a r to the i s o -s t ructura l neutral compounds Mn(C0)gX (X = C l , Br or I) (35) and W(C0)^L (L = amine or phosphine) (36)-. Of course, the C-0 st retching frequencies of the ion ic species occur at much lower frequencies due to the enhanced metal-carbonyl backbonding. Because of the i r greater s o l u b i l i t y in common organic so lvents , the [ ( P P h 3 ) 2 N ] + sa l t s are more useful than the [Et^N]"1" analogs as react ive synthet ic precursors (17, 37-40). In p a r t i c u l a r , they can be read i l y converted to the W(C0)4(N0)X (X = C l , Br or I) complexes as described subsequently. In summary i t should be noted that a wide var ie ty of (PPh 3) 2NM(C0) 5X complexes, where X i s a halogen or pseudo-halogen, have been previously prepared by diverse means (37-41). However, the preparative methods described in th is thesis are far superior simply because the desired products are obtained much more - 22 -conveniently and in quant i ta t ive y i e l d s . 2.3c Reactions of n i t rosy l ch lor ide with metal carbonyl anions. It is a well known fact that t rans i t i on metal carbonyl anions are s u f f i c i e n t l y nuc leoph i l i c to d isp lace a hal ide from both organic and inorganic hal ides according to the general react ion scheme where m = 0 or 1; n = 1-5 depending on M (11). The success of the above react ion i s dependent, among other va r i ab les , on the nuc leophi1 ic i ty of the anion, and the rate of such a react ion has been used as a measure of the nuc leoph i l i c strength of some metal carbonyl anions (42). some of these anions w i l l a lso d isp lace the ch lor ide from n i t rosy l ch lor ide thereby providing a convenient synthet ic route to neutral n i t rosy l compounds. The method can a-lso be appl ied to the d i -an ion ic complex, [Fe(C0) 4 ] 2 " . Except for the preparation of (RB(pz) 3)M(C0) 2(N0) (RB(pz) 3 = t r i s (pyrazoy l )bora te ; R = H or pz; M = Cr , Mo or W) from [(RB(pz) 3 )M(C0) 3 ] " (10), th is c lass of react ions has la rge ly been ignored. Typical examples of such react ions are summarized in eq. 5-8. [Cp m M(C0) n ]" + RX CpmM(C0)nR + X 4 . In a conversion analogous to the above react ion we f ind that (PPh 3) 2NMn(C0) 5 + C1N0 Mn(C0)4(N0) 5. Na 2 [Fe(C0) 4 ] + 2C1N0 Fe(C0) 2 (N0) 2 6. Na[CpM(C0)3] +C1N0 • (M = Cr , Mo or W) THF * ~ CpM(C0)2(N0) 7. - 23 -THF or CH 9 C1 9 A[W(C0)5X] + C1N0 L L *~ W(C0)4(N0)X 8. (A = (PPh 3 ) 2 N; X = C l , Br or I: A = Et^N; X = Cl or Me) A l l these conversions are accompanied by gas evolut ion and they proceed read i l y in reasonable y i e l d s . The attendant formation of an inorganic ch lor ide undoubtedly provides a strong thermodynamic d r iv ing force for these react ions. I t appears that n i t rosy l ch lor ide behaves as a nitrosonium s a l t in i t s react ions with anions even though the molecule i t s e l f i s bent and the N-Cl bond i s la rge ly covalent. For instance, microwave spectroscopy of i s o t o p i c a l l y labe l led ClNO molecules shows the 0-N-C1 angle to be 113.3° (43), and an N-0 bond order of 1.9 i s obtained from force constant ca lcu la t ions u t i l i z i n g inf rared data (15). Furthermore, the N-0 st retching frequency of C1N0 in a dichloromethane so lut ion occurs at 1845 cm" 1 while in nitrosonium s a l t s , which contain the t r i p l y bonded nitrosonium ca t i on , the values f a l l wi th in the 2150-2400 c m - 1 range (44). These observations therefore suggest that the n i t rosy l ch lor ide molecule ? i s mainly covalent containing an sp hybridized nitrogen atom and an N-0 double bond. Nevertheless, the anomalously large N-Cl distance of O 1.975 ± 0.005 A (43) has been explained in terms of the contr ibut ion of ion ic resonance forms such as 0 = [ : O = N : ] + C I - 24 -In the gaseous s ta te , at 20°C, n i t rosy l ch lor ide disproport ionates to NO and C l 2 to the extent of about 0.5% (44). Although the extent of th is equi l ibr ium in solut ions of dichloromethane or tetrahydrofuran i s not known, evidence for i t i s presented in Chapter IV. Chemical ly, n i t rosy l ch lor ide often behaves as a strong ox id iz ing agent, being reduced to C l " and NO or N 2 (15, 45, 46). 2.3cl Reactions of n i t rosy l ch lor ide with organometal l ic anions of  manganese, rhenium and i r on . The react ion of n i t rosy l ch lor ide with (PPh^^NMn(C0) g in dichloromethane proceeds smoothly and c leanly at room temperature to give Mn(C0)4(N0) in good y i e l d s . However, the analogous react ion invo lv ing Na[Re(C0) g] affords Re^CO) -^ as the only carbonyl containing compound. It appears that the [Re(C0) g ]~ anion is oxid ized to the dimer by n i t rosy l ch lor ide according to eq. 9. Na[Re(C0) 5] +.C1N0 y t e 2 ( C 0 ) 1 0 + NaCl + NO 9. In th is connection the use of n i t rosy l ch lor ide as an oxidant has already been mentioned and indeed, nitrosonium sa l t s have been used previously in the oxidat ion of organometall ic anions. An example of such an oxidat ion i s the formation of the paramagnetic Cr(C0) g I complex as indicated in eq. 10 (45). [C r (C0) 5 I ] " + NOPFg Cr(C0) 5 I + P F g " + NO 10. - 25 -The d ian ion ic Na 2 [Fe(C0) 4 ] complex reacts with n i t rosy l ch lor ide to form Fe(C0) 2 (N0) 2 as the only n i t rosy l containing species. The p o s s i b i l i t y that th is react ion proceeds through the well known [Fe(C0) 3(N0)]~ anion was not invest igated in our work. However, the inf rared spectrum of the f i na l react ion mixture confirms the presence of small amounts of Fe 3 (C0) - | 2 , l i k e l y produced by the n i t rosy l ch lor ide oxidat ion of [Fe(C0) 4 ] . This i s not surpr is ing in l i g h t of the fac t that a s im i l a r oxidat ion of [HFe(C0) 4] by manganese dioxide const i tu tes an important synthet ic route to F e 3 ( C 0 ) 1 2 (29, 47, 48). The r e l a t i ve n u c l e o p h i l i c i t i e s of a var ie ty of metal carbonyl and cyclopentadienylmetal carbonyl anions, i n the presence of Bu^NClO^, have been compiled and the factors which determine nuc leoph i l i c character have been discussed (42). The react ions of n i t rosy l ch lor ide with the anions described in th is chapter suggest a re la t ionsh ip between the react ion products and the nuc leoph i l i c i t y of the anions. Hence, the mi ld ly nuc leoph i l i c [Mn(C0)g]~ anion read i l y y i e l ds Mn(C0)4(N0) while the more nuc leoph i l i c [Re(CO)^] anion simply gives the oxidat ion product, Re 2(C0).|Q. Not su rp r i s ing ly therefore, the most nuc leoph i l i c anion thus fa r inves t iga ted , [CpFe(C0)2]~> i s ox id ized nearly quant i ta t i ve ly to [CpFe(C0) 2 l 2 . In an e f fo r t to reduce the nuc leoph i l i c behavior of [Re(C0)g] and-[CpFe(C0) 2] the Ph^Sn der ivat ives of these anions were prepared. General ly , complexes of the type Ph^SnM, where M i s a t rans i t i on metal carbonyl moiety, contain a predominantly covalent t in-metal bond. Consequently, i t i s not unreasonable that the t rans i t i on metal carbonyl - 26 -group w i l l possess a great ly reduced n u c l e o p h i l i c i t y . However, the subsequent react ions of n i t rosy l ch lor ide with Ph 3SnRe(C0) 5 and CpFe(C0) 2SnPh 3 in dichloromethane y i e l d only the mixed Re(C0) 5 SnCl x Ph 3 _ x and CpFe(C0) 2 SnCl x Ph 3 _ x complexes, where x = 1, 2 or 3. The cleavage of the t in-carbon bond rather than the t in-metal bond pa ra l l e l s the react ions of halogens and hydrogen hal ides with Ph 3SnMn(C0) 5 , Ph 3 SnRe(C0) 5 , and CpFe(C0) 2SnPh 3 (24, 49-51). The success of the react ion of n i t rosy l ch lor ide with (PPh 3) 2NMn(C0) 5 prompted the attempted i so l a t i on of the [Re(C0) 5 ] " and [CpFe(C0) 2]~ anions as the i r [ (PPh 3 ) 2 N] + s a l t s . Unfortunately, a l l e f fo r ts were thwarted by the pers is tent formation of Re2(C0)-jQ, [CpFe(C0) 2 ] 2 and attendant decomposition products. Even though [Mn(C0)g] and HMn(C0)5 react with Diazald to y i e l d Mn(C0)4(N0) (18), the same react ion could not be effected with e i ther [Re(C0) 5 ]~ and [CpFe(C0) 2]~ or the i r respect ive hydrido der i va t i ves . While there i s no a p r i o r i reason for the i r inherent i n s t a b i l i t y under ambient cond i t ions , the Re(C0) 4(N0) and CpFe(C0)(N0) complexes s t i l l remain unknown. 2.3c2 Reactions of n i t rosy l ch lor ide with t r i ca rbony l(n 5 - cyc lopen tad ieny l )  anions of chromium, molybdenum and tungsten, [CpM(C0)3]~  (M = Cr , Mo or W). Treatment of Na[CpM(C0)3] with n i t rosy l ch lor ide in t e t r a -hydrofuran y i e l ds a mixture of the CpM(C0) 2(N0), CpM(N0)2Cl and [CpM(C0) 3 l 2 compounds. Even though the anions of chromium and molybdenum are s l i g h t l y - 27 -less nuc leoph i l i c than [Mn(C0)g]~ (42), a s i gn i f i can t amount of oxidat ion to [CpM(C0) 3 ] 2 occurs. The formation of CpM(N0)2Cl ar ises from the oxidat ive subst i tu t ion of n i t rosy l ch lor ide on the i n i t i a l CpM(C0)2(N0) products according to eq. 11 . CpM(C0)2(N0) + C1N0 «~ CpM(N0)2Cl + 2C0 11. (M = Cr , Mo or W) This i s a pa r t i cu la r example of the broad c lass of react ions between n i t rosy l ch lor ide and neutral metal carbonyl complexes to be discussed in Chapters III and IV. The preparation of Fe(C0) 2 (N0) 2 by the treatment of Na[Fe(C0) 3N0] or Na[Fe(C0) 4H] with aqueous sodium n i t r i t e and acet ic ac id has been previously reported (52, 53). The react ion of Na[CpW(C0)3] with these reagents proceeds analogously whereupon a mixture of CpW(C0)2(N0) and CpW(C0)3H is formed. The l a t t e r complex i s undoubtedly produced by the d i rec t protonation of [CpW(C0)3]~ by acet ic a c i d , a well known synthesis (27). However, d i f f i c u l t y in separating these two products renders th is synthet ic route imprac t i ca l . The very high y i e l d syntheses of a l l three CpM(C0)2(N0) complexes developed during the course of th is work are deta i led in Chapter IV. - 28 -2.3c3 Reactions of n i t rosy l ch lor ide with b is( t r iphenylphosphine)-iminium pentacarbonylhalotunqstates, (PPhp)QNW(C0)^X (X = C l , Br  or I) and tetraethylammonium pentacarbonylchloro (or methyl)  tungstate, Et4NW(C0)5X ( X = C l o r M e ) . A l l three (PPh 3 ) 2 NW(C0)gX complexes react with n i t rosy l ch lor ide in dichloromethane at -78°C to give moderate y i e l ds of W(C0)4(N0)X according to eq. 12. If excess n i t r osy l ch lor ide i s used, (PPh 3 ) 2 NW(C0) 5 X + C1N0 *-W(C0) 4(N0)X + ( P P h ^ N C l + CO 12. or i f the react ion i s attempted at room temperature, the y ie lds of the desired products are reduced markedly. The W(C0)4(N0)X complexes have been previously synthesized by the act ion of p-toluenesulphonic acid and p e n t y l n i t r i t e , or nitrosonium hydro-gensulfate acid on Et4NW(C0)^X (30). Our repeated attempts to obtain the desired products in y ie lds which even approximate those reported met with f a i l u r e . Another reported route to the chlor ide and iodide containing compounds involves the treatment of HW2(C0)g(NO) with n i t rosy l ch lor ide and iodine respect ive ly (54). However, the required HW2(C0)g(N0) complex can be obtained from a two-step synthesis in y ie lds of only 40% (55, 56). Unlike a l l of the previous syntheses discussed above, the present react ions of n i t rosy l ch lor ide with (PPh3)2NW(C0)gX af ford the W(C0)4(N0)X complexes without the attendant formation of W(C0)g. Thus, the d i f f i c u l t task of separating the phys ica l l y s im i la r W(C0)4(N0)X and W(C0) f i compounds i s avoided. A l so , since the (PPh,) 9NW(C0)RX - 29 -complexes are read i l y obtained in quant i ta t ive y i e l d , as discussed e a r l i e r in th is chapter, th is preparative route i s indeed a t t r a c t i v e . In te res t ing ly , the choice of countercation in the react ions between the [W(C0)gX] sa l t s and n i t rosy l ch lor ide has a profound ef fect on product d i s t r i b u t i o n . Unlike the [ ( P P h ^ N ] * s a l t s , the Et4NW(C0)5X compounds read i l y y i e l d W(C0)g as the major product regard-less of the solvent employed. Et4NW(C0)gMe, when treated with n i t rosy l ch lor ide in d ich lo ro -methane, produces a mixture of W(C0) 4(N0)C1, W(C0)6 and Et 4 NW(C0) 5 Cl. The l a t t e r compound is l i k e l y formed in a manner s im i l a r to the react ion of hydrogen chlor ide with Me4NW(C0)gR, where R = Me or CHpPh. For example, treatment of Me^VKCO^CHpPh with a s l i gh t excess of hydrogen ch lor ide y i e l ds toluene (94%) and Me4NW(C0)5Cl (32). Once the primary product, Et 4NW(C0)gCl, is formed, subsequent react ion with n i t rosy l ch lor ide produces W(C0)4(N0)C1 and W(C0)g as previously described. In support of th is react ion pathway i t was found that an excess of n i t rosy l ch lor ide simultaneously reduced the f i na l y i e l d of Et 4NW(C0) 5Cl and increased the y ie lds of W(C0)4(N0)C1 and W(C0) g. The ant ic ipated product from the react ion between n i t rosy l ch lor ide and Et4NW(C0)5Me was the as yet unknown W(C0)4(N0)Me complex. This type of conversion i s not without precedent since the anions [R 3M'M(C0) g ]~ (M = Mo or W; M' = S i , Ge, Sn or Pb; R = Me or Ph) react with NOPFg to give R 3M'M(C0) 4(N0) in y i e l ds ranging from 7 to 74% (46 i ) . Our attempts to prepare W(C0)4(N0)Me by the act ion of methyl Grignard reagents, methyl l i th ium and trimethylaluminum on W(C0) / l(N0)X complexes - 30 -f a i l e d , probably due to the great l a b i l i t y of the carbon monoxide l igand in the halo-containing reactant. 2.3d Reactions of te t racarbonylhaloni t rosy l tungstens, W(C0)4(.N0)X  (X = Cl or B r ) , with tetrahydrofuran. The f a c i l e subst i tu t ion of e i ther one or two carbonyl l igands in W(C0)4(N0)X (X = C l , Br or I) has been amply demonstrated (57, 58). For example, react ion with sto ich iometr ic quant i t ies of e i ther PPh^ or AsPhg in re f lux ing chloroform y i e l ds mer-W(C0),,(N0) (L)X, whereas excess l igand produces c j^s-WtCO^NOHL^X. If carbonyl subst i tu t ion i s ef fected using bis(diphenylarsino)methane (dam) only the monodentate mer_-W(C0)3(N0)(dam)X and cis-W(C0)2(NQ)(dam)pX complexes are formed. However, when ha l f the sto ichiometr ic amount of dam is employed, the product obtained i s [ W t C O ^ N O ^ ^ d a m , which i s bel ieved to contain both hal ide and dam bridges (58). We discovered that s t i r r i n g a tetrahydrofuran so lut ion of W(C0)4(N0)X (X = Cl or Br) for 24 hours resul ted in the quant i ta t ive formation of the corresponding [W(C0)2 (NO.) (THF)X] 2 complexes. The presence of tetrahydrofuran in these compounds was confirmed by elemental analyses and proton NMR spectroscopy which displayed the cha rac te r i s t i c proton resonances at x5.60(m) and x7.85(m). As expected, these values are somewhat lower than the corresponding values of uncomplexed tetrahydrofuran. The electron donation from the THF oxygen atom to the central metal i s expected to deshield the protons on the a-carbon more than those on the 3-carbon atoms. In agreement with th is - 31 -expectat ion, the a-carbon proton resonances do indeed experience the greater downfield s h i f t . The [w^CO^NO) (THFjX^ complexes are bel ieved to be dimeric with structures s im i la r to that proposed for [W^O^NCOXlgdam except that the bridging dam i s replaced by two terminal ly bonded tetrahydro-furan l igands, as shown by two possible structures A and B. Consistent A B with th is b e l i e f , both the tetrahydrofuran and dam containing compounds d isp lay s im i l a r in f rared spectra which are character ized by two carbonyl and one n i t rosy l s t retching absorptions (58). In compliance with the "18-electron r u l e " , the dimers presumably are held together by hal ide bridges without the aid of a metal-metal bond. - 32 -CHAPTER III REACTIONS OF NITROSYL CHLORIDE WITH NEUTRAL METAL CARBONYL COMPLEXES 3.1 Introduction As described in the previous chapter the react ions of n i t rosy l hal ides with metal carbonyl or n 5-cyc1opentadieny1metal carbonyl anions had received v i r t u a l l y no at tent ion un t i l th i s study. On the other hand, the i r react ions with neutral complexes have been previously inves t iga ted, although by no means exhaust ively (9). Because the n i t rosy l hal ides are powerful ox idants, s t r i c t at tent ion must be given to the react ion condit ions which a re , by and la rge , emp i r i ca l l y determined. Thus the temperature, the so lvent , the phase and espec ia l l y the stoichiometry of the react ion are c ruc ia l in determining the react ion products. Reactive substrates include non-carbonyl as well as carbonyl containing compounds. In the former category, the n i t rosy l hal ides usual ly add ox ida t i ve ly to the metal complex with or without l igand displacement. However, the majori ty of the published reports describe the react ions of n i t r osy l hal ides with t r ans i t i on metal complexes which contain one or more carbonyl l igands , and only these are considered here. 33 -At th is point a c lear d i s t i n c t i o n must be made between the n i t rosy l hal ides and various nitrosonium s a l t s . The l a t t e r reagents invar iab ly form ca t ion ic n i t rosy l complexes, as shown in eq. 13, CpmM(C0) n + NOV [Cp mM(C0) n_ 1 (N0)]V + CO 13. (m = 0 or 1 and n = 2-6 depending on M) since anions, A " , such as PFg" and BF^~ show a remarkable propensity to remain uncoordinated. Only one mole equivalent of carbon monoxide i s d isplaced and the product formed i s a 1:1 e l e c t r o l y t e . Any remaining coordinated carbonyl l igands are usual ly quite suscept ib le to displacement by even weakly nuc leoph i l i c neutral or anionic molecules such as acetone or hal ide anions (59, 60). The weakened metal-carbon bond in ca t ion ic carbonyl compounds i s consistent with current bonding theor ies , and the resul tant enhanced l a b i l i t y of the CO l igand can be advantageously exploi ted in the synthesis of both ca t ion ic and neutral carbonyl compounds. On the other hand, the n i t rosy l hal ides almost always react with metal carbonyls to form products which contain a coordinated hal ide l i gand . However, two cases of ca t ion ic products s im i l a r to those obtained with the nitrosonium sa l t s have been reported (61, 72a). For instance, both ClNO and BrNO react with Fe (C0) 3 (PPh 3 ) 2 in ace ton i t r i l e to give [Fe(C0) 2 (N0)(PPh 3 ) 2 ] + X~. By far the most common mode of react ion i s that depicted in - 34 -equation 14 CpM(CO) + XNO rm x 'n ^Cp m M(C0) n _ 2 (N0 )X + 2C0 14. (m = 1 or 2 and n = 2-6 depending on M) which involves the coordinat ion of one mole of XNO for every two moles of CO d isp laced. Since NO is a stronger Tr-acceptor than CO, i t e f f ec t i ve l y competes with CO in the extent of u-backbonding with the central metal , thereby resu l t ing in a weaker metal-carbon bond. Any remaining carbonyl l igand in the i n i t i a l product i s now s u f f i c i e n t l y l a b i l e to be displaced even by a chlor ine atom which i s already coordinated to a t rans i t i on metal. The resu l t i s the formation of dimers, or polymers of indeterminate length, which contain ch lor ine br idges. These general p r inc ip les are exempli f ied in the fo l lowing syntheses. Re(C0) 4 (L)Cl + C1N0 * - Re(C0) 2 (N0)LCl 2 + 2C0 (63) (L = C 5 H 5 N , C 5 H 5 N0, C 4HgS, Bu 3 P, Ph 3 P0, 4 -p ico l ine or 3,4-1ut id ine) M(C0) 6 + 2C1N0 [M(N0) 2 Cl 2 ] n + 6C0 (64) (M = Mo or W) Mo(C0) 4 (PPh 3 ) 2 + 2BrN0—»-Mo(N0) 2 Br 2 (PPh 3 ) 2 + 4C0 (65) LM(C0) 2(N 2Ph) + C1N0—*-LM(N0)(N 2Ph)Cl + 2C0 (M = Mo or W; L = HB(pz) 3 : M = Mo; L = Cp) (66) - 35 -RB(pz) 3M(C0) 2(N0) + C1N0 e»-RB(pz)3M(N0)2Cl + 2CO (10) (M = Mo; R = H or pz: M = W; R = H) HB(3,5-Me 2pz) 3Mo(C0) 2(N0) + C1N0 —*-HB(3,5-Me 2pz) 3Mo(N0) 2Cl (10) + 2C0 The l as t two of these react ions have a counterpart in the cyclopentadienyl de r i va t i ves , CpM(C0)2(N0) (M = Cr , Mo or W), and the react ion of C1N0 with these complexes has been developed into a high y i e l d synthet ic route to the CpM(N0)2Cl compounds, as described in Chapter IV. In th is chapter the react ions of ClNO with Fe(C0) 5 , Fe(C0) 2 (N0) 2 , [CpFe(C0) 2 ] 2 , Co(C0) 3(N0) and CpCo(C0) 2 are descr ibed. 3.2 Experimental A l l experimental procedures described here were performed under the same general condit ions deta i led in sect ion 2 .2 . Reactions of n i t rosy l ch lor ide with neutral complexes of i ron and coba l t . To a vigorously s t i r r e d so lu t ion of Fe(C0) g (7.5 ml , 58 mmol) in CHgCl2 (30 ml) was added at room temperature a CH 2 C1 2 (50 ml) so lu t ion containing C1N0 (7.37 g, 112 mmol). Gas was rap id ly evolved and the react ion mixture became v i o l e t - b l ack . The f i na l mixture was taken to dryness and the residue was extracted into hexanes (150 ml) . The extract was cooled to -78°C thereby p rec ip i t a t i ng a dark red-brown so l i d which Table IV. Reactions of N i t rosy l Chloride with some Neutral Complexes of Iron and Cobalt . Transi t ion metal compd. (mmol) Amt. of C1N0 (mmol) Solvent (ml) Temp. Products(yields) Isolat ion and Ident i f i ca t ion Fe(C0) 2 (N0) 2 9 (28.8) 40 Pentane(20) 25° Fe(N0)3Cl(31%) Precip i tated from pentane at -78° ; infrared spectrum2>^,70 [CpFe(C0) 2 ] 2 (1.4) 4.0 CH 2C1 2(30) 25° CpFe(C0)2Cl(51%) Sublimation at 50-60° (5xl0" Jmm); infrared spectrum^ Co(C0) 3 (N0) 2 9 (4) CH 2C1 2(60) -78° [Co(N0) 2 Cl] 2 Ident i f i ca t ion in so lut ion by . r . . 2,69,70 infrared spectroscopy CpCo(C0) 9(10) a CH 2C1 2(50) -78° [Co(N0) 2 Cl] 2 Sublimation at 90-100° (5x10 rmi) ~ j . 2,69,70 infrared spectrum , elemental ana lys i s . a A CH^Cl2 solut ion of ClNO was added un t i l the disappearance of the infrared absorptions due to the i n i t i a l reactant. - 37 -was co l lec ted by suct ion f i l t r a t i o n . In th is manner 3.0 g (17 mmol, 29% y ie l d ) of F e ^ O ^ C l , i den t i f i ed by in f rared spectroscopy (2) , was i so la ted . Fe(N0).jCl i s unstable at 25°C read i l y l i be ra t i ng n i t r i c ox ide, espec ia l l y under vacuum, so that an acceptable elemental analys is for th i s compound could not be obtained. The react ions of ClNO with other neutral complexes of i ron and cobalt were performed s i m i l a r l y and the experimental de ta i l s are summarized in Table IV. 3.3 Results and Discussion 3.3a Reaction of n i t rosy l ch lor ide with pentacarbonyl i ron, Fe(CO)^ . When a dichloromethane so lu t ion of Fe(C0)g i s treated with n i t rosy l ch lor ide vigorous gas evolut ion occurs and the react ion mixture becomes v i o l e t -b l ack . The only n i t rosy l containing product, Fe(N0).jCl, i s subsequently iso la ted in 29% y i e l d and i den t i f i ed by i t s cha rac te r i s t i c in f rared spectrum (69, 70). Optimum y ie l ds are obtained when the ra t i o of n i t rosy l ch lor ide to Fe(C0)g i s 2 : 1 , and ra t i os larger than th i s resu l t in a rap id ly diminishing y i e l d of F e ^ O ^ C l . In view of the high ox id iz ing property of n i t rosy l ch l o r i de , FeCl^ i s l i k e l y a byproduct of th is reac t ion , although th is compound was not i so la ted and i d e n t i f i e d . No in f rared spectral evidence was obtained for the possib le formation of Fe(C0) 2 (N0) 2 a s a n intermediate. However, treatment of Fe(C0) 2 (N0) 2 with n i t rosy l ch lor ide under s im i la r experimental condit ions did produce F e ^ O ^ C l in comparable y i e l d . This preparative route to F e ^ O ^ d u t i l i z i n g Fe(C0) 5 i s much more convenient than the previously reported procedure (71). - 38 -Fe(N0) 3Cl i s a dark red-brown so l i d which i s soluble in common organic solvents inc luding hexanes. The complex loses n i t r i c oxide at room temperature even under n i t rogen. Sublimation under vacuum is possib le but only with extensive attendant decomposition. This substant ia l thermal i n s t a b i l i t y thwarts a l l attempts to obtain an acceptable elemental analys is for th is compound. Previous invest igat ions of the react ions of ClNO with Fe(C0) 5 demonstrate that d i f fe ren t products may be obtained depending on react ion condi t ions. In l i q u i d hydrogen ch lor ide the i so lab le product i s [Fe(C0) 5 (N0) ] + Cl~ which rap id ly d issoc ia tes to C1N0 and Fe(C0) 5 at room temperature (72a). The su rp r i s ing ly low N-0 s t retch ing frequency of 1610 cm ^ displayed by th is compound i s ind ica t i ve of a n i t rosy l l igand coordinated as NO", ije. a bent M-N-0 geometry. Apart from the di f ference in the meta l -n i t rosy l bonding modes, the equi l ibr ium behaviour of ClNO with Fe(C0) 5 bears resemblance to the coordinat ion react ion of ClNO with a var ie ty of metal ha l ides , as exempli f ied by eq. 15 (15). C1N0 + F e C l 3 , C l N 0 - F e C 1 3 - ^ - ^ N 0 + + F e C l 4 " 15. In cont ras t , other workers have found that n i t rosy l ch lor ide and Fe(C0)g, in a ra t i o of 1 .5 :1 , react at room temperature in a steel bomb to give a mixture of Fe(C0) 2 (N0) 2 and Fe(C0) 5 (72b). As the ra t i o increases, lower y ie lds of Fe(C0) 2 (N0) 2 are obtained u n t i l , at the ra t i o of 2 . 7 : 1 , only a mixture of carbon monoxide and oxides of nitrogen i s found. Unfortunately, the react ion residue has not been examined for the possib le - 39 -presence of Fe(N0) 3 Cl . If the react ion i s repeated in pentane under ambient temperature and pressure, only a mixture of Fe(C0) 2 (N0) 2 and Fe(C0)g i s obtained. 3.3b Reaction of n i t rosy l ch lor ide with b i s [d i ca rbony l (n 5 - cyc lopen ta - d i e n y l ) i r o n ] , [CpFe(C0) 2 ] 2 . N i t rosy l ch lor ide reacts with dimeric metal carbonyl complexes to produce monomeric, dimeric or polymeric n i t rosy l compounds as shown in eq. 16-18 (3, 63, 73). [CpRu(C0) 2 ] 2 + C1N0 *— CpRu(N0)Cl 2 16. [Re (C0) 4 Cl ] 2 + Cl NO [Re(C0) 2 (N0)C l 2 ] 2 17. [M(C0) 4 C1 2 ] 2 + C1N0 * - [ M ( N 0 ) C l 3 ] n + [M(N0) 2 C1 2 ] 2 18. (M = Mo or W) In contrast to the react ion depicted in eq. 16 we f ind that [CpFe(C0) 2 ] 2 i s cleaved by C1N0 without the formation of a n i t rosy l compound. The resul tant CpFe(C0) 2Cl complex may be formed according to the p laus ib le react ion scheme [CpFe(C0) 2 ] 2 + C1N0 *»CpFe(C0)2C1 + [CpFe(C0) 2]~ + N0 + followed by [CpFe(C0) 2 ] " + N0 + ^ [CpFe(C0) 2 ] 2 + NO - 40 -with the second step being ident ica l to the oxidat ion of [CpFe(C0) 2] by ClNO as described in Chapter I I . This transformation pa ra l l e l s the known a i r oxidat ion of [CpFe(C0 ) 2 l 2 in the presence of HC1 (68), fo r which the fo l lowing react ion sequence may be surmised. [CpFe(C0) 2 ] 2 + HC1 «*~CpFe(C0)2Cl + CpFe(C0)2H 2CpFe(C0)2H [CpFe(C0) 2 ] 2 + H 20 The hydrido complex i s known to undergo a i r oxidat ion to give the i n i t i a l reactant dimer. In a s im i l a r manner, the M 2 (C0 ) - JQ (M = Mn or Re) compounds are cleaved by C1N0 to af ford only the M(C0) gCl species (74). The formation of the metal hal ide complexes reported here does not comprise a useful synthet ic method since better y i e l ds are more conveniently obtained according to ex i s t i ng procedures (68, 75). 3.3c Reactions of n i t rosy l ch lor ide with t r i ca rbony ln i t r osy l coba l t , Co(C0) 3 (N0), and d icarbony l (n 5 -cyc lopentad ieny l )coba l t , CpCo(C0) 2 . Both Co(C0) 3(N0) and CpCo(C0) 2 react with n i t rosy l ch lor ide to give [Co(N0) 2 Cl ] 2 in moderate y i e l d s . The react ion i s rapid even at -78°C and the use of excess n i t rosy l ch lor ide resu l ts in extensive decomposition. The dimeric [Co(N0) 2 Cl ] 2 was previously prepared in a manner s im i la r to the preparation of Fe(N0) 3Cl (76). The displacement of o l e f i n i c l igands by n i t rosy l ch lor ide is not unknown (3) , but the displacement of the cyclopentadienyl l igand has not been previously - 41 -reported. Thus, the formation of [Co(N0) 2 Cl ] 2 from CpCo(C0) 2 and ClNO is unprecedented. S i m i l a r l y , the n 5-cyclopentadienyl l igand in CpRe(C0) 3 has been shown to undergo a s im i l a r displacement to y i e l d the [Re(C0) 2 (N0)C l 2 ] 2 dimer (74), which has been previously reported (63). - 42 -CHAPTER IV CYCLOPENTADIENYLNITROSYL COMPLEXES OF CHROMIUM, MOLYBDENUM, AND TUNGSTEN 4.1 Introduction The number of cyc lopentadieny ln i t rosy l complexes of the group VI t r ans i t i on metals has grown s tead i l y in the past two decades. Both mono- and d inuclear species are known, and most d isp lay a r i ch and varied chemistry. The CpMtCO^NO) (M = Mo or W) compounds have been obtained in very low y i e l ds by the treatment of aqueous solut ions of NaCCpMCCO)^] with n i t r i c oxide (77). Since these nuc leoph i l i c anions react with pro t ic solvents to form the hydrido complexes, C p M ^ O ^ H , the synthesis l i k e l y occurs by attack of n i t r i c oxide on these hydrido intermediates. The cleavage of the weak metal-metal bond of [CpCr(CO) .^ with n i t r i c oxide affords the chromium carbonyln i t rosy l analog in good y i e l ds (78). However, since the dimeric precursor can be obtained only in low y ie lds and with much expenditure of e f fo r t (79), th is synthet ic route i s not p r a c t i c a l . Although a number of polynuclear carbonyl complexes react with n i t r i c oxide to produce mononuclear n i t rosy l de r i va t i ves , the metal-metal bonds in [ C p M t C O ) ^ (M = Mo or W) are too strong to be cleaved by n i t r i c oxide. A more general n i t r osy la t i ng agent - 43 -is D iaza ld , which converts CpM(C0)3H (M = Mo or W) to CpM(C0)2(N0) in reasonable y ie lds (27, 80). However, i t was recent ly found that the hydrido precursors are not necessary and the synthesis can be performed d i r e c t l y with the anions [CpM(C0) 3]" (M = Cr , Mo or W) (81) thereby e l iminat ing an unnecessary synthet ic procedure. A number of subst i tu ted complexes CpM(CO)(N0)L containing a var ie ty of donar l igands has been reported (28). Another ser ies of re lated compounds can be represented by the general formula CpM(N0) 2Cl, of which the chromium der iva t ive i s the most studied. It may be obtained in modest y i e l d when a mixture of C r C l 3 and NaCgH5 i s t reated with n i t r i c oxide (27, 29, 82). The corresponding molybdenum compound i s obtained in poor y i e l ds by the react ion of T1C 5 H 5 with [Mo(N0) 2 Cl 2 ] (83), or by the react ion of NaN03 with [CpMo(C0)3NH3]Cl in hydroch lo r ic 'ac id (84). The previously unknown tungsten analog, obtained by the treatment of [CpW(N0)2(C0)]PFg with NaCl (59), was reported shor t ly a f ter our synthesis of th is complex. A number of compounds derived from CpCr(N0) 2 Cl, such as CpCr(N0) 2X (X - F, Br, I, CN, NCS, N0 2 and NCSe) (82, 85) , [CpCr(N0) 2L]C1, [CpCr(N0)L 2]Cl and CpCr(N0)(L)C1 (86) has already been obtained. However, no der ivat ives of the molybdenum and tungsten chloro complexes were known when th is research was undertaken. Pr io r to th is work, f i ve dinuclear chromium spec ies , [CpCr(N0)L] 2 (L = NMe2, SPh and SMe) (87, 88), Cp 2 Cr 2 (N0) 3 NH 2 (89), and [CpCr(N0) 2 ] 2 (90) had been character ized, and a l l these complexes contain br idging NO and/or L l igands (91-94). The molybdenum dimers, - 44 -[CpMo(N0)L]2 (L = I, SPh and SCH 2Ph), [CpMo(NO)L 2J 2 (L = I, SPh, SCH2Ph and C 0 2 R f ) and [CpMo(NO)(SCH 2Ph)I] 2 have a l l been derived from [CpMo(N0)I 2 ] 2 rather than from CpMo(N0)2Cl (95-97). The treatment of [CpMo(N0)I 2] 2 with P P h 3 , P(0Ph 3) and CgHgN y ie lds CpMo(N0)(L)I 2 (96). Unt i l now, the only known a lky l and ary l compounds of the type CpM(N0)2R were the Me, Et , Ph and a - C 5 H 5 der ivat ives of chromium (27, 98). The f i r s t three are obtained in 60, 5, and 0.5 % y i e l d s , respec t i ve ly , by the react ion of the corresponding Grignard reagent with e i ther CpCr(N0) 2Br or CpCr(N0) 2 I . In genera l , the ch lo ron i t rosy l complex gives the poorest y i e l d s , and when THF i s subst i tuted for E t 2 0 as so lvent , the CpCr(N0)2Me complex i s obtained in only 1% y i e l d . In te res t ing ly , diazomethane inser ts in to the Cr-Cl bond of CpCr(N0) 2Cl to af ford CpCr(N0) 2CH 2Cl in 3% y i e l d , a react ion s im i la r to the inser t ion into CpM(C0)3H (M = Mo or W) and CpW(C0)3CH3 to give the corresponding methyl and ethyl der iva t ives (27, 99) . The ^-CgHg der iva t ive i s obtained by the react ion of NaC^Hg or TlC^Hg with the ha lon i t rosy l compound (18, 98). Recently, an in te res t ing ser ies of complexes (C^Hg)2Mo(N0)X (X = I, Me and a-C^H^) has been prepared. Thus, the treatment of [CpMo(N0)I 2 ] 2 with 2T1C 5H 5 and 4T1C 5H 5 y i e lds (C 5H 5) 2Mo(N0)I (83) and (C 5H 5) 2Mo(N0) (0-CgHj.) (100), and the react ion of the former product with MeMgBr produces (CgH^Mo (NO)Me (83). At room temperature, the NMR spectrum of each of the three (C(-H5)2Mo(N0)X complexes exh ib i ts only one sharp cyclopentadienyl proton resonance. In order to sa t i s f y the "18-electron r u l e " , an instantaneous structure containing rap id ly - 45 -interchanging n 5 - and n 3 - C g H g r ings was proposed (83). However, the x-ray structures of (C 5 H 5 ) 2 Mo(N0) (n^Hg) (101) and (C 5H 5) 2Mo(N0)Me (102) show that the n o n - n ' - C ^ r i ngs , though magnetical ly non-equivalent, are equivalent with respect to the central metal atom. Assuming s im i l a r structures in so lu t i on , the NMR behavior over a wide temperature range then does not require the n 5 - C 5 H 5 =^==n3-C5H5 f l u x i o n a l i t y . Moreover, the complexes (C 5H 5) 2Mo(N0)S 2CNMe 2 and [PPh 4 ] [(C^H ) 2 Mo(N0)S 2 CC(CN) 2 ] , which have the chelat ing S2CNMe2 and S 2 C 2 ( C N ) 2 l i gands , contain both n^-CgHg and n 5 -C g Hg r ings which become equivalent at 70°C due to rapid r ^ - C ^ : ^ ^ n 5 - C 5 H 5 interchange (103). This chapter describes the chain of events which subsequently leads to the acqu is i t i on of the CpM(N0)2R complexes, where M = Cr , Mo or W; R = a lky l or a r y l . The synthet ic route, which i s general ly appl icable to a l l three metals, begins with the commercially ava i lab le metal hexacarbonyl compounds, as in the scheme: M(C0) 6 —Na[CpM(C0) 3 ] ^-CpM(C0) 2(N0) »-CpM(N0) 2Cl—*-CpM(N0) 2R The success of th is preparative method i s la rge ly due to the high y i e l d synthesis of each intermediate compound, as described herein. Although the CpM(C0)2(N0) species have been previously charac ter ized, the CpM(N0)2Cl and CpM(N0)2R compounds have not been thoroughly studied e i ther because of the d i f f i c u l t y in the i r preparation or simply because they were previously unknown. Therefore, not only are the syntheses of CpMo(C0) 2(N0), CpM(N0)2X and CpM(N0)2R descr ibed, but the chemical and physical propert ies of some fur ther der ivar ives of CpM(N0)9X are reported. - 46 -4.2 Experimental A l l experimental procedures described here were performed under the same general condit ions deta i led in sect ion 2.2. 4.2a Preparation of d icarbony l(n 5 -cyc1opentad ieny l )n i t rosy l complexes of chromium, molybdenum and tungsten, CpM(C0)2(N0) (M = Cr , Mo or W). The success of the high y i e l d syntheses of the C p M ^ O ^ N O ) complexes depends on the a v a i l a b i l i t y of the Na[CpM(C0)3] anions uncontaminated by any NaC^Hg. The molybdenum and tungsten sa l t s were obtained according to a published procedure (27), although a 5% mole excess of the M(C0)g compounds was used to improve the y ie lds of the desired anions. A l s o , the tungsten react ion was allowed to continue for 70 h in order to ensure more complete conversion. The chromium s a l t was e f f i c i e n t l y prepared in the fo l lowing manner. A THF so lu t ion containing NaCgHg (27) (4.18 g, 47.5 mmol) was concentrated in vacuo jus t un t i l a s lu r ry formed (approx. 20 ml) . n-Butyl ether (100 ml ; Eastman Kodak p rac t i ca l grade) and Cr(C0)g (11.0 g, 50.0 mmol; Pressure Chemical Co.) were added and the mixture was heated under gentle re f lux for 12 h with vigorous s t i r r i n g . The f i n a l mixture was allowed to cool to room temperature and f i l t e r e d . The pale yel low s o l i d thus co l lec ted was washed with n-butyl ether (3 x 30 ml) and once with hexanes (30 ml ) , and dried at 25°C (5 x 10" 3 mm) for 18 h. The Na[CpM(C0)3] complexes of molybdenum and tungsten were freed of any unreacted M(C0)g by simply taking the f i na l react ion mixture to dryness in vacuo and heating - 47 -the residue to 60° (5 x 10" mm) for 12 h. A l l three sa l t s were used without fur ther p u r i f i c a t i o n . The three CpM(C0)2(N0) complexes were prepared s i m i l a r l y and the experimental procedure using the molybdenum complex as a typ ica l example, was as fo l lows . To a rap id ly s t i r r e d THF so lu t ion (120 ml) containing NaCCpMo^O^] (13.0 g, 48.7 mmol) was added dropwise at room temperature a so lu t ion of Diazald (10.4 g, 48.6 mmol; Eastman Kodak reagent grade) in THF (50 ml) . Gas was evolved and an orange s o l i d p rec ip i ta ted . The f i n a l react ion mixture was taken to dryness in vacuo and sublimation of the residue at 60°C (5 x 10 mm) onto a water-cooled probe for 18 h produced 11.2 g (45.3 mmol, 93% y ie l d ) of a n a l y t i c a l l y pure CpMo(C0) 2(N0). The chromium and tungsten compounds were obtained in y i e l ds of 82 and 84% respec t i ve ly . Ana l . Calcd. fo r C 5 H 5 Cr(C0) 2 (N0) : C, 41.39; H, 2.48; N, 6.90. Found: C, 41.40; H, 2.60; N, 6.70. v(C0) cm" 1 ( in CHpClp): 2020(s); 1945(s).- v(N0) cm" 1 ( in CH 2 C1 2 ) : 1680(s). Calcd. for C 5H 5Mo(C0) 2(N0): C, 34.03; H, 2.04; N, 5.67. Found: C, 34.28; H, 2.24; N, 5.54. v(C0) cm" 1 ( in CH 2 C1 2 ) : 2020(s); 1937(s). v(N0) cm" 1 ( in CHpClpj: 1663(s). Calcd. for C,-HgW(C0)2 (NO): C, 25.10; H, 1.50; N, 4.18. Found: C, 25.29; H, 1.70; N, 4.13. v(C0) cm - 1 ( in CH 2 C1 2 ) : 2010(s); 1925(s). v(N0) cm" 1 ( in-CH^C"^) : 1655(s). - 48 -4.2b Preparation of chloro(n 5-c,yclopentadienyl )dini trosy1 complexes of chromium, molybdenum and tungsten, CpM(N0)2Cl (M = Cr , Mo or W) . A l l three CpM(N0)2Cl compounds were prepared in a s im i l a r manner. The y ie lds of the chromium and tungsten complexes were optimized by performing the react ions at -78°C. The molybdenum compound was obtained in exce l len t y ie lds even at room temperature and a typ ica l synthesis was as fo l lows. A CH 2 C1 2 so lu t ion (100 ml) containing CpMo(C0)2(N0) (6.5 g , 26 mmol) was treated dropwise with rapid s t i r r i n g at room temperature with a so lut ion of ClNO in CH 2 C1 2 . Gas evolut ion occurred and the i n i t i a l orange so lu t ion became dark green. The course of the react ion was followed by in f rared spectroscopy and C1N0 was added jus t un t i l the carbonyl absorptions due to the reactant disappeared. (Great care was taken not to add excessive amounts of ClNO since th i s resul ted in a s i gn i f i can t reduction in the y i e l d of the desired product. Conversely i f i n s u f f i c i e n t C1N0 was employed, then some d i f f i c u l t y was encountered in the separation of the unreacted CpM(C0)2(N0) from the desired product.) The f i n a l react ion mixture was concentrated in vacuo to ca. 30 ml and f i l t e r e d through a short ( 3 x 5 cm) F l o r i s i 1 column. The column was washed with CH 2 C1 2 un t i l the washings were c o l o r l e s s , and the combined f i l t r a t e s were taken to dryness to give 6.0 g (2.3 mmol, 90% y ie l d ) of a n a l y t i c a l l y pure CpMo(N0) 2Cl. The chromium and tungsten complexes were obtained in y i e l ds of 77 and 72% respec t i ve ly . Table V. Elemental Analyses and Physical Propert ies of CpM(N0)9X (M = Cr , Mo or W; X = Cl or I) . Compound Color Mp, °C (under N 2) Analyses, % H N Cl Proton NMR, v(N0) cm - 1 x ( i n C g D 6 ) ( in CH 2C1 2) ^ 5 " C 5 H 5 CpCr(N0) 9Cl gold 144 (dec) ca lcd : found: 28.26 28.29 2.37 2.55 13.18 12.86 16.68 16.99 5.22(s) 1816(s), 1711(s) CpMo(N0)2Cl green 116 ca l cd : 23.42 1.96 10.92 found: 23.53 1.90 10.70 4.93(s) 1759(s), 1665(s) CpW(N0)2Cl green 127 (dec) ca l cd : 17.44 1.46 8.13 10.29 found: 17.68 1.62 8.10 10.26 5.02(s) 1733(s), 1650(s) CpCr(N0) 2I dark gold 146 (dec) ca l cd : 19.75 1.66 9.22 found: 19.71 1.76 9.00 5.28(s) 1808(s), 1718(s) CpMo(N0)2I o l i ve green 114 (dec) ca l cd : 17.26 1.45 8.05 found: 17.33 1.40 7.88 5.00(s) 1764(s), 1677(s) CpW(N0)9I o l i ve green 129 (dec) ca lcd : 13.78 1.16 6.43 found: 13.78 1.17 6.36 4.94(s) 1740(s), 1657(s) - 50 -The complexes, along with the i r elemental analyses and physical p roper t ies , are l i s t e d in Table V. 4.2c Preparation of (n 5 -cyc lopentad ieny l ) iodod in i t rosy l complexes of  chromium, molybdenum and tungsten, CpM(N0),,I (M = Cr , Mo or W). A l l the CpM(N0)2I complexes were prepared in a s im i l a r manner and the customary procedure for the synthesis of the CpCr(N0) 2I compound was as fo l lows . A THF so lu t ion (150 ml) containing CpCr(N0) 2Cl (2.54g, 12.0 mmol) and Nal (9.0 g, 60 mmol; Mal l inckrodt reagent grade) was s t i r r e d at room temperature for 18 h. The react ion mixture became a very dark yellow-brown in co lor and a white s o l i d formed. The f i na l mixture was taken to dryness in vacuo and the resu l tant residue extracted into CH 2C1 2 (150 ml). The extract was f i l t e r e d through a short ( 3 x 5 cm) F lo r i s i 1 column and taken to dryness in vacuo (5 x 10 mm) thereby af fording a v i r t u a l l y quant i ta t ive y i e l d of the a n a l y t i c a l l y pure CpCr(N0) 2I complex. The elemental analyses and physical propert ies of a l l three CpM(N0)2I compounds are given in Table V. 4.2d Preparation of b is[(n 5 -cyclopentadieny1)ethoxoni t rosylchromium],  [CpCr(N0)(0Et) ] 2 . A so lu t ion of CpCr(N0) 2Cl (2.13 g , 10.0 mmol) in EtOH (120 ml) was treated with NaOEt (0.80 g, 12.0 mmol) at room temperature. Immediately, the mixture became yel low-red and a f ine white s o l i d formed. - 51 -The mixture was s t i r r e d f o r 0.5 h and the in f rared spectrum of the supernatant l i q u i d displayed absorptions at 1792 cm - 1 ( s ) and 1585 cm - 1 ( s ) ind ica t i ve of the CpCr(N0)2(0Et) complex (cf . in f rared spectrum of CpCr(N0) 2 Cl, v(N0) cm" 1 ( in EtOH): 1812(s); 1708(s)). The solvent was removed in vacuo y ie ld ing a red o i l . During f i na l drying at 25°C (5 x 10 mm) for 0.5 h, the red o i l was transformed to a green s o l i d . This product was extracted into CH^Cl^ (25 ml) and chromatographed through a F l o r i s i 1 column (2.5 x 8 cm) with CH 2 C1 2 as e luent . The eluate was taken to dryness in vacuo (5 x 10 mm) y i e l d i ng 0.64 g (3.3 mmol, 33% y i e l d ) of the o l ive-green [CpCr(N0)(0Et)] 2 compound. Anal . Calcd. fo r [C 5H 5Cr(N0)(0Et)] 2: C, 43.58; H, 5.21; N, 7.40. Found: C, 43.78; H, 5.26; N, 7.29. v(N0) cm" 1 ( in CH 2 C1 2 ) : 1660. Mp. (under N 2 ) : 233°C (dec). The CpM(N0)2Cl (M = M or W) complexes reacted with LiOEt in THF producing yel low-red solut ions which, when taken to dryness, y ie lded yel low-red o i l s . These o i l s remained unchanged even a f ter heating at 95°C (5 x 10 mm) for 2 h. Their in f rared spectra suggested that the products were CpMo(N0)2Et (v(N0) cm" 1 ( in CH 2 C1 2 ) : 1740(s); 1630(s)) and CpW(N0)2Et (v(N0) cm" 1 ( in CH 2 C1 2 ) : 1710(s); 1610(s)). 4.2e Preparation of bis[ch1oro(n 5 -cyclopentadieny1)ni t rosylchromium],  [CpCr(N0)Cl ] 2 , A sample of [CpCr(N0)2(0Et)]2 (0.19 g, 1.0 mmol) was d issolved in benzene (30 ml) and dry HCl(g) was bubbled through the so lu t i on . Immediately, the off-green react ion mixture became a very intense green - 52 -in co lo r . Enough HCI(g) was added to jus t completely consume the i n i t i a l reactant (monitored by in f rared spectroscopy). The mixture was taken to dryness in vacuo and the product c r y s t a l l i z e d from CH 2 C1 2 (20 ml) by the addi t ion of hexanes (50 ml) . The s o l i d was co l lec ted by f i l t r a t i o n and dr ied at 25°C (5 x 10~3mm) to give 0.16 g (0.88 mmol, 88% y i e l d ) of the green [CpCr(N0)C1] g complex. Ana l . Calcd. for [ C ^ C r (N0)C1 ] 2 : C, 32.90; H, 2.76; N, 7.67. Found: C, 32.50; H, 2 .61; N, 7.66. v(N0) cm" 1 ( in CHgCl 2 ) : 1678. Mp. (under N 2): 140 (dec). 4.2f Preparation of a l k y l - and a r y l -(n 5 - c y c ! o p e n t a d i e n y l ) d i n i t r o s y l  complexes of chromium, molybdenum and tungsten, CpM(N0)2R (M = Cr , Mo or W; R = a lky l or a r y l ) . Since the various a lky l and ary l der iva t ives were s i m i l a r l y prepared, two representat ive syntheses are described below. Table VI summarizes the pa r t i cu la r experimental d e t a i l s . 4 .2 f l Preparation of (n 5 -cyc lopentad ieny l )methy ld in i t rosy l tungsten,  CpW(N0)2Me . A benzene so lut ion (12 ml) containing jte^Al (0.22 g , 3.1 mmol; Texas A l ky l s ) was added dropwise at room temperature to a s t i r r e d so lu t ion of CpW(N0)2Cl (1.0 g, 2.9 mmol) in benzene (25 ml). The green so lu t ion was allowed to s t i r for 48 h during which time a red-brown o i l y s o l i d deposited on the wal ls of the react ion f l ask . (The react ion was followed - 53 -Table VI. Reaction Conditions and P u r i f i c a t i o n Methods for CpM(N0)9R . Compound A lky la t ing or Reaction P u r i f i c a t i o n Ary la t ing Agent time (hours) methods CpCr(N0) 2 C g H 5 (C 6 H 5 ) 3 A1 0.5 AB CpCr(N0) 2CH 3 (CH 3) 3A1 0.5 AB CpCr(N0) 2 C 2 H 5 (C 2 H 5 ) 3 A1 0.5 A C p C r ( N 0 ) 2 i - C 4 H g ( i - C 4 H g ) 2 A ! H 0.5 A C p M o ( N 0 ) 2 C g H 5 (C 6 H 5 ) 3 A1 1 .5 AA CpMo(N0)2CH3 (CH 3) 3A1 1 A CpMo(N0) 2C 2H 5 (C 2 H 5 ) 3 A1 1 A CpMo(N0) 2 i -C 4 H g ( i - C 4 H g ) 2 A ! H 0.5 A CpW(N0) 2C gH 5 W3A1 1 AB CpW(N0)2CH3 (CH 3) 3A1 48 AB +A-B -chromatographic separation on alumina using benzene as the eluant . sublimation in vacuum - 54 -by in f rared spectroscopy and such monitoring of several experiments showed these to be the optimum stoichiometry and react ion t ime.) Judging from the re la t i ve v(N0) band i n t e n s i t i e s of the f i na l react ion mixture, the CpW(N0)2Me product and unreacted CpW(N0)2Cl W ere present in ca_. equimolar quan t i t i es . The react ion mixture was concentrated in vacuo to ca . 15 ml and the supernatant l i q u i d chromatographed in a short ( 3 x 7 cm) column of alumina (Woelm neutral grade 1) with benzene as eluent. The eluate was taken to dryness in vacuo and the resu l tant _ q s o l i d sublimed at 30°C (5 x 10 mm) onto a water-cooled probe af ford ing 0.20 g (0.62 mmol, 20% y ie l d ) of a n a l y t i c a l l y pure CpW(N0)2Me. 4.2f2 Preparation of [n 5-cyclopentadieny1)dinitrosylphenylmo1ybdenum,  CpMo(N0)2Ph . A so lu t ion of Ph 3Al (28) (0.35 g , 1.4 mmol) in benzene (70 ml) was added dropwise to a so lut ion of CpMo(N0)2Cl (1.0 g, 3.9 mmol) in the same solvent (30 ml). A red-brown s o l i d formed and the mixture was fur ther s t i r r ed for 1 h at which point the in f rared spectrum of the supernatant l i q u i d confirmed the deplet ion of the i n i t i a l reactant . The f i na l react ion mixture was concentrated in vacuo to ca . 20 ml and the supernatant l i q u i d was chromatographed on an alumina column. The product was eluted with benzene and only the main port ion of the green product band was co l l ec ted . The solvent was removed from the eluate and the residue was dr ied at room temperature in vacuo (5 x 10 mm) for 4 h thus providing 0.65 g (2.2 mmol, 56% y i e l d ) of CpMo(N0)2Ph as an a n a l y t i c a l l y pure o l ive-green o i l . - 55 -A l l the other complexes in Table VII were obtained in y i e l ds of 30-50%. Their elemental analyses and physical propert ies are given in Tables VII and VI I I . A l l the complexes are stable in a i r fo r short periods of time but are best stored under nitrogen and below 0°C. They are very soluble in common organic solvents inc luding hexanes. 4.2g Preparation of b is [ (n 5 -cyc lopen tad ieny l )d in i t rosy lch romium] ,  [ C p O ( N 0 ) 2 ] 2 . To an amalgam made from sodium (0.5 g, 20 mmol) and mercury metal (20 ml) was added a so lut ion of CpCr(N0) 2Cl (1.06 g, 5.00 mmol) in benzene (120 ml). This react ion mixture was s t i r r e d v igorously at room temperature un t i l the in f rared spectrum of the supernatant l i q u i d contained no absorption bands due to the i n i t i a l reactant (ca_. 1.5 h). [Reaction beyond th is point led to decomposition of the desired product.] During the course of the react ion a grey so l i d was deposited and the solut ion became red-purple in co lo r . The supernatant l i q u i d was syringed from the amalgam and concentrated in vacuo to ca_. 20 ml. This so lut ion was t ransferred to a short (2 x 5 cm) column of alumina (Woelm neutral grade 1) and the column was eluted with benzene un t i l the washings were co lo r less (ca_. 120 ml) . Solvent was removed from the eluate in vacuo and the remaining purple-black s o l i d was dr ied at room temperature under high vacuum'(5 x 10 mm) for 2 h. In th is manner 0.68 g (1.9 mmol, 77% y ie l d ) of the a n a l y t i c a l l y pure [CpCr (N0) 2 l 2 complex was obtained. Ana l . Calcd. fo r [ ( C 5 H 5 ) C r ( N 0 ) 2 ] 2 : C, 33.91; H, 2.85; N, 15.82. Found: C, 33.78; H, 2.75; N, 15.82. v(N0) cm - 1 ( in C H 2 C 1 2 ) : 1667(s); 1512(m). Mp. (in a i r ) : 147°C (dec). - 56 -Table VII. Elemental Analyses and Physical Propert ies of CpM(N0)9R. Compound Color Mp,°C Analyses,% ( i n a i r ) ca lcu lated found C H N C H CpCr(N0) 2 C g H 5 dark green 48-48.5 51.97 3 .97 11 .02 52 .05 4 .10 10 .97 CpCr(N0) 2CH 3 dark green 80.5-81.0 37.51 4 .20 14 .58 37 .42 4, .19 14 .49 CpCr(N0) 2 C 2 H 5 green o i l 40.79 4 .89 13 .59 40 .74 4, .90 13 .46 CpCr (N0) 2 i -C 4 H g green o i l 46.15 6 .03 11 .96 46 .38 6, .20 11 .62 CpMo(N0) 2C 6H 5 o l i ve green o i l 44.31 3 .38 9 .40 44 .28 3, .46 9 .13 CpMo(N0)2CH3 green 61.5-62.0 30.53 3 .42 11 .87 30 .69 3 .33 11 .82 CpMo(N0) 2C 2H 5 green o i l 33.52 4 .03 11 .20 34 .05 4 .38 10 .90 CpMo(N0) 2 i -C 4 H g green o i l . 38.86 5 .07 10 .07 39 .33 5 .23 10 .06 CpW(N0)2CgH5 green 109-110 34.22 2 .61 7 .26 34 .38 2 .74 7 .03 CpW(N0)2CH3 pale green 75-76 22.24 2 .49 8 .65 22 .54 2 .42 8 .60 - 57 -Table VIII . IR and 'h! NMR Data for CpM(N0)2R. Compound IR a ] H NMR x( in CgDg) v(N0) cm" 1 n 5-C,-rL others CpCr(N0) 2Cl 1815(s) 1710(vs) b 5.22 -CpCr(N0) 2 C 6 H 5 1792 1690 5.27 2.7(m)C CpCr(N0) 2CH 3 1780 1675 5.63 9.55 (s ing le t CH 3) CpCr(N0) 2 C 2 H 5 1772 1670 5.45 8.6(m) CpCr (N0) 2 i -C 4 H g 1775 1675 5.33 8-9(m) CpMo(N0)2Cl 1758 1665 b 4.93 -CpMo(N0) 2C gH 5 1745 1658 . 4.90 2.7(m) CpMo(N0)2CH3 1728 1640 4.92 9.20 (s ing le t CH3) CpMo(N0) 2C 2H 5 1735 1643 4.90 8.2(m) CpMo(N0) 2 i -C 4 H g 1725 1638 4.93 7.6-8.8(m) CpW(N0)2Cl 1733 1650 b 5.02 -CpW(N0) 2C gH 5 1713 1630 4.95 2.6(m) CpW(N0)2CH3 1705 1620 4.98 8.82 (s ing le t CH 3) Hexane so lut ion unless indicated otherwise. Dichloromethane so lu t i on . Approximate centroid of complex mul t ip le t (m). - 58 -4.3 Results and Discussion 4.3a The d icarbony l (n 5 -cyc lopentad ieny l )n i t rosy l complexes of chromium,  molybdenum and tungsten, CpM(C0)p(N0) (M = Cr , Mo or W) . A l l three CpM(C0)2(N0) compounds were obtained according to the fo l lowing sequence of reac t ions : NaC 5H 5 + M(C0) 6 * - Na[CpM(C0)3] + 3C0 Na[CpM(C0)3] + p-CH 3C 6H 4S0 2N(N0)CH 3 — — » ~ CpM(C0)2(N0) + C0 + p-CH 3C 6H 4S0 2N(CH 3)Na The success of th i s synthet ic route depends c r i t i c a l l y on the a v a i l a b i l i t y of the corresponding Na[CpM(C0)3] sa l t s which are free of any unreacted NaCgHg. The presence of th is contaminant i s immediately evident upon subsequent react ion with Diazald since a brown-black, rather than the expected orange-red, react ion mixture i s obtained. Furthermore, the y i e l d of the desired carbonyln i t rosy l i s d r a s t i c a l l y reduced. However, once the s u f f i c i e n t l y pure anions are obtained, t he i r react ion with Diazald in THF produces the CpM(C0)2(N0) complexes in exce l l en t , reproducible y ie lds ranging from 82-93%, depending on M. A l s o , these syntheses can be eas i l y scaled to produce the desired products in quant i t ies as large as 30 g while s t i l l maintaining the same high y i e l d s . Undoubtedly, the experimental procedures described for the preparation of these complexes are the most convenient thus far developed (27, 77, 78, 80, 81 ). - 59 -The Na[CpM(C0)3] (M = Mo or W) sa l t s can be read i l y obta ined, in THF under r e f l u x , according to a published procedure (27). However, to ensure complete conversion important modif icat ions have been necessar i l y made. Thus, the syntheses are performed with NaCp as the l i m i t i n g reagent and the react ion involv ing the tungsten compound i s allowed to continue for the extended period of 72 hours. Unfortunately, under the same cond i t ions , Cr(C0)g and NaC^Hg react very slowly and the conversion a f ter seven days of react ion i s s t i l l r e l a t i v e l y low. Although diglyme has been previously employed in the preparation of Na[CpCr(C0) 3] (79), i t s strong solvat ing cha rac te r i s t i cs renders i t s use imprac t i ca l . However, i f Cr(C0)g and NaCgHg are allowed to react in n-BupO under re f lux for 18 hours, a v i r t u a l l y quant i ta t ive y i e l d of the desired product i s obtained. The Na[CpCr(C0) 3 ] , insoluble in n-BupO, prec ip i ta tes as a c r y s t a l l i n e pale yel low s o l i d during the course of the reac t ion . Subsequent p u r i f i c a t i o n , to remove excess M(C0)g, of the Na[CpM(C0)3] compounds i s eas i l y performed as described in the Experimental sec t ion . The propert ies of the C p M ^ O ^ N O ) compounds have been previously described (2, 3, 28). The complexes are orange to orange-red so l ids read i l y soluble in organic solvent and stable in a i r fo r short periods of t ime. However, they may be stored i n d e f i n i t e l y under nitrogen at room temperature. 4.3b The ch loro(n 5 -cyc1opentad ieny l )d in i t rosy l complexes of chromium,  molybdenum and tungsten, CpM(N0)9Cl (M = Cr , Mo or W). The high y i e l d syntheses of a l l three complexes are ef fected by - 60 -the treatment of CpM(C0)2(N0) with C1N0 in CH 2 C1 2 , according to eq. 19. CpM(C0)2(N0) + C1N0 e-CpM(N0) 2 Cl + 2C0 19. (M = Cr , Mo or W) In order to maximize y i e l d s , the transformations invo lv ing the chromium and tungsten containing compounds must be performed at -78°C, while the molybdenum complex can be obtained in exce l len t y ie lds at room temperature. The l a t t e r react ion is accompanied by the formation of a small amount of [CpMo(N0)Cl 2 ] 2 , i den t i f i ed by elemental analys is and i t s cha rac te r i s t i c in f rared spectrum (104). Since th is byproduct can a lso be formed by the d i rec t treatment of CpM(C0)2(N0) with C l 2 (104), i t s appearance simply re f l ec t s the fac t that ClNO ex is ts in so lu t ion as part of the equi l ibr ium 2C1N0-^ — 2N0 + C l 2 As in most react ions between the n i t rosy l hal ides and metal carbonyls, special at tent ion must be taken to avoid excess n i t rosy l ha l ide . T y p i c a l l y , the above conversions are followed by in f rared spectroscopy and enough C1N0 is added un t i l the carbonyl absorptions of the reactant have jus t disappeared. In t h i s manner, the fur ther react ion of the desired products i s e f f ec t i ve l y prevented. In any case, the general a p p l i c a b i l i t y of the react ion given by eq. 19, u t i l i z i n g the now read i l y ava i lab le s ta r t i ng mater ia ls , makes th is high y i e l d preparative route superior to a l l others thus far reported (27, 29, 59, 83, 84, 105). - 61 -The CpM(N0)2Cl complexes, along with some of the i r physical p roper t ies , are presented in Table V. They are c r y s t a l l i n e so l ids which have low s o l u b i l i t y in hexanes but are very soluble in most other organic so lvents . Contrary to a previous report (83), CpMo(N0) 2Cl, as well as the chromium and tungsten de r i va t i ves , are stable i n d e f i n i t e l y under nitrogen at room temperature, and a l l three can be exposed to a i r for short periods of time without not iceable decomposition. Furthermore, the molybdenum complex melts at 116°C without decomposition and a l l three compounds may be sublimed at 40-50°C (5 x 10 mm) although some decomposition occurs with the chromium and tungsten species. Chemical ly, the CpM(N0)2Cl compounds are useful precursors for the synthesis of a wide var ie ty of stable a lky l and ary l complexes, CpM(N0)2R, as discussed subsequently. A l l three CpM(N0)2I complexes are obtained in quant i ta t ive y ie lds by the d i s p r o p o r t i o n a t e react ion between Nal and the corresponding chloro complexes in THF. Their physical (Table V) and chemical propert ies are very s im i la r to those of the chloro compounds. The molybdenum and tungsten complexes have not been previously reported. The x-ray c rys ta l st ructure of CpCr(N0) 2Cl indicates a pseudo-tetrahedral ("piano s too l " ) arrangement of l igands about the chromium atom (106) as in C. The Cj-H^ r ing randomly occupies one of two coplanar O - 62 -or ientat ions in which a l l the Cr-C distances are approximately equal , the o average distance being 2.20 A. The Cr-NObond distances of 1.717 (0.012) and 1.704 (0.013) A, which are v i r t u a l l y ident ica l to the value of 1.716 (0.003) found in CpCr(N0)2(NC0) (107), are about 0.4 A shorter than the expected Cr-N(sp) bond length. In f a c t , the Cr-N bond order i s estimated to be 1.7, ind ica t ing the n i t rosy l i s bonded as N0 + with appreciable e lectron donation from the Cr(d) to the N(pir*) o r b i t a l s . The Cr-N-0 fragments in both the chloro and isocyanato compounds depart from l i n e a r i t y by about 10°. This i s ascribed to e l ec t r os ta t i c repuls ion between the oxygen atom of the n i t rosy l l igand and the ch lor ide or isocyanate l igand rather than to c rys ta l packing fo rces . The mass spectral data for the CpM(N0)2Cl complexes, given in Tables IX and X, exh ib i t the expected fragmentation pat terns. The presence of MCp+ and MCpCl + and the concurrent absence of M(N0) + and M(N0)C1+ fragments can be a t t r ibuted to the fac t that the M-Cp l inkage i s stronger than the M-N0 bond. The mass spectrum of CpMo(C0)2(N0) d isplays a s im i l a r behavior (108). Furthermore, as i s found in the cases of CpFe(C0) 2Cl (108) and CpMo(C0)3Cl (109), the M-Cp and M-Cl bonds in the CpM(N0),,Cl complexes are ruptured with about equal d i f f i c u l t y . The [MC 3 H 3 ] + fragments, which occur f requent ly in the mass spectra of Cp-containing complexes, are not observed for the chromium compound but become increas ing ly abundant for the molybdenum and tungsten analogs. In add i t i on , the r e l a t i ve abundance of fragments containing the n i t rosy l group suggest a M-N0 bond strength which increases as Mo < Cr < W, - 63 -Table IX. High Resolution Mass Spectral Data for CpCr(N0) 9 Cl. m/e r e l a t i ve assignment measured ' ca lcu la ted abundance 213.9423 213.9414 11.9 C 5 H 5 C r ( N 0 ) 2 3 7 C l " 211.9440 211.9444 32.6 C 5 H 5 Cr(N0) 2 Cl 183.9447 183.9434 13.8 C 5 H 5 C r ( N 0 ) 3 7 C l + 181.9476 181.9464 36.6 C 5 H 5 C r ( N 0 ) 3 5 C l + 153.9459 153.9455 36.6 37 + 5 5 151.9481 151.9484 100 35 + C 5 H 5 Cr °C1 176.9796 176.9756 5.3 C 5 H 5 C r ( N 0 ) 2 + 146.9818 146.9776 3.4 C c H c Cr(N0) + 116.9784 116.9796 18.0 C 5 H 5 C r + 88.9050 88.9063 10.6 C r 3 7 C l + 86.9089 86.9093 23.9 C r 3 5 C l + 65.0396 65.0391 13.3 C 5 H 5 + 51.9412 51.9404 13.8 C r + - 64 -Table X. Low Resolution Mass Spectral Data for CpM(N0) 2 Cl a . (M = Mo or W) CpMo(N0)2Cl CpW(N0)2Cl m/e Relat ive Abundance Assignment m/e Relat ive Abundance Assignment 258 43.7 C 5 H 5 Mo(N0) 2 Cl + 344 100 C 5 H 5 W(N0) 2 C1+ 228 33.5 C c H c Mo(N0)Cl + O 0 314 81.0 C 5H 5W(N0)C1 + 198 100 C 5 H 5 MoCl + 284 53.7 C 5H 5WC1+ 172 30.4 C 3 H 3 MoCl + 258 71.4 C 3 H 3 W C 1 + 163 7.5 C 5 H 5 Mo + 249 28.1 C 5 H 5 W+ 137 12.4 C 3 H 3 Mo + 223 13.0 C 3 H 3 W + 133 24.2 MoCl + 219 16.0 WC1 + 98 10.4 Mo+ 184 2.1 w + 65 3.7 C 5 H 5 + 65 6.8 C 5 H 5 + a The assignments involve the most abundant natura l ly occurr ing isotopes, i . e . 9 8 M o , 1 8 4 W and 3 5 C 1 , in each fragment. - 65 -s im i la r to the ordering of the M-CO bond strengths in the CpM(C0)3Cl compounds (28). A wide var ie ty of der ivat ives of the type CpCr(N0) 2X (X = F, Br, I, CN, NCS, N0 2 (82), and NCSe (85)) have been obtained by the treatment of an aqueous so lut ion of [CpCr(N0) 2 ] + , generated from CpCr(N0) 2Cl and AgNO-j, with NaX or KX. The isoselenocyanato complex decomposes read i l y in so lut ion to give CpCr(N0)2CN and elemental selenium. A l s o , CpCr(N0) 2SCF 3 i s formed when the chloro compound i s allowed to react with AgSCF3 in acetone (110). In the above reac t ions , the intermediary n i t ra te s a l t has not been previously i so l a ted . However, we f ind that treatment of CpCr(N0) 2Cl with AgNO^ or AgBF^ in water produces a p rec ip i ta te of AgCl and a dark green supernatant so lu t i on . Subsequent ext ract ion of the dr ied react ion mixture into CH^Cl 2 fol lowed by c r y s t a l l i z a t i o n from CH 2 Cl 2 /hexanes y ie lds the CpCr(N0) 2N0 3 and CpCr(N0) 2BF 4 compounds as stable green so l ids which are soluble in most organic solvents except hydrocarbons. Their in f rared spectra in CH2C12 d isp lay n i t rosy l s t retching absorptions at 1841 and 1738 c m " 1 , and at 1848 and 1744 cm" 1 fo r the N0 3 " and BF^" sa l t s respec t i ve ly . These absorptions are s im i l a r to those displayed by [ C p C r ( N 0 ) 2 ] + [ A l C l 4 ] " (111) and are consistent with reduced Cr(diO to N(pir*) donation. However, present attempts to perform the same react ion with the molybdenum complex proceeded with gas evolut ion and attendant decomposition. - 66 -4.3c Bis[ (n 5 -cyclopentadienyl)ethoxoni t rosylchromium], [CpCr(NO)(0Et)] 2 , and bis[ch1oro(n 5 -cyclopentadieny1)nitrosylchromium, [CpCr(NQ)C1] 2 . When CpCr(N0)2C1 i s treated with NaOEt in EtOH or with LiOEt in THF, the CpCr(N0) 20Et can be iso la ted as an unstable red o i l . I ts in f rared spectrum in EtOH displays absorptions at 1792 and 1685 c m - 1 , which are s i g n i f i c a n t l y lower than those of the chloro complex ( i . e . 1812 and 1708 cm - 1 in EtOH) due to the greater e lectron donating a b i l i t y of the alkoxide l igand. Upon exposure to high vacuum at room temperature, CpCr(N0) 2(0Et) spontaneously loses n i t r i c oxide to form the new o l i ve green s o l i d , [CpCr(NO)(0Et)] 2» according to eq. 20. This 2CpCr(N0) 2(0Et) [CpCr(NO) (0E t ) ] 2 + 2N0 20. same transformation can be ef fected by the e lu t ion of a CH 2 C1 2 so lu t ion of the d i n i t r osy l compound through an alumina column. The dimeric spec ies , i den t i f i ed by elemental analys is and mass spectrometry, contains in i t s in f rared spectrum a s ing le terminal n i t rosy l absorption at 1660 cm - 1 in C H 2 C 1 2 , s im i l a r to the previously reported [CpCr(N0)L] 2 (L = NMe2, SPh and SMe) compounds (87, 88). The [CpCr(NO)(OEt)] complex i s soluble in most organic solvents and can be handled in a i r fo r short periods of time without not iceable decomposition. It decomposes without melting at 233°C, under n i t rogen. On the other hand, the s im i la r react ions of the molybdenum and tungsten chloro compounds with the above reagents y i e l d only reddish o i l s s im i la r in appearance to CpCr(N0) 9 (0Et). A comparison of the i r in f rared - 67 -spectra with those of the s ta r t i ng chloro complexes, given in the Experimental sect ion and in Table V, suggests that these compounds can be formulated as CpM(N0) 2(0Et). They possess a remarkable thermal s t a b i l i t y since heating to 95°C under vacuum for two hours e f fec ts no change. A l s o , the attempted dimer izat ion on an alumina column resul ted only in complete decomposition, and a n a l y t i c a l l y pure samples of the d i n i t r o s y l s cannot be obtained. The CpM(N0)2L (L = SBu, NPh2 and NH2) complexes are prepared s i m i l a r l y and they exh ib i t a behavior s im i l a r to the ethoxide der i va t i ves . A var ie ty of [CpMo(N0)L]2 and [CpMo(N0)L212 (L = I, SPh, SCH2Ph and C02R.p) have been reported but they are obtained from [CpMo(N0)I 2 ] 2 rather than CpMo(N0)2Cl (95-97). The react ion of [CpCr(NO)(0Et)] 2 with gaseous HC1 in benzene affords the novel green [CpCr(N0)C1] 2 complex in high y i e l d , according to eq. 21. Without making any impl icat ions as to the mechanism, th i s conversion [CpCr(N0)(0Et)] 2 + 2HC1 >- [CpCr(N0)C1] 2 + 2EtOH 21. can be considered as an acid-base react ion between H + and OEt" , and in p r i n c i p l e , a s im i l a r transformation should occur with any acid stronger than EtOH. As expected, the subst i tu t ion of the ethoxide group by the chlor ide anion causes the terminal n i t rosy l s t re tch ing frequency to increase from 1660 to 1678 cm" 1 . Like [CpCr(NO)(0Et)] 2 , the chloro der iva t ive i s very soluble in common organic solvents except hexanes and, though stable in a i r for short periods of t ime, i s best stored under n i t rogen. The structures of [CpCr(NO)(0Et)] 2 and [CpCr(N0)C1] 2 are expected to be s im i l a r to those of [CpCr(NO)(SPh)] 0 (91) and - 68 -[CpCr(MO)(NMe 2)] 2 (92), which are character ized by symmetrically br idging SPh and NMe2 l igands and by a d i s t i n c t metal-metal bond. Both the trans and c i s forms, D and E, can be i so l a ted . A l s o , the structure of D Cp 2Cr 2(N0) 2(NH 2) shows a trans arrangement containing both n i t rosy l and amido bridges (94). The Cr-N l inkages of the terminal ly coordinated n i t rosy l groups have considerable double bond character , while the Cr-N-0 bond angles are approximately 170°, as they are a lso in CpCr(N0) 2Cl and CpCr(N0)2(NC0) (106, 107). The dimeric nature of [CpCr(NO)(0Et)] 2 and [CpCr(N0)Cl] 2 i s confirmed by the i r mass spectral data, shown in Table XI . The fragmen-ta t ion pat terns, ind ica t ing the loss of NO, e t h y l , ethoxo, chloro and Cj-H5 fragments, are s im i la r to those found in the mass spectra of [CpMo(N0)I] 2 and [CpMo(NO)(SCH 2Ph)] 2, in which the parent ions are a lso r e l a t i v e l y abundant (95). In the mass spectra of both the chloro and ethoxo complexes the in tens i ty pattern at m/e = 182 i s ind ica t i ve of [ C p 2 C r ] + rather than the [ ( C 3 H 3 ) 2 C r 2 ] + or [CpCr(N0)C1] + fragments. The same assignment has been made in the cases of [CpCr(NO)(SMe)] 2 (88) and Cp 9Cr 9(N0)^(NH 9) (89), where [ C p 9 C r ] + i s thought to a r i se from the - 69 -Table XI. Low Resolution Mass Spectral Data for [CpCr(N0)X] a [CpCr(N0)(0Et)] 2 [CpCr(N0)Cl] 2 m/e Relat ive Abundance Assignment m/e Relat ive Abundance Assignment 384 0.6 C p 2 C r 2 ( 0 E t ) 2 ( N 0 ) 2 364 0.4 C p 2 C r 2 C l 2 ( N 0 ) 2 354 6.8 C p 2 C r 2 ( 0 E t ) 2 ( N 0 ) + 334 3.3 C p 2 C r 2 C l 2 ( N 0 )+ 324 10.0 C p 2 C r 2 ( 0 E t ) 2 304 3.4 C p 2 C r 2 C l 2 295 1.5 Cp 2 Cr 2 ( 0E t )0 + 182 10.0 C p 2 C r + 279 1.7 C p 2 C r 2 ( 0 E t ) + 152 2.9 CpCrCl+ 250 2.1 C p 2 C r 2 0 + 117 3.1 CpCr+ 182 6.4 Cp 2 Cr + 52 2.3 C r+ 162 1.4 CpCr(0Et) + 117 0.9 CpCr + 52 1.4 C r + a The assignments involve the most common natura l ly occurr ing isotopes, i . e . ^ C r and J 0 C 1 . - 70 fragmentation of the metastable [Cp2Cr2$2] + and [Cp2Cr2(NH2)]+ species respec t ive ly . 4.3d The a l k y l - and ary1-(n 5-c,yclopentadienyl )d in i t rosy l complexes of  chromium, molybdenum and tungsten, CpM(N0)pR (M = Cr , Mo or W;  R = a.l kyl or a r y l ) . These complexes are obtained in reasonable y i e l ds by the react ion of the corresponding C p M ^ O ^ C l compounds with the appropriate organo-aluminum reagent according to the general eq. 21, CpM(N0)2Cl + R - A l ^ b - £ ! l ^ r j £ H 5 ^ CpM(N0)2R + C l - A l ^ 21. where M = Cr , Mo or W and R = a lky l or a r y l . During the course of the react ion an o i l y red-brown s o l i d of undetermined composition i s deposi ted, and the exact nature of the aluminum byproduct remains to be ascer ta ined. This synthet ic procedure appears to be quite general for the chromium and molybdenum compounds and i s l im i ted only by the a v a i l a b i l i t y of the appropriate A l r e a g e n t . However, in the case of tungsten, only the phenyl and methyl der iva t ives are obtained, the l a t t e r only a f te r a prolonged react ion time. Treatment of Cpl^NO^Cl with Et^Al or AlH(i-Bu)2 under various react ion condit ions f a i l s to give the expected a lky la ted products. In te res t ing ly , in the react ions invo lv ing A l H ( i - B u ) 2 only the i-Bu group, rather than the hydr ide, i s t ransferred to the metal. The Me, Et and Ph der ivat ives of chromium were previously reported (27) but are obtained here in better y i e l d s . The remaining a lky l - 71 -and ary l complexes were unknown pr io r to th is work. The physical propert ies of these complexes are summarized in Tables VII and VI I I . A l l the complexes are very soluble in organic sol vents, inc lud ing hexanes, and may be exposed to a i r for short periods of time without decomposition. Those compounds which are so l ids at room temperature _q sublime read i l y at 30-40°C (5 x 10 mm) without decomposition and a re , indeed, best pur i f i ed in th is manner. However, the ones which are l i q u i d s at room temperature decompose slowly under nitrogen but may be stored for many months at -5°C or lower. The methyl and phenyl de r i va -t i v e s , espec ia l l y those of chromium, are the most thermally stable and melt without decomposition. The in f rared spectra (Table VI I I ) of a l l the complexes d isp lay two strong absorpt ions, s im i l a r to those in CpM(N0) 2Cl, due to terminal n i t rosy l N-0 s t re tch ings. As expected, these s t re tch ing frequencies decrease in the order Cl > Ph > a lky l which pa ra l l e l s the a b i l i t y of these l igands to withdraw e lec t ron ic charge from the centra l metal . The proton NMR spectra (Table VII I ) exh ib i t a sharp s ing le t f o r the C^Hg protons as well as the expected patterns and in tegrat ion ra t ios for the a lky l and ary l protons. Not too su rp r i s i ng l y , the pos i t ion of the Cp resonance remains nearly independent of the ch lo ro , a lky l or ary l subst i tuent present for any given metal. Any e lec t ron ic perturbation about the central metal i s buffered by the presence of the strong T T -accepting n i t rosy l l igands. In f a c t , the N-0 st retching frequencies do vary s i g n i f i c a n t l y , as mentioned, and hence provide a more sens i t i ve measure for detect ing changes in e lec t ron ic d i s t r i bu t i on around the central F igure2. *H N M R of ( T 7 5 - C 5 H 5 ) M O ( N 0 ) 2 C H 2 C H 3 Experimental spectrum T 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 r I 1 1 1 1 1 1 1 " 1 1 1 1 1 1 1 1 1 r - 73 -metal. The presence of the a-bonded ethyl group in CpMo(N0)2Et i s unequivocally demonstrated by the computer f i t t i n g of the A 2 B 3 mu l t ip le t due to the a lky l proton resonance, from which the fo l lowing parameters can be extracted (Figure 2) : x ( C H 2 ) 8.10, T ( C H 3 ) 8.26, J ( C H 2 , C H 3 ) 7.54 Hz^. The mass spectral data for each complex in Table XII exh ib i t the molecular ion as the highest-mass fragment. The fragmentation patterns for the Et and i-Bu der iva t ives of molybdenum are s i m i l a r , but assignments are complicated by concomitant fragmentation of the a lky l groups and by the large number of molybdenum isotopes. The most s t r i k i n g di f ference between the phenyl and methyl complexes i s the systematic absence of the [CpM(N0)] + and [CpM(N0) 2 ] + fragments in the phenyl compounds, and the absence of [ (C 3 H 3 )MR] + and [CpMR]+ in the methyl de r i va t i ves . These data strongly suggest that the metal-carbon bond i s stronger in the phenyl than in the methyl compounds, and that the trend i s independent of the metal. The major d i f ference among the metals i s that the chromium-containing complexes show an abundance of C r + and [CpCr] + fragments whereas, for the molybdenum- and tungsten-containing analogs, the cor res-ponding fragments are much less abundant. The two most general preparative routes to a-bonded a lky l and ary l complexes involve the nuc leoph i l i c displacement of the hal ide from e i ther the t rans i t i on metal complex, eq. 22, or from an a lky l or ary l ha l i de , We thank Ms. V. Gibb for assistance in obtaining these spectra. Table XII. Mass Spectral Fragmentation Data for CpM(N0)9R. Compound M + C 5 H 5 M + C 5H 5M(N0)+ C 5 H 5 M(N0) 2 + . b ion C 3 H 3 M R + C 5H 5MR+ C 5H 5M(N0)R+ C 5 H 5 M(N0) 2 R + CpCr(N0) 2 C g H 5 10.0 8.3 - - - 2.3 7.5 0.7 CpMo(N0) 2C 6H 5 - - - - 2.7 3.6 8.2 3.6 CpW(N0)2CgH5- - .1-7 - - 4.2 7.2 10.0 5.6 CpCr(N0) 2CH 3 10.0 8.4 2.7 1.2 - 2.1 7.2 1.6 CpMo(N0)2CH3 5.7 3.6 10.0 6.2 - - 6.2 6.0 CpW(N0)2CH3 0.4 - 2.9 3.4 - - 4.6 6.2 CpCr(N0) 2Et 10.0 2.7 1.9 2.0 - 1.9 5.6 0.4 CpCr(NO) 2 i -Bu 10.0 9.9 3.5 4.1 7.2 - 9.9 2.9 Entr ies in th i s table are re la t i ve ion i n tens i t i es with the most intense metal containing ion assigned an arb i t rary value of 10.0 Relat ive i n tens i t i es were evaluated by measuring peak heights corresponding to the most abundant isotope of each metal: 5 2 C r , 9 8 Mo and 1 8 4 W . Only unambiguously assignable ions are given; for the poly isotopic molybdenum and tungsten overlapping of some medium to strong in tens i ty peaks in the lower mass range made assignments d i f f i c u l t . Selected compounds were run on the MS902 high resolut ion instrument which measured exact masses of a l l major peaks; ca lcu lated and measured values were in good agreement. - 75 -eq. 23, (112). The synthet ic route given by eq. 23 cannot be explo i ted L nM-X + R-M1 is— LnMR + M'X 22. (M1 = Li or MgX) [L n M]" + R-X » - LnMR + X" 23. in th is instance since a l l attempts to obtain the [ C p M ^ O ^ ] " anions have thus far f a i l e d . Indeed, the only wel l character ized organometal l ic n i t rosy l anion which has been success fu l l y used as a synthet ic precursor is [Fe(C0) 3 (N0)]" (53, 113, 114). While eq. 22 has been appl ied with modest success in the preparat ion 'of C p C r ^ O ^ R (R = Me, Et or Ph) (27), the s im i la r react ions of C p M ^ O ^ C l (M = Mo or W) with various a l k y l l i t h i u m and Grignard reagents f a i l to y i e l d even spect roscop ica l ly detectable quant i t ies of the corresponding a lky l or ary l de r i va t i ves . These reagents are not s u f f i c i e n t l y se lec t ive in the nuc leoph i l i c displacement of the hal ide and they appear to attack other funct ional groups. In cont ras t , we f ind the organoaluminum reagents to be p a r t i c u l a r l y mild and se lec t i ve in the i r react ions with C p M ^ O ^ C l complexes. This feature i s a lso i l l u s t r a t e d by the exclus ive monoalkylation of some d ich loro compounds of ruthenium even when an excess of the organoaluminum reagent i s used at elevated temperatures (115). Organoaluminum compounds are r e l a t i v e l y strong Lewis acids which are known to coordinate to the oxygen end of carbonyl l igands in a var ie ty of neutral (116) and anionic (117) n 5 -cyclopentadienylmetal carbonyl complexes. Non-bonding electron pai rs l oca l i zed on the metal atom may also - 76 -serve as a Lewis base s i t e and a number of 1:1 adducts containing the M-Al bond have been iso la ted (118). However, no in f rared spectroscopic evidence was obtained in support of any s im i l a r Lewis acid-base adducts during our preparation of the CpM^O^R complexes. Although useful in the syntheses of main group metal a l ky l and ary l compounds (119), the organoaluminum reagents have received very l i t t l e at tent ion in the formation of t r ans i t i on metal-carbon bonds (112). The general react ion of organoaluminum compounds with metal hal ides (eq. 24) i s favored when M i s subs tan t ia l l y e lec t ropos i t i ve and X i s e lect ronegat ive. The conversion does not l i k e l y take place by a d i ssoc ia t i ve and reassoc ia t ive ion ic pathway since the organoaluminum compounds are la rge ly covalent. A l s o , the react ions are t y p i c a l l y performed in solvents which do not support ion iza t ion and, indeed, the use of coordinat ing solvents or the presence of Lewis bases retard the reac t ion . Consistent with the above f a c t s , the present a l ky la t i on react ions can be considered to occur v ia a Lewis acid-base intermediate as in III or IV, where M is an organo-meta l l i c res idue. R-Al + M-X * ~ A l -X + M-R 24. R M + X X EZ - 77 -If M i s s u f f i c i e n t l y e l e c t r o p o s i t i v e , as i s the case with the a l k a l i metals, III and IV are formed as stable products rather than intermediates (119). Since the CpM(N0)2Cl complexes d isp lay a cer ta in i nc l i na t i on to form the ca t ion ic [CpM(N0) 2 ] + spec ies , the benzene inso lub le byproduct deposited during the syntheses of CpM(N0)2R may reasonably be formulated as [CpM(N0) 2 ] + [A lR^C l ] " . However, t h i s p o s s i b i l i t y was not invest iga ted. In contrast to the numerous CpCr(N0) 2R complexes, the only known isoe lec t ron ic t r icarbonyl analog i s the thermally unstable CpCr(C0) 3Me' compound. However, the CpM(C0)3R (M = Mo or W) compounds are more abundant and have been the subject of considerable study. Notably, these complexes undergo a thermal transformation to y i e l d [CpM(C0) 3 ] 2 (120, 121) or, when R = Et , Ph or CHpPh, [RC5H4M(C0)312 (121, 122). Our attempts to obtain s i m i l a r l y the analogous, but as yet unknown, [CpM(N0) 2 ] 2 (M = Mo or W) dimers by the thermolysis of the a l k y l - or a r y l d i n i t r o s y l complexes have been unsuccessful . Moreover, the n i t rosy l complexes are understandably more iner t toward subst i tu t ion than the i soe lec t ron ic CpM(C0)3R analogs, and no react ion pa ra l l e l to carbonyl " i nse r t i on " has yet been found. On the other hand, both CpCr(N0)2R and CpM(C0)3R undergo inser t ion of S0 2 af fording der iva t ives which contain the S-su l f ina te l inkage, M-'s'-R (123-125). The rates of inser t ion into the n i t r osy l 8 containing complexes are , by f a r , the greatest among the var ie ty of compounds studied (126). Infrared spectroscopic evidence (127) and k ine t i c studies (126) indicate that S0 9 inser t ion occurs with the i n i t i a l - 78 -II formation of the O-sul f inate l inkage M-OSR followed by rearrangement to the S-su l f ina te compound. S i m i l a r l y , (CN)2C=C(CN)2 reacts with the above carbonyl and n i t rosy l complexes to give the d i rec t inser t ion product, MC(CN) 2C(CN) 2R, and the keteniminato de r i va t i ve , MN=C=C(CN)C(CN)2R (124, 128). Stannous ch lor ide and bromide inser t into the metal-carbon bond of a var ie ty of a lky lcarbony l (n 5 -cyc lopentad ieny l )meta l complexes (M-R) to y i e l d MSnRX2, MSnX^ and MX, depending on react ion condit ions (129). We f ind that react ion of SnC l 2 with CpMo(N0) 2i-Bu resu l ts in the formation of CpMo(N0)2Cl exc lus i ve l y . However, SnC l 2 does inser t in to the metal-ch lor ine bond of CpCr(N0) 2Cl according to the solvent dependent equ i l i b r ium, eq. 25. In donor solvents such as THF the l e f t hand side of eq. 25 i s CpCr(N0) 2Cl + SnCl2=^===^== CpCr(N0) 2 SnCl 3 25. favored probably due to Lewis acid-base in te rac t ion between SnC l 2 and the so lvent , whereas CH 2 C1 2 and benzene s h i f t the equi l ib r ium to the side of CpCr(N0) 2 SnCl 3 - The in f rared n i t rosy l s t retching frequencies (1733 and 1825 cm - 1 in CH 2C1 2) of CpCr(N0) 2 SnCl 3 are approximately 20 cm - 1 higher than those of CpCr(N0) 2 Cl, which we a t t r ibu te to the previously demonstrated poorer o-donating and stronger ^-accept ing propert ies of the SnCl^ en t i t y (26a). 4.3e Bis [(n 5 -cyc lopentadieny l )d in i t rosy lchromium], [CpCr (N0) 2 ]Q, When a benzene so lut ion containing CpCr(N0) 2Cl i s allowed to s t i r over a sodium amalgam, [CpCr(N0) 9 ] o i s obtained in over 60% y i e l d . - 79 -This synthet ic route i s fa r superior to the one previously reported in which the desired product i s extracted in only 5% y i e l d (90). The same conversion can be effected by using a z inc amalgam and, to a lesser extent , with f i n e l y divided magnesium or ytterbium metal although a much longer react ion time i s necessary. In these l a t t e r react ions no evidence i s obtained for the existence of act ivated species (105) such as "CpCr(N0) 2MgCl". When f i n e l y div ided z inc metal i s employed, no react ion occurs and the use of a magnesium amalgam in THF causes immediate decomposition of the s ta r t i ng chloro complex. Correspondingly, the attempted reduction of the CpM(N0)2Cl (M = Mo or W) compounds using a wide var ie ty of react ion condit ions f a i l s to y i e l d the s t i l l unknown [CpM(N0) 2 ] 2 (M = Mo or W) complexes. The o r ig ina l synthesis of [CpCr(N0) 2 J 2 from CpCr(N0) 2Cl and NaBH^ i s believed to occur through the formation of CpCr(N0)2H although no evidence for th i s hydrido intermediate was obtained (90). However, we f ind that CpMo(N0)2Cl reacts with NaBH^ in MeOH or EtOH at -30°C to y i e l d a v o l a t i l e pale-green so l i d which decomposes rap id ly at room temperature. Its in f rared spectrum (1740 and 1645 cm" 1 in EtOH) bears a s t r i k i n g resemblance to those of the a lky l and ary l de r i va t i ves , and on th is basis the complex i s formulated as CpMo(N0)2H. The thermal or ox idat ive degradation of th is spec ies , e i ther in so lu t ion or in the s o l i d , f a i l s to provide the [CpMo(N0) 2J 2 compound. The in f rared spectrum of [CpCr(N0) 2 ] 2 exh ib i ts two strong n i t rosy l absorptions at 1667 and 1512 cm" 1 in CH^Cl2> ind ica t i ve of both terminal and bridging n i t rosy l l igands. In CDCl^ solut ions the dimer ex is ts in both the c i s and trans forms, F and G, as evidenced by i t s - 80 -F G room temperature proton NMR which contains two sharp s ing le ts at T5.20 and T5.00 in the ra t i o of 1:20 (93). In the s o l i d s ta te , [CpCr (N0) 2 l 2 (93), is i sos t ruc tu ra l with t r ans - [CpFe (C0)o] 2 (130), t rans-[CpCr(N0)(SPh)] 2 (91) and trans-[CpCr (NO) (NHj ] , , (92). The metal-metal o distance of 2.615 A in the d i n i t r osy l dimer i s s i g n i f i c a n t l y shorter than those of the SPh (2.90 A) and NH2 (2.67 A) containing spec ies. While the terminal Cr-N-0 bond angles in the SPh and NH2 compounds deviate from l i n e a r i t y by about 10° , ' the corresponding angle in the d i n i t r osy l species i s v i r t u a l l y l i near (176.6°) , poss ib ly as a resu l t of reduced electron density on the metal atoms of the n i t rosy l bridged compound. The terminal Cr-N bond lengths for a l l three dimers f a l l wi th in the range of o o 1.64-1.69 A and are not much d i f fe ren t from the value of 1.71 A in the CpCr(N0) 2Cl compound (106). As expected, the Cr-N distance (1.960 A) in the symmetr ical ly-br idging n i t rosy l l igands i s considerably longer than the terminal Cr-N bonds. The mass spectrum of [CpCr (N0) 2 l 2 (Table XII I ) d isplays the molecular ion peak and is consistent with the dimeric formulat ion. Since no [CpCr(N0) n] or [C^H^Cr(N0) n] (n = 1 or 2) fragments are formed, i t - 81 -Table XII I . Low Resolution Mass Spectral Data for [CpCr(N0) 9 ] 9 m/e Relat ive Abundance Assignment 354 3.1 C p 2 C r 2 ( N 0 ) 4 + 324 2.2 C p 2 C r 2 ( N 0 ) 3 + 294 0.3 C p 2 C r 2 ( N 0 ) 2 + 264 10.0 Cp 2 Cr 2 (N0 ) + 182 6.1 ( C 3 H 3 ) 2 C r 2 + 117 2.3 CpCr + 52 4.2 C r + The assignments involve the most common natura l ly occurr ing isotope, 52 r i . e . Cr . - 82 -appears that fragmentation prefers to occur without rupture of the metal-metal bond. In cont ras t , the i soe lec t ron ic non-bridged [CpCrv^CO)^] dimer does not d isp lay a molecular ion peak and, indeed, only mononuclear fragments are found (131). Unlike [CpCr (N0) (0Et ) ] 2 or [CpCr(N0)C1] 2 , and contrary to a previous report (89), we f ind that the mass spectrum of [CpCr(N0) 2 ] 2 does not contain a peak which may be assigned to the [ C p 2 C r ] + fragment. Instead we assign the peak at m/e = 182 to the dinuclear [ ( C ^ H ^ ^ C r ^ * fragment. Furthermore, the greater abundance of dinuclear species in the mass spectrum of [CpCr (N0 ) 2 l 2 suggests that the n i t rosy l l igand forms a stronger bridge than do the OEt or Cl l igands in re la ted compounds. - 83 -CHAPTER V Conclusion It should be stressed that while meta l -n i t rosy l bonds may be formed by a var ie ty of synthet ic methods,' none o f these preparative routes has general a p p l i c a b i l i t y . In cont ras t , th is work has shown n i t rosy l ch lor ide to be the s ing le most v e r s a t i l e synthet ic reagent ava i lab le for the formation of M-NO l inkages. The d i rec t formation of ch loron i t rosy l complexes from neutral carbonyl compounds i s of pa r t i cu la r i n te res t . As discussed in th is t h e s i s , the former compounds, which contain a very react ive metal-chlor ine bond, serve as useful precursors in the preparation of fur ther n i t rosy l de r i va t i ves . For example, the metal-hal ide bond may be converted to a large var ie ty of metal-heteroatom a-bonds containing elements from Groups IVA, VA and VIA. Obviously, the behavior of n i t rosy l ch lor ide with many more neutral and anionic metal carbonyl complexes remains to be invest igated. Most important ly, such studies should be undertaken with the aim of developing convenient synthet ic routes to n i t rosy l complexes, and not simply as a study of the chemistry of n i t rosy l ch lo r ide . The scarc i t y of anionic n i t rosy l complexes i s su rp r i s i ng , espec ia l l y in view of the multitude of anionic carbonyl compounds which - 84 -has been character ized. While attempts to e f fec t the chemical reduction of various n i t rosy l compounds have so fa r been unsuccessfu l , n i t r o s y l -containing anions might be obtained by electrochemical reduction at a contro l led po ten t i a l . Further work in th is d i rec t ion is current ly in progress. While numerous n i t r osy l compounds are known, many, which are expected to be stable under ambient cond i t ions , are simply nonexistent at present. 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