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Nitrosyl hydrides and cations of Group VI transition metals Oxley, Jimmie Carol 1983

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NITROSYL HYDRIDES AND CATIONS OF GROUP VI TRANSITION METALS by JIMMIE CAROL OXLEY .Sc . Ca l i fo rn ia State Un ivers i ty , Northridge, 1' A THESIS SUBMITTED IN PARTIAL FULFILLMENT 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 February, 1983 © Jimmie Carol Oxley, 1983 In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y available for reference and study. I further agree that permission for extensive copying of t h i s thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. I t i s understood that copying or publication of t h i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of CIO^A^J^ The University of B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date DE-6 H/Sl") ABSTRACT The novel b imeta l l i c hydrides [(n 5 -C 5 H 5 )W(.N0)IH] 2 and [ (n 5 -C 5 H 5 )W-(N0)H 2 ] 2 can be prepared sequent ia l ly by the metathesis of [(n5-CgHg)W(N0)-I 2 ] 2 with Na[H 2 Al(0CH 2 CH 2 0CH 3 ) 2 ] . Analyses of the *H NMR spectra of C(n 5 -C 5 H 5 )W(N0)IH] 2 and [ (n 5 -C 5 H 5 )W(N0)H 2 ] 2 show the former contains hydride l igands bound to tungsten in a terminal fash ion, while the l a t t e r possesses two terminal and two bridging hydrides. Addit ion of a Lewis base to [(n 5-CgHg)W(N0)IH] 2 resu l ts in the formation of hydride species (n 5^C 5H 5)W(N0)IHL (L = P(0Ph) 3 , P(0Me) 3 , PPh 3 ) ; in l i k e manner, the dimer [(n 5-CgHg)W(N0)H 2] 2 is cleaved by tr iphenylphosphite to form the monomer c i s or trans (n 5 -C 5 Hg)W(N0)H 2 [P(0Ph) 3 ] . A comparison i s made of the r eac t i v i t y of the tungsten-hydrogen l i nk in the n i t rosy l hydrides (n 5-CgHg)-W(N0)IH[P(0Ph) 3], (n 5 -C 5 H 5 )W(N0) 2 H, and (n 5 -C 5 H 5 )W(N0)H 2 [P(0Ph) 3 ] . 2+ The Mo(N0)2 unit is obtained as the te t rak is -so lva te v ia chlor ide abstract ion from Mo(N0) 2 Cl 2 by AgBF^ or n i t rosy la t ion of Mo(C0)g by NOPFg in coordinating solvents such as nitromethane, a c e t o n i t r i l e , or tetrahydro-furan. The unsolvated complex [Mo(N0) 2(PFg) 23 n is produced i f the l a t t e r react ion i s performed in dichloromethane; however, i t read i ly converts to [Mo(N0) 2S^](PFg) 2 upon exposure to coordinating solvents (S) . Hard Lewis bases (L = CH3CN , 0PPh 3 or L 2 = 2 ,2-b ipyr id ine replace the solvent mole-cules in [Mo(N0) 2S 4 ]X 2 (X = BF^, PFg) forming complexes [Mo(N0) 2 L 4 ] 2 + or 2 + [Mo(N0) 2 L 2 S 2 ] depending upon the solvent employed. Reagents capable of being oxidized appear to reduce the d in i t rosy l d icat ion without permanent i i i coordination to the molybdenum centre. Reduction of [MoCNO^S^CPFg^ or[Mo(N0) 2(PFg) 2] n i .s effected by sodium amalgam (one equivalent) ; addi t ion of a l igand L 2 (L 2 = 2 ,2 -b i py r i dy l , 3,4,7,8-tetramethyl-1,1O-phenanthroline) to the react ion mixture permits the i so la t i on of DMNO)^ ] 2 ( P F g ) 2 • Addit ion of excess l igand resul ts in the formation of non-ni t rosyl containing species [Mp(L 2) 3 ]PFg (L = 0PPh 3 or l_2 = 3,4,7,8-tetramethyl-1 ,1O-phenanthro-l i n e ) . Decomposition of the n i t rosy l species resu l ts from attempts to 2+ reduce [MotNO^S^] by two e lec t rons. New complexes are iden t i f i ed by the aid of IR.and 1 H , 1 9 F , or 3 1 P NMR spectroscopy and conductance measure-ments . 2+ Attempts to prepare th ion i t rosy l analogues of [Mo(N0)2L^] have met with l imi ted success; the only wel1-characterized th ion i t rosy ls iso lated in th is study are the known (n 5 -C 5 H 5 )Cr(C0) 2 NS and the new [(n 5-CgH 5)Mo-(N0)(NS)PPh 3 ]BF 4 . Also discussed i s the in teract ion of NOPFg with solvents. NOPFg has been found to react slowly with a c e t o n i t r i l e , a common solvent for n i t r o -sonium s a l t s . i v TABLE OF CONTENTS Page ABSTRACT i i TABLE OF CONTENTS iv LIST OF TABLES v i LIST OF FIGURES v i i LIST OF SCHEMES ix ABBREVIATIONS AND COMMON NAMES x ACKNOWLEDGEMENT x i i i INTRODUCTION 1 PART I NITROSYL HYDRIDE COMPLEXES OF TUNGSTEN AND MANGANESE 4 Experimental 13 Results and Discussion 26 Preparation and Reactions of .[(n 5-C 5H 5)W(N0)IL-(solvent) ]BF 4 26 Metathetical Reactions of Na[H 2Al(0CH 2CH 20CH 3) 2 ] with Some Monomeric Haloni t rosyl Complexes 31 Reaction of [ (n 5 -C 5 H 5 )W(N0) I 2 ] 2 with Na[H 2Al(0CH 2CH 2-0CH 3 ) 2 i ! 35 Reactions of [ (n 5 -C 5 H 5 )W(N0)IH] 2 with Lewis Bases 39 Reaction of [ (n 5 -C 5 H 5 )W(N0)IH] 2 with Na[H 2Al(0CH 2CH 2-0CH 3 ) 2 J 50 Reaction of [(n 5-C 5H 5)W(N0)H 2] 2.iwith. P(0Ph) 3 61 V Page PART II A. CATIONIC NITROSYL COMPLEXES OF MOLYBDENUM 72 Experimental 75 Results and Discussion 90 Generation of "Mo(.N0) 2 2 +" from Mo(C0) g and NOPFg 90 Generation of "Mo(N0) 2 2 + " from Mo(.N0) 2Cl 2 and AgBF 4 100 Conductivity Studies 106 React iv i ty of "Mo(N0) 2 2 + " 113 B. CATIONIC THIONITROSYL COMPLEXES OF THE GROUP VI TRANSITION METALS 133 Experimental 134 Results and Discussion 138 C. REACTION OF ACETONITRILE WITH"NOPFg 143 REFERENCES AND NOTES 147 SPECTRAL APPENDIX 1 5 7 vi LIST OF TABLES Table Page I Spectral Propert ies of Cn 5-C 5H 5)M(.N0)I(H)L Complexes (L = P(0Ph) 3 , P(.0CH 3) 3 , or PPh 3) 41 II 1H NMR Spectral Data of [ ln 5 -C 5 H 5 )W(.N0)H 2 ] 2 57 III 1 9 F and 31'P MR' Spectral Data for Complexes Containing PFg'or 0 2 P F 2 ~ 96 IV Molar Conduct iv i t ies 108 V Conductivi ty Measurements in Nitromethane, 112 v i i LIST OF FIGURES Figure Page 1 1 H NMR Spectrum of Hydride Region of [ ( t i . 5 -C 5 H G )W(.N0)- 3 7 I (H) ] 2 in CDC13 (400 MHz) and Computer Simulation of the Tungsten-Hydride Couplings. 2 iH NMR Spectrum of Hydride Region of ( J I 5 - C 5 H 5 ) W C N 0 ) I ( H ) - 4 3 [P(.0Ph)3] (80 MHz) in CgD g. 3 3 1 P NMR Chemical S h i f t s 2 of (n 5 -C 5 H 5 )W(N0)I(H)L Complexes. 47 4 Formation of (.n 5-C 5H 5)W(.N0) I(.H)[P(.0Ph)3] from [ ( .n 5 -C 5 H 5 )W- 4 § (N0)12D2 v i a Three Routes. 5 iH NMR Spectrum of [ C n 5 - C 5 H 5 ) W . ( N 0 ) H 2 ] 2 in CDC13 (.400 MHz). 54 6 *H NMR Spectra of [ ( .n 5 -C 5 H 5 )W(.N0)H 2 J 2 in CDC13 (400 MHz) 55 Decoupling Centered at 5 6.98, 6.54, 1.39, -2 .02 , -5 .93. 7 l H NMR Spectrum of Hydride Resonances of Isomer 2 of 58 [ ( T I 5 - C 5 H 5 ) W ( . N 0 ) H 2 ] 2 in CDC13 (400 MHz) and Computer Simu-la t i on of the Hydride Resonance of Isomer 2. vi i i Figure 8 9 Plot I Page Structural P o s s i b i l i t i e s of [Cn 5 -C 5 H 5 )W(N0)H 2 ] 2 . 60 l H NMR Spectrum of Hydride Region of c is - (n 5 -C 5 H 5 )W(N0)- 64 H 2[P(.0Ph) 3] (400 MHz) in CgD6 and Computer Simulation of Hydride Region. Plot of A e vs Sc for [Mo(N0) 2 L 2 ] 2 (RFg) 2 110 (L 2 = 2 ,2-b ipyr idy l or 3,4,7,8-tetramethyl-1,10-phenan-th ro l i ne ) . Plot of (A Q -A e ) vs / c e for [Mo( .N0) 2 L 2 J 2 (PF 6 ) 2 m (L 2 = 2 ,2-b ipyr idy l or 3,4,7,8-tetramethyl-1,10-phenan-t h ro l i ne ) . ix LIST OF SCHEMES Page Scheme I 8 Scheme II 51 Scheme III 71 Scheme IV 90 Scheme V 103 Scheme VI 128 X ABBREVIATIONS AND COMMON NAMES acac acetylacetonate anion Ana l . Calcd analysis ca lcu lated asym asymmetric atm atmospheres bipy 2 , 2 ' b ipyr id ine br broad Bu ,butyl °C degrees Celsius cm~^ wave numbers in reciprocal centimeters Cp pentahapto-cyclopentadienyl d doublet dd doublet of doublets das : o-phenylenebis(dimethylarsine) dec decomposes diglyme bis*( 2-methoxyethyl) ether diphos 1,2-bi s(.di.phenyl phosph.ino)ethane dppm 1,2-bis(.diphenyl phosphino)methane e~ electron(s) en 1,2-diaminoethane eq equivalent Et ethyl h hour(s) Hz Hertz, cycles per second hv i r rad ia t i on xi IR inf rared J magnetic resonance ind i rec t coupling constant L any unidentate l igand m medium in tens i ty (IR) or mul t ip le t (NMR) M molar Me methyl min minute(s) mL mil 1 i l i t r e ( s ) mm mi l l imeters of mercury mmol mi l l imo le(s) mp melting point NMR nuclear magnetic resonance Ph phenyl phen 1,1O-phenanthroline phen1 3,4,7,8-tetramethyl- l ,1O-phenanthrol ine ppm parts per m i l l i on PPN+ b is( t r iphenylphosphoranediy l )n i t rogen( l + ) P r 1 isopropyl psi pounds per square inch R a lky l or aryl s strong in tens i ty (IR) or s ing le t (NMR) sh shoulder sym symmetric t t r i p l e t xi i tlfl h a l f - l i f e td t r i p l e t of doublets THF tetrahydrofuran TMS tetramethylsi lane 6 NMR chemical sh i f t in ppm n 5 pentahapto v IR s t retch ing frequency ^ approximately % percent ACKNOWLEDGEMENT I wish to thank the facul ty and technical s ta f f of the Univers i ty of B r i t i s h Columbia chemistry department for the i r assistance throughout th is study, pa r t i cu la r l y Mr. P. Borda. I wish to extend special thanks to the members of my guidance committee Drs. L .S. Wei ler , F. Aubke, and R.E. Pincock and to Dr. M.D. Fryzuk and P.A. MacNeiT for the i r helpful suggestions. I'would l i ke to .thank. B.> Wassink and'A.D.' Hunter who proofread th is manuscript. F ina l l y I wish to express my grati tude to Peter Legzdins for his support and guidance throughout th is work and to the Univers i ty of B r i t i s h Columbia for f inanc ia l support through a Univers i ty Graduate Fel lowship. 1 Introduction Since the preparation of the f i r s t t ransi t ion-metal carbonyl PtCCO^CCl)^ in 1868 and the formulation of the bonding in carbonyl t r a n s i -t ion metals (1 950's) , 2 - volumes have been published on the i r preparat ion, r e a c t i v i t y , and use in organic synthesis and c a t a l y s i s . 3 In comparison t ransi t ion-metal n i t rosy l complexes are much less well s tudied. Nitrogen monoxide, though possessing one electron more than carbon monoxide, is s im i la r to that molecule in both structure and bonding. When bonded to a metal centre in a l inear fashion, analogous to a carbonyl l i gand , the n i t rosy l l igand is formally considered to be a three-electron donor; and the hybr id izat ion of o rb i ta ls around nitrogen is sp. However, un l ike the carbonyl l igand the n i t rosy l has another mode of bonding ava i lab le to i t . When the o rb i ta l s around the nitrogen atom are sp hybridized, the M-N-0 angle i s bent (^120°). A n i t rosy l group bonded in th is manner i s cons i -dered to be a formal one-electron donor. An example of a complex contain-ing both these modes of bonding is [ R u ^ P h - ^ ^ N O ^ C l ] +V h The fact that the same l igand can act as a three- or a one-electron donor of fers the p o s s i b i l i t y that an addi t ional coordination s i t e could be made ava i lab le on a metal centre without the necessity of l igand d i ssoc ia -t ion but rather through the tautomerization of a l inear n i t rosy l to a bent one. Thus, i t i s ant ic ipated that n i t rosy l complexes might have d i f fe rent chemical and ca ta l y t i c propert ies from the i r carbonyl analogues. One n i t rosy l complex which has demonstrated unique chemistry is F e ^ O ^ N O ^ - 5 When butadiene is treated with a ca ta l y t i c amount (1% by weight) of th is 2 iron n i t rosy l , the ant ic ipated dimer, 4 -v iny lcyc lohex- l -ene , is formed as the only product despite the introduct ion of other possible reactants such as ethylene or propene. Nor do the addi t ives tr iethylaluminum, tr iphenylphosphine, or pyridine have any inf luence on the y i e l d or spec i -f i c i t y of the reac t ion . Evidently the presence of the n i t rosy l l igand is essent ial since a var ie ty of carbonyl der ivat ives of iron exhib i t no ca ta l y t i c a c t i v i t y . Further, i t has been reported that Fe(N0) 2S 2 ;.(S- = a donor so lvent ) , a possible intermediate in the d imer izat ion, performs the reaction with equal s p e c i f i c i t y . 6 More recent ly th is group has studied the behaviour of [ (n 5 -C 5 Hg)Cr (N0) 2 ] 2 a n c l that ° f the isoe lec t ron ic carbonyl [ ( r i 5 -CgHg)Fe(C0) 2 ] 2 . 7 The two compounds exhib i t some chemical s i m i l a r i t i e s , e . g . , react ing with halogens to form the monomeric ha l ides ; but in other aspects the i r chemistry is quite d i f f e ren t , e . g . , reduction . of the iron dimer by sodium amalgam leads to [(n 5-CgHg)Fe(C0) 2 ]~ while under ident ica l condit ions the chromium dimer decomposes. The dominant feature of the n i t rosy l dimer's r eac t i v i t y is i t s propensity to abstract halogen atoms from inorganic or organometall ic ha l ides . It has been employed [ ( r , 5 -C 5 H 5 )Cr(N0) 2 ]2+2[ (n n -C 5 H 5 )Fe(C0) 2 Cl] 3 ^ 2 [ ( n 5 -C£H 5 rCr {N0) 2 Cl ] + [ ( n 5 - C 5 H 5 ) F e ( C 0 ) 2 ] 2 to s p e c i f i c a l l y abstract v i c ina l halides from organic reagents. 8 CgHgCHBrCHBr [ (n 5 -C 5 H 5 )Cr (N0) 2 ] 2 3 The general object ives at the outset of th is work were to prepare new transi t ion-metal n i t rosy l species and to study the i r r e a c t i v i t y . Accordingly, Part I deals with the preparat ion, charac te r iza t ion , and reac t i v i t y of some n i t rosy l hydrides of the Group VIB and VIIB metals; and Part II describes the synthesis of Group VIB n i t rosy l and th ion i t rosy l cat ions. 4 Part I Ni t rosy l Hydride Complexes of Tungsten and Manganese 9 Hieber in 193] reported the discovery of the f i r s t d iscrete com-plexes containing t rans i t ion metals covalent ly bonded to hydrogen; these were the unstable species H2Fe(C0)^ and HCo(CO)^. For some years these compounds were incor rec t l y formulated as Fe(COH)2(00)2 and Co (C0H)(C0)2 because they were ac id ic in character. These complexes remained a cu r ios i t y un t i l 1955 when th is f i e l d was opened up by the discovery of b i s (n 5 - cyc l0-pentadienyl)hydridorhenium by W i l k i n s o n . 1 0 This was followed by the d i s -covery of (n 5-CgHg)M(C0)2H {M=Cr or Mo) by F i s h e r 1 1 in the same year and two years l a te r by the preparation of t r ans -HP tC l (PE t - ^ by Chatt, Duncanson, 12 and Shaw. These l a t t e r d iscover ies came at a time when NMR spectrometers were becoming ava i lab le as commercial instruments. This was important in the character izat ion of these compounds for the i r hydride resonances were discovered to have enormous upf ie ld chemical sh i f t s compared to those of hydrogens attached to main group elements. This aided in the i r detection and i d e n t i f i c a t i o n . In the twenty year period 1939-1959 t ransi t ion-metal hydride com-plexes were studied using IR, NMR, broad-l ine NMR, and electron d i f f r ac t i on techniques. The conclusion of these invest igat ions was that the hydrogen atom exerted no stereochemical in f luence; i t was buried in the electron core of the metal atom. (This idea was used to explain the large high f i e l d chemical sh i f t of the hydride resonance observed by NMR). But th is 5 was not the case. With the f i r s t X-ray d i f f r ac t i on studies performed on t ransi t ion-metal hydrides in 1960 and la te r with neutron d i f f rac t i on studies i t was determined that the hydride l igand occupies a normal coor-dinat ion posi t ion in these compounds, which in terminal hydride ligands i s an essen t ia l l y covalent, two-electron bond and in doubly bridging hydrides 1 3 i s considered as a three-centre, e lec t ron-def ic ien t bent bond. The two techniques used most frequently for es tab l ish ing the pre-sence of a metal-hydrogen bond are infrared and nuclear magnetic resonance spec t roscopy. 1 4 The inf rared spectra of most t ransi t ion-metal hydride complexes show absorptions in the region 1700-2300 cm~^ which can be assigned to the metal-hydrogen stretching mode. Since other absorptions can occur in th is range (e .g . vCO, CN, for the purposes of unambiguous assignment the metal-deuteride analogue i s prepared and i t s infrared spectrum compared with that of the hydride; a sh i f t in the stretching frequency to lower wavenumbers by a factor of 1.4 i s expected. Hydrogens bridging two metal atoms exhib i t stretching frequencies in the range 900-1400 cm~^ . The metal-hydrogen deformation absorption (.700-950 cm~^)-i s d i f f i c u l t to assign due to i t s low in tens i ty and to the presence of other absorptions in th is region. Even the in tens i ty of the metal-hydrogen st retching absorption i s sometimes too weak to be observed. Nuclear magnetic resonance spectroscopy has proved to be the most valuable diagnost ic tool for detecting t rans i t i on metal hydrides. Hydrogens attached to t rans i t ion-meta ls usual ly have nuclear magnetic resonance absorp-tions, in a region of the proton spectrum completely separated from the reso-nance of hydrogen in other chemical environments. The proton resonances 6 of most organic molecules and of the main group hydrides l i e downfield. of TMS (6>0). Transit ion-metal hydrides, with the exception of some con-ta in ing the ear ly t r ans i t i on -me ta l s 1 5 exhib i t a proton resonance upf ie ld of TMS in the range 6 = 0 -> -50; most are in the region 6 = -5 -> -20. Thus nuclear magnetic resonance studies are regarded as a r e l i a b l e method for hydride detect ion. Further, NMR experiments can be used to determine the number of hydride l igands present and the nature of the i r chemical and magnetic environments. Observation of metal-hydrogen coupl ing, possible with the spin 1/2 nuclei such as 1 0 3 R h , 1 8 3 W , 1 8 7 0 s , and 1 9 5 P t , provides strong evidence for d i rec t metal-hydrogen bonding. Nuclear magnetic reso-nance studies of other nuclei to which the hydride i s coupled y i e l d addi t ional information about the molecular conformation. 3 1 P NMR studies 1 6 are widely employed in th is regard. . Pr ior to the development of spectroscopic techniques, chemical reactions were used to determine the presence and number of hydride l igands , though none were completely quant i ta t ive ly or qua l i t a t i ve l y r e l i a b l e . Among transi t ion-metal hydride chemistry four patterns of r eac t i v i t y were frequently observed. I. Thermal decomposition to produce Hp, For the simple carbonyl hydrides or cyclopentadienyl hydrides hydrogen i s evolved quant i ta t ive ly upon thermolysis, but thermal behaviour var ies great ly according to the metal and the other l igands attached to i t . Ligands which s t a b i l i z e a low-oxidation state of the metal centre usual ly 1 7 increase thermal s t a b i l i t y , e . g . , HCoCCO^PPh^ decomposes to H 2 and 7 and [Co(C0) 3 PPh 3 ] 2 at ^20°C, while H C o ( C 0 ) 2 ( P P h 3 ) 2 i e i s stable to ^140°C. L ikewise, thermal s t a b i l i t y general ly increases with increasing atomic number for a ser ies of congeneric hydride complexes, e .g . , for the ser ies ( , n 5 -C 5 H 5 )M(C0) 3 H the decomposition point increases 57° < 110°.<. 180°C as M = Cr. < Mo < W . 1 1 I I . Ac id i c character The ac id i c strength of t ransi t ion-metal hydride complexes var ies great ly depending on the nature of the other l igands. Most hydrido-carbonyls appear to act as Lowry-Brjfinsted ac ids , but subst i tu t ion of phosphine for carbonyl great ly reduces the acid strength of the metal -hydrogen bond, e .g . , the K a determined for HCo(C0) 4 1 9 i s <2 while for HCo(C0) 3 PPh 3 1 7 i t i s ^10~ 7 . I I I . Reaction with halogens and halogenated hydrocarbons Treatment of hydride complexes with halogens general ly resu l ts in the replacement of the hydride l igand by a hal ide along with the formation of H 2 or HX (X = CI , Br , I ) . Halogenated hydrocarbons can react with the metal-hydrogen bond to produce metal ha l ides ; the hydride i s transferred to the halogenated hydrocarbon. The reac t i v i t y of the halogenated hydro-carbon toward the metal hydride increases with increasing hal ide subs t i tu -t i o n ; thus, the react ion of metal hydrides with CCl^ i s often used to estab l ish the presence of a metal-hydrogen l i n k . 8 IV. Treatment with acid to produce H ? The react ion of hydridometal complexes with aqueous or a lcoho l ic acids often gives complete replacement of the hydrides. This react ion has sometimes been employed to determine the number of hydride ligands by measurement of evolved hydrogen; however, i t i s not completely r e l i a b l e , e . g . , IrHg(PEt2Ph) was o r i g i n a l l y formulated as a t r ihydr ide on the basis 2 0 of i t s degradation by HC1. Transit ion-metal hydride complexes are ei ther postulated or ob-served to par t ic ipate in a number of important homogeneous cata lyses. One of the most important roles of the metal-hydrogen bond i s to add to an unsaturated substrate. When the substrate i s an o l e f i n , the overa l l resu l t can be isomer izat ion, hydros i la t ion , hydrogen exchange, hydrogenation, or hydroformylation. The "oxo" reac t ion , a hydroformylation react ion em-ployed commercially to convert o le f ins to saturated aldehydes, i l l u s t r a t e s the type of mechanism postulated for these reactions (Scheme I ) . 2 1 Scheme T Co2(CO); H C o ( C 0 ) 4 HCo(CO)3 •Co(CO) 3 HCo(CO)3 CO Co(CO)3 ir R2 HC-C-CF^ H 9 There are a number of routes used in the synthesis of t r ans i t i on -metal hydrides: I. Direct hydrogenation 0s(C0) 4 PPh 3 + H 2 1 2 0 atm^130°C > c o ) 3 P P h 3 2 2 : (1 ) W(ECBu t ) (C l ) 3 [P (CH 3 ) 3 ] 2 + H 2 ^ - ^ ^ HW(=tHBu!XCl ) 3 [P(CH 3 ) 3 ] 2 1 5 a (2) I I . Protonation of organometal1ic anions W(C0)4L(amine) 2 ; ^ O H ^ ' " 7 8 ° > HW(C0)4L~ " (3) Na°/naph = sodium naphthaleni.de L = P (0CH 3 ) 3 , P ( C H 3 ) 3 , PPh 3 I I I . Reactions with HX, X = ha l ides , CN~, S i R ? , or SnR^ (a) oxidat ive addit ion I rC l (C0)L 2 + HX —> HI r (X) (C l ) (C0)L 2 2 t f (4) L = PEt 9 Ph; X = CI or Br 10 (b) protonation HIr(C0)(PPh) 3 + HC1—» [H 2 I r(CO)(PPh 3) 3 ]Cl 2 5 ' 2 6 (5) IV. Reactions with complex hydrides I r C l 3 L 3 + L i A l H 4 ^ > ^ I r l ^ 2 0 (6) L = AsEt 2 Ph ' (n -C 5 H 5 )M(C0) 4 + + NaBH, 4 —* (n-C 5H 5)M(C0) 3H + CO 2 7 (7) M = Mo or W M o ( C 0) 6H - N a B H 4 d 6 ° - 1 1 ^ C > [HM 2 (C0) 1 0 ] " 2 8 (8) M = Cr, Mo, W V. El iminat ion reactions from a lky ls (a) Grignard A 2 9 RhCl(PPh 3 ) 3 + A l ( P r 1 ) 3 — » HRh(PPh 3) 3 + CH3CH = CH2 (9) (b) a lky l hal ide (- : ; -C 5 l l 5 )Mo(C0-) 2 L" + Pr 'Br (. f :-C 5H 5)Mo(C0) 2LH + CH3CH = CH2 L = P(0Ph) 3 0 0 ) 11 (c) solvent ^ I r C l 3 L 3 E t 0 H / 0 H > H I r C l 2 L 3 + CHgCH 3 1 (11) L = PEt 2Ph (d) [ I r C l ( C 0 T ) 2 ] 2 - U H 2 I rG l [P(C 6 H 9 )Cy 2 ]L 3 2 (12) L = P(cyc lohexy l ) 3 - PCy 3 ; COT = cyclooctene Hydridocarbonyls are known for the major i ty of the t rans i t i on metals... For the group VIB metals alone there are at least twenty such species. Yet only a handful of n i t rosy l hydride complexes have been reported; of these only a few are organometal1ic hydrides, three m o n o m e r s 3 3 ' 3 4 ' 3 5 and a few ruthenium and osmium c lus te rs " . 3 ! The f i r s t organometall i c n i t rosy l hydride was prepared in 1972 by Graham3 3 v ia the route shown in react ion 13. Et-N/H ? 0 - C 0 ? CpRe(C0)2(N0) — —> GpRe(C0)(N0)(C00H) — ^ CpRe(CO)(N0)H (13) Subsequently, the phosphine analogue has been synthesized by Gladysz and co-workers . 3 4 In 1978 in our group (n 5 -C 5 H 5 )M(N0) 2 H (M = Mo or W) were prepared by the route shown in react ion 14, but only the tungsten species 3 5 was of su f f i c i en t thermal s t a b i l i t y to be i s o l a t e d . 12 Na[H?Al(OCH?CH?OCH~)p] (n 5 -C 5 H 5 )M(N0) 2 Cl — ^ - v (n§C5H5)M(N0)2H (14) Spectroscopic measurements show that (n54^Hg)w(N0)2H exhib i ts a r e l a t i v e l y low f i e l d hydride resonance (NMR 6 2.77 CgDg) and a vM-H (IR) at 1900 cm"^ (CH 2 C1 2 ) . I ts charac te r i s t i c chemistry i s to function as a source of H"; hence, i t i s iner t to CHC1 3, C C l ^ , and Et 3N but reacts readi ly with p-toluenesulfonic acid and t r i t y l tetraf luoroborate ( in CH3CN) to y i e l d ( n 5 -C 5 H 5 )W(N0) 2 0S0 2 CgH 4 CH 3 and [ (n 5 -C 5 H 5 )w(N0) 2 (CH 3 CN)]BF 4 , respect ive ly . In view of the surpr is ing hydridic character of th is species i t is of in terest to prepare other organometal1ic n i t rosy l hydride species of the same metal . The choice in the manner used to generate n i t rosy l hydrides i s . based upon the abundance of possible precursors. Since a large number of n i t rosy l halide complexes are ava i l ab le , two methods are employed to synthesis n i t rosy l hydrides: (1) the react ion of a n i t rosy l cation (generated from a n i t rosy l hal ide) with BH 4 ~; (2) the metathesis of a n i t rosy l hal ide with Na[H 9Al (0CH~CH 9 0CHJ 9 ] . 3 7 13 Experimental Section A l l manipulations were performed so as to maintain a l l chemicals under an atmosphere of prepur i f ied nitrogen ei ther on the bench using o p conventional techniques for the manipulation of a i r - sens i t i ve compounds or in a Vacuum Atmospheres Corporation Dri-Lab model HE-43-2 dry box. A l l chemicals used were of reagent grade or comparable pur i ty . A l l reagents were e i ther purchased from commercial suppl iers or prepared according to published procedures, and the i r pur i ty was ascertained by elemental analyses and/or melting point determinations. Melting points were taken in c a p i l l a r i e s using a Gallenkamp Melting Point apparatus and are uncorrected. A l l solvents were dried by standard procedures 3 9 and d i s t i l l e d just pr ior to use. Unless spec i f ied otherwise, the chemical reactions described below were effected at ambient temperatures. Infrared spectra were recorded on Perkin-Elmer 457 or 598 spectro-photometers and were ca l ibrated with the 1601 cm~^ band of polystyrene f i l m . Proton magnetic resonance spectra were obtained on a Varian Asso-c iates T-60 spectrometer with tetramethylsi lane employed as an internal standard or on Bruker WP-80, WH-400, Varian Associates XL-100, or N ico le t -Oxford H-270 spectrometer: with reference to the solvent used. A l l 1H chemical sh i f t s are reported re la t i ve to Me^S.i.. at 0.0 ppm. Mrs;. M .M. Tracey, Ms. M.A. Heldman, Ms. L.K. Darge, and Mrs. M.T. 'Austr ia assisted in -obtaining these data. Solut ion 3 1 P NMR spectra were recorded at 40.5 MHz on a Varian Associates XL-100 spectrometer using 2D as the internal lock . Resonances were referenced to external P(OCHo)-, which is considered to be 14 +141 parts per m i l l i on downfield from HgPO^. A l l samples were prepared in the dry boXj using dry, deoxygenated CgDg in f i ve-mi l l imeter tubes. Solut ion 1 9 F NMR spectra were recorded on a Varian Associates EM-360 L spectrometer at 56.45 MHz. CFCl^ was used as the external reference. Fluorine-19 chemical sh i f t s are reported in parts per m i l l i on from CFCl^ ; pos i t ive chemical sh i f t s are upf ie ld of the external f luor ine standard. Mass spectra were recorded at 70eV on an At las CH4B or a Kratos MS-50 spectrometer using the d i rec t - i nse r t i on method with the assistance of Dr. G.K. Eigendorf, Mr. J.W. Nip, and Mr. M.A. Lapawa. Elemental analyses were performed by Mr. P. Borda. Computer simulations of NMR spectra were performed on a Bruker Aspect 2000 using the program: Parameter Adjustment in NMR by I terat ion Ca lcu la t ion . Reaction of (ji 5-C 5H 5)W(N0)Ig(PPhj) with AgBF,, and PPh, . To an ace ton i t r i l e (.10 mL) so lut ion of AgBF^ (0.14 g, 0.69 mmol) was added an orange, dichloromethane (30 mL) solut ion of (n 5-CgHg)W(N0)l2P p n3 (0.55 g, 0.69 mmol). Immediately a white prec ip i ta te formed, but the mixture was allowed to s t i r 2 h to insure completion of the reac t ion . Monitoring of the inf rared absorption during th is time indicated the loss of the vNO band at ^1645 cm - ^ , cha ra te r i s t i c of the s tar t ing mate r ia l , and the appearance of a new vNO band at ^1665 cm~^. F i l t r a t i o n of the f i na l react ion mixture through a 3 x 2 cm column of Ce l i te supported on a medium porosity f r i t and dropwise addit ion of d iethyl ether (15 mL) led to the p rec ip i ta t ion of an orange s o l i d , presumably [(n 5-CrHc)W(N0)lCPPho)-15 (CH^CN)]BF^ (vide i n f r a ) . I f pr ior to the addit ion of diethyl ether s o l i d PPhg (0.18 g , 0.69 mmol) was added to the dichloromethane f i l t r a t e , the IR band of the vNO sh i f ted from 1665 to 1645 cm""' . Subsequent addi t ion of diethyl ether led to the i so la t i on of orange crys ta ls of [(n 5-C 5Hg)W(N0)-i P P h 3 ] 2 B F 4 , (0.40 g , 57% y i e l d ) , mp • 213°C dec. Anal . Calcd for C 4 1 H 3 5 WN0IP 2 BF 4 : C, 48.38; H, 3.44; N, 1.38. Found: C, 47.98; H, 3.39; N, 1.41. IR (CH 2 C1 2 ) : v(N0) 1646 ( s ) ; a lso 1092 ( s ) , 1057 ( s ) , 1036 (s) cm" 1 . IR (Nujo l ) : v(N0) 1657 ( s ) ; v(BF) 1084 (s) c m " 1 ; also 1045 ( s ) , 1031 ( s ) , 845 (w), 749 (m), 693 (m) cm" 1 . *H NMR (CD 3 N0 2 ) : 6 7.64 (m, 30H, P( C $ s ) 3 ) , 5.97 ( t , 5H, C ^ ) [ 3 J i H - 3 i P = 2Hz]. 3 1 P NMR (CD 3 N0 2 ) : 6 1.9 [ 1 J 1 8 3 w _ 3 i p = 220 Hz] (broad-band proton decoupled). 1 9 F NMR (CD 3 N0 2 ) : 6 151 ( s ) . Reaction of (n 5-C 5H 5)W(N0)Io[P(0Ph) 3 ] with AgBF^ and NaCl. When an orange, dichloromethane (40 mL) so lu t i on , containing 0.50 g (0.59 mmol) of (n 5 -C 5 H 5 )W(N0) I 2 P(0Ph) 3 , was added to a 10 mL ace ton i t r i l e so lut ion of AgBF 4 (0.12 g, 0.62 mmol), a white prec ip i ta te formed immediately. The IR band of the n i t rosy l func t iona l i t y was observed to sh i f t from 1660 cm - 1 to 1680 c m - 1 . After i t was s t i r r ed for lh the react ion mixture was f i l t e r e d through a 3 x 2 cm Ce l i t e column supported on a medium porosity f r i t . The solvent was removed from the f i l t r a t e in vacuo; the resu l t ing orange o i l presumably contained the cation {(n 5-C 5H 5)W(N0)I[P(0Ph) 3 ](CH 3CN)}BF 4- The orange o i l was dissolved in nitromethane (10 mL); 0.04 g of NaCl were added; the mixture was s t i r r ed 14 h; and then the solvent was removed under reduced pressure. The red-orange o i l which resul ted was extracted with d ich lo ro -methane (4 x 5 mL). These combined al iquots were f i l t e r e d , and the f i l t r a t e 16 was concentrated to~10 mL. Dropwise addit ion of d iethyl ether (35 mL) prec ip i ta ted a rust-orange s o l i d , (.n5-C5H5)W(N0)I(.Cl) [P(0Ph) 3] (0.30 g , 68% y i e l d ) , mp 144°C dec. Anal . Calcd for C 2 3 H 2 0 WN0 4 IC1P: C, 36.73; H, 2.66; N, 1.86; 0, 8.52; I, 16.90. Found: C, 37.70; H, 2.86; N, 2.08; 0, 8.86; I, 16.09. IR (CH 2 C1 2 ) : v(N0) 1657 ( s ) ; also 1588 (m), 1487 ( s ) , 1210 (m), 1182 ( s ) , 1160 ( s ) , 1074 (w), 1026 (w), 1010 (w), 930 ( s , b r ) , 836 (w) cm" 1 . IR (Nujo l ) : v(N0) 1651 ( s ) ; also 1587 (m), 1208 ( s ) , 1180 ( s ) , 1156 ( s ) , 1071 (w), 1024 (w), 1009 (w), 957 ( s ) , 936 ( s ) , 912 ( s ) , 897 ( s ) , 857 (m), 782 ( s ) , 766 ( s ) , 688 (m) cm" 1 . lH NMR (C g Dg): 5 7.11 (m, 15H, P ( 0 C g H 5 ) 3 ) , 5.45 (d, 5H,CRH I-)( 3 J X 3 i = 2.93 Hz). *H NMR (CDCU): 6 7.29 (m, 15H, |-|_ p P ( 0 C 6 j y 3 ) , 6.01 ( d , C 5 H 5 , ^2.5H) ( 3 J ^ = 2.93 Hz) , 5.99 ( d , C 5 H 5 , ^2.5H) ( 3 J = 2.93 Hz). l H _ 3 l p Reaction of ( T I 5 - C 5 H 5 ) W ( N 0 ) I 2 [ P ( O P h ) , ] with AqBF^ and (CH 3 CH 2 ) 4 NBH / [ . In order to generate a solut ion of { (n 5 -C 5 H 5 )W(N0)I [P(0Ph) 3 ] (CH 5 CN)}BF 4 , an ace ton i t r i l e so lut ion (10 mL) of AgBF 4 (0.23 g , 1.2 mmol) and a d ich lo ro -methane solut ion (60 mL) of (n 5 -C 5 H 5 )W(N0) I 2 [P (0Ph) 3 ] (1.0 g , 1.2 mmol) were s t i r red together 3h and then were f i l t e r e d through a Ce l i te column ( 2 x 3 cm) which was supported on a f r i t . The orange f i l t r a t e was cooled to -78°C and a solut ion of (CH 3 CH 2 ) 4 NBH 4 (0.17 g , 1.2 mmol) dissolved in dichloromethane (10 mL) was added dropwise. No color change was observed, 17 but the in f rared spectrum showed that the vNO absorption of the cat ion at 1660 cm - 1 had disappeared and a band of much smaller in tens i ty had appeared at 1640 cm ^. The solvent was removed in vacuo, the product was suspended in benzene (10 mL), and the s lu r ry was transferred to the top of a 2 x 4 cm F l o r i s i l column. Elut ion of the column with benzene resulted in the development of a s ing le yellow-orange band which was co l lec ted and taken to dryness under reduced pressure. Recrys ta l l i za t ion from dichloromethane/hexanes afforded orange crys ta ls of (n 5-CgHg)W(N0)-( I ) (H) [P(0Ph) 3 ] (0.11 g, 13% y i e l d ) . Anal . Calcd for C ^ H ^ W N O ^ I : C, 38.52; H, 2.95; N, 1.95. Found: C, 38.46; H, 2.93; N, 1.94. IR ( C H 2 C 1 2 ) : v(N0) 1642 ( s ) ; also 1589 ( s ) , 1482 ( s ) , 1217 (m) , 1186 (s) , 1158 (s) , 1070 (w) , 1023 (m) , 1006 (w), 926 ( s ) , 862 (w), 827 (w) cm" 1 . IR (Nujo l ) : v(W-H) 1865 (w) ; v(N0) 1627 ( s ) ; also 1586 ( s ) , 1420 (w), 1290 (w), 1218 (m) , 1195 ( s ) , 1173 ( s ) , 1153 ( s ) , 1073 (m) , 1021 (m), 1009 (w) , 1002 (w) , 936 (s) , 914 ( s ) , 905 ( s ) , 887 ( s ) , 843 (w), 826 (m) , 786 (m), 766 ( s ) , 693 (s) cm" 1 . l H NMR (CgDg): & 7.45 (m, 6H, P(0Cg^ 5 ) 3 ortho),7.00 (m, 9H, P (0C 6 H 5 ) 3 para/meta), 4.82 ( s , 5H, CgHg), -2.07 ( IH, W-H), [ 2 J 112 Hz, l J = 55 Hz]. l H NMR (CDC/U) : 6 7.33 (m, 15H, P (0C ,H K ) Q ) , 1 H - 1 8 3 W 5.32 (s , 5H, C n H j , -1.98 ( IH, WTH) , [ 2 J = 111 Hz, 1 J b ^ b ^ " l H - 3 1 P 1 H - 1 8 3 W 54 Hz] . 3 1 P NMR (CgDg): 6 115 [ 2 J 3 I p J h = 112 Hz] . Mp. 112°C dec. Mass spectrum (probe temperature 150°C): [ (c 5 H 5 )W(N0' ) I (H)P(0Ph) 3 ] + , [ (C 5 H 5 )W(N0)HP(0Ph) 3 ] + , [ (C 5 H 5 )W(N0) I 2 ] + , [ ( C g H 5 ) W I 2 ] + , [ W I 2 ] + , [(C5H5)W-(,N0)IH2] + , and [ (C 5 H 5 )WI] + . 18 Reaction of (n 5-C 5H 5)W(N0)Io[P(0Ph) 3 ] with N a [ H 3 A 1 ( 0 C H 2 C H Q 0 C H 3 ) 2 ] . While a benzene suspension (50 mL) of (n 5-G 5Hg)W(NO)I 2[P(OPh) 3] (1.0 g, 1.2 mmol) was s t i r r ed at room temperature, a benzene solut ion (3.5M) con-ta in ing 1.2 mmol (0.34 mL) of NaH 2 Al(0CH 2 CH 2 0CH 3 ) 2 3 7 was added dropwise. The or ig ina l orange-red solut ion became brown, a brown so l id p rec i p i -ta ted, and the vNO infrared absorption sh i f ted from 1660 cm" 1 to 1640 cm" 1 ; i t s in tens i ty decreased. The f ina l reaction mixture was treated with d i s t i l l e d water (0.04 mL) and f i l t e r e d through a column of anhydrous MgSO^; the f i l t r a t e was taken to dryness in vacuo. The resu l t ing brown product in a benzene (10 mL) s lu r ry was transferred to the top of a 2 x 4 cm F l o r i s i l column. Elut ion of the column with benzene resulted in the development of a s ingle yellow-orange band which was co l l ec ted . R e c r y s t a l l i -zat ion from a dichloromethane/hexanes mixture resul ted in orange crys ta ls of (n 5 -C 5 H 5 )W(N0)( i ) (H) [P(0Ph) 3 ] (0.20 g, 34% y ie ld ) (vide supra). Reaction of ( n 5 -CH 3 C 5 H 4 )Mn(N0) (PPhJI with Na[HpAl(0CH 2CH 20CH 3) 2 ] . To a s t i r r ed benzene solut ion (40 mL) containing 2.0 g (3.6 mmol) of (n 5 -CH 3 CgH 4 )Mn(N0) (PPh 3 ) I 4 1 at ambient temperature was added a benzene solut ion (1.0 mL) containing an equimolar amount of Na [H 2 Al (0CH 2 CH 2 0CH 3 ) 2 ] . As the addi t ion proceeded, the colour of the former solut ion changed immediately from brown to red-brown; some gas evolut ion occurred; and a brown so l i d p rec ip i ta ted . Water (15 mL) was added to the f ina l reaction mixture, and i t was s t i r r ed for an addit ional 5 min. The benzene layer was then removed by syr inge, and the remaining contents of the reaction f lask were washed with benzene (6 x 20 mL). The benzene solut ions were combined and were f i l t e r e d through a 3.5 x 4 cm column of alumina ( a c t i -v i t y grade 1 ) . The solvent was removed from the f i l t r a t e under reduced pressure to obtain a red o i l . Subsequent manipulations were performed in an argon atmosphere. The red o i l was suspended in hexanes (60 mL), and the suspension was transferred onto a 2 x 8 cm column of alumina ( ac t i v i t y grade 4 ) . Elut ion of the column with hexanes f i r s t developed a green band which was co l l ec ted . Removal of solvent from the eluate afforded a small amount of a green so l i d which has yet to be i den t i f i ed and a large amount of tr iphenylphosphine. Continued e lu t ion with hexanes developed next a broad, orange band which required a 50/50 mixture of hexanes/benzene for complete removal from the column. The orange eluate was taken to dryness in vacuo to obtain 0.30 g (20% y ie ld ) of (n 5-CH 3C 5H 4)Mn(N0)(PPh 3)H as an orange, a i r - sens i t i ve s o l i d . Ana l . Calcd for C 2 4 H 2 3 MnN0P: C, 67.45; H, 5.42; N, 3.28. Found: C, 67.68; H, 5.57; N, 3.05. IR (CgHg): vNO 1683 cm" 1 . XH NMR (CgDg): 6 7.66-6.98 (m, 15H, P ( C g H 5 ) 3 ) , 4.60 ( s , IH) . 4.46 ( s , IH) , 3.92 ( s , 2H), 1.86 ( s , 3H.-CH,) , -6.48 (d , IH, Mn-H) [ 2 J 88.8 Hz] . Mp (under N 9) ™ ^ lu^.31p <L 42.5°C dec. Further e lu t ion of the column with benzene as eluant resul ted in the development of a dark green band which was co l lec ted and taken to dryness under reduced pressure. The residue was rec rys ta l l i zed from CH 2Cl 2 /hexanes to obtain a i r - s t a b l e , green microcrystals (0.016 g, 1% y ie ld ) of (n 5 -CH 3 C 5 H 4 ) 3 Mn 3 (N0) 4 , 1 + 2 which was characterized by i t s mass spectrum (probe temperature 190°C): [Mn ? (C f i H 7 )~(N0) Y ] + ( for X = 4 , 2, 20 or 1 and [Mn 2 (CgH 7 ) 2 (N0)y] + for y = 2 or 1 ) ; and spectral propert ies (IR in CH 2 C1 2 : v(.N0) 1538, 1483, and 1333 cm" 1 ; *H NMR in CDC1 3: 6 4.78 ( s , 12H, C 5 H 4 ) , 1 .83 (s , 9H, - % ) ) . Reaction of [ (n 5 -C 5 H 5 )W(N0) I 2 ] 2 with Na[H2Al ( O C H Q C H Q O C H J Q ] . To a green-brown solut ion of [ (n 5 -CgHg)W(N0)I 2 ] 2 L + 3 (3.0 g, 2.8 mmol) in dichloromethane (40 mL)/benzene (160 mL) at ambient temperature was added dropwise a benzene solut ion (3.5M, ^0.8 mL) containing 2.8 mmol of Na[H2Al (OCh^Q^OCH^)^ . The solut ion became deep green in colour and a green so l i d p rec ip i ta ted ; in f rared monitoring showed the disappearance of the n i t rosy l absorption at ^1660 cm"1 of the s tar t ing material and the appearance of a new n i t rosy l absorption at ^1640 c m - 1 . The f i na l reaction mixture was treated with d i s t i l l e d water (0.1 mL) and f i l t e r e d through a short (3 x 4 cm) column of anhydrous MgSO^ supported on a medium porosi ty f r i t . As the f i l t r a t e was concentrated in vacuo to a to ta l volume of~8 mL, deep green microcrystals formed. These were co l lec ted on a f r i t and rinsed with benzene ( 3 x 8 mL) . This preparation led to a n a l y t i c a l l y pure [ ( n 5 - C 5 H 5 ) W ( N 0 ) ( I ) ( H ) ] 2 (1.4 g, 61% y i e l d ) , mp (under N 2) 174°C dec. Anal . Calcd for C j g H ^ W ^ O ^ ; C, 14.74; H , 1.47; N, 3.44; I, 31.20, Found: C, 14.91; H , 1.51; N, 3.40; I, 30.95. IR (CH 2 C1 2 ) : v(N0) 1640 cm" 1 . IR (Nujo l ) : v(N0) 1634 ( s ) , 1616 ( s ) ; a lso 846 (m) c m ' 1 . *H NMR (CgDg): 6 5 .25 ( s , 5H, C 5 H 5 ) , -1.24 ( s , I H , W-H) . XH NMR ( C D C I 3 ) : 6 6.13 ( s , 5H, C , H S ) , -1.24 ( I H , W-H), ("J = 3.7 Hz, * J = 88.3 Hz, and 3 j i ^ - 1 8 3 ^ = 7 0 - 8 H z ) (see Figure 1 and d iscuss ion) . Mass spectrum (probe temperature 130°C : [ (C 5 H 5 ) 2 W 2 (N0) 2 IH 2 ] + , [(.C5H5)W(N0)I2H] + , [ (C 5 H 5 )WI 2 ] + , [ f l ^ +,..[(C5H5)W(N0)IH2]+, and,[(.CgHg)WI] + . 21 Reactions of [(n 5 -C 5 H 5 )W(N0)IH] 2 with Lewis Bases (L) These experiments were performed s i m i l a r l y , and the react ion with L = P(0Ph) 3 i s described as a representative example. To a green benzene solut ion of [ (n 5 -C 5 H 5 )W(M0)IH] 2 , generated from [(.n.5-C5H5)W CN'O-liy ' (1 . 5 , 1 .4 mmol) and-Red-al(vide supra), was added by syringe neat tr iphenylphosphite (0.70 mL, 2.7 mmol). Af ter a few minutes the solut ion colour darkened to orange. The react ion mixture was concentrated under reduced pressure to 10 mL and transferred to the top of a 2 x 5 cm F l o r i s i l column. Elut ion of the column with benzene resulted in the development of a s ingle yellow-orange band, which was co l l ec ted . The benzene was removed in vacuo; the orange o i l was dissolved in dichloromethane (25 mL); hexanes (15 mL) was added; and the solut ion was concentrated to y i e l d orange c rys ta ls of a n a l y t i c a l l y pure (n 5-C 5H 5)W(N0)(I)(H)[P(0Ph 3 ] (0.86 g, 70% y ie ld ) (vide supra). For L = P(0CH 3 ) 3 the y i e l d of (n 5 -C 5 H 5 )W(N0)(I)(H)[P(0CH 3 ) 3 ] was 69%. '.Mp -102-103°C. Anal . Calcd for C g ^ gWN0 4IP: ' 0 ,18 .08 ; H, 2.82; N, 2.64; I, 23.92; 0, 12.05. Found: C, 18.19; H, 2.88; N, 2.58; I, 23.71; 0, 12.17. IR (CH 2 C1 2 ) : v(N0) 1627 ( s ) ; also 1060 (m), 1 023 (s) c m " 1 . IR (Nujo l ) : v(W-H) 1918 (w); v(N0) 1616 ( s ) ; a lso 1174 (m), 1071 (m), 1012 ( s , b r ) , 845 (w), 840 (w), 824 (m), 797 ( s ) , 750 (s) cm" 1 . lW NMR ( C 6 D 6 ) : 6 5.12 ( s , 5H, C ^ ) , 3.36 (d , 9H, P(0CH 3 ) 3 ) , P J ^ . s i p = 12 Hz], -1.41 (IH, W-H), [ 2 d i H _ 3 i p = 101 Hz, i d i H _ i 8 3 w = 5 y H z ] _ 1 H N M R ( C D C l 3 , : 6 5.77 (s , 5H, CVH,), 3.67 (d, 9H, P ( 0 C h L ) J , P J = 12 Hz] , -1.42 O'vo 'VS 5 l H - 3 1 P (IH, W-H), [ 2 J = 101 Hz, i j = 57 Hz]. 3 1 P NMR (C.D, ) : ~ i H - 3 l p ! H - 1 8 3 W 6 131 [ 2 J 3 l ^ _ l H = 101 Hz]. 22 For L = P P h 3 , the product was (n 5-C 5H 5)W(N0)(I)(H)(PPh 3) i so la ted in 66% y i e l d . Mp 142°C dec. Ana l . Calcd for C^H^WNOIP: C, 41.26; H, 3.14; N, 2.09. Found: C,41.20; H, 3.18; N, 2.15. IR (CH 2 C1 2 ) : v(N0) 1615 ( s ) ; also 1482 (w), 1094 (m), 823 (tn) cm" 1 . IR (Nujo l ) : v(W-H) 1 936 (w); v(N0) 1617 ( s ) ; also 1 095 (m) , 1087 (m), 821 (w) , 693 (m) cm" 1 . *H NMR (CgDg): 6 7.70 (m, 6H, P(CgH 5 ) 3 ortho) , 7.05 (m, 9H, P ( C g H 5 ) 3 para/meta), 5.10 ( s , 5H, CgHg), 0.10 ( IH, W-H), [ 2 J = 85 Hz, 1 J = 58 Hz]. *H NMR ( C D C l J : 6 7.44 (m, 15H, l H - 3 1 p l H - ! 8 3 W * P(CgH 5 ) 3 ) , 5.63 ( s , 5H, C ^ g ) , 0.31 (IH, W-H), [ 2 J ^ 3 = 85 Hz, l J = 58 Hz]. 3 1 P NMR (C R D, ) : 6 14.1 [ 2 J 3 i D i u = 85 Hz]. 1 H _ 1 8 3 W b b P- H Reaction of [ (n 5 -C 5 H 5 )W(N0)( I ) (H)] 2 with Na[H 2 Al(0CH 2 CH 2 0CH 3 ) 2 ] . To a suspension of green c r y s t a l l i n e [(n 5-CgHg)W(NO)(I)(H)] 2 (0.65 g, 0.80 mmol) in toluene (100 mL) was added 0.3 mL (1.05 mmol) Red-al by syr inge. Both the col'o.ur of the solut ion and that of the par t icu la te matter changed from green to brown; inf rared monitoring indicated the loss of the vNO absorption at ^1640 cm" 1 , charac te r i s t i c of the s ta r t ing mate r ia l , and the appearance of a new vNO absorption at ^1600 c m - 1 . D i s t i l l e d water (0.04 mL) was added, and the react ion mixture was f i l t e r e d through a 3 x 4 cm column of anhydrous MgSO^ supported on a medium porosi ty f r i t . The f i l t r a t e was concentrated in vacuo to approxi-mately 15 mL at which point a f ine orange powder had prec ip i ta ted . The so l i d was co l lected on a f r i t and washed with 8 mL portions of toluene un t i l the washings had no green t i n t but were s l i g h t l y orange in color (about six a l i quo t s ) . Ana l y t i ca l l y pure [(n 5-CgHg)W(N0)H 2] 2 was thus obtained in 16% y i e l d (0.07 ig), mp 130°C dec. 23 Anal . Calcd for c T 0 H - | 4 W 2 N 2 Q 2 : C ' 2 1 - 3 5 ' H ' 2 , 4 9 ; N ' 4 , 9 8 ; ®' 5 - 6 9 - F o u n d : C, 21.69; H, 2.63; N 4.95; 0, 6.00. IR (CH 2 C1 2 ) : v(N0) 1596 (s) cm" 1 . IR (Nujo l ) : 3108 (w), 3088 (w); v(W-H) 1934 (m); v(N0) 1563 (s , b r ) ; also 1430 (m), 1421 (m), 1365 (w), 1317 (w), 1064 (w), 1016 (m), 927 (w), 845 ( s ) , 749 (m) cm" 1 . *H NMR (CgDg): 6 7.01 (m, 2.6H, W-H), 6.64 (dd, 2H, W-H), 5.26 ( s , 10H, CgHg), 5.23 ( s , 13H, CgHg), 1.66 (m, IH, W-H), -1.90 (m, 2.6H, W-H), -5.99 ( td , IH, W-H). lH NMR ( C D C I 3 ) : 6 6.98 (m, 2.6H, H 5 and H g ) , M l J l H i 8 3 W + ^ l u _183 W) = 94 Hz] , 6.54 (dd; 2H, H] and H 2 ) . [ 2 J ] 3 = 2 J 2 3 = 2.9 Hz; * J U = 2 ^ = 8 . 6 H z . h { 1 j _ i Q ^ + ] J l H 2 _ i 8 3 W ) = 97 Hz] , 5.94 (s , 13H, CgHg), 5.93 ( s , 10H, CgHg) , 1.39 (m, IH, H3) [ 2 J 3 1 = 2 J 3 2 = 2 . 9 Hz; 2 J 3 4 = 2.3 Hz ; ^ l u . i s s w = 91 Hz] , -2.02 (m, 2.6H, H y and Hg) [Jg(1 J i H 7 _ i 8 3 W + ^ l U g - i B S y ) = 92 Hz], -5.93 ( td , IH, H 4) [ 2 J 4 1 = 2 j ^ = 8 . 6 H z . z j ^ = 2 . 3 Hz; ^ l u . i s s y = 95 Hz] (see Figure 5 and d iscuss ion) . Mass Spectrum (probe temperature 120°C): [ ( C 5 H 5 ) 2 W 2 ( N 0 ) 2 H 3 ] + . Reactions of [ ( r i 5 -C 5 H 5 )W(N0)H 2 ] 2 with P(0Ph) 3 . Neat tr iphenyl -phosphite (0.30 mL, 1.6 mmol) was added by syringe to a benzene (50 mL) suspension of [(n 5-CgHg)W(N0)H 2] 2 (0.30 g , 0.50 mmol). The react ion mixture was s t i r red un t i l most of the so l i d had dissolved and a burgundy-coloured solut ion had formed (about 3h). The solut ion was f i l t e r e d , con-centrated to ^15 mL, and d i lu ted with 10 mL hexanes. A brown so l i d p rec i -pi tated which was removed by f i l t r a t i o n and discarded. Further addi t ion of hexanes (^30 mL) to the purple solut ion resulted in the formation of a deep purple powder (n 5-C 5H 5)W(N0)H 2 [P(0Ph) 3 ] (0.20 g , 32% y i e l d ) . 24 Anal . Calcd for C 2 3 H 2 2 WN0 4 P: C, 46.70; H, 3.72; N, 2.37. Found: C, 47.10; H, 3.75; N, 2.65. IR (CH 2 C1 2 ) : 1591 ( s ) ; v(N0) 1575 (s , b r ) ; a lso 1487 ( s ) , 1194 ( s ) , 1186 ( s ) , 1160 (m) c m - 1 . IR (Nujo l ) : 1589 ( s ) ; v(N0) 1574 ( s ) ; a lso 1217 (m), 1196 ( s ) , 1185 ( s ) , 1159 ( s ) , 1069 (w), 1023 (w), 1005 (w), 913 ( s ) , 895 ( s ) , 881 ( s ) , 822 (w), 780 ( s ) , 770 ( s ) , 708 (w), 694 (s) cm" 1 . lH NMR (CgDg); 6 7.58 (d , 6H, P ( C g H 5 ) 3 . ortho) , 7.20 ( t , 6H, P ( C g H 5 ) 3 meta), 6.94 ( t , 3H, P ( C g H 5 ) 3 para) , 5.17 ( s , 5H, C 5 H 5 ) , 1.32 (m, 2H, W-H). *H NMR (CDC1 3): 6 7.35 (m, 15H, P ( C g H 5 ) 3 ) , 4.97 ( s , 5H, C 5 H 5 ) , 1.10 (m, 2H, W-H). 3 1 P NMR (CgDg): 151 (t) • ^ ( ' J 3 i p . i H l + 2 J 3 i p j H 2 ) = 2 4 Hz; i J a i p . i s s w = 595 Hz]. Mp 85°C dec. Mass spectrum (probe temperature 120°C): [(CgH 5)W(N0)HP(0Ph) 3] +, [ (C 5 H 5 )WP(0Ph) 3 ] + , and,[WH 2 P(0Ph) 3 J + . When rec rys ta l l i za t ion of purple (n 5-C 5H 5)W(N0)H 2f_P(0Ph) 3] was attempted employing dichloromethane/hexanes instead of benzene/hexanes, the colour of the purple solut ion slowly l ightened un t i l in approximately 3 hours the so lut ion was orange. The l i gh t orange powder iso la ted from th i s so lut ion s t i l l had the empir ical formula (CgH 5)W(N0)H 2[P(0Ph) 3]. Anal . Calcd for C 2 3 H 2 2 WN0 4 P: C, 46.70; H, 3.72; N, 2.37. Found: C, 46.55; H, 3.84; N, 2.50. IR (CH 2 C1 2 ) : v(N0) 1606 ( s ) ; also 1591 ( s ) , 1487 ( s ) , 1220 (m), 1194 ( s ) , 1164 (m), 1073 (w), 1025 (m) , 1009 (w), 965 (w), 916 ( s ) , 865 (m), 827 (m) cm" 1 . IR (Nujo l ) : v(W-H) 1856 (w), 1831 (w); V(N0) 1601 ( s ) ; also 1586 ( s ) , 1190 ( s ) , 1151 ( s ) , 1069 (w), 1028 (w), 1004 (w), 928 (m) , 913 (m), 903 ( s ) , 887 ( s ) , 824 (w), 820 (w), 776 ( s ) , 770 (m), 691 (m) cm" 1 . XH NMR (CgDg): 7.42- 6.92 (m, 15H, P(CgH 5 ) 3 ) ,4 .69 (s , 5H, CgHg), -1.58 (2H, W-H) [ 2 J i H . 3 l p = 87 Hz; 1 J i H _ i 8 3 W = 8 7 H z ^ - l R N M R (CDC1 3): 6 7.28 (m, 15H, P (CgH 5 ) 3 ) , 5.10 ( s , 5H, C 5 H 5 ) , -1.82 (2H, W-H) [ 2 J i H _ 3 l p = 86 Hz; ^ i ^ i s s w = 88 Hz]. 3 1 P NMR (CgDg): 6 137 (t) ( 2 J 3 ^ p i i t | , = 87 Hz). Mp 91 °C dec. 26 Results and Discussion Preparation and Reactions of r(,n 5-C 5H 5)W(.N0)IL(solvent)lBF / [ ( I ) . When the iodine bridges in [(n 5 -CgHg)W(N0) I 2 ] 2 a r e cleaved by a Lewis base, L, (n 5 -CgH 5 )W(N0)I 2 L i s formed in good y i e l d . A "four-legged piano s too l " geometry is assumed for the molecular structures of the (n 5-CgHg)W(N0)I 2L complexes; and although th is allows for the p o s s i b i l i t y of c i s - t rans geometric isomers, 1H and 1 3 C NMR spectra indicate the presence of only one isomer in s o l u t i o n . 4 3 When (n 5 -C 5 H 5 )W(N0) I 2 L i s treated with one equivalent of AgBF^ in a dichloromethane/acetoni t r i le mixture, s i l v e r iodide rap id ly forms. Monitoring the react ion by inf rared spectroscopy shows a sh i f t in the vNO absorptions from that of the s tar t ing material to that of the product (I) [1645 to 1665 cm - 1 for L = PPh 3 and 1660 to 1680 cm - 1 for L = P(0Ph) 3 ] . For L = PPh 3 attempts to i so la te the product lead to an orange so l i d [v(NO) = 1 657 (s) cm! 1 ,(XH 2 'C1 2), v(N0) = 1656 cm" 1 (s) (Nujo l ) , v(CM) = 2310 (w), 2275 (w) cm - 1 (Nu jo l ) , and v(BF) = 1054 (s.br). CNujoT)]. The 1 H NMR spectrum (CD 3N0 2) consists pf three mul t ip le ts : phenyl ( 6 8 . 1 7 .4) , cyclopentadienyl (6 6.23 ( t ) , 2 J i ^ . 3 i p = 2 - 2 H z ) a n c ' a ce ton i t r i l e {$. 2 . 8 2.2) of re la t i ve i n tens i t i es 15 to 5 to 3. These observations are consistent with the abstract ion of one iodo l igand to y i e l d a ca t ion ic product which in time loses some of i t s coordinated a c e t o n i t r i l e : 27 CH^CN (,n 5-C 5H 5)W(NO)I 2L + AgBF^ — - — • [ ( T I 5 - C 5 H 5 ) W ( N 0 ) IL(CH 3CN)]BF 4 + Agl+ (15) L = PPh 3 (a) Reaction of I with PPh 3 - Addit ion of PPh 3 to the solvated cat ion [CpW(.N0)I(PPh3)(CH3CN)]BF4 sh i f t s the vNO in the IR spectrum of the react ion solut ion from 1665 cm - 1 to 1645 cm - 1 as i s expected when the more electron-donating l igand PPh 3 replaces CH3CN. The resu l t ing cat ion [(n 5-C 5Hg)W(N0)l(PPh 3) 2]BF 4 i s a yel low-orange, diamagnetic so l i d which is soluble in ace ton i t r i l e and nitromethane and s l i g h t l y soluble in d ich loro-methane. Its IR spectrum (Nujol) exhib i ts a strong n i t rosy l absorption at 1657 cm - 1 and a tetraf luoroborate absorption at 1084 c m - 1 , which are charac te r i s t i c of a terminal n i t rosy l 1 igand 4 3 >41+ and an uncoordinated a n i o n , 4 5 respec t ive ly . The 1H NMR spectrum of [ (n 5 -C 5 H 5 )W(N0) I (PPh 3 ) 2 ]BF 4 consists of a mul t ip le t at 6 7.64 (30H) due to the phenyl protons and a t r i p l e t at <$ 5.97 (5H) [ 3 J i H _ 3 i p = 2 . 0 H z ] corresponding to the cyclopentadienyl protons. The t r i p l e t pattern exhibi ted by the cyclopentadienyl protons must be the resul t of coupling to two equivalent phosphorus atoms; a more complex pattern would be expected in the case of inequivalent phosphine l igands. The order of magnitude of the coupling i s the same as. that found in U 5 -C 5 H 5 )W(N0) I 2 L ( 3 J j H _ 3 i p = 3.0 Hz for L = P(0Ph) 3 ; 3 J i H _ 3 i p = 1 .2 Hz for L = P P h 3 ) . 4 3 The equivalence of the phosphines i s confirmed by the broad-band proton decoupled 3 ^P NMR spectrum which is a three l ine p a t t e r n — a 28 large s ing le t centred in a small doublet which i s of the proper in tens i t y ra t io to the larger resonance (1 to 11.4 to 1) to be at t r ibuted to the NMR pattern of the isotopomer [ ( n 5 -C 5 H 5 ) 1 8 3 w(N0 ) I (PPh 3 ) 2 ]BF 4 (the natural abun-dance of 1 8 3 W = 14% 4 6 ) . The observed tungsten-phosphorus coupling ( !J 3ip_i83y = 220 Hz) is of the same order of magnitude as that reported for 4 7 tungsten phosphinocarbonyl complexes. The presence of a tetraf luoroborate anion with tetrahedral symmetry i s confirmed by the s ing le t at 6 151 observed in the 1 9 F NMR spect rum. 4 8 It seems l i k e l y that the [ (n 5 -C 5 H 5 )w(N0) IL 2 ] + cat ion (L = PPh 3) i s i sos t ruc tura l with (n 5-CgHg)w(N0)I 2L and possesses the same "four-legged piano s too l " conformation. For t h i s structure both c is and trans geometries are poss ib le ; but as the nuclear magnetic resonance experiments indicate two equivalent phosphine l igands , only the trans isomer appears to ex i s t in so lu t i on : (b) Reaction of I with NaCl. The mixed hal ide complex (jn5-CgH5)W-( N 0 ) I ( C l ) [ P ( 0 P h ) 3 ] i s formed when sodium chlor ide and .{(n 5 - C 5 H ^ ) W (N 0) 11P -(0Ph ) 3 ] (CH 3 CN) }BF 4 are s t i r red together in nitromethane for 14 h.. The net 29 react ion is simply the subst i tu t ion of ch lor ide for iod ide: CpW(N0)I 2[P(0Ph) 3] A g B F ^ 3 ^ U { C p W ( N 0 ) I [ P ( 0 P h ) 3 ] ( C H 3 C N ) } B F 4 j^j1 > CpW(N0)I(Cl)[P(0Ph) 3] (16) (n 5-C 5H 5)W(N0)I(Cl ) [P(0Ph) 3 ] has spectral propert ies s imi la r to the parent hal ide (n 5 -C 5 H 5 )W(N0)I 2 [P(0Ph) 3 ] , 1* 3 Both exhib i t a n i t rosy l absorption at 1651 cm - 1 in the i r IR spectrum (Nujo l ) . The 1H NMR spectrum of the di iodo precursor d isplays a mul t ip le t at 6 7.19 (CDC13) due to the tr iphenyl phos-phite protons and a doublet at 6 5.90 due to the cyclopentadienyl protons with 3 J i ^ j _3 i p = 3.0 Hz; thus, though both c i s and trans di iodo ligands are poss ib le , only one isomer is observed. Only one isomer of (n 5-C gHg)W(N0)I-(Cl ) [P(0Ph) 3 ] appears to ex is t in d 6-benzene: 6 7.17 (m, 15H, P(0C g H 5 ) and 5.45 (d, 5H, C 5 H 5 ) with 3 J ! ^ 3 1 p = 2.9 Hz. However, a proton NMR spectrum of the mixed halide species obtained in d-chloroform on a 270 MHz spectro-meter manifests two sets of CgHg resonances; both are doublets, 3 J i ^ 3 1 p = 2.9 Hz, of approximately equal in tens i ty centred at 6 6.01 and 5.99. Thus, of the three potential geometric conf igurat ions two are in evidence in ch loro-form so lu t ions . (c) Reaction of I with (CHgCH^NBH^. Previous e f for ts in these laborator ies have succeeded in synthesizing (n 5-C 5Hg)W(N0) 2H in good y ie lds 30 (^ 60%) both by metathesis of the corresponding chlor ide complex (react ion 35 ' ' 14) and by addit ion of a hydride source to "CpW(N0)2+" generated in s i t u . 4 9 I t , thus, seemed l i k e l y that (n 5-C 5H 5)W(N0)IH[P(0Ph) 3] could be obtained in good y i e l d from the react ion of the cation and an H source. Indeed, the organometall ic hydride i s formed in the react ion of t e t ra -ethylammonium borohydride with a cold (-78°C) dichloromethane solut ion of { (n 5 -C 5 H 5 )W(N0)I [P(0Ph) 3 ] (CH 3 CN)}BF 4 and can be iden t i f i ed by i t s IR spectrum (Nu jo l ) : v(W-H) 1865 (w); v(N0) 1627 (s) and l H NMR spectra (CDC13) : 6 7.33 (m, 15H, P ( 0 C g H 5 ) 3 ) , 5.32 ( s , 5H, C ^ ) , -1.98 ( IH, W-H), ( 2 j i H 31p = H I Hzj, 1 J 1 ^ | 1 8 3 ^ = 54 Hz). (A deta i led discussion of the propert ies of th is hydride w i l l fo l low in a l a te r sect ion. ) Unfortunately, the y i e l d of react ion 17 i s poor (13%). IR monitoring reveals that as CH Cl o {(n 5-C 5H 5)W(N0)l [P(0Ph) 3 ] (CH 3CN)}BF 4 + Et 4 NBH 4 _fQoC> (n 5-C 5H 5)W(N0)IH[P-(0Ph) 3 ] + Et 4 NBF 4 (17) (CH 3CH2) 4NBH 4 is dripped into the cation solut ion the VNO band of the cat ion (1660 cm - 1 ) disappears and the only n i t rosy l absorption which appears is small in in tens i ty and i s that associated with the product (1640 c m - 1 ) . Borohydride i s chosen as the hydride source because i t i s a r e l a t i -vely mild reducing agent, but under some circumstance i t can contr ibute more than one hyd r i de . 5 0 Further d i f f i c u l t i e s may ar ise' from coordination of the BH:4 group to the. metal centre as has been'found for 31 [RuC l 2 ( t t p ) ] x + excess NaBH4 re f lux ing > HR u( j 1 -2_BH, 4) ( t t p ) 5 1 Cl8). t tp PhP( .CH 2CH 2CH 2 PPh 2 ) 2 Another complication may ar ise from the n i t rosy l l i gand , which, i t s e l f is, suscept ible to hydride at tack, e .g . [CpCr(N0) 2 ] 2 Cp 2 Cr 2 ( .N0) 3 (NH 2 ) 5 2 (.191 Evidently another react ion occurs besides simple addi t ion of H" to the metal centre'which results in the loss of the n i t rosy l moiety. That the iodide abstract ion i s not the low y i e l d step can be assumed from the good y ie lds of [(.n 5-C 5H 5)w(N0) I ( .PPh 3 ) 2 ]BF 4 and h 5 -C 5 H 5 )W(N0) r (C l ) [P (0Ph) 3 ] produced v ia the same abstract ion step (vide supra).. Metathetical Reactions of Na[H 2 Al(0CH 2 CH 2 0CH 3 ) 2 ] with Some Monomerici  Haloni t rosyl Complexes. (a) Cn 5-C 5H 5 )W(.N0)I 2 [PC0Ph) 3 ] . Formation of Cn 5-C 5H 5)W(N0)I(.H)-[P(.0Ph) 3 ] , produced by the react ion of (_CH3CH2) 4 NBH 4 with {(.n5-C5H5)W.(.N0) I-[P(OPh) 3](CH 3CN)}BF 4, i s also successfu l ly effected by the react ion of one equivalent of sodium dihydridobis(2-methoxyethoxy)aluminate on (n5-CgHg)W-(N0) I 2 [P(0Ph) 3 ] in a benzene solut ion at room temperature. As the Red-al i s added, the o r i g i n a l l y orange suspension darkens and a brown s o l i d forms. The n i t rosy l inf rared absorption sh i f t s from 1660 cm - 1 to 1640 c m - 1 , 32 decreasing markedly in i n tens i t y . Then a s l i gh t sto ichiometr ic excess of water is added to quench the aluminum reagent. The yellow-orange species iso la ted from chromatography on a benzene/F lor is i l column is i den t i -f ied by IR and by 1 H, NMR spectroscopy (vide in f ra) to be the hydride ( ' r -Cgh^W-(N0)I(H)[P(0Ph) 3 ] . The y i e l d of react ion 20 Na[H ?Al(0CH ?CH ?0CH^) 9] U 5 -C 5 H 5 )W(N0)I 2 [P(0Pih) 3 ] - — (n 5-C 5H 5)W(N0)I(H)-[P(0Ph) 3 ] (20) (34%) represents a s l i gh t improvement over the quantity of hydride obtained v ia the cation (react ion 17). (b) (n 5-CH 3C 5H / 1)Mn(N0)[PPh : ;JI,. Just as with (n 5 -C 5 H 5 )W(N0) I 2 -[P(0Ph) 3 ] , sodium dihydridobis(2-methoxyethoxy)aluminate also undergoes a simple metathetical react ion with (n 5-CH 3C 5H 4)Mn(N0)CPPh 3)r 1 + J L to produce the hydr idonitrosyl species. Na[H 9 Al(0CH ? CH ? 0CHj ? ] (n 5-CH 3C 5H 4)Mn(N0)(PPh 3)I 1 benzene — > • (Ti5-CH3C^H4)Mn( NO)-(PPh3)H ( 2 1 ) Again, the optimum stoichiometry of the reactants i s 1:1, and the t rans-formation proceeds to give the hydride in low y i e l d . (n5-CH3C,-H4)Mn(N0) (PPh 3)H i s an orange, a i r - s e n s i t i v e so l i d (mp 42.5°C dec.) which i s f ree ly soluble in benzene, i s spar ingly soluble in hexanes, and reacts with CH ? C1 ? . The XH NMR spectrum of the compound in 33 CgDg exhib i ts resonances assignable to the PPh 3 [5 7.66-6.98 (m, 15H)], n 5 ; q 3 C 5 H 4 [6 4.60 ( s , IH), 4.46 ( s , IH) , 3.92 ( s , 2H), 1.86 ( s , 3H)], and W-H [6 -6.48 ( d , 1H); 2 J i H _ 3 i p = 88.8 Hz] l igands. Its IR spectrum in benzene displays a strong absorption at 1683 cm - 1 a t t r ibu tab le to a terminal n i t rosy l group. However, the complex decomposes slowly both in solut ion and in the so l i d state when maintained in an atmosphere of pre-pur i f ied argon. For instance, a red benzene solut ion of (n 5 -CH 3 C 5 H 4 )Mn(N0)-(PPh 3)H at room temperature slowly becomes dark green and deposits a brown s o l i d . Monitoring of th is transformation by 1H NMR spectroscopy reveals a gradual diminution of the resonances due to the hydrido complex and a concomitant increase in in tens i ty of two sharp s ignals at 6 1.64 and 4.60 of re la t i ve in tens i ty 3:4 due to the well-known, green t r i m e t a l l i c complex ( n 5 - C H 3 C 5 H 4 ) 3 M n 3 ( N 0 ) 4 . 7 , l + 2 The transformation i s complete af ter 48 h. Consequently, pu r i f i ca t i on of the hydrido product of react ion 21 by column chromatography also affords trace amounts of the t r i m e t a l l i c species. The fact that (n 5-CH 3CgH 4)Mn(N0)(PPh 3)H decomposes thermally in th is manner rather than to [(n 5-CH 3CgH 4)Mn(N0)(PPh 3) ] 2 i s presumably a re f l ec t i on of the considerable l a b i l i t y of the PPh 3 group. When a s im i la r react ion i s performed with Red-al and (n5-CgHg)Mn(CO) (NO)I the hydr idonitrosyl species i s not the product. Instead, the product is the dimer [(n5-CgHg)Mn( CO) (N0)J 2 - . Dimers are also produced by the react ion of Red-al with e i ther (n5-CgHg)Co(NO)I or (n 5-CgHg)Cr(N0) 2X (X = N0 3 , N0 2 , 5 2. I.n-1 -CgHg, or BF 4 ) as summarized in eqs. 22 , 23, and 24. 34 CpMn(CO)(NO)I b e ^ e n e > [CpMn(C0)(N0)]2 (22) C P C o ( N 0 ) I to?uene,-78°e ^ ( N O ) ] , (23) C P C ^ N 0 ¥ benzine or C H ^ ^ ^ h h (24) These dimeric products probably a r i se from the thermal decomposition of the corresponding monomeric hydridonitrosyl complexes (such a decomposition 5 3 pathway has been reported for (n 5-C^Hg)Cr(C0) 3H ), but no d i rec t physical evidence for the existence of these species has been obtained. Support for the involvement of (n 5-CgHg)Cr(N0) 2H as an intermediate is provided by the observation t ha t | (D 5 -CgH g )C r (N0 ) 2 ] 2 i s formed in comparable y ie lds during the react ion of Red-aT-with a var ie ty of (n 5 -CgH 5 )Cr(N0) 2 X precursors 52 35^ (X = N 0 3 , N 0 2 , I, n 1 -C 5 Hg or BF^ or CI ), while the reactions of Red-al 35 with (n 5-CgKg)M(N0) 2Cl (M = Mo or W) produce the hydride species (n 5 -C 5 H 5 )M(N0) 2 H.. Consistent with the view that (n 5-C 5H 5)Mn(C0)(N0)H is the l a b i l e intermediate in react ion 22 is the fact that (n5-CH3CgH4)Mn(N0) C.PPh3),H can be iso la ted from react ion 21. Ev ident ly , introduct ion of the better electron-donating C H ^ H ^ and PPh 3 groups into the coordination sphere of the manganese atom s t a b i l i z e s the l a t t e r hydride, whereas the analogous hydridocarbonyl complex in react ion 22 i s so unstable that i t cannot be detected by conventional spectroscopic techniques. 35 Reaction of [(,n 5-C 5H 5)W(N&),I 2] 2-with Na[H2Al (OCHoCHgOGH,),,]. In view of .the r eac t i v i t y patterns of Na[H 2Al(0CH 2CH 20GH 3) 2] described above, i t was of in terest to invest igate i t s react ions with complexes containing both bridging and terminal halide l igands. It seemed reason-able that se lec t ive subst i tu t ion of the terminal halides could be achieved while leaving the halide bridges i n tac t . Indeed, just such a transform-at ion does occur when [ (n 5 -C 5 H 5 )W(N0) I 2 ] 2 the precursor of (n 5-C 5H 5)W(N0)-I 2 [P(0Ph) 3 ] is treated with one equivalent of Red-al at room temperature, i . e . n 5 - C 5 H 5 n 5 - C 5 H 5 ON-/ ii — \ n 5 - C 5 H 5 .NO Red-al benzene n=-C 5H 5 IT x W — NO -> ON / S ^ H (25) The unprecedented product of react ion 25 i s a bright green, a i r - s e n s i t i v e so l id which is soluble in most common organic solvents except paraf f in hydrocarbons. However, the compound i s thermally unstable in .so lu t ion (benzene > CH 2C1 2 > THF in order of decreasing s t a b i l i t y ) , decomposing to a brown,- in t ractable s o l i d . Nevertheless, a n a l y t i c a l l y pure samples of th is compound can be obtained. Its physical propert ies are consistent with i:t having- the mol eeular structure shown in eq. 25. The so l i d state infrared spectrum (Nujol) reveals two strong n i t rosy l absorptions (1634 and 1616 ..cm - 1), but 'no tungsten-hydride, stretching, absorpt-36 t ion is evident. The two n i t rosy l absorptions may resu l t from packing disorder in the crysta l l a t t i c e . Its IR spectrum in dichloromethane displays a strong n i t rosy l absorption at 1640 cm" 1 . Only one isomer of [ (n 5 -C 5 H 5 )W(N0) I (H) ] 2 i s observed in i t s l H NMR in d -benzene or d-chloroform. The l H NMR spectrum of a d i lu te sample consists of two s ing le ts at 6 5.25 and -1.25 in d -benzene or at 6 6.13 and -1.24 in d-chloroform of re la t i ve in tens i ty 5:1 assignable to the cyclopentadienyl protons and hydrides, respec t ive ly . The two hydride l igands are isochronous but not magnetical ly equivalent; with a more ooncentrated sample the signal to noise ra t io increases such that 1 H - 1 8 3 W coupling becomes observable, and the NMR pattern of the hydride region becomes more complex (see Figure l a ) . An AA'X pattern emerges around the central resonance which i s the expected 86% of the to ta l i n tens i t y . Coupling constants were ten ta t ive ly assigned using algebraic equations derived for the in terpretat ion of second order spect ra ; these ass ign-ments were confirmed by computer simulation of the 1 8 3 W s a t e l i t e region of the spectrum (Figure l b ) . It i s assumed that there i s small probabi-l i t y of both tungsten atoms in the same molecule being the spin h isotope. Where H is the hydride d i r ec t l y attached to 1 8 3 W , the coupling constant assignments are ^ J ^ . = 3.7 Hz, 1 J i H _ i 8 3 ^ = 8 8 - 3 H Z > A N D 3 J I H * - l a 3 W = 70.8 Hz) . The dimeric nature of the complex i s further confirmed by i t s mass spectrum (at a probe temperature of 130°C) which exhib i ts peaks a t t r ibu tab le to the parent ion and ions corresponding to the sequential loss of l igands. Unfortunately, overlapping of some medium to strong in tens i ty peaks in the 37 Figure 1. a . 2H NMR Spectrum of the Hydride Region o f [(n 5-C 5H 5)W(N0)I(H)], in CDC13 (400 MHz) b. Computer Simulation of the Tungsten-Hydride Couplings 38 lower mass range makes unambiguous assignments d i f f i c u l t , espec ia l l y in the l i gh t of the poly isotopic nature of tungsten. The dimeric product of react ion 25 can also be characterized chemically since i t read i ly reacts with a var ie ty of Lewis bases L to produce new tungsten hydrido-n i t rosy l complexes, i . e . n 5 - C 5 H 5 O N — .1 ^ 5 : C 5 H 5 H W I H NO + 2 L benzene 2(n 5-C 5H 5)W(N0)(H)(I)L (26) Wh.enE(n5-C5H5)Mo(.N0)I2]2 i s treated with one equivalent of Red-al 5 5 at room temperature, the well-known dimer [ (n 5 -C 5 H 5 )Mo(N0)I ] 2 i s formed in 6% y i e l d . The y i e l d can be improved to 18% when two equivalents of Red-al are employed, i . e . 5 2 ON — M o ^ X M o NO I R e d ~ a l > ^ - M o ^ - ^ M o (27) y v b e n z e n e / \ s \ 1 1 1 NO I NO By analogy with the tungsten congener (c f . react ion 25) , i t seems l i k e l y that react ion 27 probably proceeds v ia the unstable dihydrido intermediate L(n 5-CgHg)Mo(N0)(H)I] 2. During the reac t ion , a green colour perhaps due to the intermediate, appears af ter the addit ion of each a l iquot of Na[H 2Al(.0CH 2CH 20CH 3) 2 ] ; but th is col our persi sts only for several seconds 39 before being replaced by the charac te r i s t i c orange colour of the f i na l product. The species responsible for the green color cannot be detected by IR spectroscopy. Cur ious ly , thermal decomposition of [(n5-CgHg)W(N0)-(H)I^2 in solut ion does, not resu l t in the formation of the analogous [Cn5-CgHg)W.(N0)IJ2> a complex which has yet to be prepared. Mention needs to be made of the stoichiometry of reactions 20, 21 and 25. In each of these transformations one equivalent of the aluminum!!! reagent per equivalent of reactant is necessary to ensure completion of the reac t ion . For the monomeric reactants (n 5-C 5Hg)W(N0)l2[P(0Ph) 3] and (n 5-CH 3C 5H 4)Mn(N0)(PPh 3) I th is means Na[H 2Al(0CH 2CH 20CH 3) 2 ] i s act ing as the source of only one hydride. For b is [ (n 5 -cyc lopentad ieny l )d i iodo-ni t rosyl tungsten] the aluminum reagent must be act ing as a source of two hydrides. Unlike the case in react ion 27 an extra equivalent of Red-al does not increase the y i e l d of the product, the hydr idoni t rosyl dimer; ra ther , i;t i n i t i a t e s a further react ion (vide i n f r a ) . Since in a l l cases the t ransfer of one hydride from the aluminum reagent would be expected to resu l t in the same aluminum byproduct, i t must be the re la t i ve inertness of the monomers that prevents acceptance of a hydride from th is source. Reactions of [(n5-C^H^)W(NO) IH] 2 with Lewis Bases. The iodine bridges in [(n5-C5Hg)W(N0)I(H)]2 are eas i l y cleaved by a var ie ty of Lewis bases, L, to form the monomeric complexes (n 5-C gHg)W(N0)-I(H)L (eq. 28): 40 [CpW(N0)I(H)]2 * 2L b e n z e n e o r C H 2 C l 2 > 2CpW(N0)I(H)L (28) L = P(0Ph) 3 , P(0Me) 3 , or PPh 3 The products of react ion 28 are orange, diamagnetic so l ids which can be handled in a i r for short periods of time without the occurrence of not ice-able decomposition. They are quite soluble in polar organic so lvents , but only spar ingly soluble in nonpolar ones, to give a i r - sens i t i ve orange so lu t ions . Their spectral propert ies confirm the monomeric nature of the complexes and the presence of the W-H bond. Their IR spectra (Table I) d isplay s ingle n i t rosy l stretching absorptions in the range 1615 - 1642 cm (CHgClg) and a weak hydride stretching absorption in the range 1865 -1936 cm - 1 (Nujo l ) . The decrease in vNO as L var ies in the order P(0Ph) 3 > P(0Me) 3 > PPh3 i s consistent with the documented e lec t ron-donating and -accepting properties of these 1 i g a n d s . 5 6 ' 5 7 The tungsten-hydride stretching absorptions are broad, weak bands in the range expected -1 14 for organometal1ic hydrides*1900 ± 300 cm . u ' The mass spectrum of (n 5-C 5H 5)W(N0)I(H)[P(0Ph) 3 ] (at a probe temperature of 150°C) displays peaks corresponding to the parent ion [CpW(N0)I(H)P(0Ph) 3] +, [CpW(N0)HP(0Ph) 3] +, [CpW(N0)I 2 ] + , [CpWI 2 ] + , [WI 2 ] + , [CpW(N0)I(H) 2] +, and [CpWI] +. I f the molecular structure of these complexes is assumed to be a 5 8 4-legged piano stool geometry, then there ex is ts the p o s s i b i l i t y of three geometric isomers (configurat ions I, II and III) as well as the i r corresponding enantiomers. Table I. Spectral Propert ies of ( n b -C 5 H 5 )W(N0)I(H)L XL = P(0Ph). 3, P(_0CH3);3, or PPh 3] Complexes IR cm" 1 IR cm"1 IR cm"1 CH2C1.2 Nujol Nujol v(N0) v(N0) v(W-H) L,6. CCDC13) :H NMR CgHg ,6 H.,6 CCDClgl (CDC13) 2 J j H _31p I J l H _ J 8 3W 3 1 P Hz Hz 6 , C g D 6 2 J ? : 1 P - 1 H re la t i ve Hz to H 3 P0 4 P(.0Ph)3 1642 1627 1865 7.33(15H,m) 5.32(5H,s) -1.98()H) 111 54 115 112 7.45 and 7.00(15H,m) 4.82(5H,s) -2.07(1H) 112 55 P(0Me)3 1627 1 61 6 1 918 3 .67(9H,d)(2J r H_ 3 ] p=12Hz) 5.77(5H,s) -1.42(1H) 101 3.36(9H,d)6jiH_3ip=12Hz) 5.12(5H,s) -1 .41 (IH) 101 57 57 131 101 PPh 3 1615 1617 1936 7.44(15H,m) 5.63(5H,s) 0.31(1H) 7.70 and 7.05(15H,m) 5.10(5H,s) 0.10(1H) 85 85 58 58 14.1 85 42 However, the i r spectral properties (Table I) suggest that only one isomer ex is ts in so lu t ion . Thus, the J H NMR spectra consist of a s ing le sharp resonance in the range 6 4.82 - 5.12 (CgDg) assignable to the cyc lo -pentadienyl protons and a high f i e l d resonance pat tern, a doublet each hal f of which is surrounded by a smaller doublet, assignable to the hydrides which, r e f l ec t s couplings to both the I 8 3 W and 3 J P atoms (see Figure 2) . When L = P(0Ph) 3 or PPh 3 there i s a broad phenyl resonance around 6 7.4 (CDC13) which i s s p l i t into ortho and meta/para proton regions when the solvent is changed to d -benzene. When L = P(0CH 3 ) 3 there i s a sharp doublet ^ 6 3.4 (CgDg), coupling between the methyl protons and the phosphorus atom being 12 Hz. - 2 Figure 2, 'H NMRSpect™ (80 MHz) of Hydride R e g i „ „ o f ( l 5 -C 5 H 5 )H(N0) I (H) [P(0Ph) , ] i „ y 3 6 6 44 The NMR pattern of the hydride region of (n 5-C 5H 5)W(N0)I(H)[P(0Ph) 3 ] i l l u s t r a t e d in Figure 2 is representative of a l l three hydride species. The centre of the hydride pattern ranges from 6 +0.10 to -2.07 (CgDg ), 3 5 somewhat upf ie ld from the hydride resonance in ( r ^ - C g H g ^ N O ^ H [6 2.77 ( C r D , ) ] . Nevertheless, these hydride resonances are at r e l a t i v e l y b o low f i e l d ; these resonances are usual ly observed at high f i e l d s , t y p i c a l l y in the range 6 -5 to - 2 0 . 1 4 For example, (n 5-CgH 5)Re(C0)(N0)H 3 3 and (n 5 -C 5 H 5 )Re(PPh 3 ) (N0)H 3 1 + d isplay signals^due to the hydride l igand at 6 -8.2 (CgDg)and <s -9.15 (CgDg), respec t ive ly . A low f i e l d resonance i s not unknown for t ransi t ion-metal hydrides, but to date i t has been charac-t e r i s t i c only of ear ly t ransi t ion-metal complexes. 1 5 The s h i f t of the hydride resonance of (n5-CgHg)W(N0)IHL to lower f i e l d as L varies in the order P(0Ph) 3 > P(0CH 3 ) 3 > PPh 3 fol lows the same trend as previously noted for the decrease in vNO in the inf rared spectrum. However, the tendency toward higher f i e l d hydride resonance with a var ia t ion in L toward better electron donating l igands (judging donor/acceptor character 5 7 of L by vCO frequencies) has been reported by Tolman for the coord i -2 3 nation hydrides HNil_3CN. While Darensbourg claims to f ind no cor re la t ion between the hydride chemical sh i f t and a var ia t ion in L l igands in the [HW(C0)4L]~ system, the hydride resonance when L = PPh 3 i s at lower f i e l d than when L = P (0CH 3 ) 3 . The sp in-spin coupling of the hydrogen with tungsten provides addi t ional evidence for a d i rec t W-H bond. The major factors in determining the magnitude of the coupling constant are the magnetogyric ra t i o of the nuclei concerned and the Fermi contact i n te rac t ion . For tungsten-hydride, 45 coupling constants in the range 20-70 Hz have been observed. 1 6 For (n 5-C 5H 5)W(N0)I(H)L 1 J i H _ i 8 ^ w are in a narrow range 54-58 Hz. The s l i gh t increase in 1 J i H _ i 8 3 W observed as L var ies from P(0Ph) 3 < :> P(0CH 3 ) 3 < PPh 3 may re f l ec t the donor a b i l i t y of the Lewis base, but the var ia t ion i s probably too small to be of any real s ign i f i cance . The phosphorus-hydrogen coupling constants are observed to increase ( 2 J l H _ 3 1 p = 85, 100, and 111 Hz for L = P P h 3 , P (0CH 3 ) 3 , and P(0Ph) 3) in the same order as the hydride chemical sh i f t s move up f ie ld . This trend has been observed in CpMo(eO).2HL58 and [HW(CO) 4L]~ 2 3 and been at t r ibuted to shortening of the M-P bond due to the s t e r i c or e lec t ron ic prop-e r t ies of L. Observation and analys is of hydrogen-phosphorus couplings have been instrumental in the establ ish ing of the stereochemistry of hydride species. In most octahedral and square-planar complexes 2 j i H 3lp C 1 S (^5-30 Hz) i s much smaller than 2 J \ ^ 3 i p trans (^60-150 H z ) . 1 6 However, for other systems th i s cor re la t ion does not hold; for (n 5 -C 5 H 5 )M(C0) 2 HL where M = MoorW 2 J i H _ 3 i p c is - 60 while 2 J i H _ 3 i p trans = 2 0 . 5 8 > 5 9 I f th is trend can be appl ied to (n 5-C 5H 5)W(N0)I(H)L, then the observed 2 J ^ 3 1 p ranging from 85-112 Hz are ind ica t i ve of a c i s geometry (conf igurat ion I or I I ) . The c is geometry of the hydrogen and phosphorus is not surpr is ing in view of the trend for strong trans ef fect l igands (which H", PR 3 , and P(0R) 3 are) to avoid occupying a posi t ion trans to one another. What i s surpr is ing is the fact that no c i s / t rans tautome-rism is indicated in the solut ion spectra of these tungsten hydr idoni t rosyl compounds while (n5-CgHg)M(N0)2LH for M = Mo and W undergo rapid isomerizat ion at room t e m p e r a t u r e . 5 8 ' 5 9 46 The 3 1 P NMR spectra of the (n 5-C 5H 5)W(N0)I(H)L complexes hav-e been obtained with off-resonance decoupling of only the protons of the phosphorus l i -gands and cyclopentadienyl Tiga.nds/In a l l three cases only a sharp doublet is observed which confirms the presence of only one conformer in so lu t ion . When a phosphine is coordinated to a metal atom i t s 3 1 P NMR resonance is sh i f t ed , usual ly downfield, re la t i ve to the posi t ion of the free l i g a n d ; 6 0 no cor re la t ion has been made with phosph i tes . 4 7 In the 3 1 P NMR spectra of these hydr idoni t rosyls a downfield sh i f t was observed for L = t r ipheny l -phosphine, while for L = tr iphenylphosphite or tr imethylphosphite a s l i gh t up f ie ld s h i f t was detected (see Figure 3) . The y ie lds of react ion 28 with any of the chosen l igands are close to 70%. For L = P,(0Ph)3 a 70% y i e l d represents a considerable improvement over the y ie lds of (n 5-C 5H 5)W(N0)I(H)[P(0Ph) 3 ] obtained from react ion 17 (13%) or react ion 20 (34%). I f the overal l y i e l d from the i r common s tar t ing material [(n 5-CgHg)W(N0)I 21 2 i s considered (Figure 4 ) , i t becomes apparent that the low y i e l d step is consis tent ly the addit ion of H~. As in the case when borohydride i s the hydride source, several react ion modes of NalH^Al (OCH^CHijCH^)^] can be envisioned which would not lead to the desired tungsten n i t rosy l hydride. The n i t rosy l l igand can be los t through reduction (see react ion 19). A l te rna t i ve l y , coordination of the alkoxyaluminum 6 J. reagent to the metal atom may occur as has-been reported for Ta(Cl) 2(dmpe) 2 + Na[H 2Al(0CH 2CH 20CH 3) 2 ] ^ [Ta(H 2 Al(0CH 2 CH 2 0CH 3 ) 2 (dmpe) 2 ] 2 (29) dmpe = (CH 3 ) 2 PCH 2 CH 2 P(CH 3 ) 2 47 [p(bMe)3 W-P(QMel ^ ( O P h ) 3 W-P(OP^ 1 0 0 J 3 - W - P P h 3 "3 P O . P h 3 Figure 3. 3 1 P NMR Chemical Sh i f ts in 6. W = (n 5 -C 5 H 5 )W(N0)I(H). AQBF4 (CH3CH 2 ) 4 NBH 4 2 B | ( ^ H ) A » fj"A-C8H5)W(N0)IZP(0Ph)J H ' ' 3 % ^ , , % r(n5-C5H5)W(N0)l2l _ _ 3 4 % (Ti5C,H,)W(N0)I(H)[p(0Ph)3l 2 7 % «% L = 9 J 2 7 0 % ^ 43% Figure 4. Formation of (n 5-C 5H 5)W(N0)I(H)[P(0Ph) 3 ] from [ (n 5 -C 5 H 5 )W(N0) I 2 ] 2 v ia Three Routes, 00 49 Nevertheless, i t appears that react ion 28 represents the best method as well as a general ly appl icable one for the synthesis of a ser ies of com-plexes of the type (n5-CgHg)W(N0)I(H)L where L i s any l igand capable of donating two electrons to the metal centre. React iv i ty of (n 5-C 5H 5(W)N0)I(H)lPC0Ph.), 3.]. In l i gh t of the anomalous hydridic character of (n 5^CgHg)W(N0) 2H, i t was ant ic ipated that other hydridonitrosyl complexes of tungsten might show s im i la r r e a c t i v i t y . (n 5 -C 5 H 5 )W(N0) I (H) [P(0Ph) 3 ] , however, is sur-p r i s i ng l y i ne r t . Whereas many hydridocarbonyls are Lowry-Br0nsted acids in polar s o l v e n t s 1 4 react ing with ( C H 3 C H 2 ) 3 N and (n5-CgHg)W(N0)2H acts as a H " source react ing with p-toluenesulfonic a c i d , (n 5 -C 5 H 5 )W(N0) I (H) [P(0Ph) 3 ] i s la rge ly unchanged by exposure to ei ther of these reagents. Although some decomposition occurs, af ter 24h no sh i f t i s observed in the n i t rosy l absorption of the in f rared spectrum of the react ion s o l u t i o n ; and the hydride resonance remains v i s i b l e in the 1H NMR spectrum, exh ib i t ing i t s charac te r i s t i c hydrogen-phosphorus and hydrogen-tungsten coupl ings. (n 5-C gHg)W(N0) 2H s t i r red in an ace ton i t r i l e solut ion with the well-known hydride abstractor triphenylcarbenium tetraf luoroborate is converted to the cat ion [(n 5 - C 5 H 5 ) W ( N 0 ) 2 ( C H 3 C N ) ] B F 4 . 3 5 But although { ( T 1 5 - C 5 H 5 ) W ( N 0 ) I . [P(0Ph) 3](CH 3CN)}iBF 4 has been shown to be a v iab le species (vide supra) an ace ton i t r i l e solut ion of (n 5 -C 5 H 5 )W(N0) I (H) [P(0Ph) 3 ] and (.CgH 5) 3CBF 4 af ter 24h of s t i r r i n g shows no sh i f t in its. vNO; and though some p rec i -p i ta te forms, ^ NMR reta ins the charac te r i s t i c hydride pat tern. 50 Reactions with chloroform or carbon te t rachlor ide are often employed to es tab l ish the presence of a metal-hydrogen bond ; 1 4 however, (n5-CgHg)W-(N0)2H does not react with e i ther halocarbon. (n 5-C 5H 5)W(N0)I(H)[P(0Ph) 3 ] is stable for days in chloroform but does react with CC1 4 forming (n 5 -C 5 H 5 )W(N0)I (Cl ) [P(0Ph) 3 ] . But even with excess CC1 4 > a f ter two weeks J H NMR monitoring of the react ion reveal that the react ion i s incomplete ( t i ^ - 280 h). A stoichiometr ic amount of hydrochloric acid added to a dichloromethane solut ion of (n 5-C 5H 5)W(N0)I(H)[P(0Ph) 3 ] also induces the formation of the chlor ide as well as an int ractable blue p rec ip i ta te . Again, both the resonance patterns of the hydride and the chlor ide species are v i s i b l e in the 1H NMR spectrum. Reaction of [(n5-C5Hg)W(..N0) I (H) ] ? with Na [H^Al (0CH 2CH 2QCH 3) 2 ] . The solut ion colour darkens to brown, a brown prec ip i ta te forms, and the n i t rosy l absorption in the IR spectrum sh i f t s from -^1640 cm - 1 to ^1600 cm - 1 when one equivalent of sodium dihydridobis(2-methoxyethoxy)-aluminate is added to a green toluene or benzene suspension of E(n 5 -C 5 H 5 )W(N0)I(H)] 2 . F i l t r a t i o n followed by concentration of the f i l t r a t e under reduced pressure leads to the prec ip i ta t ion of [(n 5-CgHg)W(N0)H 2] 2 as an orange powder in 16% y i e l d . The reaction sequence shown in Scheme II is the net conversion of [ (n 5 -C 5 H 5 )w(NO) I 2 ] 2 into [ (n 5 -C 5 H 5 )W(N0)H 2 ] 2 in approximately 10% y i e l d . Direct synthesis of the orange hydride dimer from the iododimer can be e f fec ted ; however, for optimum y ie l d the aluminum byproduct should be removed af ter the f i r s t equivalent of Red-al has Lf) Scheme l i 4H"" I J O N - W ^ W - N O - 2 * — O N - ^ w C T > - N O O N ^ W ^ = > - N O I I H H H Colour: purple green orange I R (Nujol) z/NO(cm-1) 1 6 5 7 1 6 4 0 1596 52 produced the green solut ion of [ (n 5 -C 5 H 5 )W(N0)I (H) ] 2 . Then less than one equivalent (^0.6 eq.based on the i n i t i a l amount of [(n 5 -CgHg)W(N0)I 2 ] 2 ) of the alkoxyaluminum hydride y ie lds [(n 5 -CgH g )W(N0)H 2 ] 2 . This novel product i s a bright orange, diamagnetic s o l i d which i s f ree ly soluble in dichloromethane, less soluble in chloroform and benzene, and completely insoluble in hexanes. Its solut ions are a i r s e n s i t i v e , but the so l id i t s e l f can be handled in a i r for short periods of time without noticeable decomposition. An in f rared spectrum of a dichloromethane solut ion of the species exhib i ts a strong absorption at 1596 cm - 1 which can probably be assigned to terminal n i t rosy l 1 igands.'+a,44 ^ - | s o v i s i b l e in the in f rared spectrum of the Nujol mull of the complex i s a band of moderate in tens i ty at 1934 cm~\ This can be at t r ibuted to terminal ly bonded hydrides. -The compound is best formulated as a dimer [(n 5 -CgH g )W(N0)H 2 ] 2 with a tungsten tungsten double bond since a monomeric formulation would leave the tungsten atom with two electrons less than the favored 18-electron conf igurat ion. Its dimeric nature is confirmed by i t s mass spectrum (at a probe temperature of 120°C) which exhib i ts peaks a t t r ibu tab le to the parent ion and ions corresponding to the sequential loss of l igands. Unfortunately, overlapping of some medium to strong in tens i ty peaks makes unambiguous assignment d i f f i c u l t , espec ia l ly in l i gh t of the poly isotopic nature of tungsten. The proton NMR spectra recorded both in d -benzene and d-chloroform on 80 and 400 MHz instruments as well as se lec t ive decoupling experiments provide further ins ight as to the structural nature of [(n 5 -C c ; H c ; )W(N0)H 9 ] 9 . 53 Figure 5 shows i t s proton NMR spectrum in deuteroch.loroform. Evident are two large s ing le ts at 6 5.94 (13H) and 5.93 (10H) assignable to cyclopentadienyl protons. In addit ion there are f i ve other complex resonances at 6 6.98 (2.6H), 6.54 (2H), 1.39 ( IH), -2.02 (2.6H) ... and -5.93 (IH) which are at t r ibuted to hydride resonances due to the v i s i b l e tungsten-hydride coupl ings, which are approximately 94 Hz. Se lec t -ive decoupling experiments in d-chloroform reveal the manner in which these resonances are re lated (see Figure 6) . I r rad ia t ion at the frequency corresponding to 66.98 a l te rs only the mul t ip le t at 6 -2.02; i t becomes a sharp s ing le t . L ikewise, with i r rad ia t i on at 6 -2.02 the mul t ip le t at 6 6.98 becomes a s i ng le t . When decoupling i s centered at 8 6.54 the mul t ip le t at 6 1.39 becomes a doublet, while the t r i p l e t of doublets (6 -5.93) becomes a simple doublet. Decoupling at 6 +1.39 changes the doublet of doublets centered at <5 6.54 into a doublet, and the t r i p l e t of doublets (6 -5.93) becomes a t r i p l e t . F i n a l l y , i r r ad ia t i on at 5 -5.93 transforms the pattern at 6 6.54 into a doublet and that at 5 1.39 into a t r i p l e t . This study not only f a c i l i t a t e s the assigning of coupling constants but also demonstrates that two d i s t i n c t species, two isomers, ex is t in the so lu t i on . Careful integrat ion of the peak areas allows pair ing of the cyc lo -pentadienyl proton resonances with the hydride groupings. The C^H^ resonance at 6 5.94 is grouped with the hydrides resonating at 6 6.98 and -2.02 with the internal ra t i o 10:2:2 (isomer 1) . The C^Hg resonance at 6 5.93 i s grouped with the hydride resonances at 6 6.54, 1.39, and -5.93 Figure 5. *H NMR Spectrum of [ (n 5 -C 5 H 5 )W(N0)H 2 ] 2 in CDC13 (400 MHz). J j j 6.54 t - 5 . 9 3 Figure 6. *H NMR Spectra of [ (n 5 -C 5 H 5 )W(N0)H 2 ] 2 at 400 MHz, Decoupling Centred at * 56 with the internal ra t i o of th is grouping being 10:2:1:1 (isomer 2 ) . The ra t io of isomer 1 to isomer 2 is approximately 1.3 to 1, a ra t io which i s invar iant in d -benzene or d-chloroform. Detailed analys is of the hydrogen patterns allows speculat ion as to the conformation of these isomers. The hydride pattern in isomer 1 i s an AA'XX pattern. Unfortunately, the pattern i s not s u f f i c i e n t l y resolved to permit unambiguous assignment of the hydrogen-hydrogen coupl ings. Isomer 2 displays an A2MX hydride pattern for which coupling assignments have been made with the a id of computer simulation (see Table II and Figure 7) . An important feature of the 1H NMR spectra of both these isomers i s the abnormally low f i e l d values for the tungsten-hy-drogen protons at 6 6.98 (2H) (isomer 1) and 6 6.54 (2H) (isomer 2 ) . The only tungsten complex with a comparably low- f ie ld hydride s h i f t is Schrockis recent ly reported w(CHCMe 3)HCl 3(PMe 3) 2 (6 WH = 9 . 8 8 ) . 1 5 3 I t has been noted 1 4 0 * that , for der ivat ives of the same metal , the resonance of the bridging hydrogen in a hydridometal c lus ter i s often evidenced at 2 3 higher f i e l d than that of terminal ly bonded hydrogen. Darensborg, for example, has observed the hydrogen resonance in PPN[HW2(C0)QP(0Me)3] at <5 -12.2 (CD 3CN), a compound assumed on the basis of the s i m i l a r i t y of i t s vCO in the IR spectrum to that of the wel l -character ized u-H[Mo(C0)4(PMePh2)]2 to have a br idging hydrogen l i gand ; under s imi lar condit ions the terminal hydride of PPN[HW(C0)4P(0Me)3] has a chemical sh i f t of 6 - 4 . 5 . Following th is l i ne of reasoning, the lowest f i e l d resonance of each isomer, each of which represents two protons, i s assigned to terminal ly bonded hydrogens. Table I I . lH NMR Spectral Data of [U 5 - C 5 H 5 ) W ( N 0 ) H 2 ] 2 C 5 H 5 (6) H U) H (6) H Isomer 1 CDClo C 6 D 6 5.94 (s , 10H) 5.23 (s , 1 OH) 6.98 (m, 2H) 7.01 (m, 2H) -2.02 (m, 2H) -1 .90 (m, 2H) Isomer 2 CDCU 5.93 (s , 10H) H l , 2 6.54 (dd, 2H) ( J 1 3 - J 2 3 (J 14 J 2 4 = 8.6 Hz) H, 1 .39 (m, IH) 2.9 Hz) (J 34 2.3 Hz) •5.93 ( td , IH) C 6 D 6 5.26 (s , 1 OH) 6.64 (dd, 2H) 1 .66 (m, IH) -5.99 ( td , IH) V^iTes0! ^d%RVr,V? ° f I S ° m e r 2 ° f t ^ 5 - C 5 H 5 ) W ( N 0 ) H 2 ] 2  r n m n i | . 3 c . ' • 3 ?. !_ - l r .93 , l e f t to r ight) at 400 MHz. Computer Simulation of the Hydride Resonances of Isomer 2 . 00 59 The proton NMR data makes i t possible to preclude from consideration t o t a l l y symmetrical molecular conformations for [(n 5-CgHg)W(N0)H 2] 2 such as a l l four hydride or both n i t rosy l l igands bridging the two metals or four terminal and mutually trans hydride l igands. In such arrangements a l l the hydrides would be chemically and magnetical ly equivalent , and only one hydride resonance would be observed in the proton NMR spectrum; such i s not the case. There remains a number of possible st ructural configurat ions (see Figure 8) : an arrangement in which a l l the l igands are terminal ly bonded and the hydride l igands are mutually c is (A) ; a structure possessing two terminal ly bound and two bridging hydrogens e i ther perpendicular (B or D) or para l le l to the plane of the cyclopentadienyl rings (C or E) . The dominant species in so lu t i on , isomer 1, in which the hydride l igands exh ib i t an AA'XX' pattern in the proton NMR spectrum, may adopt one of the configurat ions i l l u s t r a t e d in Figure 8 by A, D, or E. Although structure A cannot be dismissed t o t a l l y , one would not expect two terminal hydrides in such an environment to have chemical sh i f t s d i f fe r ing by almost 9 ppm. For example, the hydride resonances of R e H ^ N O K P P h ^ overlap to form a mul t ip le t at - 1 . 5 ; the ind iv idual hydrogens are considered to have chemical sh i f t s -0.9 and^2.1. Therefore, i t seems more feas ib le that isomer 1 assumes the conformation shown in example D or E; the resonance at 6 6.98 would then be assigned to the two terminal hydrides and the one at 6 -2.02 to the two bridging ones. The requirement that isomer 2 have a hydride pattern A2MX can be sa t i s f i ed by structures B or C. It then fol lows that the resonance at 5 6.54 can be assigned to the two terminal hydride l igands and the resonances at 6 1.39 and 5 -5-93 can each be at t r ibuted to F igure 8 . S t r u c t u r a l P o s s i b i l i t i e s o f [ ( n 5 - C 5 H 5 ) W ( N 0 ) H 2 ] 2 60 : W--NO ON- -W=W--NO H, A. For c i s or t rans Cp r i n g s A A ' X X ' For c i s Cp r i n g s and c i s te rmina l H For c i s Cp r i n g s and t rans te rmina l H A 2MX H ON----W—W----NO H, HA 1 O N - - W = w - . . N O H, For c i s Cp r i n g s and c i s te rmina l H D. For t rans Cp r i n g s and c i s te rmina l H A2MX For t rans Cp r i ngs and t rans te rmina l H For t rans Cp r i n g s and c i s te rmina l H A A ' X X ' ON--W=W--NO is Cp r i n g s and t rans te rmina l H For c i s Cp r i n g s and t rans te rmina l H A A ' X X ' 61 one of the inequivalent bridging hydrogens. The inf rared spectrum consis t ing of a s ing le n i t rosy l absorption at 1596 cm - 1 in dichloromethane provides no further clues as to s t ructura l nature of these species. Reaction of [ (n 5 -C 5 H 5 )W(N0)H 2 ] 2 with P(0Ph) 3 . B is [ (n 5 -cyc lopentadienyld ihydr idoni t rosy l tungsten] reacts with the Lewis base tr iphenyl phosphite in benzene to form the purple complex (n 5-C 5H 5)W(N0)H 2 [P(0Ph) 3 ] in 32% y ie l d (react ion 30). [ (n 5 -C 5 H 5 )W(N0)H 2 ] 2 b e ^ e n > 2(n 5-C 5H 5)W(N0)H 2L (30) L = P(0Ph) 3 When the product of react ion 30 i s iso la ted by f rac t iona l c r y s t a l l i z a t i o n from a benzene/hexanes mixture, the major component is th is purple product. However, when recrys ta l1 iza t ions are performed from dichloromethane/hexanes the major product is an orange so l i d which a lso has the empirical formulation (C 5 H 5 )W(N0)H 2 lP(0Ph) 3 ] . Purple (n 5-C 5 H 5 )W(N0)H 2 [P(0Ph) 3 ] i s an a i r - s e n s i t i v e , diamagnetic so l i d which is f ree ly soluble in common organic solvents but only spar ingly soluble in paraf f in hydrocarbons to give highly a i r - s e n s i t i v e intensely purple solut ions which turn yellow in minutes upon exposure to a i r . An in f rared spectrum of the so l i d in a Nujol mull d isplays a s ing le n i t rosy l absorption at 1574 c m - 1 , but the tungsten-hydride st retching absorptions are not observable. Its mass spectrum shows a peak corresponding to 62 [(C 5H 5)W(N0)HP(0Ph) 3 ] + (m/z 590) as well as peaks due to [(C 5H 5>ip(0Ph) 3 ] + and [WH ?P(0Ph),] + c l e a r l y i den t i f i ab le by the correct tungsten isotope pat tern. Orange (n 5-C 5Hg)W(N0)H 2[P(0Ph) 3] i s an a i r - s e n s i t i v e so l i d which can be formed from the purple complex with attendant decomposition. I ts IR spectrum displays a vNO absorption at 1601 cm - 1 (Nu jo l ) , s l i g h t l y higher than i t s purple analogue. Furthermore, there are weak bands at 1856 and 1831 cm - 1 which can be assigned as terminal ly bonded W-H stretching absorp-t i ons . However, i t i s best characterized by i t s *H NMR spectrum. The phenyl and cyclopentadienyl protons resonate at a s imi lar frequency to the purple spec ies, 6 7.32 (15H) and 5.10 (5H) (CgDg); but the hydride resonances are centered at 6 -1.82 (2H) and d isplay the fami l ia r s i x - l i n e pattern (1 :5 .9 :1 , 1:5.9:1) (c f . Figure 2) re f l ec t i ng coupling to both the tungsten and phosphorus atoms. The 1 J 1 ^ 1 8 3 ^ coupling (88 Hz) aff irms the tungsten-hydride l ink while the 2 J l H 3 1 p coupling (86 Hz) allows the dihydride species to be eas i l y dist inguished from i t s monohydrido-monoiodo analogue. Lack of any observable hydride-hydride coupling and the s i m p l i -c i t y of the resonance pattern indicate that the two l igands are magnetical ly as well as chemically equivalent and, therefore, must be trans to each other. The 3 1 P NMR spectrum confirms 63 the equivalence of the hydride ligands displaying a s ing le resonance, a t r i p l e t , only s l i g h t l y shi f ted from that of the c is isomer (6 137 ( t ) , as the c is isomer is based on i t s TH NMR spectrum. There are three d i s t i nc t i ve patterns in the phenyl region 6 7.54 -> 7.20 (15H) a t t r ibu tab le to the ortho, para, and meta protons of the phenyl r ings of t r i pheny l -phosphite. In addit ion there i s a sharp s ing le t at 6 5.10 (5H). assignable to the cyclopentadienyl protons and a complex hydride pattern centred at 6 1.32 (2H) (shown in Figure 9) . The spectrum in deuterochloroform is s i m i l a r , though with less deta i l in the phenyl region; but in th is solvent the c is -d ihydr ide is observed by *H NMR to rearrange to the trans i s o -mer; with time the mul t ip le t centred at 6 1.10 is l os t and the fami l ia r s i x - l i n e pattern of the t rans-dihydr ide appears at 6 -1 .82 . The same re-arrangement occurs to some degree in benzene, but in th is case i t takes a mat-ter of days instead of hours. The proton coupled 3 1 P NMR spectrum is a t r i p l e t centred at 6 151 ( re la t i ve to H 3 P 0 4 ) ; average 2 J 3 1 p 2 = 24 Hz. This phosphorus chemical sh i f t has the expected downf ie ld 6 0 sh i f t from the free tr iphenylphosphite (6 1 2 6 ) . 4 0 The complex hydride resonance pattern is invar iant on an 80 or 400 MHz NMR instrument. For the c i s structure an ABX pattern would be expected. In an ABX spectrum the AB portion may be divided into two 87 Hz). The designation of the purple form of [(n 5-C 5H 5)W(N0)H 2P(0Ph) 3 ] 64 Figure 9. ( l e f t ) i H NMR Spectrum (400 MHz) of Hydride Region of cls-(n 5 -C 5 H 5 )W(.N0)H 2 [P(0Ph) 3 ] in C g D 6 ( r ight) Computer Simulation of Hydride Region 65 54 AB-type quartets. In th is case there is an overlap of the two quartets which produces the observed seven-l ine pattern. From the analys is of the spacing of these quartets and computer simulation (Figure 9), the best f i t designates the chemical sh i f t s of and Hg as coincidental (6 1.32 CrDr) and assigns the couplings 2 J U , u =27.7 Hz, 2 J U n = 67-5, and o D H A~ H B H A H X 2 J" H B P X = -19 .5 . Thus, the 2 J l H 3 1 p observed in the coupled 3 1 P NMR spectrum is an average j ( 2 J D u + 2 J D H ) = 24 Hz. (Note that the signs P X H A P X H B of the phosphorus-hydrogen couplings are only re la t i ve to each other and do not represent an absolute assignment.) The hydride l igand trans to the phosphite is assigned the smaller coupling constant (-19.5 Hz) based on the analogy to the (n 5 -C 5 H 5 )M(C0) 2 HL s y s t e m 1 6 ' 5 8 ' 5 9 (vide supra). The large hydrogen-hydrogen coupling is aw anomaly, but th is assignment appears to be the only reasonable one. When react ion 30 i s performed using L = P^CHg)^ , the orangeisolution of [(n5-CgHg)W(N0)H2]2 darkens to a red-v io le t colour upon addi t ion of the phosphite. However,if the solvent i s not removed in vacuo within 90 min . , the solut ion colour begins to l ighten un t i l i t i s yellow-orange. The J H NMR spectrum of the react ion mixture indicates that t rans -C j^ -CgH^WONO^PCOCH^ is formed: (CCDC). 6 5.63 ( s ,5H ,C c H, ) s & 3.63 (P(0CH,) , ) , -1.90 "DO " 0^0 ' ^ 0 0 (2H, W-H) [ 2 J i H _ 3 i p = 81 Hz, 1 J i H _ i 8 3 W = 81 Hz]. Again, as in the case with (n5-CgHg)W(N0) IHL, a decrease in 2 J 1 ^ ) 3 1 p i s seen with a change in L from P(0Ph) 3 to P t O C H . ^ . The same corre la t ion is also observed in the in f rared spectrum — vNO moving down from 1601 cm - 1 (Nujol) in 66 t rans-(n 5 -C 5 H 5 )W(N0)H 2 P(0Ph) 3 to 1564 cm - 1 in t rans- (n 5 -C 5 H 5 )W(N0)H 2 -P(0CH 3 ) 3 < The mass spectrum of the l a t t e r confirms i t s formulat ion; at probe temperature 120°C two groupings of peaks are seen with the charac-t e r i s t i c tungsten isotope pat tern: one at 403 corresponding to [ (C 5 H 5 )W(N0)P(0CH 3 ) 3 ] + ) (P) + 5 and.one at 372 corresponding to (P-N0) + . Attempts to i so la te th is dihydride as a pure so l i d have so far been f rustrated by the large amount of attendant decomposition in th is reac t ion . Y ie lds of product are estimated to be less than 10% of that iso la ted when L = B(0Ph) 3 . It appears that when L i s tr imethylphosphite the purple isomer i s much shorter l i ved and converts read i l y to the orange isomer t rans- ( n 5 -C 5 H 5 )W(NO)H 2 L. The Nature of the c i s - t rans Isomerism Detailed 1 H NMR studies of the c i s - t rans conversions of complexes of the general form (n5-CgHg)Mo(C0)2LR (where L i s a phosphine or phosphite and R i s hydrogen, halogen, benzyl , or methyllhave been discussed by F a l l e r 5 8 and by P o i l b l a n c . 5 9 Both conclude that the isomerizat ion i s an intramolecular exchange phenomenon occurring v ia angle bending, not by l igand d i ssoc ia t i on . The purple-orange conversion d i f f e rs markedly from the reported systems. K inet ic Considerat ion: Fa l l e r observes that the rates of isomerizat ion vary less than 25% from solvent to solvent . In the (n5-CgHg)W(N0)H2[P(0Ph)^]case a dramatic di f ference in rate i s observed —the purple->orange conversion taking place in days in benzene and in hours in dichloromethane. However, decomposition i s detected in both these s o l -67 vents occurring more slowly in benzene than in dichloromethane. Free phosphite is observed in aged so lu t ions . It i s possible that l igand d issoc ia t ion is one pathway to th is isomer izat ion. Triethylamine promotes the formation of the orange isomer within an hour, a lbe i t with some de-composition (vide i n f r a ) . Thermodynamic Considerat ions: Poil.blane observes that the c i s carbonyl compounds are thermodynamically more stable than the t rans. This means in the case of CpM(C0)2HL that c is hydri phosphorus geometry is favored. T h e l R NMR spectra of (n s-C 5H 5)W(N0) H 2 [P(0Ph) 3 ] make evident that the isomer with trans hydride ligands is the one favored thermodynamically, for the transformation from the purple (c is ) to the orange (trans) isomer occurs in a matter of hours in any polar solvent and in a matter of days in benzene. This trans arrangement of the hydrides allows both to remain c i s to the phosphorus atom, a requi re-ment which is evident ly more important for the hydride l igands than for the carbonyl l igands in ( n 5 - C 5 H g ) M o ( C 0 ) 2 L R . 5 8 ' 5 9 This c is arrangement of the hydrogen and phosphorus atoms is the only one observed in the monohydrido compounds (n 5-C gHg)W(N0)I(H)L (vide supra). It appears that a primary st ructura l constra int is that the hydride l igand i s not trans to another strong trans ef fect l igand such as phosphine or phosphite. React iv i ty of (n 5 -C 5 H 5 )w(N0)H 2 [P(0Ph) 3 ] . The-principal .mode of reaction of c i s - (n 5-C- 5H g)W(N0)H 2[P--(0P.h)3] is rearrangement, forming a mixture of the eis and trans isomers in a matter of hours in chloroform, dichloromethane, 68 or tetrahydrofuran so lu t ions . Due.to the intense purple colour of the c is isomer, no change in solut ion colour can be noted un t i l most of the species is t rans. The c i s / t rans mixture can be t o t a l l y converted to the trans isomer by exposure to (CH 3CH 2) 3N for 1 hour as evidenced by a colour change in the dichloromethane solut ion from purple to orange, a loss of the c is hydride pattern in the lH NMR spectrum and the appearance of the trans hydride resonance pattern. No further reaction with tr iethylamine is evident. Addit ion of p-toluenesulfonic acid to a THF solut ion of (n 5rCgH 5)W(N0)-H 2 [P(0Ph) 3 ] resul ts in an immediate colour change in the solut ion from purple to green-brown. Most of the n i t rosy l -con ta in ing species prec ip i ta tes out of so lut ion as an in t rac tab le green so l i d (determined by an IR spectrum of a Nujol mull of th is s o l i d ) . No hydride resonance can be observed in the 1H NMR of the supernatant. A purple a c t o n i t r i l e solut ion of c is and trans ( r ^ -CgH^WtNOH^P-(0Ph) 3 ] immediately takes on an orange-brown colour when the hydride abstractor triphenylcarbenium tetraf luoroborate is added to i t . The pr inc ipa l featu-res of the XH NMR spectrum of the reaction solut ion are a hydride pattern centred around 5 -1.99 (IH) with 3 J i H _ 3 1 p = 112 Hz and cyclopentadienyl resonances at 6 5.29 (5H) and 5.56 (12H). This suggests the presence of two species — a new hydride-containing species possibly a monohydride such as {(n 5-C 5H 5)W(N0)H[P(0Ph) 3](CH 3CN)}BF 4 ( c f . (n 5-C 5H 5)W(N0)IH[P( 0Ph) 3 ] with hydride resonance at 6 -1.98 and 2 J i H _ 3 i p = 112 Hz) and a non-hydride-containing species. 69 Prolonged exposure of trans-(n 5-C 5Hrpw(N0-)H 2 [P(0Ph) 3 ] ' to carbon te t ra -ch lor ide resu l ts in the formation of a new hydrido-containing species. Although the doublet of the or ig ina l (.n 5-C 5H 5) 1 8 Hl(N0)H 2 [P(0Ph) 3 ] i s s t i l l v i s i b l e in the J H NMR spectrum at 6 -1.28 and -2.35 . [ 2 J i H _ 3 i p = 86 Hz) , a new doublet which overlaps with the or ig ina l one grows in at 6 -1.28 and -2.70 ( 2 J i H _ 3 i p = 113 Hz). It i s possible th is i s evidence of the formation of (.n.5-CgHg) 1 8 4W(N0)C1 (H) [P(.0Ph)3] (c f . hydride pattern of (n 5-C 5H 5)W(N0)I(H)[P(0Ph) 3 ] — 5 -1 .98 , 2 J i H _ 3 i p = 112 Hz). The appearance of new cyclopentadienyl proton resonances in the I H. NMR spectrum ind icate new non-hydride-containing complexes are also formed. Thus (n 5-C 5H 5)W(N0)H 2 [P(0Ph) 3 ] undergoes the most common of typ ica l hydride reactions — react ion with halocarbons and hydride abstract -ion by tr iphenylcarbenium. But l i k e (n5-C5Hg)W(.N0)2H i t acts as a H" source in teract ing with the ac id i c reactant , p-toluenesulfonic a c i d , rather than the basic one t r ie thy lamine. Ove ra l l , i t i s much more react ive than (n 5 -C 5 H 5 )W(N0)I(H)[P(0Ph) 3 ] . To f a c i l i t a t e further study of th is unique n i t rosy l dihydride i t would be desirable to improve the y i e l d from the basic s tar t ing material [(n 5-CgHg)W(.N0)I 2] 2 which is unoptimized at 3.2%. Nevertheless, i t appears react ion 30 represents a general route for the ser ies of complexes of the type (n 5-CgH 5)W(N0)H 2L where L is a two-electron donor. In comparing the r eac t i v i t y of the three hydrido n i t rosy l species (n 5-C 5H 5)W(N0)I(H)L, (n 5-C 5H 5)W(N0)(N0)H, and (n5C5H5)W(N0)'HHL (where L = P(0Ph) 3 ) , the inertness of the iodohydride is s t r i k i n g . It may be that the 70 halogen l igand provides a cer ta in s t a b i l i t y to the tungsten-hydrogen l i nk due to i t s a b i l i t y both to donate electrons , as a n donor, and to withdraw electrons by i t s induct ive e f fec t . Tlhe inf luence of the halogen deserves further study. The r e a c t i v i t i e s of ( n 5 -C 5 H 5 )W(N0) o H and ( n5 -C 5 H 5 )W(N0)H o L are s i m i l a r — b o t h appear to act as a source of H~. However, one would hesitate to draw a conclusion about the general ef fects of the n i t rosy l l igand un t i l other metal centres have been employed. Successful syntheses of organometal1ic n i t rosy l hydrides by metathesis of the corresponding halides with a hydridoaluminate reagent opens the door to a great number of n i t rosy l hydride complexes. The pre-paration in th is manner of (n 5-C 5H 5)W(N0) 2H in 61% y i e l d , of [ ( n 5 - C 5 H 5 ) -W(N0)IH]2 in 61% y i e l d , and of (n 5-C 5H 5)W(N0)I(H)L (L = PPh3„ P(.0Me)3 > P(0Ph) 3) in ^43% y i e l d i s promising. The low y i e l d obtained in the pre-paration of (n 5-C 5H 5)W(N0)IH[P(0Ph) 3 ] (34%) by metathesis of the d i iodo monomer and in the preparation of [ (n 5 -C 5 H 5 )W(N0)H 2 ] 2 (16%) ,notwithstanding , metathesis by Na[H 2Al(0CH 2CH 20CH 3) 2 ] appears to be the method of choice. In shor t , the hydrido complexes, the syntheses of which are summarized in Scheme I I I , embody the f i r s t such group of organometallic n i t rosy l hydrides ava i lab le for systematic s tud ies. Scheme III (n6-C5H6)W(NO)I9L A g / C H , C N [(n5-C5H5)W(NO)I2] 2H" 4 H ' [(n5-C5H5)W(NO)I(H)] 2 H ~ » [(n5-C5H5)W(NO)HJ 2 L -C5Hs)W(NO)IL(CH3CN)| (n 5-C 5H 5)\ 2 L )W(NO)I(H)L (n5-C5H5)W(N0)H2L L= P ( 0 P h ) 3 , P P h 3 , P(0Me) 3 72 Part II A. Cat ionic Ni t rosy l Complexes of Molybdenum The n i t rosy l l igand i s general ly acknowledged to be a better TT acceptor than C O . 6 3 Yet, though a great many antionic carbonyl species e x i s t , 3 attempts by th is group to prepare anionic n i t rosy l complexes have been repeatedly f rus t ra ted . This dilemma suggested the d e s i r a b i l i t y of invest igat ing the redox propert ies of a simple metal n i t r o s y l . However, binary n i t rosy l s M x(N0)^, unl ike simple carbonyls, M x (C.0)^,are unstable compounds. Of the few reported, i . e . , Co(N0) 3 , 5 1 t C r ( N 0 ) 4 , 6 5 F e ( N 0 ) 4 , 6 6 Ru(.N0) 4 , 6 7 only the former two have been wel l -character ized. Although simple neutral n i t rosy l complexes are a r a r i t y , i t has been known for 2+ some time that solvated der ivat ives of the [M(N0)2] cations where M = Cr, Mo, or W may be synthesized by reactions such as N0PFf i 6 8 Mo(C0)3(CH3CN)3 C H cg> [Mo(N0) 2(CH 3CN) 4](PF 6) 2 + 3C0 (31) NOPF. 6 9 Mo(C0)g C H c ° ? [Mo(N0) 2 (CH 3 CN) 4 ] (PF 6 ) 2 + 6C0 (32) CH.CN 7 0 [Mo(N0) 2Cl2]n+ 2 AgPFg r e f l u * [Mo(N0)2( CH 3CN) 4] ( P F £ ) 2 + 2 AgCl (33) Thus, binary n i t rosy l cations being more read i ly a t ta inab le , a study was 2+ i n i t i a t e d to invest igate the fundamental moiety "Mo(N0)2 " . 73 Choice of solvent can have a profound ef fect on the outcome of reactions involv ing NOPFg. The stereochemistry of the product may vary from solvent to s o l v e n t : 7 1 CHp CI n cis-Mo(CO) 2 (d iphos) 2 + NOPFg ^ c i s + trans [Mo(C0) 2(diphos) 2]PFg + NO (34) CH 30H/toluene "> trans LMo^uu^ciipt + NO  [ (CO) 2(diphos) 2 ]PF g CH3CN > c is [Mo(C0) 2(diphos) 2]PFg + NO Protonation sometimes occurs when the solvent system i s toluene/methanol due to the equ i l ib r ium: 72> 7 3 CH30H + N0 + c—»CH 3 0N0 + H + , for example C/-H/-/CH-iOH 7ti Mo(N 2 ) 2 (d iphos) 2 + NOPFg —> [MoF(N 2H 2)(diphos) 2]PFg (35) As has already been demonstrated a solvent which is a good donor may become 7 5 attached to the metal centre. CH-CN Cr (C 6 H 6 ) (C0) 3 + NOPFg * [Cr(N0) 2( CH 3CN) 4] ( P F g ) 2 + CgHg (35) CH3N02 » [Cr(CgH 6)(.C0) 2(N0)]PFg + CO 74 Consequently, i t was expected that transformations of types 32' and 33 when effected in solvents of poor coordinating and good solvat ing a b i l i -t i e s 7 6 would afford the desired binary n i t rosy l cat ions. 2+ Herein is reported the successful synthesis of the [ f M N O ^ ] cation and described in deta i l i s i t s charac te r i s t i c chemistry which provides some ins ight concerning: (a) the Lewis acid propert ies of the binary n i t rosy l cations and how they are modified by the presence of anc i l l a r y l igands, and (b) the f e a s i b i l i t y of forming neutral n i t rosy l complexes by reduction 2+ of M(.N0)? -containing compounds. 75 Experimental A l l experimental procedures described here were performed under the same general condit ions out l ined in Part I with the exception that 3 1 P NMR spectra were recorded at 32.3 MHz on a Bruker WP-80 spectrometer using 2D as the internal lock. Chemical sh i f t s were referenced to external NaPFg (6 -144. (CD3QN)) upf ie ld of H 3P0 4) but are reported in ppm upf ie ld from H^PO^. A l l samples were prepared in a dry box using dry deoxygenated deuteroacetoni t r i le and sealed in 10 mL tubes. Low-temperature 1H NMR spectra were obtained on a Bruker WP-80 spectrometer equipped with a Bruker B-VT-1000 probe. The conduct iv i t ies of solut ions of various com-plexes were measured at ambient temperature with a YSI, Model 31 conducti-v i t y bridge and a micro solut ion ce l l with p la t in ized electrodes. The ce l l -4 was cal ibrated with a 9.49 x 10 M nitromethane solut ion of Et^NBr; i t had a ce l l constant of 1.08 c m - 1 . The spec i f i c conductance of the n i t r o --7 -1 -1 -3 methane employed was 4.3 x 10 ohm cm . EPR spectra of ^10 M n i t r o -methane solut ions were recorded on a Varian E-3 spectrometer at ambient temperature. Reactions of Mo(.C0)6 with NOPFg. (a) In CHQCIQ (Procedure A) . To a rapid ly s t i r redV colourless solut ion of Mo(CO)g ,(3.02 g v I T . 4 . mmol-) in. CH 2C1 2 (140 mL) -was added so l i d NOPFg -(2.00 g, 11 .4 mmol'),-whereupon gas evolution occurred,., and the mixture- developed a yellow-brown co lourat ion. . Af ter 40 h, the f ina l react ion mixture consisted of a green so l i d and a green solut ion whose IR spectrum displayed two weak 76 n i t rosy l absorptions at ^1815 and ^1685 (br) cm" in addit ion to the strong v(C0) at ^1980 cm - 1 charac te r i s t i c of Mo(.C0)g. The s o l i d was co l lected by f i l t r a t i o n , washed with CH 2C1 2 (.3 x 20 mL), and dried in vacuo (5 x 10 mm) for 1 h to obtain 1.23 g (.48.4% y i e l d based on NO) of Mo(N0)2( P F 6 ) 2 . [Unreacted Mo(C0)g (1.60 g) could be recovered by sublimation (60°C, 5 x 1 0 mm) of the residue remaining af ter the f i l t r a t e had been taken to dryness under reduced pressure.] Ana l . Calcd for M o N 2 0 2 P 2 F 1 2 : C, 0.00; H, 0.00; N, 6.28; Mo, 21.52. Found: C, 0.76; H, 0.54; N, 6.32; Mo, 23.0. IR (Nujol mu l l ) : v(N0) 1811 ( s ) , 1683 ( s , br) c m - 1 ; also 1265 (m, b r ) , 1154 (m), 948 (m,br)-., 885 (m,br) , 843,(:m,br) 565 (s) cm" 1 . 1 9 F NMR (CD 3CN): 6 72.0 (d , 1 J i 9 F _ 3 i p = 707 Hz). 3 1 P NMR (CD 3CN): 6 -144 (sep t . , 1 J 3 i p _ i 9 F = 707 Hz). Mp: 110°C dec. The ana ly t ica l data presented above are representat ive. Some prepa-rat ions of th is complex, however, afforded materials having s l i g h t l y higher carbon and hydrogen contents. Nevertheless, the fol lowing modif icat ions of the given experimental procedure did not a l te r the basic nature of the iso la ted product: (a) seal ing the react ion vessel under N 2 , (b) bubbling NO continuously through the react ion mixture, or (c) re f lux ing the i n i t i a l react ion mixture for 2 - 6 h e i ther under an N 2 or NO atmosphere. I f r igorously anhydrous condit ions were not maintained the iso la ted green so l i d had the fol lowing proper t ies. Ana l . Calcd for MoN 2 0gP 2 F 4 : C, 0.00; H, 0.00; N, 7.82. Found C, 0.64; H, 0.36; N, 8.02. IR (Nujol mu l l ) : v(.N0) 1821 ( s ) , 1693 ( s , br) cm" 1 ; also 1265 (m, b r ) , 1163 (m), 955 (m), 901 (m), and 569 (m) cm" 1 . 77 1 9 F NMR ( C B 3 C N ) : 6 81.7 .(,-d, J 1 9 j r _ 3 1 p =. 957 Hz).. 3 i P N M R (CD^e'N'): 6- -17.9: ( t , J'3.a!p .1.9 -—-957 fitzj-.. Mp: >220?. (b) ...In CH-gNOg (Procedure B) . To a s t i r r ed suspension of Mo(C0)g (1.50 g, 5.68 mmol) in CH3N02 (.10 mL) was added dropwise a solut ion of NOPFg (2.00 g , 11.4 mmol) in CH3N02 (10 mL) over a period of 0.5 h. Gas evolut ion occurred throughout. When one-half of the NOPFg solut ion had been added, the supernatant solut ion was red-brown in colour and i t s IR spectrum displayed a number of absorptions in the carbonyl (^2185 (w), 0,2100 ( s ) , ^1980 (s) cm - 1 ) and n i t rosy l (^1830 (m), ^1815 (m), ^1780 (m), ^1710 ( s , b r ) , ^1690 (s) cm" 1) regions. When the addit ion of NOPFg was complete, the carbonyl reactant had dissolved and the react ion mixture consisted of a green so lu t ion . The IR spectrum of th is solut ion ve r i f i ed that a l l the Mo(C0)g had been consumed (.i.e. the absorbance at 1980 cm - 1 was absent) and revealed three new bands at ^1880 (w), ^1850 ( s , b r ) , and ^1745 (s) cm - 1 in addit ion to the other absorptions noted above. The green solut ion was s t i r red for an addit ional 2.5 h, whereupon i t s f i na l IR spectrum exhibi ted only two strong vNO at ^l860 and ^1750 c m - 1 . The solut ion was then concentrated to one-half of i t s or ig ina l volume in vacuo before being treated dropwise with CH^Cl 2 (40 mL) to induce the p rec ip i ta t ion of a green s o l i d . The so l id was co l lec ted by f i l t r a t i o n , washed with CH 2C1 2 (3 x 20 mL) and dried in a stream of dini trogen for 0.5 h to obtain 2.41 g (61% y ie ld ) of .[Mo(.N0) 2(GH 3N0- 2) 4J(-PF 6) 2. Ana l . Calcd for M o N g 0 1 0 C 4 H 1 2 P 2 F 1 2 : C, 6.96; H, 1.74; N, 12.17. Found: C, 7.43; H, 1.77; N, 11.70. IR (Nujol mu l l ) : v(N0) 1853 ( s ) , 1743 ( s , br) cm" 1 ; also 1570 ( s ) , 1316 ( s ) , 1162 (w), 1103 (m), 843 ( s , b r ) , 741 Cm), 673 (m) cm" 1 , : H NMR (CD3CN) : 6 4.34 ( s ) . 1 9 F NMR (CD 3CN): 6 72.0 78 ( d > J i 9 F . 3 l p = 7 °6 Hz) . 3 1 P NMR (CD 3CN): S -144 (sept J 3 i p _ i 9 F = 706 Hz). Am ( C H 3 N 0 2 ) ; 2 0 2 o h m " 1 c m 2 m o 1 - 1 - M P : 8 8 ° c d e c -As with Procedure A, the ana ly t i ca l data presented above are representat ive. Dif ferent preparations of th is complex afforded materials having s l i g h t l y d i f ferent C, H and N contents, a feature which re f lec ted the varyirig:amounts of CH3N02 present. For instance, attempts to dry the iso la ted so l ids in vacuo (5 x 10" mm) produced complexes containing less CH3N02 than indicated above. Mater ials s im i la r to those described above prec ip i ta ted when the o r ig ina l reaction was performed in a mixed solvent system using NOPFg in CH3N02 (10 mL) and Mo(C0) g suspended in CH 2C1 2 (50 mL). Reactions of [Mo(NO)2Clo]nwi th AqBF/j. (a) In CHgNOg (Procedure C). To a s t i r r ed green suspension of p a r t i a l l y dissolved [MotNO^Cl^ * 7 (0.50 g, 2.2 mmol) in CH3N02 (20 mL) was added s o l i d AgBF4 (0.86 g, 4.4 mmol). Gradual ly, the solut ion i n tens i f i ed in colour and a f locculent white prec ip i ta te formed. Monitoring of the progress of the conversion by IR spectroscopy of the supernatant solut ion revealed the disappearance of the V ^ Q ' S charac te r i s t i c of the n i t rosy l reactant at ^1805 and ^1695 cm"1 and the concomitant growth of new absorptions at ^1860 and a/1750 cm" 1 . After 2h, the prec ip i ta ted AgCl was removed by f i l t r a t i o n , and the green solut ion of [Mo(N0)2(CH 3N0 2) 4](BF 4)2 thus generated was used d i r ec t l y in subsequent react ions. 79 (b) In THF (Procedure D). A bright green THF solut ion of [Mo(N0) 2 (THF) 4 ] (BF 4 ) 2 was generated-in a manner analogous -to that described in the preceding paragraph. During th is transformation in THF, however, the n i t rosy l absorptions displayed by the supernatant so lut ion remained invar iant at M795 and ^1675 c m - 1 . Preparation of [Mo(N0)2(CH3CN) 4 ] ( ,PFg) 2 . A sample of [Mo(N0l 2 (CH 3 N0 2 l 4 ] -.(.PFg)2 (0.45 g, ^0.65 mmol) prepared by Procedure B was dissolved in CH3CN (20 mL), and the resu l t ing green solut ion was s t i r r ed at ambient temperature for 40 h. At the end of th is time, the volume of the solut ion was reduced to 10 mL under reduced pressure, and CH 2C1 2 (50 mL) was added. Cooling of the resu l t ing solut ion to -78°C for 2 h induced the c r y s t a l l i -zat ion of 0.28 g (V70% y ie ld ) of [Mo(.N0) 2(.CH 3CN) 4 ](.PF 6) 2 6 8 as bright green c rys ta ls which were co l lec ted by f i l t r a t i o n . Ana l . Calcd for M o N ^ C ^ ^ F - , 2 : C, 15.75; H, 1.98; N, 13.77; Mo, 15.73. Found: C, 15.83; H, 1.93; N, 13.59; Mo, 15.41. IR (Nujol mu l l ) : v(N0) 1863 ( s ) , 1754 ( s , br) c m " 1 ; a lso 2333 (m), 2305 (m), 844 ( s , br) cm" 1 . M.p: 95°C dec. , Mo(N0)2(.PFg)2 (prepared by Procedure A) afforded the same product in comparable y i e l d when subjected to the ident ica l experimental procedure. Preparation of [Mo(,N0) 2(bipy) 2 ](PFg) 2 . To a bright green so lut ion of [Mo(N0) 2(CH 3N0 2) 4]( ' .PF 6) 2 (1.00 g , ^2.24 mmol, prepared by Procedure B) in CH3N02 (15 mL) was added a quantity (0.70 g, 4.5 mmol) of so l i d 2,2-bipy-80 r id ine (.bipy, C-|gHgN2) • The resu l t ing solut ion was s t i r r ed for 18 h whereupon i t became darker green in colour. IR monitoring of the react ion in the n i t rosy l region of the spectrum revealed the gradual replacement of the absorptions due to the reactant by four s t rong, lower energy bands at a,1825, 0,1800 (b r ) , o,l725 and ^1685 (br) cm" 1 . Vo la t i l es were removed from the f i na l solut ion in vacuo, and the remaining green o i l was dissolved in CH3CN (4 mL). Dropwise addit ion of CH 2C1 2 (40 mL) to the CH3CN solut ion caused the prec ip i ta t ion of [Mo(N0) 2 (bipy) 2 ] (PF5) 2 as a green so l i d (0.47 g, o,28% y ie ld ) which was co l lec ted by f i l t r a t i o n , washed with CH 2C1 2 (2 x 8 mL), and dried at 5 x 10"3.mm. Ana l . Calcd for M o N g O ^ ^ g P 2 F ] 2 : C, 31.66; H, 2 .11; N, 11.08. Found: C, 31.59; H, 2.00; N, 11.08. IR (Nujol mu l l ) : v(N0) 1816 (s) , 1716 ( s , br) cm" 1 ; ailso 1603 (m), 1497 (w), 1321 (m), 881 (m), 840 ( s , br) , 765 ( s ) , 730 (m) cm" 1 . IR (CH 3 N0 2 ) : v(N0) 1825 ( s ) , 1726 (s) cm" 1 ; also 878 (w), 849 (s) cm" 1 . IR (CH 3CN): v(N0) 1824 ( s ) , 1724 (s) cm" 1 ; also 1605 (m), 1500 (w), 1323 (m), 880 (m), 847 ( s ) , 752 (m) , 733 (w) c m - 1 . l H NMR (CD 3CN): 6 7.5 - 9.2 (m) . 1 9 F NMR (CD 3CN): 6 71.3 (d , J i 9 F _ 3 i p . = 7 0 7 H z ) • 3 1 P NMR (CD 3CN): 6 ^144 (sep t . , J 3 i p _ i 9 F = 707 .Hz). Mp: 182°C. dec. Preparation of [Mo(N0) 2 (b ipy) 2 ] (BF / | ) 2 • 0-75 CH 2 C1 2 . To a s t i r r e d , bright green THF solut ion (20 mL) of [Mo(N0)2(.THF)a] ( B F 4 ) 2 (^2.2 mmol, gene-rated by Procedure D) was added dropwise a colour less THF solut ion (10 mL) of b ipyr id ine (b ipy, C-j o H 8 N 2 ' 9 ' 4.4-mmol). As the addit ion proceeded, the solut ion darkened to a green-black colour , and a black prec ip i ta te 81 formed. Solvent was removed from the f ina l react ion mixture under reduced pressure, and the remaining green-black tar was extracted with CH3N02 (20 mL) to obtain a deep green solut ion whose IR spectrum exhibi ted absorptions at -^1830 ( s ) , 0,1795 (s) , o,1725 ( s ) , and a-1690 (m) cm"1 a t t r i -butable to n i t rosy l groups. The extracts were taken to dryness in vacuo, and the resu l t ing green o i l was c r y s t a l l i z e d by d isso lu t ion in CH^CN (3 mL) and the dropwise addit ion of CH 2C1 2 (25 mL). In th is manner, 0.54 g (38% y ie ld ) of ana l y t i ca l l y pure [Mo(N0) 2 (b ipy) 2 ] (BF 4 ) 2 . o,0.75 CH 2C1 0 were obtained as a green s o l i d . Ana l . Calcd for MoNgO^g 7 5 H 1 7 ^ F g C l - , g : C, 35.28; H, 2.48; N, 11.90. Found: C, 35.39; H, 2.67; N, 11.92. IR (Nujol mu l l ) : v(N0) 1816 ( s ) , 1707 ( s , br) cm" 1 ; also 1603 (m) , 1503 (w) , 1329 (w) , 1057 ( s , br) , 775 (m), 737 (m) cm" 1 . IR (CH 3 N0 2 ) : v(.N0) 1828 ( s ) , 1727 (s) cm" 1 ; also 771 (m), 733 (m) cm" 1 . IR (CH 3CN): v(N0) 1828 (s) , 1727 (s) cm" 1 ; also 1606 (m), 1059 ( s ) , 750 (m), 731 (w) cm" 1 . *H NMR (CD3CN) 6 7.5 - 9.2 (m, 16H), 5.44 ( s , 1.6 H). Mp: 194°C dec. A m (CH 3 N0 2 ) : 191 ohm"1 cm2 m o l " 1 . The analogous react ion between .[Mo(N0.) 2(CH 3N0 2) 4] (BF 4) 2(generated_. by Procedure C) and b ipyr id ine in CH3N02 afforded the same product in comparable y i e l d . Preparation of [Mo(N0) 2(diphos) 2 ] (PFg) 2 . A s t i r r e d , green suspension of Mo(N0) 2 (PF 6 ) 2 (0.60 g , 1.35 mmol i prepared by Procedure A) in CH 2C1 2 (20 mL) was treated with so l i d Ph 2 PCH 2 CH 2 PPh 2 7 8 (diphos, 1.07 g, 2.69 mmol), whereupon the supernatant solut ion became s l i g h t l y darker green in colour. 82 The react ion mixture was ref luxed for 18 h and then s t i r r ed at ambient temperature for 14 days unt i l a l l v i s i b l e traces of the n i t rosy l reactant had disappeared. The f ina l red-brown solut ion (displaying v^g 's at ^1800 and ^1675 cm"1 in i t s IR spectrum) was taken to dryness in vacuo, and the remaining brown o i l was washed with benzene (3 x 20 mL). The o i l was then dissolved in CH 2C1 2 (10 mL) and transferred by syringe to the top of a s i l i c a gel column (2.5 x 6 cm) made up in CH 2 C1 2 . E lut ion of the column with C H 2 C I 2 produced a brown band which was removed and co l l ec ted . The volume of the eluate was reduced in vacuo to ^10 mL, and benzene (45 mL) was added dropwise to induce the prec ip i ta t ion of a brown powder. This powder was co l lec ted and dried in the customary manner (vide supra) to obtain 0.8 g (48% y i e l d based on Mo) of [Mo(N0) 2 (d iphos) 2 ] (PF g ) 2 . Anal . Calcd for MoNgOgCggH^PgF^: C, 50.24; H, 3.86; N, 2.25. Found: C, 50.00; H, 4.00; N, 2.24. IR (CH 2 C1 2 ) : v(N0) 1800 (m), 1676 (s) cm" 1 ; also 1593 (m) , 1481 (w), 1437 ( s ) , 1310 (m), 1127 (s , b r ) , 1029 (m), 1000 (m), 845 ( s , br) cm" 1 . lH NMR (CD 3CN): 6 7.37 7.59 (m, 40H), 2.78 (br,8H). 19F NMR ( C D 3 C N ) : 6 71.0 (d , J i 9 p _ 3 1 p - 707 Hz). 3 i p m R fc^CN., 5mm tube): 6-144 ( m , J 3 J p r _ J 9 . F = 70.7 Hz), 38.5 ( s ) . Mp: 150 - 151°C. Preparation of [Mo(N0) 2(0PPh 3) /|]( P F ^ ) 2 . A s t i r red green suspension of [Mo(NO) 2(CH 3N0 2) 4 ] (PFg) 2 (0.5 g , ^1.1 mmol, prepared by Procedure B) in CH 2C1 2 (20 mL) was treated with Ph3P0 (0.62 g , 2.2 mmol). Af ter being s t i r red for 18 h, the react ion mixture consisted of a green solut ion and a l i gh t green s o l i d . The so l i d was co l lec ted by f i l t r a t i o n , redissolved 83 In a minimum of CH^CN (5 mL), and reprec ip i ta ted by the addit ion of CH 2C1 2 (>300 mL). The f ina l prec ip i ta te was iso lated by f i l t r a t i o n , washed with cold (0°C) CH 2C1 2 ( 4 x 2 mL), and dried in vacuo (5 x 10 " 3 mm) to obtain 0.40 g [46% y i e l d based on Ph3P0) of [Mo(N0) 2 (0PPh 3 ) 4 ] -(PFg) 2 as a lime green s o l i d . Anal . Calcd for M o N 2 0 5 C 7 2 H 6 Q P 6 F 1 2 : C, 55.46; H, 3.85; N, 1.80. Found: C, 55.09; H, 4.15; N, 1.63. IR (.CHgCN) : v(N0) 1800 ( s ) , 1680 (s) cm" 1 ; also 1594 (w), 1125 ( s ) , 1000 (m), 847 ( s ) , 731 ( s ) , 697 (m) cm" 1 . XH NMR CCD3CN): 6 7.0 - 7.8 (m). Mp ( in a i r ) : >220°C. Preparation of [Mo(N0)2( CH 3 CN) 2 (0PPh 3 ) 2 ] (BF / | ) 2 . To a s t i r r e d , 7 9 green solut ion of [Mo(.N0)2( CH 3ON), 4 i](BF 4) 2 (3.06 g , 6.20 mmol) in CH3CN (20 mL) was added so l i d 0PPh 3 (3.00 g, 10.8 mmol). No colour change in the green solut ion was apparent, but i t s IR spectrum showed a general sh i f t of the or ig ina l n i t rosy l absorptions to lower wave numbers ( i . e . from ^1860 ( s ) , 0,1830 (m) , v]760 (s) and ^1730 (m) cm"1 to o/|832 ( s ) , o/|810 (m), ^1720 (s) and o,1695 (m) cm" 1 ) . Af ter 15 min, the solvent was removed in vacuo, and the green o i l remaining was dissolved in CH 2 C1 2 (100 mL). Addit ion of toluene (40 mL) to th is l a t te r so lut ion induced the formation of bright green crys ta ls (3.10 g , 59% y ie l d based on 0PPh3) of [Mo(N0) 2 (CH 3 CN) 2 (0PPh 3 ) 2 ] (BF 4 ) 2 which were co l lec ted by f i T t r a t i on . Anal . Calcd for M o N 4 0 4 C 4 0 H 3 g P 2 B 2 F 8 : C, 49.59; H, 3.72; N, 5.79. Found: C, 49.33; H, 3.69; N, 5.77. IR (Nujol mu l l ) : v(N0) 1827 ( s ) , 1713 84 (-s) c m ' 1 ; also 2320 (w), 2300 (w), 1143 (m), 1126 (m), 1056 ( s , b r ) , 1036 (m), 766 (w), 726 (m) c m - 1 . IR (CHgCN): v(N0) 1832 ( s ) , 1721 (s) c m ' 1 ; also 1140 (w) , 1124 (m), 1059 (s)>, 733 (m) cm" 1 . IR ( C H 0 C 1 2 ) : v(N0) 1831 ( s ) , 1720 (s) c m " 1 ; also 1446 (m), 1125 ( s ) , 1067 (s , b r ) , 1049 (m), 1001 (w) c m - 1 . 2H NMR ( C D C I 3 ) : 6 7.5 - 7.7 (m, 30H), 2.22 (s , 6H).. 1 9 F NMR ( C D C I 3 ) : 6 147 (s ) . 3 J P NMR ( C D 3 C N ) : 5 50.6 (s , I P l , 28.8 (s , IP ) . Mp:134°C dec. A m ( C H 3 N 0 2 ) . : 179 ohm"1 era2 m o l " 1 . Preparation of [Mo(.N0) 2 (bipy)] 2 (PF 6 ) 2 . A sample of [Mo(N0) 2 (CH 3 N0 2 ) 4 J-(PF5I2 C - 0 9» ^1 .5.mm;ole) prepared by Procedure B) was dissolved in ace ton i t r i l e (20 mL) and s t i r r e d for 6 h. The solut ion was then cooled to 0°C, and a sodium amalgam (1.5 mmole Na in 7 mL of mercury) was added dropwise over a period of 15 min. The solut ion darkened from bright green to o l i ve green, and a sh i f t in v-^' was observed by IR, i . e . 1828 and 1716 cm" 1 to 1800 and 1682 cm" 1 . Af ter being s t i r red for 1 h the supernatant solut ion was f i l t e r e d and so l i d 2,2 ' b ipyr id ine (0.46 g, 3.0 mmoles) was added, whereupon the colour of the solut ion darkened to brown green. The acetonitrile-was removed in vacuo and the product was recrys ta l1 ized twice: f i r s t by adding THF (60 mL) dropwise to a CH3N02 (5 mL) so lu t i on ; second by dropping CH 2C1 2 (40 mL) into anCH3CN (2 mL) so lu t i on . By th is method was obtained 0.35 g (51% y i e l d ) of green-brown microcrystal s of [Mo(N0) 2(bipy)J 2_. ( P F 6 ) 2 . Anal . Calcd for MoN 4 0 2 C 1 0 HgPF 5 : C, 26.26; H, 1.75; N, 12.25. Found: C, 26.15; H, 2.00; N, 12.40. IR (Nujol M u l l ) : v(N0) 1775 (s) , 1639 (s , br) cm" 1 ; 85 also 1602 ( s ) , 1492 (w), 1318 (m), 1244 (w), 1163 (w) 1109 (w), 1075 (w), 1060 (w), 1047 (w), 1032 (w) , 1020 (w), 845 ( s ) , 768 (m), 733 (m) cm" 1 . IR (.CHgCN) : v (N0 ) 1774 ( s ) , 11650 (s , br) cm" 1 ; a lso 1602 ( s ) , 873 (w), 850 (s) cm" 1 . l H NMR ( C D 3 C N ) 6 10.2 - 7.0 (m, vbr) . 1 9 F NMR (CD CN) ; : 6 71.2 (d, J j ^ a i p = 707 Hz). 3 1 P NMR. (CD^CN).:- 6 -144 (sept . , J 3 1 p : 1 c i F = 707 Hz). Mp; 208°C dec. Preparation of [Mo(N0) 2(,phen')] 2(PF 6)g. To a green THF (40 mL) sus-pension of [Mo(N0) 2 (CH 3 N0 2 ) 4 ] (PF 2 ) 2 (.1.0 g , ^1.5 mmol, prepared by Procedure B) was added successively, sol id ^2% sodium amalgam (1.55 g, 1.5 mmol of Na) and mercury (0,5 mL), and the mixture was s t i r r ed un t i l a l l the n i t rosy l reactant had dissolved ( /v l20 min) . IR monitoring of the progress of the react ion revealed a s h i f t in the i n i t i a l n i t rosy l absorp-t ions to lower wave numbers, i . e . from 1790 and 1680 cm - 1 to 1780 and 1673 c m - 1 . The o l i ve green supernatant solut ion was removed from the f i na l react ion mixture by syringe and was f i l t e r e d through a Ce l i te column (4 x 5 cm) supported on a medium porosi ty f r i t . The f i l t r a t e was treated dropwise with a THF/CH 2C1 2 solut ion (20/10 mL) of 3,4,7,8 tetramethyl-1 ,10-phenanthroline (phen1 , 0.64g, 2.7 mmol) whereupon a f ine pale yellow prec ip i ta te formed. The prec ip i ta te was removed by f i l t r a t i o n . The solvent was evaporated from the f i l t r a t e in vacuo, and the resul tant green tar extracted with CH3CN ( 3 x 5 mL). The CH3CN was removed in vacuo and the green o i l d issolved in CH 2C1 2 (30 mL). The dichloromethane solut ion was f i l t e r e d and to \ t toluene (5 mL) was added dropwise; the solut ion was 86 concentrated to ^8 m l . The prec ip i ta ted green brown so l i d was co l lec ted on a medium porosity f r i t and r insed with toluene (3 x 8 mL) then hexanes ( 3 x 8 mL) to bbtain 0.4 g (47% y ie ld ) of golden-green [Mo(.N0) 2 (phen')3 2 (PF g ) 2 . Anal . Calcd for M o N ^ C , g H 1 g P F g : C, 35.75; H, 2.98; N, 10.43. Found: C, 35.80; H, 3.20; N, 10.12. IR (Nujol mu l l ) : v(N0) 1786 ( s ) , 1660 ( s , br) cm" 1 ; also 1530 (m), 1304 (w) , 1007 (w), 845 ( s ) , 740 (w) , 723 (m) cm" 1 . IR (CH 2 C1 2 ) : v(NO) 1782 ( s ) , 1661 (s , br) cm" 1 ; also 1530 (w), 849 (s) cm" 1 . *H NMR(CD2C12) : 6 9.5 - 7.2 (m, 2H), 3.1 - 0.8 (m, 12H). 1 9 F NMR (CDgCI^) : 6 71.5 (d,'Ji9 F_aip= 707 Hz). 3 1 P NMR (CD 3 N0 2 , 5 mm tube): 6 -147 ( m, J 3 i p ^ i 9 F = 7 0 7 H z ^ - M p : - 1 8 ^ °C dec. Preparation of Mo(.N0) 2 (acac) 2 . A quantity of so l i d [Mo(N0) 2 (CH 3 N0 2 ) 4 ] -( JPFg)2 (1.40 g , O-2.02 mmol, prepared by Procedure B) was added to a suspen-sion of Na 2 C0 3 (0.34 g, 3.3 mmol) in acetyl acetone (acacH, 10 mL), and the mixture was s t i r r ed for 3 days. During th is t ime, the or ig ina l green super-natant so lut ion gradual ly became brown, but white so l i d matter remained suspended throughout. Solvent was removed from the f i na l mixture under reduced pressure, and the remaining brown o i l was extracted with hot hexanes (2 x 80 mL). The hexanes extracts were concentrated in vacuo to ^5 mL in volume and were then transferred to the top of a F l o r i s i l column (1 x 12 cm) made up in hexanes. Development of the column with hexanes afforded a green band which was eluted with benzene. Removal of v o l a t i l e s from the eluate under reduced pressure produced 0.50 g (70% y i e l d based on Mo) of a green s o l i d . This so l i d was iden t i f i ed by i t s IR [ (CH 2 C1 2 ) : v N Q 1773 ( s ) , 1658 (s) 87 c m ; also 1570 ( s ) , 1 524 ( s ) , 1 373 ( s ) , 1024 (m), 934 (m) cm" 1] and lti NMR [(CDC1 3): 6 5.60 (s , 2H), 2.20 ( s , 6H), 1.98 ( s , 6H)] spectra as Mo(N0 ) 2 ( acac ) 2 . 6 8 > 7 0 > 8 0 Subsequent e lu t ion of the column with THF removed an orange-brown band which was co l lec ted and taken to dryness in vacuo, The residue was rec r ys ta l l i zed from CH2C1 ^/hexanes to obtain 0.23 g (25% y i e l d based on Mo) of Mo(N0)(acac) 2(CH 3C(0)C(N0)CC0)CH 3) 8 1 as an orange-brown s o l i d . Ana l . Calcd for M o C 1 5 H 2 ( ) N 2 0 8 : C, 39.82; H, 4.42; N, 6.19. Found: C, 39.73; H, 4.64; N, 6.18. IR ( C H 2 C 1 2 ) : 1718 (m), 1680 ( s ) , 1 637 (m) , 1580 ( s ) , 1522 ( s ) , 1377 ( s ) , 1177 (m), 1023 (m), 934 (w). ^ NMR ( C D C I 3 ) : 6 5.62 (s , 2H), 2.23 (m, 18H). Reaction of [Mo(N0) 2Cl 2^with Na[ (n 5 -C 5 H 5 )w(CO), ] . To a green solut ion o f (Mo(N0) 2 Cl 2 ] n 7 7 (0 .50 g, 2.2 mmol) in THF (10 mL) at -78°C was added N a [ ( n 5 - C 5 H 5 ) W ( C 0 ) 3 ] 5 3 > 8 2 a (1 .59, 4.47 mmol) p a r t i a l l y dissolved in THF (30 mL) at -78°C, and the mixture was s t i r red at th is temperature for 1 h before being permitted to warm to room temperature. The f i na l react ion mixture consisted of a brown prec ip i ta te and a dark red solut ion whose IR spectrum displayed absorptions at o,2300 (w), 0,2075 (w), o,2020 (m), 0,1980 (m), o,1950 ( s ) , o,]915 ( s , b r ) , o,1785 (m), o,1745 (w), and o/l640 (m, br) cm" 1 . The mixture was f i l t e r e d through a medium-porosity f r i t , and solvent was removed from the f i l t r a t e in vacuo to obtain a red residue. A s lu r ry of th is residue in benzene (5 mL) was transferred to the top of a F l o r i s i 1 column (1 x 17 cm) made up in benzene. Elut ion of the column with benzene 88 developed f i r s t an orange band and then a red band. The orange band was eluted with benzene and co l lec ted . Removal of solvent from the eluate and sublimation of the residue (60°C, 0.005 mm) onto a water-cooled probe afforded 0.05 g (4% y ie ld ) of an orange so l i d which was iden t i f i ed as (n 5 -C 5 H 5 )W( .C0) 2 (N0) 8 2 a by i t s IR [ (CH 2 C1 2 ) : v C Q 2010 ( s ) , 1925 ( s ) ; v N Q 1655 (s) ] and i t s lH NMR [ ( C D C I 3 ) : 6 5.60 ( s , C ^ ) ] 82b a n d i t s m a s s s p e c t r a . Further e lu t ion of the column with CH 2C1 2 removed the red band which was co l lec ted and taken to dryness under reduced pressure to obtain [ (n 5 -C g Hg)-W(C0) 3 ] 2 (0.43 g , 29% y ie ld ) as a red so l i d i den t i f i ab le by i t s characte-r i s t i c spectral properties [IR (CH 2C1 2) : v e Q .1958 ( s ) , 1910 ( s ) ; *H NMR (CDC13) : & 5 . 3 3 ( s , C^) . ] 8 3 F i n a l l y , e lu t ion of the column with THF produced a yellow solut ion (V C Q at o,2070 (m), o/|970 (m), ^1940 (s) and ^1880 (m) cm \ which when taken to dryness in vacuo provided only trace amounts of a yellow s o l i d . In a s im i la r manner, IR spectral monitoring of the react ion between [Mo(N0) 2 Cl 2 J j0 .23 g , 1.0 mmol) and K[( n 5 -C 5 H g ) F e ( C 0 ) 2 ] 8 4 (0.43 g , 2.0 mmol) in THF (35 mL) at -78°C revealed the disappearance of the n i t rosy l absorptions at a,1795 and o,1675 cm - 1 due to [Mo(N0) 2Cl 2^and only the appearance of carbonyl absorptions at a/1985, a/1945 and o,1780 cm - 1 charac te r i s t i c of [ ( n 5 -C 5 H 5 )Fe -(C0) 2 1 2 (compared to an authentic sample). Analogous reactions between .[Mo( N0) 2 (CH 3 N0 2 ) 4 J (P f 6 ) 2 -and .Na[(r.ib-C5H5)W-(C0) 3 ] or K[(n 5 -CgH 5 )Fe(C0) 2 ] in THF resul ted in products ident ica l to those desdribed in the preceding paragraphs. In no case were any molybdenum-con-ta in ing products i so l ab le . 89 Reaction of [Mo(,N0) 2(,CH 3CN) 4](PF 6) 2 with [ (T i 5 -C 5 H 5 )C r (N0) 2 J 2 . So l id [Mo(N0) 2CCH 3CN) 4 ] (PF g) 2 (0.31 g, 0.50 mmol) was added to a v i o l e t dichloromethane (20 ml) solut ion of [ (n 5 -C 5 H 5 )Cr (N0) 2 ] 2 8 5 (0.18 g , 0.50 mmol). Af ter three days the react ion mixture was brown in colour and a green-brown prec ip i ta te had formed. An IR spectrum revealed the complete loss of the n i t rosy l absorption at 0,1510 cm - 1 of [(n 5-CgHg)Cr(N0) 2 ] 2 ( i t s IR spectrum in CH 2C1 2 consist ing of two n i t rosy l absorptions 1667 (s) and 1512 (m) c m - 1 ) ; new n i t rosy l absorptions were v i s i b l e at o,1845 ( s ) , o,1775 (w), and o,1745 (s) cm" 1 ) ; and the i n i t i a l V^Q band at 1665 cm - 1 ([(n5-CgHg)-Cr(N0) 2 ] 2 ) had diminished in in tens i t y . The brown react ion mixture was f i l t e r e d ; THF (15 mL) and hexanes (10 mL) were added to the f i l t r a t e ; and the f i l t r a t e was concentrated in vacuo to giye a gr,een gold . so l i d (0.15 g, 83% y ie ld ) which was iden t i f i ed by i t s spectral propert ies to be [ (n 5 -C 5 H 5 )Cr(N0) 2 (CH 3 CN)]PF 6 . 8 6 IR (Nujol )rv ("NO) 1862 ( s ) , 1757 (s ) ;v (GN) 2312 (m); v(PF)840 ( s , br) c m - 1 . 1H NMR (CD 3N0 2) : 6 5.97 ( s , 5H, C g H 5 ) , 2.40 (s , 3H, CH 3 ) . 90 Result and Discussion Generation of "Mo(N0) 2 2 + " from Mo(C0)6 and NOPFg A. Dichloromethane Solvent. Due to the e l e c t r o p h i l i c nature of the nitrosonium s a l t s , they can function as ox id iz ing as well as n i t r o -sy la t ion agents. Conne l l y 8 7 has proposed a general mechanism that accounts for th is dual mode of r e a c t i v i t y as is seen in Scheme IV. Scheme IV M L n + + NO M L n + N O + — • [ML n(NO)f ^ ML n.i (NO) + 91 Spec i f i c react ion condit ions determine whether oxidat ion or subst i tu t ion occurs; accordingly, these are examined minutely. The mixing of NOPFg with a dichloromethane solut ion of molybdenum hexacarbonyl always resul ts in the prec ip i ta t ion of an amorphous, du l l -green so l id which exhib i ts two n i t rosy l stretching bands in the inf rared spectrum of i t s Nujol mu l l . The ra t io of the two reactants, ( i . e . Mo(C0)g to NOPFg being 1:1, 1:2, or 1:3) does not appear to inf luence the outcome of the react ion. Nitrosonium hexafluorophosphate, being extremely hygros-copic , i s weighed in an- iner t atmosphere glove box and:,on the bench'is t rans-ferred "into the react ion f lask under a strong stream of N^. The iner t gas is introduced into the f lasks v ia gas in le ts connected by latex hosing to a s i l i c a gel drying tower. The react ion f lask is kept under dry dini t rogen atmosphere e i ther by passing N 2 over the mouth of the f l ask or by maintaining a constant pos i t ive nitrogen pressure. Since minor CO bands are v i s i b l e in the IR spectrum of some of the co l lec ted samples, the react ion f lask i s flushed with N 2 to f a c i l i t a t e removal of the CO gas d isp laced. However, the solut ion is not sparged with N 2 as Connelly has 6 9 claimed that in ace ton i t r i l e the d in i t rosy l cation resu l ts from the react ion of generated NO and that e f f i c i e n t removal of the NO gas resu l ts in a mononitrosyl containing product: C H o C N ,Mo(C0) 6 + 2N0PFg ——> [Mo(NO)(CH 3CN) 5](PF g) 2 + NO —> [Mo(N0) 2(CH 3CN) 4 ]-(PFg) 2 (37) 92 Nevertheless, with these precautions a reproducible product cannot be obtained and etching of the react ion vessel and discolouration of the latex hosing i s sometimes observed. When further e f fo r t ,-fs expended * to ensure rigorous exclusion of water from the react ion vessel by use of Schlenk-type glassware attached to the nitrogen manifold of a double manifold high vacuum l i ne v ia a l l glass connections, glassware remains unetched and a product which from i t s elemental analys is is formulated as Mo(N0) 2 (PF g ) 2 i s obtained reproducibly. "Mo(N0) 2(.PFg) 2 is a highly a i r - s e n s i t i v e , hygroscopic green s o l i d which decomposes upon heating to 110°C. The infrared spectrum of i t s Nujol mull contains two strong n i t rosy l st retching absorpt ions, 1811 and 1683 cm - 1 and several bands of medium in tens i ty 1265 (b r ) , 1154, 948, 885, ?843, arrd 565 c m - 1 , which are not ind ica t ive of a hexafluorophosphate anion with octahedral symmetry (a strong v D r - 830 c m - 1 ) . 8 8 The fact y~<~sym that the species Mo(N0) 2^ + would be extremely electron de f ic ien t suggests that Mo(N0)2(.PFg)2 might possess coordinated PFg". A coordinated FPFg has been claimed in the case of (n 5 -C 5 H 5 )Mo(C0) 3 PFg 8 9 and in that of ( n 5 - C 5 H 5 ) -C r (N0 ) 2 PFg . 8 6 However, l i t t l e s ign i f i can t a l tera t ions are observed in the IR spectrum of a coordinated PFg a n i o n . 8 9 ' 9 0 The strong absorption at a,840 cm - 1 may s p l i t into bands at o,880 and 810 c m - 1 , but th is s p l i t t i n g may be obscured by the broadness of the bands. The absorptions seen in the IR spectrum of Mo(.N0)2(PFg)2 at 1265, 1154, and 948 cer ta in ly do not or ig inate from a PFg anion coordinated or uncoordinated. The o r ig in of these bands • w i l l be discussed in the next sec t ion . 93 Beck reports that the metal - f luor ine l i nk in (n5-CgHg)Mo(C0)3PFg is so weak that even a weakly donating solvent such as dichloromethane can displace i t . 8 9 Indeed, when Mo(N0) 2(PFg) 2 i s placed in any solvent in which i t d issolves an octahedral ly symmetric PFg~ is detectable by infrared and 3 1 P or 1 9 F NMR spectroscopy (a septet 6 -144, 1 J 3 i p _ i 9 F = 707 Hz (CD 3CN), in the 31PUNMR spectrum and a doublet 6 72 , 1 J 1 9 F _ 3 1 p = 707 Hz (CD^CN)^ in the 1 9 F NMRspectrum are charac te r i s t i c of an octahedral hexa-fluorophosphate a n i o n 4 0 ' 4 8 ) . Proton NMR spectroscopy performed in deutero-ace ton i t r i l e v e r i f i e s that no dichloromethane i s incorporated into the green s o l i d , but in ace ton i t r i l e Mo(N0) 2(PFg) 2 i s converted to [Mo(N0)2 (GH-^eN3)4](PFg)2 and can be iso la ted as such. Mo(N0)2( PFg^formed by react ion 38 can be compared to [Mo(N0) 2C1 2] , CH CI ? Mo(C0)g + 2N0PFg * > Mo(N0) 2(PFg) 2 (38) the product of a s im i la r react ion 39..- [Mo(N0) 2Cl 2] n is also a hygroscopic green CHp CIp Mo(C0)5 + excess N0C1 — — [ M o ( N 0 ) 2 C l 2 ] n (39) so l id with n i t rosy l st retching absorptions in the Nujol mull in f rared spectrum 1805 and 1690 c m - 1 . It i s apparently a polymer which read i ly d issociates into monomeric species in coordinating solvents. Its polymeric structure is suggested as 94 ON-, CI NO Mo CI CI CI Mo" NO .CI NO I t i s possible that M o C N O ^ P F g ^ is a l i k e polymer with c is n i t rosy ls accounting for the two NO absorptions in the IR spectrum. The al ternate resu l t of react ion 38, seemingly produced when condi-t ions are not r igorous ly anhydrous, i s a lso a green s o l i d the in f rared spectrum (Nujol) of which displays two strong n i t rosy l absorptions 1821 and 1693 cm - 1 and bands of medium in tens i ty at 1265, 1163, 955, 901, and 569 cm" 1 . It is highly a i r sens i t i ve , fumes when exposed to the atmosphere, but does not 95 show noticeable decomposition when heated under a dini trogen atmosphere to 220°C. Its 3 1 P and 1 9 F NMR spectra d i f f e r markedly from that of [ M o ( N 0 ) 2 ( P F 6 ) 2 ] n . The 3 1 P NMR spectrum consists of a t r i p l e t 6 -17 .9 , l j 3 i p _ i 9 p = 9 5 7 H z> while the 1 9 F spectrum i s a doublet centred at 6 81.7 ( J i 9 p _ 3 i p '~ 957 Hz). This data i s not in accord with the presence of a PFg anion but, rather , with that of 0 2 P F 2 " (see Table I I I ) . For th is formulation the f ingerpr in t region of the infrared spectrum can be assigned 1265 (asym P 0 2 ) , 1163 (sym P0 2) , 955 (asym P F 2 ) , and 901 (sym PF 2 ) c m - 1 . Since a l l these v ibrat iona l bands c lose ly match those reported in the system R 2 S n ( 0 2 P F 2 ) 2 9 t f > 9 5 in which the 0 2 PF 2 "moiety is bidentate, i t seems l i k e l y th is is also the mode of i t s coordination in th is molyb-denum n i t rosy l ca t ion . Cole-Hami l ton 9 2 has suggested that the symmetric P0 st retching frequency can be correlated to the bonding mode of 0 2 PF 2 '7 i . e . , monodentate 1130 - 1140 c m - 1 , chelat ing 1165 - 1200 cm" 1 ; br idg ing, bidentate 1157 - 1175 c m - 1 . Ionic 0 2 PF 2 ~ has been observed to possess va c>, m p 0 1 2 7 0 " 1 3 1 0 a n d v p „, P0 1137 - 1164 c m - 1 . 9 6 Guided by these asym sym c l a s s i f i c a t i o n s the difluorophosphate under consideration would a lso be said to coordinate in a bidentate fashion though whether to one or two molybdenum centres i s not ce r t a i n . Further evidence is needed in order to make a more spec i f i c assignment; conductance data which w i l l be presented la te r along with the elemental analys is suggest the correct formulation to be [ M o ( N O ) o ( O o P F 0 ) ] O o P F o with one coordinated and one ion ic dif luorophosphate. Table I I I . 1 9 F and 3 1 P NMR Spectral Data for Complexes Containing PFg" or 0 2 P F 2 " 1 9 F NMR 3 1Jl9p_31p 3ip N M R b Reference (Hz) («) Re(C0 ) 5 ( 0 2 P F 2 ) 969 -12 .7 ( t )C 91 Re(C0) 3 (b ipy)(0 2 PF 2 ) 969 - 12 .7 ( t )c 91 trans-[Ru(CO)(dppm) 2(0 2PF 2)]PF 6 76.8(d ,0 2 P^ 2 ) 955 - 1 6 . 8 ( t , 0 2 ^ F 2 ) d 92 74 (d,PF 6 ) 708 -145 (septet,JPF 6) t rans- { [Ru(C0)(dppmy 2 (0 2 PF 2 ) } (PF 6 ) 3 89 (d ,0 2 P ^ 2 ) 951 - 1 5 . 3 ( t s 0 2 P F 2 )d 92 74 (d,PF 6 ) 708 -145(septet,P£g) { [ ( n 5 -C 5 H 5 )Rh ] 2 ( 0 2 PF 2 ) 3 }PF 6 65.3(d) 952 -33 .1 ( t , 3P ,0 2 ^F 2 ) 6 93 74.4(d) 708 -166.2(septet , lP,PFg) (n 5 -C 5 H 5 )C r (N0) 2 FPF 5 75.5 d 750 86 ! M o ( N 0 ) 2 ( P F 6 ) 2 ] n 72.0(d) d > f 707 -144(septet) f th is work Mo(N0) 2 (0 2 PF 2 ) 2 81 .7(d) 957 -17.9(t) f th is work [Mo(N0) 2 (CH 3 N0 2 ) 4 ] (PF 6 ) 2 72.0(d) 706 -144(septet) f th is work (a) values standardized to CFC13 (b) values standardized to H 3 P O 4 (c) CD 2C1 2 (d) nitromethane (e) solvent unspecified (f) CD3CN to cn 97 The hexafluorophosphate ion undergoes slow hydrolysis in ac id ic media to form the phosphate s a l t ; cer ta in metal centres have been reported to f a c i l i t a t e th is h y d r o l y s i s . 9 7 The transformation of hexafluorophosphate into difluorophosphate in organometallic compl exes is unusual but not unpre-cedented. For example, when [WCo-phenylenebis(.dimethylarsine))(.C0)2(N0)]-PFg i s ref luxed in "dry" acetone the 0 2 PF 2 sa l t f o rms . 9 8 1 9 F NMR samples of [Mo(N0) 2 (PFg) 2 ] n in d 3 - a c e t o n i t r i l e when allowed to age in unsealed NMR tubes show a decrease in the in tens i ty of the doublet at 8 72 ( / ^ i p igp = 707 Hz) charac te r i s t i c of PFg~ and the growth of a new doublet at 6 82 C.1 J 3 l p 1 9 p = 957) charac te r i s t i c of 0 2 PF 2 ~ and a broad resonance at 6 +160. Thus, the source of v a r i a b i l i t y in react ion 38 i s evident; [Mo(N0) 2(.PFg) 2] n i s the i n i t i a l product in any case, but in the presence of trace amounts of water i t i s converted to the di f luorophos-phate sa l t and HF. HF can in turn i n i t i a t e the production of more water and cause the observed etching of glassware v ia react ion 40. 6-HF + S i 0 2 > 2H20 + S i F g 2 " + 2 H + (40) Indeed, .aqueous: solut ions, of. EMoCN0) 2(PF 6)g] n and [Mo(N0") 2 '(CH 3N0 2 '^(PF 6) 2- have pH-= 3.35. The previously c i ted IR spectrum of'[Mo(N0)2( PFg)]n as a Nujol mull appears to d isplay some inc ip ien t decomposition to 0 2 P F 2 ~ ( e . g . the bands at 1265, 1154, 948. c m - 1 ) . This re f lec ts the d i f f i c u l t y in obtaining a mull IR spectrum under anrhydrous condi t ions. In th is case the 1 9 F and 3 1 P NMR spectra prove the more useful diagnost ic tools sinceNMR samples can.be 98 sealed from the environment more e f f ec t i ve l y than the in f rared samples. B. Nitromethane Solvent. In performing react ion 38 i t was i n i t i a l l y of concern that since n i t rosy l hexafluorophosphate i s insoluble in dichloromethane, i t might be occluded in the equal ly insoluble product. Accordingly, the analogous react ion was attempted in nitromethane with the thought that as a good solvator i t i s capable of d isso lv ing NOPFg 7 6 but as a poor donor i t i s not l i k e l y to become involved in the reac t ion . Unfortunately, the la t te r did not prove to be the case. Instead the product formed i s [Mo(N0) 2 (CH 3 N0 2 ) 4 ] (PFg) 2 . The addit ion of a nitromethane solut ion of NOPFg to a nitromethane s lu r ry of Mo(C0)g resu l ts in v io lent bubbling. IR monitoring of the react ion so lut ion shows a decrease in the band ofCMp(-C0)g at 1980 cm - 1 and an appearance of two new bands at 2185 and 2100 c m - 1 . This suggests a react ion path leading through a CO containing intermediate such as [Mo(N0) 2 (C0)(so lvent) 3 ] (PF 6 ) 2 which has been reported for M = W . 6 8 » 8 0 After two hours two IR bands are v i s i b l e , 1860 and 1750 cm" 1 , ind icat ing the presence of c is n i t rosy l func t iona l i t i es as well as a strong absorption at 843 cm - 1 ind icat ing an octahedral ly symmetric PFg a n i o n . 8 8 The reaction solut ion fumes and is extremely hygroscopic. Indeed, infrared monitoring i s d i f f i c u l t for the V^Q bands of both the react ion solut ion and the iso la ted product s h i f t to 1ower wave numbers i f the solut ion i s allowed to s i t in the IR c e l l as long as 4 minutes. Since th is sh i f t i s not affected by the u t i l i z a t i o n of KRS-5 (TIBr /T lCl) instead of NaCl IR windows i t i s not 99 due to react ion with the NaCl plates as i s observed with some organometal1ic c a t i o n s . " It i s probably due to hydrolysis since the aged solut ion also exhib i ts at 3400 c m - 1 . A s im i la r sh i f t in V^Q absorptions has been reported for [Mo(N0) 2(CH 3CN) 4](.PFg) 2 but was speculated to be due to an equi l ibr ium between the t e t r ak i sace ton i t r i l e and the b i sace ton i t r i l e spec ies 8 0 The solvate l igands are l a b i l e ; 1H NMR studies have demonstrated t h i s . 7 0 [Nuclear magnetic resonance experiments performed in d 3 -ace ton i -t r i l e on [Mo(.N0) 2 (CH 3 N0 2 ) 4 ] (PF 6 ) 2 confirm the presence of the CH 3N0 2 ( X H: 6 4.34 (m)) and the PF g [ 3 1 P : <5 -144 (septet) (CD3CN or CD3N02) : 1 9 F : 6 +72, 1 J i 9 p _ 3 i p = 706 Hz]. However, in ace ton i t r i l e the nitromethane l igand i s d isp laced; [Mo(N0) 2 (CH 3 CN) 4 ] (PF g ) 2 can be iso la ted from th is so lu t ion . Monitoring of the 1 9 F NMR spectrum reveals the ease with which the compound is hydrolyzed from the PF g sa l t (<5 +72, J 1 9 . 3 1 = 706 Hz) to the 0 2 PF 2 sa l t (8 +82, J i 9 F - 3 1 p - = 957 Hz) (vide supra). [Mo(N0) 2 (CH 3 N0 2 ) 4 ] (PF g ) 2 i s an amorphous green so l i d which loses nitromethane when subjected to high vacuum and decomposes upon heating to 88°C. I t is highly hygroscopic and must be handled only in a dry atmosphere. It deliquesces upon exposure to atmospheric condi t ions. Coordination of nitromethane to the metal centre in an organometal1ic compound is unusual, but the presence of the nitromethane i s establ ished by the IR (1570 (s) (Nujol)) and the l H NMR (S 4.34(CD3CN)) spectra and by the elemental analysis of the complex. Donation would l i k e l y be through one oxygen in a monodentate fashion so an octahedron such as 100 2 + C H 3 N 0 . 0 C H . N O N O Mo N O Q ^ 0 N C H 3 O N C H , can be envis ioned, f u l f i l l i n g the requirement of c i s n i t rosy l l igands. Generation of "Mo(N0) 2 2 + " from fMo(N0) 2 Cl 2 l n and AqBF^. C. Nitromethane Solvent. Like l M o ( N 0 ) 2 ( C H 3 C N ) 4 ] ( B F 4 ) 2 , 7 9 [Mo(N0) 2 (CH 3 N0 2 ) 4 ] (BF 4 ) 2 can be prepared by abstract ion of chlor ide from [Mo(N0)2C12] 7 7 by AgBF 4 in the appropriate so lvent . [Mo(N0) 2 Cl 2 ] n + 2AgBF4_§^ [Mo(N0) 2 S 4 ] (BF 4 ) 2 + 2AgCH (41) Unfortunately at room temperature when S = CH3CN, react ion 41 does not go to completion as i s apparent from the continual p rec ip i ta t ion of AgCl over a period of days. The analogous react ion employing AgPFg is reported to go to completion under ref lux cond i t i ons 7 0 but stops at an intermediate [Mo(N0) 2Cl(CH 3CN) 3 ](PF 6) i f only s t i r red at room temperature. 1 0 1 AgPFg M o ( N 0 ) 2 C l 2 C H c ° > [Mo(.N0) 2Cl(CH 3CN) 3]PFg + AgCH ( 4 2 ) However, in nitromethane react ion 41 i s complete upon s t i r r i n g 2 hours at ambient temperature, possib ly due to decreased s o l u b i l i t y of AgCl in th is solvent . 2+ The product [ M o(N0 ) 2 S 4 ] with coordinated nitromethane has cer ta in advantages over the complex with S = a c e t o n i t r i l e . In addi t ion to the ease of producing the product v ia the chlor ide abst rac t ion , the n i t r o -methane is less l i k e l y to be retained in subsequent react ions, i . e . [Mo(N0) 2S 4 ]X, OPPh, [ M o ( N 0 ) 2 S 2 ( 0 P P h 3 ) 2 ] ( B F 4 ) 2 ( 4 3 ) C H 3 C N [Mo(N0) 2 (0PPh 3 ) 4 ] (PF 6 ) . ( 4 4 ) S = C H 3N0 2 These products w i l l be discussed in deta i l l a t e r . D. Tetrahydrofuran Solvent. In terest ing ly no s h i f t in the n i t rosy l st retching frequences is observed when chlor ide abstract ion (react ion 4 1 ) i s performed in tetrahydrofuran. Eyen i f only one chlor ide i s removed, as is the case when the solvent is C H 3 C N (react ion 4 2 ) , some V^Q change would be expected. The fact that the same product [ M o(N0 ) 2 ( b i p y ) 2 ] ( X ) 2 X = PFg or BF d ~(react ion 4 5 , vide in f ra) is formed when 2,2-'bipyridine is added to the ]02 n i t rosy l cation whether i t i s generated in CH3N02 or THF cannot be taken as proof that react ion 41 goes to completion in THF, for the same product 70 . , i s obtained from the react ion solut ion of react ion 42 (see Scheme V) . (Although no mention i s made of the fact in the or ig ina l paper , 7 0 further chlor ide abstract ion must be evidenced in the presence of 2 ,2-b ipyr id ine .) However, the fact that no further p rec ip i ta t ion of AgCl i s evident does seem to argue that the ch lor ide abstract ion does go to completion in THF media. Tetrahydrofuran solut ions of the dicat ions cannot be eas i l y d i f fe rent ia ted on the basis of the i r in f rared spect ra; lMo (N0) 2 (PFg ) 2 J n , [Mo(N0) 2 (CH 3 N0 2 ) 4 ]CPF 6 ) 2 , and [Mo(N0) 2 C0 2 PF 2 ) ] (0 2 PF 2 ) a l l have v i r t u a l l y the same V^Q absorpt ions. This may be due in part to the fact that they a l l become THF so lva tes . But when a THF solut ion of e i ther of the hexa-fluorophosphate dicat ions i s exposed to a sodium amalgam, product formation is accompanied by very small sh i f t s in the V^Q bands as compared to those seen when the comparable react ion i s performed in ace ton i t r i l e (vide i n f r a ) . No attempt has been made to i so la te [Mo(N0) 2(THF) 4](BF4) 2 from the react ion so lut ion (41); rather the species is used in s i t u . Four coordinated THF are assumed on the basis of the analogous d icat ions formed in CH^CN or CH 3 N0 2 . In p rac t i ce , an undesirable complication makes tetrahydrofuran a less a t t rac t i ve solvent for react ion 41 than nitromethane. When th is react ion is effected in THF or when ei ther [Mo(N0) 2(.PFg) 2] n or [Mo(.N0)2( CH 3 N0 2 ) 4 ] (PFg) 2 are s t i r r ed in tetrahydrofuran for any length of time (longer than two hours), the green solut ions became v iscous. After 12 hours the solut ions are extremely syrupy and in some instances form ge l s . CO o Scheme M_ + 2AgBF 4 - ^ ^ [ M O ( N O ) 2 ( C H 3 N 0 2 ) 4 ] ( B F 4 ) [MO (N0)2( bipy) 2] ( B F 4 ) 2 ^Mo(N0 2)ClJ^ + 2AgBF 4 - J Q 1 £ — • reaction solution -+ 2AgPF 6 C H B C N ^ [MO(NO) 2 CI (CH3CN) 3 ]PF 6 2 B I P Y » [MO(N0) 2(bipyjj ( P F 6 ) 2 in reaction solution 104 If the ge l l i ng has occurred to only a s l i gh t extent the desired molybdenum species can be salvaged by removal of the solvent under vacuum and extract ion of the resul tant green tar with nitromethane or ace ton i t r i l e to produce a green solut ion and leave a gummy white residue. In the progress of these experiments i t was observed and i t has since been r e p o r t e d 1 0 0 that NOPFg reacts v io len t l y with THF, evolving gas, and in hours polymerizing the THF. In f ac t , i t has been claimed that NOPFg i s one of the most promising cata lysts for the polymerization of t e t rahyd ro fu ran . 1 0 1 In l i gh t of th is i t i s surpr is ing that THF i s occas ional ly employed as a solvent for react ions involv ing N O P F g . 1 0 2 ' 1 0 3 It i s possible that polymerization occurs at a rate appreciably slower than that of the desired reac t ion . Polymerization of THF is believed to occur only by an ion ic mechanism — a ca t ion ic r i n g - o p e n i n g . 1 0 1 The propagating species in the polymerization i s a t e r t i a r y oxonium ion : Propagation occurs by an S^2 mechanism: a tetrahydrofuran monomer adds to the tert iary-oxonium ion chain end: ^ C H 2 0 © 105 •0-(CH2)4-0£> 0-(CH 2 ) 4 - 0-(CH 2 ) 4 - 0 e o The required t e r t i a r y oxonium ion can be formed by several methods: (1) d i rec t acy la t ion or a l ky la t ion of the oxygen of THF; (2) in s i tu generation by a var ie ty of reagents such as a hal ide and a Lewis acid or a halide and a metal sa l t or sometimes a Lewis acid alone: (3) strong protonic acid addit ion to the oxygen of THF to form an in te r -mediate secondary oxonium ion which i s subsequently converted to a t e r t i a r y oxonium ion . Depending upon the presence or absence of a react ive hal ide, n i t rosy l hexa-fluorophosphate can i n i t i a t e polymerization of tetrahydrofuran by ei ther method 2 or 3. Or ig ina l l y i t appeared the d icat ions might be losing N0 + and thus promoting THF polymerizat ion. But CpMo(C0)2(N0) and (CH 3C 5H 4)Mn(C0) 3 which are both read i l y n i t rosy la ted by N O P F c , 1 0 4 * 1 0 5 f a i l to form any 106 n i t rosy l products when s t i r red in an ace ton i t r i l e so lut ion of [MolNO^CCH^NOg^KPFg^ even under re f lux condi t ions. A paper has recent ly been p u b l i s h e d 1 0 6 claiming i t i s a general phenomenon that e lec t roph i1 ic t rans i t i on metal complexes react with o le f ins to generate inc ip ien t carbonium ions which can then ol igomerize. I t reports that [M(N0) 2 (CH 3 CN) 4 ] (BF 4 )2, where M = Mo, W, i n i t i a t e s the polymerization of a number of subst i tuted o l e f i n s . Thus, i t appears to be an i n t r i n s i c property of the dicat ions [MotNO^S^lO'PFg^ to react with monomeric THF probably v ia method 3 to generate the t e r t i a r y oxonium ion which in turn i n i t i a t e s THF polymerizat ion. Conductivi ty Studies Conductance studies are used to determine the e l e c t r o l y t i c character of a complex and by comparison with conduct iv i t ies of re lated compounds can provide ins ight into i t s solut ion s t ructure. Molar conductance ( in - 1 2 -1 units ohm cm mole ) is ca lcu la ted : A ce l l constant m where R i s the resistance of the solut ion (ohms) and C m i s the molar con-3 -1 centrat ion (moles/cm ). The c e l l constant (cm ) is determined by measuring the resistance (R) across a Wheatstone bridge of a known concentration (Cm) of a sa l t for which the molar conduct iv i ty (Am) is known: 107 ce l l constant = A "R -C m m The pur i ty of the solvent employed is judged by i t s spec i f i c conduct iv i ty K , determined by measuring i t s i n t r i n s i c resistance R in a ce l l of known c e l l constant: ce l l constant K = R Table IV contains conduct iv i ty values determined for various compounds 107 containing PFg~and 0 2 P F 2 moiet ies. Geary /• has compiled conductance data in nonaqueous media to produce expected ranges for molar conduct iv i t ies 1 2 1 (ohm cm mole ) for the d i f fe rent e l e c t r o l y t i c types in various solvents. In nitromethane the range is 6 0 - 1 1 5 for 1:1, 115 - 250 for 2 : 1 , and 220 - 260 for 3:1 e lec t ro l y tes . In acetone 1:1 e lec t ro ly tes range from 100 to 140, 2:1 from 160 to 200, and 3:1 s tar ts about 270 ohm"1 cm2 mo le" 1 . For d i l u te nitromethane solut ions H 0 " 3 M ) of NaPFg and of [Mo(N0) 2 (CH 3 N0 2 ) 4 ] --1 2 -1 (PFg) 2 the molar conduct iv i t ies were found to be 116 and 202 ohm cm mole , respec t ive ly . These values place NaPFg in Geary's range for 1:1 e lec t ro ly tes and [Mo(N0) 2 (CH 3 N0 2 ) 4 ] (PF 6 ) 2 in that of the 2:1 e lec t ro ly tes (see Table IV). The d i f f i c u l t y with th is method i s that i t requires the assumption of a molecular weight which may be erroneous. In a case in which the degree of molecular complexity of a compound -1 2 is unknown ([M[_n]Xm vs [ML n ] g [X m ] a ) equivalent conductance (ohm cm equ iva len ts - 1 ) is determined 108 Table IV. Molar Conduct iv i t ies ; A~ Elect ro ly te Solvent Reference 1 2 -1 (ohm" cm mole ) Type [ (n 5 -C 5 H 5 )Co(N0)PPh 3 ]PF 6 147 1 :1 acetone 73 [ (n 5 -C 5 H 5 )Rh(N0)PPh 3 ]PF 6 132 1 :1 acetone 73 [Mn(C0)5(.CH3CN)]PF6 143 1 :1 acetone 73 [ (n 5 -C 5 H 5 )V (CH 3 CN) 2 ] (PF 6 ) 2 315 2 :1 acetone 73 trans[Ru(CO)(dppm) 2(0 2PF 2)]PFg 82 1 :1 unspecif ied 92 c is [Ru(C0) 2 (dppm) 2 ] (PF 6 ) 2 197 2 :1 unspecif ied 92 NaPFg 116 1 :1 nitromethane th is work [Mo(0PPh 3)g]PF 6 77.9 1 :1 nitromethane th i s work [Mo(N0) 2 (CH 3 N0 2 ) 4 ] (PF 6 ) 2 202 2 :1 ni tromethane th i s work [Mo(N0) 2 ( . b i py ) 2 ] (BF 4 ) 2 - 3 / 4 CH 2 Cl 2 191 2 :1 nitromethane th is work [Mo(.N0) 2(.CH 3CN) 2(0PPh 3) 2 ](BF 4) 2 179 2 :1 nitromethane th is work 109 ce l l constant  A e " R-C e (where C g = equivalent concentration in equivalents/cm ) over a range of concentrations,and a s imp l i f i ca t i on of Onsager's law i s app l ied : A - A = K ( C j o e e where K i s a combination of terms dependent on such factors as the charges on the ions concerned, the i r m o b i l i t i e s , and A , >molar conduct iv i ty . 'at ' - inf ini te is d i l u t i o n . The p lo t t ing of A Q vs ( C g ) 2 gives an intercept A . A sample of is such a plot is seen in Plot 1. A second plot of A Q - A G vs ( C g ) 2 has slope K which re f l ec t s the e lec t ro ly te type (e .g . see Plot 2) . Feltham and H a y t e r 1 0 8 have elaborated th is technique. From published slope values (see Table v ) 1 0 8 ' 1 0 9 ' i t appears that K ranges from 150 to 220- for 1 ;1 e lec t ro -ly tes and from 390 to 570-for 2:1 e lec t ro l y tes . I f i t i s ambiguous whether or not the anion i s in the coordination sphere of the metal , K values must be determined for each possible case, i . e . for [MLplXg and for [MI_nX]X. Hopeful ly, only one of these K values w i l l f a l l in i t s proper range. Conductivity data for D M N O ^ C H g N O g J ^ K P F g ^ confirm that i t i s a simple 2:1 e lec t ro l y te in nitromethane so lu t ion . For the hydrolyzed species MotNO^tOgPFg^ Table V shows the two p o s s i b i l i t i e s for which A G vs / c and (A - A G) vs / c plots were drawn. Comparing the K values for each to the acceptable range of values for K, i t can be seen that only [Mo(NO)o(OoPF ?)](0 ?PF ?) with a slope of 179 f a l l s close to the proper range I l l PLOT 31 A ~ A e vs ^ [Mo(NO) 2 (b ipy)J 2 (PF 6 ) 2 [ M o ( N O ) 2 ( p h e n ' ) ] 2 ( P F 6 ) 2 521 3 6 8 1 2 J C ^ x 1 0 2 3 Table V. Conductivi ty Measurements in Nitromethane 112 AQ Slope E lec t ro ly te Reference Type [Ru 2 Cl 3 (PEt 2 Ph)g]Cl 85 .5 151 1 :1 108 [CoBr(N0)(das) 2]Br 93 8 150 1 :1 109 [CoI(N0)(das) 2]I 96 .5 213 1 :1 109 [CoCl(N0)(en) 2 ]C10 4 101. 3 172 1 :1 109 [Pd 2 (PE t 2 ) 2 (phen ) 2 ] (BPh 4 ) 2 88 .0 392 2 •1 108 [Pd 2 (PE t 2 ) 2 ( d i phos ) 2 ] (BPh 4 ) 2 76 .0 410 2 :1 108 [Pd 2 (PPh 2 ) 2 ( en ) 2 ] (BPh 4 ) 2 86 .4 430 2 :1 108 [Co(N0)(das) 2 ] (C10 4 ) 2 126 5 571 2 :1 109 [Mo(N0) 2 (0 2 PF 2 ) ] (0 2 PF 2 ) 33 .2 178 1 :1 th is work u r [Mo(N0) 2 ] (0 2 PF 2 ) 2 16 .5 68.4 th is work [Mo(N0) 2 (PF 6 ) 2 J n 874 4320 ? th i s work [Mo(N0) 2 (b ipy) ] 2 (PF 6 ) 2 67 .8 ', 521 2 :1 th is work [Mo(N0) 2 (phen ' ) ] 2 (PF 6 ) 2 74 .8 .. 368 2 :1 th is work [(n 5-C 5H 5)Mo(N0)(NS)PPh 3 ]BF 4 77 0 186 1 :1 th is work 113 for i t s type, i .e .150 - 220 for 1:1 e lec t ro l y tes . However, the AQ value seems abnormally low, possibly due to incomplete d i ssoc ia t i on . The data obtained for [Mo(N0) 2 (PF 2 ) 2 ] n does not lend i t s e l f read i l y to in te rpre ta t ion . Clear ly in nitromethane so lut ion i t does not convert immediately to [Mo(N0) 2 (CH 3 N0 2 ) 4 ] (PF 6 ) 2 React iv i ty of "Mo(,N0) 3 2 +" With Neutral Ligands: The molybdenum dicat ions react read i ly with-neutral l igands: [Mo(N0) 2 (solvent) 4 ]X 2 X = PFg,BF 4- ^ > _ J ^ [Mo(N0) 2L 4 ]X 2 (45) [Mo(N0) 2 (PF 6 ) 2 ] n L = CH 3CN, 0PPh 3 L 2 = bipy, diphos The ace ton i t r i l e adduct is well k n o w n , 6 8 ' 7 0 ' 7 9 ' 8 0 and does not merit further de l ineat ion . For X = PFg", the b ipyr idy l complex has been reported, but only i t s V^Q IR absorptions have been p u b l i s h e d 7 0 ' 8 0 so i t s propert ies w i l l be detai led here. [Mo(N0) 2 (bipy) 2 ] (PFg) 2 i s formed in good y i e l d from the addit ion of 2,2 rbipyridine to a so lut ion of [Mo(N0) 2 (CH 3 N0 2 ) 4 ] (PFg) 2 . Addit ion of dichloromethane to the solut ion prec ip i ta tes deep green micro-c rys ta ls which decompose upon heating to 182°C. The IR spectrum (Nujol) consists of two V^Q absorptions 1 8 1 6 and 1 7 1 6 cm" 1 which indicate c i s 114 n i t rosy l l igands and a band at 840 cm - 1 due to an octahedral ly symmetric PF stretching absorpt ion. It i s only soluble in strongly solvat ing so lvents , i . e . , ace ton i t r i l e and nitromethane. 3 1 P NMR shows at septet <5 -144 (• J 3 1 1 9 p = 707 Hz), while the 1 9 F NMR pattern i s a doublet 6 +71.3. The BF 4 sa l t [Mo(N0) 2 (b ipy) 2 ] (BF 4 ) 2 can be formed in nitromethane although here the react ion i s reported in THF. I t is qua l i t a t i ve l y the same as the PFg~sal t . Upon heating i t decomposes at a s l i g h t l y higher temperature (194°C) than the P F g ' s a l t . The infrared spectrum of the so l id (Nujol mull) or of the solut ion (CH3CN or CH3N02) i s v i r t u a l l y the same as that of the PFg~salt except for the absence of the PF stretching band at 840 cm - 1 and the presence of the BF^'band at 1057 c m - 1 . The *H NMR spectra of both [Mo(N0) 2 (bipy) 2 ]X 2 (X = BF^ or PFg) in CD^CN are a complex series of resonances extending from 6 9.22 to 7.53. Free 2,2-bipyridine adopts a trans conf igurat ion in s o l u t i o n ; 1 1 0 i t s proton chemical s h i f t s are somewhat solvent dependent, but the basic pattern i s a doublet 6 8.68 ( H 6 ) , a doublet 8.49 (H 3 ) , a t r i p l e t 7.80 (H 4) and a t r i p l e t 7.28 (H g) ( C D C l 3 ) . 1 1 1 » 1 1 2 115 When dipyr idyl is coordinated symmetrically to a metal centre the basic pattern i s maintained, two doublets and two t r i p l e t s ; although H g may experience an upf ie ld s h i f t , there i s a general downfield sh i f t of the proton resonances due to less charge density on the l i gand , e .g . Mo(CO) ( b i p y ) 1 1 2 iH NMR (CD 2 C1 0 ) : 6 9.12 (H g ) , 8.16 (H 3 ) , 7.95 (H 4 ) , 7.39 (H 5 ) . This would be the expected pattern i f the n i t rosy l l igands in [Mo(N0) 2-2+ (b ipy) 2 ] assume a trans conf igurat ion. However, in the case of c i s -2+ [Mo(N0) 2(bipy) 2 ] the pyridyl r ings of each ligands are not magnetical ly equivalent. An eight l i ne pattern i s poss ib le , but resonances may over lap. The protons of the pyr idyl without a d ipyr idy l neighbour would be shi f ted furthest downfield due to the absence of sh ie ld ing by the aromatic r i n g ! 1 1 For c is[Mo(NO) 2 (b ipy) 2 ] a basic pattern of four resonances i s d is t ingu ishab le : a doublet 9 . 2 2 ( J H 6 - H 5 5 , 4 H Z^ ^ 1 H^' A M U L T I P L E T 8 - 6 1 ( 3 H)> a mul t ip le t 8.13 ( 2 H ) , and a mul t ip le t 7 . 5 3 ( 2 H ) . From i t s coupling c o n s t a n t , 1 1 1 the f i r s t resonance can be assigned as H 5 on a pyr idyl r ing not inf luenced by an adjacent r i n g ; the other coupling constants cannot be determined. 116 When the green so l i d [Mo(.N0) 2(.PFg) 2] n i s s t i r red in a d ich lo ro -methane diphenylphosphinoethane (diphos) so lut ion for a number of days, the green so l i d slowly disappears, the solut ion becomes red brown in co lour , and the IR spectrum evidences n i t rosy l stretching bands at 1800 and 1676 c m - 1 . The brown so l i d [Mo(N0) 2(diphos) 2]( PFg) 2 i so la ted from th is solut ion has a sharp melting point 150 - 151°C. Its 1H NMR spectrum consists of a mul t ip le t 6 7.56 (40 H) produced by the phenyl protons and a broad signal 2.78 (8 H) due to the methylene protons. It is not unusual for the methylene protons of R2PCH2CH2PR2 to be broadened. 1 1 3 The 1 9 F NMR is a doublet typ ica l of PFg"salts 6 +71.0 ( 1 J i 9 F _ 3 i p = 707 Hz). 3 1 P NMR experiments show the usual septet 6 -144 for PFg sa l ts and a broad signal 6 38.6 due to the phosphorous atoms of the diphos l igands. For the c i s n i t rosy l formation demanded by IR evidence, the four phosphorus nuclei of the two diphenylphosphinoethane ligands cannot be chemically equivalent, for two phosphorus must be trans to NO l igands. Broad resonances have been reported as evidence of inequivalent diphenylphosphinoethane l i g a n d s , 7 4 ' but in th is case some broading may be due to P-H coupl ing. Unfortunately, th is react ion proves d i f f i c u l t to repeat. The brown so l i d obtained from subsequent attempts does not melt sharply at 150°C but decomposes around 170°C. Elemental analysis are s l i g h t l y low in carbon and s l i g h t l y high in nitrogen content. Of in terest is the fact that reactions which potent ia l l y could generate [Mo(N0) ? (d iphos) ? ] (PF f i ) ? f a i l to do so: 117 7k 2N0PF f i C 6H 6 /CH 30H > CMoF(N 2H 2)(diphos) 2 ]PF 6 (35) excess NOBF, 1 1 5 Mo(N 2 ) 2 (d iphos) 2 > unident i f ied (46) excess N0BF4 1 1 5 ^-^j — [ M o ( N 0 ) ( C H 3 C N ) ( d i p h o s ) 2 ] B F 4 (47) U 1 5 > unident i f ied (48) C H 7 4 Mo(N 9 ) 9 (d iphos) 9 + NO — — — > "[Mo(N0)(diphos)]-2C cH c" —> brown powder d ' 1 b b (49) J H F / h v — ^ unident i f ied (50) 7h Mo(N 2 ) 2 (d iphos) 2 + excess N0C1 t o l u e n e > MoiCI 3(N0) (0,0 diphos) + MoCl 2 (N0) 2 (0,0 diphos) (51) 0,0 diphos = 0P(Ph) 2CH 2CH 2(Ph) 2P0 Mo(C0)(N 2 ) (d iphos) 2 - j C g H 6 (52) 2H0PFe [Mo(C0)(N0)(diphos) 9]PF f i C 6 H 5 / C H 3 0 H ? c 0 Mo(C0)(C 2H 4)Xdiphos) 2 (53) C f iH f i/CH 30H l h Mo(C 2 H 4 ) 2 (d iphos) 2 + 2 NOPFg -2 -2 ±—v [Mo(C 2H 4)(N0)(diphos) 2]PFg (54) 118 R i c h a r d s 1 1 5 who de l ibera te ly set out to generate Mo(N0) 2(diphos) 2 reports f a i l u r e . The product of react ion 49 as well as the ten ta t i ve ly assigned products of react ion 51 are both said to contain phosphine o x i d e s . 7 4 Uncharacterizable products have been reported for the react ion of phosphine donors PPh 3 or P(0CH 3 ) 3 with [Mo(N0)(CH 3 CN) 5 ] (PF g ) 2 . 6 9 Moreover, phosphine attack on coordinated n i t rosy l l igands has been reported: the phosphines PR2Ph and PRPh2 have been claimed to attack the nitrogenrof nitrogen ox.i.de, weaking the N-0 bond and thus f a c i l i t a t i n g the removal of oxygen by another phosph ine . 1 1 6 MoCl 5 + MO ^ e n e ^ ^ 2 C H 3 * Mo(Cl 2 )(N0)(PPh 2 CH 3 ) 2 (0PPh 2 CH 3 ) (55) Mo(Cl 4)(NPh 2CH 3)(0PPh 2CH 3) [Mo(Cl 3)(NH 2)(0PPh 2CH 3)]Cl These resu l ts suggest that the d i f f i c u l t y encountered in reproducibly forming [Mo(NO) 2 (d iphos) 2 ] (PF g ) 2 may a r i se from phosphine ox idat ion . Reactions of phosphines with N0 2 PF g have been extensively studied by O l a h . 1 1 7 N0 2 PF g + PPh 3 3» OPPh (56) 119 In order to circumvent the d i f f i c u l t i e s encountered when the coordinating l igand is a phosphorus donor, the less basic l igand t r i -phenylphosphine oxide i s employed. When OPPh^ i s added to a d ich loro-methane s lur ry of [Mo(N0) 2 (CH 3 N0 2 ) 4 ] (PFg) 2 and the mixture is s t i r r ed for days, the solut ion acquires a green co lour ; and the colour of the undism • .v solved so l id changes from medium green to l i gh t green. The l i gh t green prec ip i ta te is s l i g h t l y soluble in CH 2C1 2 and t o t a l l y soluble in CH^CN and CH^NOg and THF. It is recrysta l1 ized by dropwise addi t ion of dichloromethane to an ace ton i t r i l e solut ion of i t . In CH^CN the IR spectrum indicates c i s d in i t rosy l s 1800(s) and 1680(s) c m - 1 . The lH NMR spectrum in CD^CN or CD3N02 consists of a wide resonance about 6 7 .5 , typ ica l for phenylphosphine protons. The green so l id does not decompose upon heating to 220°C. Elemental analysis gives resul ts which are in good agreement with the formula [Mo(N0) 2 (0PPh 3 ) 4 ] (PFg) 2 . In teres t ing ly , when the comparable react ion i s performed using [Mo(N0) 2(CH 3CN) 4 ] (BF, 4) 2 , generated in s i t u , the same product is not obtained. The bright green microcrystals formed in th is react ion are soluble in CH 2C1 2 and chloroform, and they decompose upon heating to 134°C. The IR spectrum (CH^CN) shows the v N Q bands are at higher frequency than [Mo(N0) 2 (0PPh 3 ) 4 ] (PFg) 2 , i . e . , 1832 and 1721 cm" 1 , ind icat ing less electron density on the n i t rosy l l igands. The proton NMR (CDC1^) spectrum consists of two mul t ip le ts 6 7.65 (30H, P-CgH5) and 2.2 (6H, CHgCN). 1 9 F NMR shows a s ing le t at 6 +147 normal for BF4~ s a l t s . 4 8 The spectral data and the elemental analys is are consistent with the formulation [Mo(NO) ? (OPPh^) ? (CH q CN) 0 ] (BF d ) ? ; only two 120 CH^CN are replaced by OPPh^. IR evidence requires that th is d icat ion have c is n i t rosy l moieties so there are three possible conf igurat ions: trans 0PPh 3 l igands (A); trans CH3CN ligands (B); a l l l igands c i s (C) . 2+ ON-.. NO Mo . . -OPPh, | P h 3 P 0 1 TMCCH, NCCH, 2+ ON-HjCCN' NO Mo . . -NCCH, r O P P h , O P P h , B ON-H 3 C C N 1 NO Mo . .-OPPh, ' O P P h , NCCH, However, the 3 1 P NMR spectrum consists of two s ingle peaks +50.6 and +28.8; therefore, the phosphorus atoms must be inequivalent . Only the a l l c i s structure C sa t i s f i e s th is requirement. 121 This r eac t i v i t y with triphenylphosphine oxide serves to emphasize the possible advantages of employing [Mo(N0) 2 (CH 3 N0 2 ) 4 ] (PF 6 ) 2 rather than [Mo(N0) 2(CH 3CN) 4](.PF f i) ? in reactions requir ing a l a b i l e l i gand . lMo(N0) 2 S 2 (0PPh 3 ) 2 J( .BF 4 ) ; (.43) [Mo(.N0) 2S 4]X 2 S = CH3CN lMo(N0) 2 (0PPh. 3 ) 4 ] (PF 6 ) , (44) S = CH.3N02 With Sodium Amalgam: The reduction of [Mo(N0) 2 (PFg) 2 ] n or [Mo(N0) 2 (CH 3 N0 2 ) 4 ] (PFg) 2 i s effected by one equivalent of sodium amalgam in ei ther a THF or CH^CN so lu t ion . As previously mentioned the degree of 122 sh i f t in NO absorption bands in the IR spectra during the reductions in THF are not nearly as marked as in ace ton i t r i l e (1790 and 1680 sh i f t to 1780 and 1673 cm"1 in THF; 1828 and 1716 sh i f t to 1800 and 1682 cm" 1 in CH^CN). To f a c i l i t a t e the i so la t ion of the reduction product a Lewis base is added to the react ion so lu t i on . Choice of the l igand is prescribed by two considerat ions. F i r s t , phosphorus donating bases are avoided due to problems encountered with the d icat ion (vide supra). Second, s o l u b i l i t y of the resu l t ing product has to be such that i t can be separated from the side product of the reduction — NaPFg (soluble in THF, C H 3 C N , and C H 2 N O 2 ) . For example 1,10,-phenanthroline does not prove to be a sa t is fac tory l i gand . When i t is added to a warm THF solut ion of the reduction product, immediately, a grey green prec ip i ta te forms, which has l i t t l e s o l u b i l i t y in any solvent . I f th is s o l i d is ref luxed in CH^CN, the solut ion becomes l i gh t green in co lour . F i l t r a t i o n , which leaves most of the o r ig ina l s o l i d behind, and cool ing of the f i l t r a t e resul t in the formation of a small amount of green powder that is v i r t u a l l y insoluble in even the most polar so lvents. It has been formulated a s impure [Mo(N0) 2(phen) 2](PFg) on the basis of i t s so l i d state proper t ies. Anal . Calcd for MoNc09C„ H P F C : C, 43.57; H, 2.42; t w 2 4 1 6 b N, 12.71. Found: C, 43.72; H, 2.80; N, 13.46. IR (Nujol mu l l ) : v(N0) 1767 (s) , 1645 (s) cm" 1 ; also 1 627 ( s ) , 1605 (m), 1 586 (m), 1500 ( s ) , 1320 (s , b r ) , 1220 (m), 1145 (m), 1055 (m, b r ) , 850 ( s , br) , 730 (s) cm" 1 . Mp. 165°C dec. The l igands which, best meet th.e c r i t e r i a are nitrogen donor l igands 2,2-bipyrid.ine (bipy) and 3,4,7,8- tet ramethyl - l ,1 0-phenanthroline (phen 1 ) . Judged from the elemental analysis and the IR data each reacts with the 123 reduction product to give a complex with the formula [Mo(N0)2l_2]PFg where l_2 is the bidentate l igand 2,2-b ipyr id ine or 3,4,7,8-tetramethyl-^ ,1 O-phenanthrol ine . Both species are obtained in approximately 50% y i e l d , and many of the i r physical properties are s i m i l a r . For l_2 = bipy the compound is green brown in co lour , decomposes upon heating to 208°C, and has strong IR absorptions at 1775(N0), 1639(br)(NO), and 845(PF) cm"1 (Nujol mu l l ) . Its 1 9 F and 3 1 P NMR spectra in CD3CN are typ ica l for PFg" s a l t s , 4 8 ' 4 0 being 6 +71 .2(d) ( 1 J 1 9 p _ 3 1 p ; 7 0 7 Hz) and <S -144(septet) , respec t ive ly . For l_2 = 3,4,7 ,8-tetramethyl-1 ,10-phenanthrol ine , the so l id i s golden brown, decomposes at 187°C, and has strong IR bands in Nujol at 1786(N0), 1660(br)(N0), and 845(PF) cm" 1 . As expected for a PF g sa l t the 1 9 F NMR (CD 2C1 2) consists of a doublet at 6 +71.5 ( ^ ^ s i p = 707 Hz) and the 3 1 P NMR shows a septet pattern centered at 6 -147.-The so lub i l i t y of each complex is dependent on l_2. For l_2 = 2 ,2-b ipyr id ine [Mo(N0) 2L 2 ]PF 6 i s soluble in CH3CN, CH 3 N0 2 , and very s l i g h t l y soluble in THF. This lack of s o l u b i l i t y in THF permits the NaPFg byproduct to be separated from the product. When phen' is the l igand used, i t imparts a greater s o l u b i l i t y to [Mo(N0) 2L 2]PFg so that i t i s soluble in d ich lo ro-methane, and thus th is n i t rosy l species can be separated from the NaPFg. D in i t rosy l compounds of the type [M(N0)2l_2] + are known for c o b a l t 1 1 8 with L = PPh 3 ,CH 3 CN, (CH 3) 2CO or 1_2 = diphos, phenanthrol i ne , 1,5-cyclo-octadiene. These are reported to be monomeric, obeying the eighteen electron r u l e . But a monomeric formulation for the case M = molybdenum would leave the metal centre with formally only f i f t een e lect rons. In such a case an 124 E.P.R. signal might be expected to be detected, but none i s detected with a nitromethane (^10 M) solut ion of the ca t ion . Conductance data (Table V) give slopes for the plots A Q - A e vs /c in the range of 2:1 e lec t ro ly tes (vide supra). Taken together, these data suggest that the molybdenum d in i t rosy l monocationic species are dimers, [ M o ( N 0 ) 2 L 2 ] 2 ( • ^ 1 S possible that under more forcing condi t ions, with the proper coordinating l i gand , the metal-metal bond can be broken and another l igand introduced into the coordination sphere of the molybdenum. Such may be the explanation for the formation of [ M o ^ O ^ p h e n ^ l P F g . The 1H NMR spectra which might be expected to elucidate the structure of these compounds are very complex. For 1_2 = bipy a very broad resonance i s observed f rom7.0to8.5 ppm with small doublets at 9.2 and 10.2 ppm in C D 3 C N . Cooling the sample to -40°C, the solvent l i m i t , did not improve the reso lu t ion . The lH NMR of [Mo(N0) 2 phen' ] 2 (PF g ) 2 i s also d i f f i c u l t to in te rpre t . Free 3,4,7,8-tetramethyl-1 ,10-phenanthroline has a simple four l i ne pattern in CDC13: 6 8.91 ( s , 2H a ) : 8.01 ( s , 2H b ) ; 2.66 (s , 6H C ) ; 2.31 ( s , 6H d ) . 125 Upon complexing to the molybdenum cation a myriad of resonances i s seen in the regions 6 9.45 - 7.2 ( IH, r ing protons) and 3.2 - 0.8 (3H.-CH,) . The multitude of resonances in the methyl region of the phen1 species seems to indicate the presence of several isomers. If one envisions a f i ve coordinate molybdenum species with a Mo-Mo bond, a number of isomers i s poss ib le . The phenanthroline l igands may be c is or trans to each other; the metal-metal bond order may be one (a 16 electron species) or three (an 18 electron 126 spec ies) ; the arrangement of l igands around the molybdenum centres may be tr igonal bipyramidal or square pyramidal. Slow addi t ion of one equivalent of L i B E t ^ H 1 1 9 to a co ld , -78°C, THF solut ion of the [Mo(.N0) 2 (solvent) 4 ] 2 + species also produces the same molybdenum d in i t rosy l complex"formed with one equivalent of sodium amalgam or sodiUJH benzophenone. No evidence for a hydride species is detected by *H NMR. In some instances, when a large excess of a Lewis base L 2 i s added to the react ion solut ion containing the monoreduced molybdenum d in i t rosy l spec ies, a white so l i d p rec ip i ta tes . This phenomenon has been observed when L 2 = 1,10-phenanthroline, 3,4,7,8-tetramethyl-1,10-phenanthrol ine, or two triphenylphosphine oxides, Spot t e s t s 1 2 0 reveal the presence of molybdenum, and IR data indicate the presence o f L 2 a n d of P F g " . For example, when L 2 = 2(0PPh 3) strong IR (Nujol) absorptions are • v i s i b l e at 1440, 1200, 1122, 843 (br) cm" 1,and when L 2 = (phen 1) absorptions are observed at 1514 (m), 1016 (m), and 842 ( s , br). *H NMR spectra merely confirm the presence of a coordinated L 2 in a symmetric environment {lH NMR for L 2 = 2(0PPh 3 ) (CD 3 N0 2 ) : 6 7.61 (m); for L 2 = phen' (CD 3 N0) 2 : <5 8.76 ( s , 2H), 8.21 (s , 2H), 2.75 ( s , 6H), 2.53 ( s , 6H)). 1 9 F NMR spectra confirm the presence of the anion ( 1 9 F NMR for L 2 = 2(0PPh 3 ) (CD 3 N0 2 ) : 6 72.7 (d, 1 J l 9 F _ 3 l p = 7 0 7 H z ) an d for L 2 = phen'(CD 3 N0 2 ) : 5 73.0 (d , 1 J i 9 F _ 3 i p = 707 Hz)). The 3 1 P NMR spectrum of the product L 2 = 2(0PPh 3) not only aff irms the presence of the PFg" anion (6 -144 (m, 1 J 3 i p _ i g F = 707 Hz, CD3CN)) but also that of equivalent phosphine oxide. l igands (6 29.8 (s , CD.XN)). 127 On the basis of the elemental analyses and the data already c i ted these white so l ids have been ten ta t ive ly formulated as [Mo(L 2) 3 ]PFg (L 2 = 2(0PPh3),phen', or phen). [Elemental analyses: (a) L, = 2(0PPh 3 ) , ana l , calcd for M o O g C j 0 8 H 9 Q P 7 F 6 : C, 67.89; H, 4 .71 ; N, 0.00; found: C, 68.13; H, 4.56; N, 0.00; (b) l_2 = phen' , ana l , ca l cd . for M o N 6 C 4 8 H 4 8 P F 6 ; C ' 6 0 - 7 0 > H, 5.06; N, 8.85; found: C, 61.99; H, 5.54; N, 9.01; and (c) L £ = phen, ana l , calcd for MoNgC^H^PFg: C, 55.31; H, 3.07; N, 10.76; found C, 56.30; H, 3.33; N, 10.82.] These species appear to be extremely hygroscopic. A nitromethane solut ion of Mo(0PPh3)gPFg (^10~4M) has a molar conduct iv i ty - 1 2 - 1 of 77.9 ohm cm mole" and is therefore in G e a r y ' s 1 0 7 range for a 1:1 e l ec t ro l y te . Cr (phen) 3 + has been c l a i m e d 1 2 1 as the product of dispropor-2+ t ionat ion between Cr(phen) 3 and Cr(phen) 3 , but the molybdenum analogue has not previously been reported. A l l attempts to i so la te a neutral molybdenum n i t rosy l compound by addi t ion of two equivalents of reducing agent have f a i l e d . IR monitoring reveals a sh i f t in the two V^Q absorptions to even lower wave numbers than the monoreduced species. The solut ions darken from the bright green colour of the.d icat ion to the dark green of the monocation to brown of the supposed neutral spec ies, the transformation out l ined in Scheme V I . 2+ Providing "Mo(N0)2 " with two electrons e i ther through the agency of sodium amalgam or that of an anionic reagent (vide in f ra) in a l l cases produced the gradual decomposition of the resu l t ing product. Formation of the non-ni t rosyl containing species when a Lewis base i s added to the monocationic n i t rosy l suggests one pathway of decomposition is through loss of the n i t rosy l l i gand . CO CvJ solution colour: bright green (THF) Z/(NO)(cm-1) I790, I680 h erne JQ[ ' r n + M L M o ( N O ) 2 S N J ie % olive green 1780,1675 '[MO(I\IO) 2]' brown 1775, 1665 129 With Anionic Reagents: A.Sodium Acetylacetonate: Treatment of [Mo(N0) 2(CH 3CN) 4](PF 6) 2 or [Mo(N0)2Cl2) r |with acetylacetone in the presence of sodium carbonate leads to the formation of c i s - M o ( N 0 ) 2 ( a c a c ) 2 . 6 8 > 7 0 > 8 0 The analogous react ion with [Mo(N0) 2 (CH 3 N0 2 ) 4 ] (PFg) 2 leads to the formation of green cis-Mo(NO) 2 (acac) 2 as the major product and a minor amount of Mo(NO)(h ia)(acac) 0 8 1 where 0 0 N 0 il i: i: hia = C H 3 C - C - C - C H 3 . The former compound was iden t i f i ed by i t s charac te r i s t i c IRand 1H NMR spectra. The l a t t e r was i den t i f i ed by i t s IR, !H NMR, and .mass spect ra, and elemental ana lys is . It has been i den t i f i ed p rev ious l y 8 1 as a product of the react ion of acac with dinitrosylmolybdenium der ivat ives in aqueous aerobic condi t ions. A s im i la r transformation of acetyl acetonate has been observed in the react ion of RuC^NO with that reagent in an ac id i c aqueous solut ion and has been ascribed as the resu l t of nuc leophi l ic attack on the nitrogen of the coordinated n i t rosy l l igand by the y carbon atom of an acetylacetonato l i g a n d . 1 2 2 0 M r ' C M e r3° 130 The fo l lowing reactions f a i l to give i so l able molybdenum n i t rosy l products. B. Sodium Cyclopentadienides : Like JMo(N0) 2 Cl 2 ] n 1 2 3 [Mo(N0) 2 (CH 3 N0 2 ) 4 ] -(PFg) 2 f a i l s to give a t ractab le species when a THF or toluene solut ion of i t i s s t i r red with one or with two equivalents of sodium cyclopentadienide at room temperature or at -78°C. When NaCp is added, the green solut ion turns red brown in colour and a brown so l i d p rec ip i ta tes . A s im i la r t rans-formation i s observed when the base i s sodium methylcyclopentadienide. There i s no observable change in colour or IR spectrum when cyclopentadiene is added to a THF solut ion of the d i ca t i on . Neither of the hoped for products [CpMo(N0) 2S] + nor Cp(n 1-Cp)Mo(N0) 2 is i so la ted . C. Potassium Cyclooctatetraene: When ei ther [Mo(N0)2C12] or [Mo(N0) 2-( C H 3 N 0 2 ) 4 ] ( P F 6 ) 2 are treated with one equivalent of K2C0T at -78°C, the solut ion changes from green to red brown in co lour ; and on warming to room temperature a red brown, in t rac tab le so l i d p rec ip i ta tes . In the case of the react ion with the PFg _ sa l t V^Q bands are s t i l l v i s i b l e in the IR spectrum of the supernatant, but no t ractable species can be i so la ted . No react ion i s observed when 1,3,5,7-cyclooctatetraene is added to a THF solut ion of the molybdenum hexafluorophosphate d i ca t i on . No COT n i t rosy l complex can be i so la ted . 131 D. Na[CpW(.C0)3] and K[CpFe(C0) 2] : Adding Na[CpW(C0)3] or K[CpFe(C0) 2] to a cold (-78°C) THF solut ion of e i ther Mo(N0) 2 Cl 2 or Mo(N0) 2 (CH 3 N0 2 ) 4 (PFg) 2 resu l ts in a react ion from which no molybdenum containing product can be i so la ted . In the case of the tungsten reagent two products are iden t i f i ed by means of the i r mass and infrared spect ra: the major, [CpW(C0) 3] 2 and the minor, CpW(,C0)2(N0). With the iron reagent only the formation of [CpFe(C0) 2 ] 2 i s observed by infrared monitoring. The lack of any i ron n i t rosy l species i s not surpr is ing as i t has been previously observed to be a strong nucleophile with N0C1, preferr ing to be oxidized rather than n i t r o s y l a t e d . 1 2 4 However, i t had been hoped that e i ther the Lewis b a s e 1 2 5 [ (n 5 -C 5 H 5 )W(C0) 3 ] _ or [ (n 5 -C 5 H 5 )Fe(C0) 2 3~ might combine with the Lewis acid [Mo(N0) 2S 4] toform'a multimetal 1 i c species with the molybdenum centre attached to the Lewis base e i ther v ia a metal -metal bond or through a carbonyl oxygen. A tungsten-molybdenum b imeta l l i c species is a possible intermediate in n i t rosy l l igand t ransfer from 2+ molybdenum to tungsten. But electron t ransfer from [CpFe(C0) 2] to Mo(N0)2 may occur by an inner or outer sphere mechanism. With [ ( n 5 - C 5 H 5 ) C r ( N 0 ) 2 ] 2 : Although the molybdenum dicat ion f a i l s to react with CpMo(C0)2(N0) or (;CH3C5M4)Mn(C0)3 (vide supra) , [Mo(N0)2UH 3CN). 4]-( P F 6 ) 2 has. been .obs'eryedHoact as an ox id iz ing agent with another neutral organometal1ic species. When [CpCr (N0 ) 2 ] 2 8 5 i s s t i r r ed with the molybdenum n i t rosy l in CH^Cl 2 in a 1 :1 r a t i o , a f ter three days the chromium dimer i s consumed ( in ferred from loss of i t s bridging n i t rosy l absorption (1510 cm - 1 ) in the IR spectrum). The chromium complex iso la ted i s [CpCr(NO) 2(CH 3CN)]-PF f i , i den t i f i ed by i t s charac te r i s t i c IR and XH NMR s p e c t r a . 8 6 Although 132 v^Q bands are v i s i b l e in the react ion solut ion that.are not those of the i den t i f i ed chromium product, no molybdenum containing species can be i so l a ted . Since th is react ion and a l l subsequent work-up do not employ a c e t o n i t r i l e , that coordinated to the chromium must have or ig inated from the molybdenum d ica t ion . Once again an acid/base adduct i s presumably an intermediate. The molybdenum d in i t rosy l d icat ions appears to be Lewis acids which prefer to coordinate hard Lewis bases such as OPPhg, 2 ,2 " -b i py r i d i ne , CH^CN. However, any reagent capable of being oxidized read i ly gives up an electron to the molybdenum n i t rosy l without resu l t ing coordinat ion, forming the molybdenum d in i t rosy l monocation which can be iso lated with bases such as 2,2bipyridine and 3,4,7,8-tetramethyl-1,10-phenanthrol ine. "Mo(N0) 2 2 + " read i l y accepts one or two e lec t rons , but the neutral species i s unstable and cannot be i s o l a t e d . Just as hydride a t t a c k 5 2 (vide supra) sometimes occurs at the coordinated n i t rosy l resu l t ing in the loss of that moiety, so i t i s possible electron t ransfer may disrupt the in teg r i t y of the n i t rosy l l i gand . This may account for the paucity of anionic n i t rosy l complexes . 1 2 6 133 B. Cat ionic Thioni t rosy l Complexes of Molybdenum and Other Group VIB Metals Few th ion i t rosy l complexes e x i s t 1 2 7 because no convenient source of NS+ has been ava i l ab le . In th is group (n 5 -CgH 5 )C r (C0) 2 NS 1 2 8 has been prepared by the react ion of N 3 S 3 C 1 3 1 2 9 in THF on Na[(n 5 -CgH 5 )Cr(C0) 3 ] ( react ion 57) 3Na[ (n 5 -C 5 H 5 )Cr (C0) 3 ] + N 3 S 3 C 1 3 (n 5 -C 5 H 5 )Cr(C0) 2 (NS) + (57) C(n 5 -C 5 H 5 )Cr (C0) 2 ] 2 S Unfortunately, th is has not proved to be a general synthetic route to new th ion i t rosy l compounds. Recently, Herberho ld 1 3 0 has reported that three equivalents of AgPFg added to a nitromethane solut ion of N 3 S 3 C 1 3 produce an in s i t u source of NSPFg presumably v ia react ion 58. CH3N09 N 3 S 3 C 1 3 + 3 A 9 P F 6 > 3NSPFg + 3AgCl 4- (58) The f i l t r a t e when added to an ace ton i t r i l e so lut ion of Cr(C0)g produced [Cr(NS)(CHgCN)5](PFg)2 in 23% y i e l d . Here are reported attempts to use th is in s i tu NS + to prepare the th ion i t rosy l analogues of several known n i t rosy l species which can be formed with nitrosonium s a l t s , including some of these reported in Part IIA. 134 Experimental A l l experimental procedures described here were performed under the same general condit ions out l ined in Part I and IIA. N^S^Cl^ was prepared by the method of J o l l y . 1 2 9 A nitromethane solut ion of "NSBF^" was 13 0 prepared fol lowing the out l ine reported-by Herberhold. Both, (NS CI)3 and AgBF 4 were weighed and transferred into a three-necked f lask in an iner t atmosphere glove box. Once outside the glove box and attached to the dini trogen manifold of a high vacuum l i n e , the react ion f lask was charged with nitromethane (15 mL). The orange react ion mixture was s t i r red for three or four minutes and then was f i l t e r e d through a medium porosity f r i t , to remove the precip i tated AgCl , through a l l glass connec-t ions d i r ec t l y into the f lask containing a solut ion or s lu r ry of the organo-meta l l i c reactant . Reaction of "NSBF/," with Na[(n 5 -C 5 H 5 )M(C0) 3 ] (M - Cr or Mo). When a f resh ly prepared nitromethane solut ion (10 mL) of "NSBF^" (^2.0 mmol) was added to a cold (0°C) nitromethane solut ion (20 mL) of Na [ (n 5 -C 5 H 5 )C r r ( C 0 ) 3 ] 5 3 » 8 2 (0.45 g , 2.0 mmol), the solut ion turned green in colour and gas evolved. The solvent was removed in vacuo, and the residue extracted with hexanes (10 x 25 mL) and f i l t e r e d . The f i l t r a t e was taken to dryness in vacuo, and sublimation of the green brown residue onto a dry- ice-cooled probe (30°C, 5 x 10~ 3 mm) afforded red c rys ta ls of (n 5 -C 5 H 5 )Cr(C0) 2 (NS) (0.05 g , 11% y i e l d ) , i den t i f i ed by i t s spectroscopic p r o p e r t i e s ; 1 2 8 IR (hexanes): v C Q 2033, 1 962 cm" 1 ; v N S 1180 cm" 1 ; : H NMR (CDC13).:,;6 5.08 ( s ) . 135 The green hexanes residue which did not sublime was recombined with the or ig ina l react ion residue. These combined so l ids were suspended in toluene and transferred to the top of a 3 x 10 cm F l o r i s i l column. Elut ion of the column with toluene afforded a broad green band which was co l lec ted and taken to dryness under reduced pressure. The green residue which resul ted was rec r ys ta l l i zed from dichloromethane/hexanes to give green c rys ta ls of [(n 5 - C 5 H 5 ) C r ( C 0 ) 2 ] 2 s (0.15 g, 11% y ie ld ) which were i den t i f i ed by the i r charac te r i s t i c IR and lH NMR s p e c t r a : 1 2 8 IR(hexanes): v c o 2000, I960 , ; . ; 1932, 1924 cm" 1 ; *H NMR ( C D C I 3 ) : 6 4.87 ( s ) . When N a[(n 5 - C 5 H 5 ) M o ( C 0 ) 3 ] 8 2 (0.50 g , 1.9 mmol) was treated in an analogous manner, the main product proved to be the well-known red [ ( n 5 - C 5 H 5 ) M o ( C 0 ) 3 ] 2 8 3 (0.13 g , 28% y i e l d ) . IR(CH 2 C1 2 ) : vCO 1960, 1915 cm" 1 . 1H NMR (CDC1 3): 6 5.20. The orange product which sublimed from the hexanes extracts in trace amounts was indent i f ied as (n 5-CgHg)Mo(C0) 2(N0) by i t s charac te r i s t i c spectral p r o p e r t i e s : 8 2 J_( IR( CH 2 C1 2 ) : v C Q 2020, 1 937; vNO 1663 cm,'1-; NMR QEDC13): • & 5.53 (s)J.. No th ion i t rosy l -conta in ing species was i so la ted . Reaction of "NSBF^" with (n 5 -C 5 H 5 )Mo(C0) 2 (N0) . Into an orange n i t r o -methane (5 mL) or ace ton i t r i l e (10 mL) solut ion of (n 5 - C 5 H 5 ) M o ( C 0 ) 2 ( N 0 ) 8 2 (0.68 g , 2.45 mmol) was f i l t e r e d a nitromethane solut ion (10 mL) of "NSBF^" (o,2.45 mmol). The react ion mixture became deep purple in colour. The solvent was removed under reduced pressure, and the residue was washed with d ich loro-methane (4 x 20 mL). The remaining purple black so l i d was redissolved in nitromethane (10 mL), and to i t triphenylphosphine (0.64 g, 2.4 mmol) was 136 added. Once again the nitromethane was removed in vacuo, and the residue dissolved in dichloromethane (40 mL) and ref luxed for one hour. The react ion so lut ion was taken to dryness under reduced pressure and washed with toluene (3 x 15 mL). Subsequent r e c r y s t a l l i z a t i o n from dichloromethane/ d ie thy l ether (25 mL/15 mL) led to the i so l a t i on of a brown so l i d I ( n 5 - C 5 H 5 ) -Mo(N0)(NS)PPh3]BF4 (0.70 g, 66% y ie ld ) Anal . Calcd for MoC 2 3 H 2 Q N 2 0SPBF 4 : C, 47.10; H, 3.41; N, 4.78. Found: C, 47.37; H, 3.65; N, 5.00. IR (Nujol mu l l ) : v(.N0) 1636 ( s , b r ) ; v(NS) 1092 ( s ) , v(BF) 1054 (s , b r ) ; also 830 (w, b r ) , 746 (w), 693 (m). IR (CH 2 C1 2 ) : v(N0) 1647 (s , b r ) ; v(NS) 1069 ( s ) ; v(BF) 1030 ( s ) . *H NMR (CDC1 3): 7.44 (m, 15H, P ( C g H 5 ) 3 , 5.93 (br m, 5H, CgHg). Conductivi ty (CH 3 N0 2 ) : A Q = 77.0 ohm"1 cm2 e q " 1 ; slope A Q - A e vs / c = 186. Mp (a i r ) 133°C dec. Reaction of "NSBF^" with Mo(C0)g. As a deep orange nitromethane (20 mL) solut ion of "NSBF 4" (^3.1 mmol) was f i l t e r e d into a c lear d i ch lo ro -methane (25 mL) solut ion of Mo(C0) g (0.41 g , 1.5 mmol) the react ion mixture turned black and a black prec ip i ta te formed. The solvent was decanted, and the black so l id was r insed with dichloromethane ( 3 x 1 5 mL) and redissolved in nitromethane (10 mL). To th i s solut ion triphenylphosphine (1.6 g, 6.1 mmol) was added. The solvent was removed in vacuo, and the brown residue was dissolved in dichloromethane (30 mL) and ref luxed one hour. The i n f r a -red spectrum of the dichloromethane solut ion ( v M C =1.165 cm" 1) was 410 unaffected by re f l ux ing . F i l t r a t i o n of the dichloromethane mixture, addit ion of toluene (25 mL), and par t ia l removal of the solvent under reduced 137 pressure produced a brown so l id (0.40 g) . Anal . Found: C, 58.05; H, 4.19; N, 5.65. IR (CH 2Cl 2):v(NS) 1105 ( s ) ; y^BF) ^1057 ( s ) ; also 1555 cm" 1 . lti NMR (.CD\,N09): 6 7.28 (m). Molar conduct iv i ty : Am = 198 ohm"1 cm2 mole" 138 Results and Discussion Reactions of "NSBF 4" with Transi t ion Metal Cyclopentadienyl Carbonyl Species A fresh solut ion of "NSBF 4" combined with NaCpCr(C0)3 in nitromethane gives the same products obtained when N 3 S 3 C 1 3 i s employed as the t h i o n i t r o s y l -at ing agent, i . e . CpCr(C0)2NS and [ C p C r ( C 0 ) 2 ] 2 S . 1 2 8 Both products are i den t i f i ed by the i r spectral propert ies: IR and *H NMR. However, l i k e N^SgClg> in s i tu "NSBF 4" f a i l s to produce the carbonyl th ion i t rosy l analogues when reacted in a s im i la r mode with NafcpMoCCO)^. The major product of th is react ion is [CpMo(C0) 3 ] 2 ; 8 3 a trace product is iden t i f i ed as CpMo(C0) 2 (N0). 8 2 Both are i den t i f i ed by the i r IR and 1H NMR spect ra . Observation of a n i t rosy l product suggests some oxidat ion of the t h i o n i t r o s y l . Su rp r i s ing l y , no react ion is evidenced when a fresh nitromethane solut ion of "NSBF^" is f i l t e r e d into an ace ton i t r i l e solut ion of (CH^CgH^) Mn(C0) 3. This organometallie species i s read i l y n i t rosy la ted by NOPFg 1 0 5 to produce [(CH 3CgH 4)Mn(C0) 2(N0)]PFg. An orange ace ton i t r i l e so lut ion of CpMo(C0)2(N0) turns deep purple in colour when a nitromethane solut ion of "NSBF 4" i s f i l t e r e d into i t . Addit ion of d iethyl ether to the react ion mixture resu l ts in the p rec ip i t a -t ion of a purple s o l i d , which from IR and 1H NMR spectral evidence may be [CpMo(N0)(NS)(CH3CN)]BF4. IlR (Nujol mu l l ) : v(0N).2:320 (w), 2350 (w); v(N0) 1650 ( s , b r ) ; v(NS) 1065 ( s ) ; v(BF) 1035 (s , b r ) . lH NMR (CDgCN) 6.21 (m, b r ) . ] To s t a b i l i z e th is ca t ion , which appears to lose s o l u b i l i t y in so lut ion with the passage of t ime,PPh 3 i s added to replace the ace ton i t r i l e l i gand . The 139 purple product now forms a dichloromethane solut ion from which [CpMo(NO) ( N S ) ( P P h ^ ) ] B c a n be precip i tated by addit ion of toluene. The overal l transformation i s shown in react ion 59. CH.CN PPh ? CpMo(C0)2(N0) + NSBF4 > [CpMo(NO)(NS)(CH3CN)]BF 4 4 [CpMo(NO)(NS)-CPPh 3 ) ]BF 4 i (59) The inf rared spectrum (CHgCl 2) confirms th is formulation exh ib i t ing a n i t rosy l absorption at 1647 (s , b r ) , a th ion i t rosy l absorption at 1069 ( s ) , and an absorption at 1030 (s , br) cm - 1 charac te r i s t i c of a BF 4" anion with tetrahedral symmetry. The proton NMR (CDC13) displays resonances at 6 7.44 (m, 15H) and 5.93 (br m, 5H) which are in the r igh t range and of the correct in tens i ty to be due to the phenyl protons of triphenylphosphine and the cyclopentadienyl protons. The puzzl ing feature i s that instead of a sharp cyclopentadienyl resonance which i s usual ly found in cyclopentadienyl complexes a very broad signal is observed. No sa t is fac to ry explanation has been found for th is phenomenon. Conductivi ty measurements of a nitromethane solut ion (^10 M) of the cation are consistent with i t s being a 1:1 e lec t ro -ly te (see Table V). A s im i la r react ion occurs when a nitromethane "NSBF 4" solut ion is added to ( n 5 C 5 H 5 ) W ( C 0 ) 2 ( N 0 ) . 8 2 The infrared and lH NMR spectra are analogous to the molybdenum th ion i t rosy l ca t ion . The IR spectrum (CH 2C1 2) exh ib i ts a V ^ Q at 1630 ( s ) , a v^ s at a,n00 ( s ) , and a v B F at 0,1055 ( s , br) c m - 1 ; the 1H NMR spectrum has a mul t ip le t at 6 7.58 assignable 140 to the phenyl protons of PPh^ and the same strange broad resonance at 8 6.12. The 1 9 F NMR spectrum (CD-^ CN)! shows at s ing le t at 6 148 which i s charac te r i s t i c of BF^" . However, a sa t i s fac to ry elemental analysis has not been obtained to substantiate the formulation [(n 5-CgHg)W(N0)(NS)PPh 3l-B F 4 . Reactions of "NSBF^" with Mo(.C0)6. In hopes of i so la t i ng a [Mo(NS)2l_ 4](BF 4) 2 species analogous to the d in i t rosy l d icat ions discussed e a r l i e r in th is work, a nitromethane solut ion of "NSBF 4" i s f i l t e r e d into a c lear dichloromethane solut ion of Mo(C0)g. The solut ion turns dark purple in co lour , and a black prec ip i ta te forms. This so l i d i s dissolved in nitromethane and treated with a Lewis base, L. When L i s ace ton i t r i l e or i sobu ty ron i t r i l e the product can be prec ip i ta ted by dropwise addi t ion of CHgClg- In each case the iso la ted prdduct appears to be hydrolyzed, despite handling in a dry dini t rogen atmosphere. The Nujol mull IR spectra show bands at ^2300 (w) (CN) and o,1050 ( s , br) (NS and/or BF) , and 3300 (s) (OH) c m - 1 . I f the mull of the purple i sobu ty ron i t r i l e product is exposed to the atmosphere for two hours, i t becomes completely green in co lour ; the OH stretching band increases in i n tens i t y , while the CN band disappears. The elemental analyses are not consistent with there being four n i t r i l e s around the molybdenum centre. The carbon, n i t rogen, and hydrogen contents are low; th is taken with the IR data suggests n i t r i l e l igands are read i l y replaced by water. Further attempts to character ize these species have been abandoned due to the i r extreme moisture s e n s i t i v i t y . 141 When PPh 3 i s used as the Lewis base instead of a n i t r i l e , a dichloromethane-soluble, purple so l i d can be i so la ted . Spectral data is not inconsistent with the formulation [Mo(NS) 2 (PPh 3 ) 4 ] (BF 4 ) 2 ; [IR (CH 2 C1 2 ) : v(NS) 1105 ( s ) ; v(-BF) 1057 ( s ) ; a lso 1555 cm" 1 ; *H NMR (CDgNO-,): 6 7.28 (m)]. A conductance measurement of a nitromethane solut ion (%10 M) of th is th ion i t rosy l d icat ion confirms i t as a 2:1 e lec t ro l y te . However, the elemental analysis of C, H, and N i s not consistent with the formulation [Mo(NS) 2 (PPh 3 ) 4 ] (BF 4 ) 2 (MoN 2 S 2 C 7 2 Hg Q P 4 B 2 Fg) which requires a C:H:N ra t io of 36:30:1 while the one obtained is 12:10:1. The tendency of phosphines to react with coordinated n i t rosy l l igands has already been discussed (see react ion 55). Phosphines are such strong th iophi les that triphenylphosphine i s sometimes employed to abstract sul fur as in react ion 6 0 . 1 3 1 c s (n 5 -C 5 H 5 )Mo(C0) 2 (C 8 H 1 4 ) + PPh 3 —^ (n 5 -C 5 H 5 )Mn(C0) 2 (CS)+CgH 1 4 +SPPh 3 • (60) It i s possible that the react ion of Mo(C0)g with in s i tu "NSBF 4" produces the th ion i t rosy l analogue of the molybdenum d in i t rosy l d icat ion, but because NS + i s a strong ox id iz ing agent further react ions occur in the presence of phosphine. Use of triphenylphosphine oxide as the coordinating l igand instead of PPh^ does not appear to a l l ev ia te the problem. No sa t is fac to ry elemental analys is has been obtained for the green product formed though i t s spectral propert ies were those expected for [Mo(NS^(pPPh 3 ) 4 ] (BF 4 ) 2 \ [ IR (CH 2 C1 2 ) : 142 v(NS) <\,n20 ( s ) ; v(BF) o/|055 (s , br ) . lH NMR (CDClg): 6 7 .3] . Use of the nitrogen l igand 2,2-bipyridine produces a red so l i d which is only soluble in nitromethane or a c e t o n i t r i l e , thus, making separation from the residual "NSBF 4" d i f f i c u l t . Although N0C1 reacts with a var ie ty of Lewis acids to form N0 + , (SNC1)3 reacts with Lewis acids to form numerous p r o d u c t s . 1 3 2 Further, chlor ide abstract ion from P^N^Clg does not form PN + c leanly though react ion with s i l v e r sa l ts resu l ts in the prec ip i ta t ion of s i l v e r c h l o r i d e . 1 3 3 Therefore, i t appears that the react ion of (SNC1) 3 with AgBF^ y ie lds a complex mixture which does not provide a clean source of NS + . Moreover, i f th ion i t rosy l species are produced they may be prone to form th io rather than th ion i t rosy l complexes. It should be noted that the pr inc ipa l product of the attempted th ion i t rosy la t ion of Na[(n 5 -C 5 Hg)Cr(C0) 3 ] with N 3 S 3 C 1 3 or "NSBF 4" i s not the th ion i t rosy l (n 5-CgHg)Cr(C0) 2NS but the bridging su l fur complex [ ( n ^ C j j H g K K C O ^ ^ S . Thus, th ion i t rosy l organometall ic complexes remain a r a r i t y . 143 C. Reaction of Ace ton i t r i l e with NOPFg. Recently Herbe rho ld 1 3 4 has reported that a binary n i t rosy l d icat ion [Fe 2(N0)g](PFg) 2 can be formed from the reaction of NOPFg with iron powder in nitromethane media. I t would seem that both the solvent and the n i t r o -sy la t ing agent are c r i t i c a l in th i s react ion since in ace ton i t r i l e NOBF^ with any of the metals M n , F e , C o , N i , Z n , C u , 1 3 5 or P d 1 3 5 forms the d ipos i t i ve 2+ metal ace ton i t r i l e species [M(CH3CN)n] ( B F 4 ) 2 ; and n i t rosy l metal chlor ides are produced from the act ion of N0C1 on cer ta in metals A l , G a , I n , P t , A u . 1 3 7 In an attempt to form simple, binary n i t rosy l complexes of the group yiB elements, tungsten beads were treated with N0C1 in THF or dichloromethane or with NOPFg in nitromethane; no n i t rosy l species formed. However, when tungsten beads and NOPFg were s t i r red in ace ton i t r i l e for one day the c lear so lut ion over the tungsten acquired a pinkish t i n t and bands began to appear in the 1850 - 1650 cm" 1 region of the IR spectrum. After three days the solut ion over the tungsten beads was deep red purple in colour and the V ^ Q IR band of NOPFg had disappeared. The purple solut ion was decanted from the tungsten; dichloromethane was added dropwise; and a purple brown so l i d was i so la ted . Conventional wet analys is methods 1 2 0 determined that the so l i d contained no tungsten. Subsequently, i t was found that the same react ion could be effected by using chromium powder or with no metal present at a l l would proceed s lowly , i n i t i a t i n g af ter seven days. However, the purple colour was only produced i f the NOPFg/CH^CN solut ion were in a dry nitrogen atmosphere. I f ace ton i t r i l e was replaced by i sobu t y ron i t r i l e , no react ion with N0PF f i was evidenced even in the presence of tungsten. 144 The purple brown so l i d i s d i f f i c u l t to character ize as i t i s extremely hygroscopic. It i s soluble in polar and donating solvents: butanol, acetone, water, a c e t o n i t r i l e , nitromethane, tetrahydrofuran, methanol, and e thy l -acetate. It i s insoluble in a l l hydrocarbon solvents and in d ich loro-methane and diethyl ether,-Aqueous solut ions have a pH of 2 .1 . The physical and spectral propert ies of th is purple brown so l i d are reported below. IR (Nujol mu l l ) : 3328 (s , b r ) , 1751 (m), 1690 (m), 1634 - 1575 (m, vb r ) , 1267 (m, br),1203 (m, b r ) , 1137 (m, b r ) , 1039 (m, vb r ) , 844 (s , b r ) , 743 (m) cm" 1 . (Florolube mul l : 3320 (s , b r ) , 2947 (w), 1755 (m), 1696 ( s ) , 1627 (m, b r ) , 1526 (s , b r ) , 1425 (m), 1377 (m), 842 (s , br) cm" 1 . NMR (CD 3 N0 2 ) : *H: 6 12.8 - 11.1 (br, IH), 9.0 - 8.0 (br, IH), 2.08 - 2.05 (m, 8H); 1 9 F : 6 71.5 (d, PFg, 1 J i 9 p _ 3 i p = 696 Hz). Mass spectrum (common peaks of three) : 117 (C 2 HN 3 PF, C H 4 0 2 P F 2 ) ; 107 ( P F 4 ) ; 104 (0PF 3 ) ; 101 (CH 4 -0 P F 2 ) ; 88 ( P F 3 ) ; 85 (0PF 2 ) ; 59 (C 2 N0H 5 ) ; 51 (CHF 2 ) ; 45 ( C ^ O ) ; 43 (CH 3 N 2 ) ; 41 (C 3Hg). Elemental analysis (average of four ) : C, 21.7; H, 2.74; N, 16.4 (C:H:N = 1.54/2.34/1.00). When the polymerization of THF by NOPFg was studied by Eckstein and D r e y f u s s , 1 0 0 they noted that lower y ie lds of polymeric THF were obtained when CH3CN was the solvent , suggesting some side react ion involv ing CH3CN. Ace ton i t r i l e has been known to par t ic ipate in reactions with nitrosonium and nitronium s a l t s : 145 NOPFfi 1 3 8 H90 8 R X + C H 3 C N or NOgBF^ias [ R _ N ^ C C H 3 ^ RNHCCHg (61) N O p B F , H ? 0 I102 RCH = CHR' C H C N > - = - * RCH-CHR' (62) 3 NHCOCH3 RCH = CHR N 0 B F 4 141 C H 3 C N . 5 - I 5 to 0°C v . © NOH BF, CH, HN R e d - a l 3 7 aqueous CH, (63) It is known that commercial ace ton i t r i l e often contains traces of a c r y l o n i t r i l e which are d i f f i c u l t to remove . 1 4 2 I f ac ry lon i t r i 1e reacts with NOPFg as an o l e f i n , a react ion such as 62 or 63 might occur. Indeed,ad-d i t ion of a c r y l o n i t r i l e to an ace ton i t r i l e solut ion of NOPFg causes i n i t i a l colourat ion to appear in one day. Since th is i s about the same rate of colour formation observed when tungsten i s present, i t i s possible that the metal catalyzes the decomposition of ace ton i t r i l e to a c r y l o n i t r i l e . 146 This in t r igu ing purple s o l i d , although apparently a PFg" sa l t of some sort of oligomerized a c e t o n i t r i l e , i s de f i n i t e l y not the desired binary metal n i t r o s y l ; therefore, further attempts to ascertain i t s ident i ty have been abandoned. It i s evident, however, since NOPFg reacts with tetrahydrofu a c e t o n i t r i l e , and methanol, that nitromethane is the only solvent in which NOPFg can dissolve and maintain i t s i n t eg r i t y ; i t should be the solvent of choice in reactions involv ing nitrosonium s a l t s . 2+ This study has shown the f e a s i b i l i t y of preparing the Mo(N0)2 uni t both with and without coordinated solvent molecules and of reducing i t to a monocationic Mo centre. 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SPECTRAL APPENDIX [ C p W ( N O ) l , ( p P h 3 ) 2 ] B F 4 158 I R N U J O L M U L L 4000 3600 3200 2800 2400 FREQUENCY (CM-') 2000 1800 1600 1400 1200 1000 800 600 H N M R M e N 0 2 [ C p W ( N O ) l ( p P h 3 ) 2 ] B F 4 159 I R C H 2 C I 2 4000 3600 3200 2800 2400 FREQUENCY (CM"') 2000 1800 1600 1400 1200 1000 800 600 3.5 4.0 9 10 n 12 13 1- I t - A 151 1 J 9 ' H d e c o u p l e d F N M R M e N 0 2 P N M R 160 C p W ( N O ) l ( C I ) P ( O P h ) 3 I R N U J O L M U L L I FREQUENCY (CM-1) j 4000 3600 3200 2800 2400 2000 1800 1600 1400 1200 1000 800 600 I FREQUENCY (CM"') C p W ( N O ) l ( C I ) P ( O P h ) 3 1 H N M R 161 1 6 2 [Cp W(NO) I HJ IR NUJOL MULL 4000 3600 3200 2800 2400 100 FREQUENCY ( C M 2000 1800 1600 1400 1200 1000 800 i I : 1 : | l r r i 1 1 -TTTil • i1 •• . : ' M l i 1 ' 1 • : | : ; 1 1 . 1 j i 1 ! !i!i i: , 11 i 11 i i Ml' i > ! ; . . | . . , i i 1 : > : 1 ! 1 1 i j i i I j i i i : ' I.-' ! : | , i "I . 1 ! I ; i I i i j i I 1 -Tj-...| ,. ' i • f\nt ] 1 • i i i i i I : : i : ' 1 i • W - N \i \ \  i i I i ! i \ l> i ! , ; . MM •1 ! ^ 1 1 1 i • [ 1 i 1 i i l, ' ' l1 •: i \ J • i • • \ . 1 ! I ! i i 1!1 1 ] [' i n I I 1 ; *= - r — — ! ; | M i V '1 1 •' i Ill i 1 ' ; 1 ] ' f \ : 1 ' 1 , ' . ! / i • i ' i' ' ' — ; — : i i 1 1:11 f ! i \ M ' I ' 1 • j : i I I ' 1 • ..•1 . 1 1 I j • .1 1 ! 1 i 1' I r •. i . 1 i j 1 i ; ! 1 ; i 1 :i i 1 ' 1 . 1 J 1 1 \ : ! ! j : • i i • i .! n 1 I 1 i — 1 I • i < :i : i •_. i | j : : ! j i I ! — ! — ! i • ! ; I , 1 - | | : , I I I ! ! ; i i 1 , ! I 1 i i ; 90 80 —70 t 5 0 § 4 0 < H 3 0 20 10 0 z o 3.5 4 .0 5 (MICRONS) 6 9 10 11 12 13 14 16 • R CH 2CI 2 4000 3600 3200 2800 100 I 90 80 —70 t 5 0 s z40 < K 3 0 20 10 0 FREQUENCY (CM-1) 2400 2000 1800 1600 1400 1200 1000 800 600 3.5 4 .0 1 1 I ' 1 : I I ' 1 : 1 -U r 1 ' J - " 1 • ! t 1 • • ! I . I i i i l l / 1 n i: M I M 1' 1' >v^I i • /TV 1 \ I 1 ! - iii i l l, • Ml / u \ ~\\ / \ 1 1 / / V I F ^  I | \ | III ! . 1 1 1 ! V i j ! j 1 i 11 ' I ' • i \ \ \ \ 1 — X •— i ! u i 1 i nil I I I / 1 . . 1 1 I i in ' i i 1 : I I ' _ _ / ! 1 • — i . i 1 I I ! I'M Ml! ' M j 1 . . . . . . I 1 > • I • j : ! | i ill! ! ! ! ; 1 • ; I I I ' - ; — - r • ! i I 1 1 i 1 ill! Mi: i M i MM 111 • ! , — I . . -' — ! | • • 1 1 1 | j i 1 1 i I i 1 1 ' i 1 1 ; i . i 1 • 111 1 1 i i 1 ! 1 | i 1 11 Mil I i i ! ! i i : 1. . , , ' 1 : ! 1 ' ' } ! _ 1 I - 1 1 i i ! 1 j j III MM > I j Mii ! ! Mil • ' . : i 1 ' • ; ! j : 1 1 ! I 1 ! I Mi ill ; ! — . 1 • l . I 1 , 1 I -l- ! | i l MM 1 ! ; Mil i | II • i , i • - - - - - i l . . . . ! i ' < i 1 j ! i 1 MM | j Ml — i ! 1 1 i 1 1 i 1! T MM MM M ; 1 i • i i i , 1 | 1 ' i 1 1 j I J i I II MM i'li MM . • • , ! i 1' ) ' ! 1 ; i i 1 II | MM ill! M i : ; : . • - _4 J "IT"" j -----M i ! • 1 • 1 ! i 1 1 ! 1 1 liil ill: MM —*— • >' • 5 (MICRONS) 6 9 10 11 12 13 14 16 Cp W(NO) I H| J 2 H NMR 163 C 6D 6 164 C p W ( N O j l H P ( O P h ) 3 I R N U J O L M U L L C p W ( N O ) I H P ( O P h ) 3 P N M R C 6D6 166 o « f r e s o n a n c e 1 H d e c o u p l e d 167 C p W ( N O j l H P ( O M e ) I R N U J O L M U L L 3 1 P N M R ' H d e c o u p l e d C p W f N O j I H P P h 170 C p W ( N O ) I H P P h , IR N U J O L M U L L 4000 3600 3200 2800 2400 FREQUENCY (CM-1) 2000 1800 1600 1400 1200 1000 800 600 3.5 4 .0 5 (MICRONS) 9 10 11 12 13 M 16 I R C H 2 C I 2 9 10 11 12 13 14 16 C P W ( N O ) , H P P h 3 1 „ N M R 171 C D C I 3 172 [ c p W(NO)HJ I R NUJOL MULL 4000 100 3600 3200 2800 2400 90 80 - 7 0 J,60 30 20 10 0 FREQUENCY (CM') 2000 1800 1600 1400 1200 1000 1 ! ! ! ! ! 1 i ! i ! i ! i Iii! 1 | mi MM Mil Ml ! ' 1 1 ii i j | j i : ; , . . : 1 • M i 1 1 ! ! i i • i 1 ! 1 i ! i Mil 1 1 llii M M Mil MM I ! ' ', 1 ! 1 i i 1 , l i 1 ; j i i 1 i i 1 i i 1 1 i mi i 1 \y~ i i i ! 1 ' ; "l i i MM M • 1 I ; i 1 i j i i 1 1 1 l I mi i l l. i1 •1 1 ' ' ! M.i .i MM n i • 1 • 1 i i | ! i s 1 i i, J<ii yf\ I ! 11 111 i : : , ; ; ; •Vi / , i i ! ! 1 l • i I j. i i [-i ' M I I i i I I I : , , . 1 I i ! 1 i 1 ! 1 ! i / ! i i / I I ; ; •; i III MM'M i, J... • . i I | : 1 : M • ! 1 i j 1 i ! i i i 1 nil MM II! MM i: 1 1 I I : : M l i ; i i i i ! ! 1 1 i mi MM 1 i i ill! Mi' Mi; : 7 j ; : i;' i • • I i 1 j i i i i i ! ! i I nn !! 1! i I i Ml' Mi (i M ' I' • 1 • i 1 I ! 1 1 ' 1 1 ; \ i i I i i Mil 1 i 1 ! 1 i i M ' 1 , ; • 1 > I hi ' : 1 I I . . . . . 1 " \ i i i i i ! i ! i nn i j | nil MM 1 i M i 1 M i l i i i, 11 . ! - \ ! 1 i 1 : i ; ! Mi I | I 1  • i f 1 ' , ! | 1 ; 1 i 1 MM ! ' 1 I'M ; i ; ' 1 : • : | M i i ; : i i MM 1 ; 1 1 n i • ; ; M • I 1 ; ! MM ! ! I Ml; : I 1 I • ; | i ; • : ! IM, i ' 1 Ml: . i : I / 1 •: M ' , i 1 , MM ! . MM I • 1 1 i i ' ; • 1 M MM 1 1 1 • ' i i i | A l l , | i ! 1 , 1 1 Mi M 1 ; 800 •c m o z o 3.5 4.0 5 (MICRONS) 10 11 12 13 14 16 R CH2CI2 3600 3200 2800 2400 FREQUENCY (CM"') 2000 1800 1600 600 O H JJ C z o 173 174 c i s C p W ( N O ) H 2 P ( O P h ) ^ IR N U J O L M U L L 3200 2800 FREQUENCY (CM"') 2000 1800 1600 800 600 10 11 12 13 14 16 IR CH2CI2 10 11 12 13 14 16 175 C p W ( N O ) H 2 P ( O P h ) 3 1 P N M R 176 6 U6 c i s 1 5 1 t r a n s 1 3 7 c o u p l e d 1 H d e c o u p l e d 177 t r a n s i c P W ( N O ) H 2 P ( O P h ) , I R N U J O L M U L L I FREQUENCY (CM"1) 4000 3600 3200 2800 2400 2000 1800 1600 1400 1200 1000 800 100 . . . . . . . . . I R C H 2 C I 2 FREQUENCY (CM-') 2000 1800 1600 10 11 12 13 14 16 C p W ( N O ) H 2 P ( O P h ) 1 H N M R M o ( N O ) 2 ( P F 6 ) 2 179 1 4 4 P N M R M e C N F N M R M e C N M o (NO) ( P F J 2 6 ' 2 j 7 2 . 0 81.7 M o ( N O ) 2 ( 0 2 P F 2 ) 2 M o ( N O ) 2 ( 0 2 P F 2 ) 2 181 IR N U J O L M U L L - 1 7.9 P N M R M e C N [ M o ( N O ) 2 ( M e N 0 2 ) 4 ] ( P F 6 ) 2 182 * * • • • *" f " r i ••*- • " rr- -r !•• i iiyriniiii^ vp fr-p m m i ^ i i.u*\nf H N M R M e C N [ M o ( N O ) 2 ( M e N 0 2 ) 4 ] ( P F 6 ) 2 3 1 P N M R M e C N 0 1 9 F N M R 7 2 . [ M o ( N O ) 2 ( b i p y ) 2 ] ( P F 6 ) 2 1 H N M R M e C N [ M o ( N O ) 2 ( b i p y ) 2 ] ( p F 6 ) 2 185 - 1 4 4 3 1 P N M R M e C N 186 [ M o ( N O ) 2 ( b i p y ) 2 ] ( P F 6 ) 2 IR C H 3 N 0 2 I FREQUENCY (CM-') , 0 T ° , 3 6 ° ° , . 3 2 0 ° . 2 8 0 0 2 4 0 0 2 0 0 0 '800 ,600 ,400 1200 1000 600 3.5 4.0 J 71.3 19 F N M R M e C N [ M o ( N O ) 2 ( b i p y ) 2 ] ( B F ) 2 • 3 / 4 C H , , C I 2 187 / 188 [ M o ( N O ) 2 ( b i p y ) 2 ] ( B F ) 2 - 3 / 4 C H 2 C , 2 189 [ M O ( N O ) 2 ( d i p h o s ) 2 ] ( p F 6 ) : •R C H 2 C I 2 11 12 13 14 16 1 H N M R M e C N [ M o ( N O ) 2 ( d i p h o s ) 2 ] ( p F 6 ) 2 190 3 1 P N M R 3 8 . 6 1 4 4 M e C N 71.0 19 F N M R 191 1 H N M R M e C N 192 [ M o ( N O ) 2 ( O P P h 3 ) 2 ( M e C N ) 2 ] ( B F ^ IR N U J O L M U L L 4000 100 I 3600 3200 2400 FREQUENCY (CM-1) 2000 1800 1600 1400 1200 10 11 12 13 14 16 -t r-H N M R C D C l 3 4 [ M o ( N O ) 2 ( O P P h 3 ) 2 ( M e C N ) 2 ] ( B F ^ 3 1 p N M R M e C N 194 [ M o ( N O ) 2 ( O P P h 3 ) 2 ( M e C N ) 2 ] ( B F ^ A 1 4 7 1 9 F N M R C D C I - , 195 [ M o ( N O ) ( b i p y ) J ( P F J J « 6 2 I R N U J O L M U L L 3600 2400 FREQUENCY (CM"') 2000 1800 1600 1400 11 12 13 14 16 H N M R M e C N [ M o ( N O ) 2 ( b i p y ) J 2 ( P F 6 J 196 19 F N M R [ M o ( N O ) 2 ( b i p y ) ] 2 ( P F 6 ) 6 ' 2 197 M e C N 71 .2 71.5 [ M o ( N O ) 2 ( p h e n " ) ] 2 ( P F 6 ) 2 C D 2 C I 2 [ M o ( N O ) 2 ( p h e n ' ) ] 2 ( P F 6 ) 2 198 H N M R M e N O 2 [ M o ( N O ) 2 ( p h e n " ) ] 2 ( P F 6 ) 2 199 I R C H 2 C I 2 H N M R C D 2 C I 2 3 1 P N M R [ M o ( N O ) 2 ( p h e n ' ) ] 2 ( P F ), 6 ' 2 M e N C - 2 - 1 4 7 2 9 . 8 l M o ( O P P h 3 ) 6 ] P P • 1 4 4 M e C N [ M o ( O P P V E ] P F 201 I R N U J O L M U L L [ M o ( O P P h 3 ) 6 ] P F 6 202 • R CH2CI2 800 600 9 10 11 12 13 14 16 7 2 . 7 19 F N M R M e N O 2 [ M o ( p h e n - J 3 ] PFg H N M R M e N O 2 I .1 i. .1 i 19 F N M R 7 3 . 0 I I, [ C p M o ( N O ) ( N S ) p p h 1 B F 3 J 4 IR N U J O L M U L L I 4000 3600 3200 2800 2400 204 FREQUENCY (CM-') 2000 1800 1600 1400 1200 1000 800 I R C H 2 C I 2 H N M R C D C I 3 

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