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J. CHEM. SOC. DALTON TRANS. 1986 743Formation of N-C Bonds via Alkylation of Transition Metal Nitrosyls. Reactionof Ruthenium and Other Transition Metal Nitrosyls with Benzyl BromideJon A. McCleverty *Department of Chemistry, University of Birmingham, P.O. Box 363, Birmingham B 15 2TTClive W. Ninnes and lwona WoiochowiczDepartment of Chemistry, University of Sheffield, Sheffield S3 7HF[Ru(NO),(PPh,),] reacts with benzyl bromide in refluxing toluene under CO to give[RuBr(CO)(NO)(PPh,),], [RuBr,(CO),(PPh,),], PhCH=NOH, PhCN, PhCONH,, PhCHO, andPhCH,OH. In the absence of CO, [Ru(NO),(PPh,),] reacts with benzyl bromide to give[RuBr,( NCPh),( PPh,),], [RuBr,( NO) (PPh,),], PhCN, PhCONH,, (PhCH,),, and PhCHO, but inamounts smaller than those obtained under CO.In the absence of a metal, NO gas reacts withbenzyl bromide in refluxing toluene to give PhCH,NO, (major product, 45%) and small amounts ofPhCN, PhCHO, and PhCH,OH. Reaction of [Ru(NO),(PPh,),] with Ph'CH,CI and other alkylb r o m i d es, a n d of [ R u ( N 0) , ( P h, P C H ,C H , P P h ,) 3 , [ R u ( N 0 ) 1{ P ( 0 P h ) ,},I , [ C o ( N 0) { P ( 0 Et ) ,},I ,[Rh(NO) (PPh,),], and [RhCI,(NO)(PPh,),] with PhCH,Br are briefly discussed.The reactivity of metal-co-ordinated NO has been reviewed,'and it is apparent that there are relatively few homogeneousreactions which lead to the formation of N-C bonds. A selectivelist of these, indicating general reaction types, is given in Table 1.Related to these reactions is the heterogeneously catalysedformation of acrolein oxime (CH,=CHCH=NOH) and acrylo-nitrile (CH,=CHCN) from propene and NO over nickeloxide., Most of the processes indicated in Table 1 involve ionicnitrosyl complexes which function in strongly polar reactionmedia. Only the reactions of [CoBr(CO),(.NO)] - with benzylbromide3 and of [Co(q-C,H,)(NO)]- with R14 involve thedirect alkylation, via an alkyl halide, of co-ordinated NO.However, NO undergoes 'insertion' reactions with do, d', andd 1 transition metal alkyls affording species containing RNOor [ON(R)NO]- (R = e.g.Me or Pr"), and some of thesereactions occur in non-polar solvent^.^,^ It has also beenobserved recently that thermolysis of [Ru(q-C,Me,)(NO)-(CH,R'),] (R' = H or Me) in benzene at 150°C in the pre-sence of PMe, gave [Ru(q-C,Me,)(CN)(PMe,),] (whereR' = H) and [Ru(~-C,M~,)(PM~,),(ON=CHM~)].~While looking for potential routes to the formation oforganonitrogen compounds by the direct alkylation of readilyprepared transition metal nitrosyl complexes in non-polarsolvents we were intrigued by the simplicity of the reactionbetween [CoBr(CO),(NO)] - and PhCH,Br3 in dimethyl-formamide.The organic reaction products were mainlyPhCH=NOH and PhCH,CO,H, and the mechanism offormation of the oxime was thought to involve addition ofPhCH,Br to NO, perhaps via oxidative addition of benzylbromide to the Co species followed by group migration, givingPhCH,NO which then tautomerised to PhCH=NOH. Adisadvantage of this reaction was the parallel, but notunexpected, formation of the carbonylation product PhCH,-C0,H produced, presumably, via CO 'insertion' into aCoCH,Ph bond.It occurred to us that such an undesirable side-reaction could be eliminated by using non-carbonyl-containingmetal complexes, e.g. the readily available nitrosyl triphenyl-phosphine complexes of ruthenium or rhodium, [Ru(NO),-(PPh3),] or [Rh(NO)(PPh,),]. These nitrosyls are particularlyeasy to prepare and are soluble in hydrocarbon solvents.'We reasoned that benzylation of co-ordinated NO shouldoccur readily to form the easily identified benzyl oxime and,indeed, preliminary experiments indicated that addition ofPhCH,Br to [Ru(NO),(PPh,),] did cause loss of theNO groups. However, isolation and characterisation of theproducts proved initially difficult, but introduction of CO intoTable 1.Formation of N-C bonds uiu transition metal nitrosylsReactants" Intermediate or stable product Organic product:Fe(CN),(N0)l2-, acetone, OH- [ Fe(CN), { N(=O)CH2COMe}]2- MeCOCH=NOH:R~Cl(bipy),(NO)]~+, PhNMe, [RuCl(bipy), { N(=O)C,H4NMe2-p)]2 + -IRu(N0)(NH,),l3 +, 'CH,CMe,(OH) [Ru(NH,),{ N(=O)CH,CMe2(OH))]2 + -:CoBr(CO),(NO)] -, PhCH,Br - PhCH=NOH, PhCH,CO,H I { M(q-C 5 H 5)(NO)}nl7 LiBu' { M-NHBu'-M}, etc.' -:WMe,],NO [WMe,{ON(Me)N=O},] -0[ { Co(q-C,H,)(NO)} ,I, 2-norbornene (+{;:yJ) HON HoNDa 2-Norbornene = bicyclo[2.2.l]hept-2-ene, bipy = 2,2'-bipyridyl. Cluster species of Co and Ni containing p-NHBu' and p3-NBu'744the reaction system permitted us not only to identify the metal-containing species formed at various stages of the reaction, butalso to recover smoothly the organic products.A preliminaryaccount of this work has been given,'V8 and in this paper wedescribe in full our studies of reactions between benzyl bromideand various nitrosyl ruthenium complexes.Results1. Reactions under CO Gas.-The complex [Ru(NO),-(PPh,),] reacted smoothly with PhCH,Br under CO in tolueneat various temperatures, giving [RuBr(CO)(NO)(PPh,),] and[RuBr,(CO),(PPh,),], the former appearing in the early stagesof the reaction and being converted into the latter as thereaction proceeded (Table 2). These complexes were readilyidentified by their i.r. spectra, and by isolation followed byelemental analyses of the solids obtained.The organic products of the reaction were identified, by acombination of gas-liquid chromatography and mass spectro-metric techniques, as mainly PhCH=NOH, PhCN, andPhCONH, together with small amounts of PhCHO andPhCH,OH as well as, depending on conditions, unreactedPhCH,Br.From a study of the relative concentrations of the organiccompounds formed in the reaction at 90 "C over 30 h (Table 2),we observed that the concentration of PhCH,Br decreasedand PhCH=NOH, PhCN, PhCHO, and PhCH,OH quicklyappeared.The concentrations of these new products graduallyincreased at the expense of the benzyl bromide, and it was onlyafter 30 h at 90 "C that significant quantities of the PhCONH,appeared. These results indicated that PhCONH, is not aprimary product of the reaction, and must be produced fromeither PhCH=NOH or PhCN, probably the latter.We alsonoted that the amount of PhCH,OH steadily increased duringTable 2. Reaction of [Ru(NO),(PPh,),] with PhCH,Br (1 :2) at 90 "Cin toluene: inorganic and organic products as a variable with timeTime (h)rCompound 1 2 4[Ru(NO) z (PPh3) 2 1 a 4 4 1[RuBr(CO)(NO)(PPh,),] a 1 2 2[RuBr,(CO),(PPh,),]" 0 1 1PhCH,Br 94.8 79.7 64.5PhCH=NOH 1.4 14.5 28.4PhCN 2.8 4.2 3.9PhCHO 0.7 1.1 1.4PhCH,OH 0.3 0.5 1.6Relative ratios, established by i.r. spectralpercentages, established by V.P.C. methods.PhCONH,b 0 0 0I6 23 301 0 01.5 0 04 1 153.8 39.4 39.436.2 37.0 35.96.3 10.0 9.50 0 1.71.5 5.8 5.72.1 7.8 8.3methods. RelativeJ.CHEM. SOC. DALTON TRANS. 1986the reaction, and since great care was taken to excludemoisture, both from the solvent and the CO gas, we concludethat the production of the alcohol occurs via hydrolysis ofPhCH,Br. The water could originate from the dehydration ofPhCH=NOH to PhCN, perhaps in a metal-assisted process. At90 "C this dehydration must be a relatively slow and inefficientprocess, since the concentration of PhCH=NOH is significantlygreater than PhCN. Clearly, after some considerable time and asignificant decrease in the amount of PhCH,Br, rehydrolysis ofPhCN to PhCONH, must become competitive with alcoholformation.By varying the temperature and time of the reaction (Table 3),we established that the most efficient conversion of the NOin the dinitrosyl complexes into organonitrogen derivativesoccurred at 110 "C (refluxing toluene) over 48 h.Indeed, underthese conditions, the major organonitrogen product wasPhCONH,, and production of PhCH,OH was totallysuppressed.For comparison purposes, we investigated the reactionof PhCH,Br with NO gas in toluene (Table 4). At 80"C,conversion to other organic products was very inefficient, butwe identified PhCN, PhCHO, PhCH,OH, and two species notfound in the reaction mediated by [Ru(NO),(PPh,),], namely(PhCH,), and PhCH,NO,. At 110 "C over 48 h, however,reaction with NO led to conversion of more than half of thebenzyl bromide into a significant amount of PhCH,NO, aswell as to PhCH,OH, PhCHO, and PhCN. The absence ofnitrobenzyl would seem to suggest that in reactions involving[Ru(NO),(PPh,),], dissociation of NO from the complex priorto reaction with PhCH,Br does not occur or, in other words,that alkylation of NO occurs while the nitrosyl group is co-ordinated to the metal.This is consistent with the observationthat [Ru(NO),(PPh,),] does not react with CO in refluxingtoluene, the complex being recovered unchanged after 25 h. Wealso observed that there was no significant reaction betweenNO and toluene at 110 "C.Because mononitrosyl species are formed during the reactionbetween [Ru(NO),(PPh,), J and PhCH,Br, we investigated thereactions of several known mononitrosyl halide complexes ofruthenium with PhCH,Br (Table 5). [RuBr(CO)(NO)(PPh,),]was identified as the mononitrosyl complex formed in reactionsunder CO, but treatment of the readily prepared [RuCl(CO)-(NO)(PPh,),] with PhCH,Br in refluxing benzene undernitrogen gave only a very small conversion to organic products,possibly reflecting the relatively unreactive nature of thisspecies.However, reaction of the co-ordinatively unsaturated[RuCl(NO)(PPh,),] with benzyl bromide in benzene undernitrogen at room temperature, when oxidative addition,presumably to give [RuBrC1(CH,Ph)(N0)(PPh3),], is knownto O C C U ~ , ~ followed by treatment of the mixture with CO underrefluxing conditions did afford PhCHNOH, PhCN, PhCHO,and traces of PhCONH,, PhCH,OH, and (PhCH,),. Theseobservations imply that oxidative addition of PhCH,Br to theruthenium may occur at an early stage of these overall reactions,Table 3.Reaction of [Ru(NO),(PPh,),] with PhCH,Br (1 : 2) in toluene: variation of organic products (relative percentages) with time andtemperatureTemp. ("C) 50 65 80 110 65 80 110" 90b 90Time (h) 90 20 20 20 48 48 48 20 23PhCH,Br 63.0 96.0 70.9 19.1 59.6 23.9 0 39.1 39.4PhCH=NOH 0 0 22.4 4.1 4.1 42.3 9.0 50.2 37.0PhCN 1.5 0.4 4.4 54.0 12.8 10.8 17.2 5.0 10.0PhCONH, 0 trace trace 9.2 6.2 19.4 77.0 trace 0PhCHO 11.2 0.8 1.7 7.2 7.3 2.2 5.4 4.0 5.8PhCH,OH 11.3 0.9 1 .o 5.2 9.4 0.6 0 1 .o 7.8" 1 : 1 Molar ratio. In the presence of MgSO,J. CHEM. SOC. DALTON TRANS. 1986 745and is followed by a migration of the benzyl group to the co-ordinated NO. Such an oxidative addition process is unlikely tooccur with PhCH,Br and [RuCl,(NO)(PPh,),] and, indeed,under CO in refluxing toluene, only very small amounts oforganic products are formed from these reactants.As both PhCN and PhCH=NOH are produced rapidly in thetreatment of [Ru(NO),(PPh,),] with PhCH,Br under CO, weinvestigated their reactions with nitrosyl complexes whichmay be formed as intermediates during the overall reaction.Benzonitrile does not react with [RuCl(CO)(NO)(PPh,),] evenin refluxing toluene, but may, judging by colour changes, forma weak adduct with [RuCl(NO)(PPh,),], viz.[RuCl(NO)-(NCPh)(PPh,),]. However, when treated with CO this adductis rapidly converted to [RuC1(C0)(NO)(PPh3),]. There wassimilarly no significant reaction between [RuCl(CO)(NO)-(PPh,),] and PhCH=NOH, but the results obtained using[RuCl(NO)(PPh,),] are summarised in Table 6.WhenPhCH=NOH is allowed to react with the chloro-nitrosyl it ispresumed that an adduct is formed but on passage of CO someof this is removed before dehydration can occur. This couldexplain the recovery of nearly 27% of the unreacted oxime whenthe reaction mixture is refluxed under CO. However, it is clearthat dehydration of the oxime to the nitrile is significantlyassisted by [RuCl(NO)(PPh,),], as judged from the resultsobtained in the absence of CO. It may also be noted thatbenzaldehyde can be formed from either the oxime or the nitrileunder these conditions.2. Reactions in the Absence of C0.-Our early studies ofthe reaction between [Ru(NO),(PPh,),] and PhCH,Br werefrustrated by difficulties in product purification and character-isation, although we did establish that PhCONH, could beformed when the reagents were refluxed in toluene undernitrogen.Once we understood the nature of the productsformed under CO however, it was relatively easy to~~ ~ ~ ~~Table 4. Percentage yields for the products of the reaction of PhCH,Brwith NO in tolueneCompound 80 T / 1 9 h 110 "C/48 hPhCH,Br 91.5 40.0PhC H=N OH - -PhCN 0.4 0.4PhCHO 1.8 3.5PhCH,OH 2.4 9.2PhCH,NO, 1.8 45.1PhCONH, - -(PhCH,), 0.1 -reinvestigate those reactions involving less reactive gases, e.g.C2H4 and N,. We chose to use ethylene partly because of thepossibility of alkene insertion into M-C bonds which might beconcomitant with 'NO insertion' but in the event, this did nothappen.The results of our study are summarised in Table 7.In these reactions, which give results broadly similar to eachother, it was clear that there was only a ca. 30% yield of 'free'organic product, taking into account that in the reaction underN,, an excess of PhCH,Br was used. However, the inorganicproducts were shown to be [RuBr,(NCPh),(PPh,),] and[RuBr,(NO)(PPh,), 3, which accounted for the overall con-sumption of benzyl bromide. We also noted that dibenzyl wasformed in these three reactions, a species conspicuously absentin those processes carried out under CO. Also PhCH=NOH andPhCH,OH were absent, and the relative yields of PhCHO werelow. It is clear, however, that when CO is present, the organicproducts of the reaction are readily released from their Rucomplexes.3.Reactions with Other Organic Halides.-Benzyl chloridereacted with [Ru(NO),(PPh,), J under CO in refluxing toluenebut much less efficiently than its bromo analogue, theorganic products being PhCN (3.0%), PhCH=NOH (7.0%), andunreacted PhCH,Cl (9.0%). The inorganic products, identifiedspectroscopically, were unreacted starting material, [RuCl-(CO)(NO)(PPh,),],and[RuC12(CO),(PPh3)2]. PhCH,CH,Br,o-C,H4(CH,Br),, and (CH,),CHBr also reacted with[Ru(NO),(PPh,),], as evidenced by denitrosylation, but onlyextremely low yields of new organic products were formed,which were not identified. When [Ru(NO),(PPh,),] wasrefluxed for 17 and 26 h in toluene under CO with PhMeCHBr,which cannot form an oxime or a nitrile, the organohalide wasrecovered virtually qualitatively, although traces of PhMe-CHOH were detected.4.Reactions with Other Ruthenium Phosphine and PhosphiteComplexes.-[ R u(NO),(dppe)] (dppe = P h, PCH ,CH , PPh,)and [Ru(NO),{ P(OPh),),] both reacted with benzyl bromidein refluxing toluene under CO, but not as effectively as[Ru(NO),(PPh,),] (Table 8). In general, the same organicproducts were identified, although with the triphenyl phosphitecomplex, PhCH,NO, was also observed.Reaction of .the hydrido-acetate [RuH(O,CMe)(PPh,),]with benzyl bromide in refluxing toluene under NO (Table 8)also afforded organic products whose nature and distributionwere strongly reminiscent of the reaction between free NO andbenzyl bromide in refluxing toluene alone (Table 4).Table 5.Reactions of ruthenium nitrosyl halides with benzylOrganicproductsPhCH,BrPhCH=NOHPhCNPhCONH,PhCHOPhCH20HPhCH,NO,(PhCH,),[RuCl(CO)(NO)(PPh,),], N,, benzene aA I \80 OC/l h 80 "C/17 h85.0 75.01 .o 0.57.0 10.00.5 0.5- -- -- -- -Inorganic unreacted s.rn.c.d +products trace [RuX,(CO),(PPh3),]bromide[RuCl(NO)(PPh,),], N,, benzeneb(10 min; then reflux + CO, 17 h)64.110.38.0trace14.2tracetrace-[RuCI,(NO)(PPh,),], CO, toluene'(110 "C/17 h)96.41 .o1.4----unreacted s.m.c.d +trace [RuX,(CO),(PPh,),] 'Metal complex: PhCH,Br ratio 1 : 2.complex. X = C1 and/or Br.Metal complex: PhCH,Br ratio 1 : 1 .5 . Metal complex: PhCH,Br ratio 1 : 1. s.m.c. = Starting meta746 J. CHEM. SOC. DALTON TRANS. 19865. Reactions of Benzyl Bromide with Other Transition MetalNitrosy1s.-On the basis of the successful denitrosylation of[Ru(NO),(PPh,),] by benzyl bromide under CO, we thoughtthat the reaction could be made more general providing that aTable 6. Reaction of [RuCl(NO)(PPh,),] with PhCH=NOH (1 : 1) intoluene *Reaction conditionsr 1OrganicproductsAt r.t. under N,, 10 min;reflux under CO, 20 hPhCH=NOH 26.5PhCN 51.0 95.0PhCHO 5.1 5.0Reflux under N,, 20 h-- PhCONH, 9.8* Relative percentages of products as determined by v.P.c.; r.t. = roomtemperature.reaction pathway leading to a stable metal carbonyl bromidecould be envisaged, equations ( l F ( 3 ) .[M(NO)L,] + RX + CO-[M(NO)L,X,] + RX + CO-[M(NO),L,X] + 2RX + 2CO-[M(CO)L,X] + 'RNO' (1)[M(CO)L,X,+ 11 + 'RNO' (2)[M(CO),L,X,] + 2'RNO' (3)Accordingly, we studied the behaviour of [Co(NO){ P-(OEt),},], [Rh(NO)(PPh,),], and [RhCl,(NO)(PPh,),] withPhCH,Br under CO in refluxing toluene (Table 9).The reactions with [Co(NO)(P(OEt),} ,] and [RhCl,-(NO)(PPh,),] gave only low conversion to organic products,but indicated a product distribution essentially similar to thosereactions involving [Ru(NO),(PPh,),].With [Rh(NO)-Table 7. Reactions of [Ru(NO),(PPh3),] with PhCH,Br under CzH4 and under N, in toluene *Reaction conditionsOrganicproductsPhCH,BrPhCNPhCONH,PhCHzOHPhCHOTotal(PhCH,),6 1Under CzH4 mole ratio 1 : 2I-A-,65 "C/20 h 110 "C/20 h 65 "C/20 h7.6 - 30.13.2 14.2 5.119.2 4.9 9.60.7 8.2 6.00.3 2.0 4.331.3 30.0 55.1Under N,, mole ratio 1 : 3,- - -* Relative percentages of products as determined by V.P.C.Table 8.Reactions of various iuthenium complexes with benzyl bromide and NO in toluene *Organic r.Ru(NO),(dPPe)l, [Ru(NO)z(P(OPh)3) 21,products mole ratio 1 :2, under CO,90 OC/l8 hmole ratio 1 :2, under CO,110 "C/18 hPhCH,BrPhCH=NOHPhCNPhCONH,PhCH,NO,PhCHOPhCH,OH(PhCH,),42.527.75.31.18.45.0--* Relative percentages of products as determined by V.P.C.61.0trace13.023.01 .otrace--CRuH(O,CMe)(PPh3)J,mole ratio 1 : 2, under NO,110 "C/18 h42.60.526.61.618.10.1--Table 9.Reactions of cobalt and rhodium nitrosyls with benzyl bromide (1 : 1) under CO in refluxing toluene (1 10 "C)"Organic [Co(NO)( P(OEt) 3 1 31, [Rh(NO)(PPh 3131 9 CRh Clz (NO)(PPh3)217products 17 h 20 h 48 hPhCH,Br 80.0 19.5 71.1PhCH=NOH - - -PhCN 18.4 6.0PhCONH, 3.3 - 4.0PhCHO 3.3 11.2 18.0-PhCH,OH 5.9 9.4 2.0PhCH,NO, - - -- - (PhCH,), 5.6Others b -Relative percentages of products as determined by V.P.C. Two unidentified products with column retention times of 42 and 45 min.J. CHEM. SOC. DALTON TRANS. 1986 747(PPh,),], significant conversion of benzyl bromide occurred,although two unidentified organic species were detected. In thisreaction, however, the inorganic products were [RhBr(CO)-(PPh,),] and [PPh,(CH,Ph)]Br (identified spectroscopically).DiscussionIrrespective of whether the attack of benzyl bromide on[Ru(NO),(PPh,),] occurs under CO, N,, or C2H4, we considerthat ruthenium-co-ordinated PhCH,NO must be formed veryrapidly.This may occur either by nucleophilic attack on benzylbromide by a co-ordinated NO group, Scheme 1, withconcomitant attachment of Br to the metal, or by oxidativeaddition of the benzyl bromide, giving a transient intermediate,containing a bent RuNO group which then undergoes a NO'insertion' reaction (Scheme 2).The known distortion of the Ru-N-0 bonds detected in thestructure of [Ru(NO),(PPh,),] l o would be consistent withpathway A. However, coupling of the ally1 group and NO bytreatment of [Ru(q3-C,H,)(N0)(PPh3),] with CO," whichmay involve the intermediate [Ru(o-C,H,)(CO)(NO)(PPh,),lwould seem to be consistent with pathway B.We cannotdifferentiate between the two pathways. Alternative routesinvolving either oxidative addition to give [RuBr,(CH,Ph)-(NO)(PPh,),] with release of PhCH,NO, or a reaction thatresults in loss of NO which subsequently combines withPhCH,Br, can be dismissed since these could not account forthe early observation of [RuBr(CO)(NO)(PPh,),], the failureto observe v(N0) values being commensurate with the pres-ence of [Ru(N0)I3+ species (> 1800 cm-I), the fairly rapidappearance of PhCN, the absence of acyl products derived fromCO insertion into Ru-C bonds, and the fact that PhCH,NO,(expected and usually found in reactions of 'free' NO andPhCH,Br) was not detected in the products of thedenitrosylation reactions carried out under CO.Anotherpossible intermediate, [Ru(CH,Ph)(NO),(PPh,),]Br, alsoseems unlikely since it proved impossible to isolate or obtainany evidence for the existence of [Ru(NO),(PPh,),R][BF4](R = Me or Et), analogous to [Ru(NO),(PPh,),X]+ (X = C1Br,- 5 H 2P h CHzPhIScheme 1.PhCH, .. p-... / NO PhCH2Br 9. I ,.* N=O**FluP' I .NOP4 Ru\ NO Pathway 68 rD PhCH,,..Scheme 2.or OH),', in the reaction between [Ru(NO),(PPh,),] and[R,0][BF4] and because, in toluene, PhCH,Br bond cleavageto give such ionic species would seem to be disfavoured.It seems highly probable that the nitrosobenzyl in theintermediate [RuBr(NO) { N(=O)CH , Ph} (PPh,) ,] undergoesrapid tautomerisation, giving the oxime species [RuBr(NO)-{ N(OH)=CHPh)(PPh,),], which is then quickly dehydratedto the nitrile complex [RuBr(NO)(NCPh)(PPh,),].ThatPhCH=NOH can be rapidly dehydrated in the presence ofruthenium nitrosyl complexes was demonstrated by reaction of[RuCl(NO)(PPh,),] with the oxime in refluxing toluene. UnderN,, the yield of PhCN was almost quantitative, while under COit was the major species formed, some hydrolysis products andunreacted oxime also being present. The lower yield ofbenzonitrile in the reaction under CO might be expectedbecause of competition of oxime and CO for the site at the metalin the co-ordinatively unsaturated [RuX(NO)(PPh,),] (X =C1 or Br). These processes are related to those reported for thethermolysis of [Ru(q-C,Me,)(NO)Et,] in the presence ofPMe,, where both the oximato species [Ru(q-C,Me,)(PMe,),-(ONXHMe)] and the acetamidato compound [Ru(q-C,Me,)-(PMe,),(NHCOMe)] could be formed.6 Thus, we propose thatthe initial steps in the reaction of [Ru(NO),(PPh,),] withPhCH,Br, irrespective of the gaseous atmosphere, are as inequations (4)-(6).Under CO, two reactions can causerelatively slow release of PhCH=NOH and PhCN, respectively(7) and (8). Subsequent denitrosylation under CO will pre-sumably follow according to reactions (9)-( 12). Reactionbetween [RuCl(CO)(NO)(PPh,),] and PhCH,Br under N, inrefluxing toluene was very slow, yielding some PhCHO, tracesof PhCN, and [RuX,(CO),(PPh,),]. These data are consistentwith the observation that [Ru(NO),(PPh,),] is rapidlyconverted into [RuBr(CO)(NO)(PPh,),] but that the latteronly slowly forms [RuBr,(CO),(PPh,),].[Ru(NO),(PPh,),] + PhCH,Br - [ Ru Br(NO)( N(=O)CH , Ph} (PP h 3)2] (fast) (4)[RuBr(NO)(N(OH)=CHPh)(PPh,),l--[RuBr(NO)(NCPh)(PPh,),] + H,O (fast) (6)[RuBr(NO){N(OH)=CHPh)(PPh,),] + CO - [RuBr(CO)(NO)(PPh,),] + PhCH=NOH (7)[RuBr(NO)(NCPh)(PPh,),] + CO - [RuBr(CO)(NO)(PPh,),] + PhCN (8)[RuBr(CO)(NO)(PPh,),] + PhCH,Br -[RUB r , (CO) { N (OH)=CH P h ) (PP h ,),I (slow ) (9)[RuBr2(C0){N(OH)=CHPh}(PPh3),] + CO - [RuBr,(CO),(PPh,),] + PhCH=NOH (10)[RuBr2(CO)(N(0H)=CHPh}(PPh,),l -[RuBr,(CO)(NCPh)(PPh,),] + H,O (slow) ( 1 1)[RuBr2(C0)(NCPh)(PPh3),] + CO - [RuBr,(CO),(PPh,),] + PhCN (12)The occurrence of PhCONH,, PhCHO, and PhCH,OH inthe organic reaction products can be rationalised as arisingfrom (metal-assisted) hydrolysis of PhCN, PhCH=NOH, andPhCH,Br.All of the reactions described were carried out unde748 J. CHEM. SOC. DALTON TRANS. 1986strictly anhydrous conditions, but the metal-assisted de-hydration of PhCH=NOH [reactions (6) and (1 l)] will providesufficient water to accomplish these hydrolyses. There is ampleevidence of the metal-catalysed hydration of nitriles toamides. 'When the benzylation reaction is carried out in the absenceof CO, that is under N, or ethylene, we believe that the reactionsequence (4)-(6) is repeated. However, after that point wepropose that reactions (13)--(17) can occur. It may be notedthat [RuCl(NO)(PPh,),] is known to undergo oxidativeaddition reactions with alkyl halide^,^ and that a mixtureof benzyl bromide and [RuBrCl(CH,Ph)(NO)(PPh,)J inrefluxing toluene afforded small amounts of (PhCH,),, which isconsistent with the proposed reactions (13) and (14).The slowbenzylation of NO would lead, by analogy with reactions(9)--(12), to formation of benzonitrile, which remains co-ordinated to the metal. Thus reactions (13H17) may accountfor the relatively low yields of 'free' organic products and forthe appearance of [RuBr,(NCPh),(PPh,);] and [RuBr,-(NO)(PPh3) 21 -[RuBr(NO)(NCPh)(PPh,),] + PhCH,Br[RuBr,(CH,Ph)(NO)(PPh,),] + PhCN (13)[RuBr,(CH,Ph)(NO)(PPh,),] + PhCH,Br --+CRuBr,(NO)(PPh,),] + (PhCH,), (14)[RuBr(NO)(NCPh)(PPh,),] + PhCH,Br - [RuBr, (N(=O)CH,Ph}(NCPh)(PPh,),] (1 5)[RuBr,(N(=O)CH,Ph}(NCPh)(PPh,),] - [RuBr,(N(OH)=CHPh)(NCPh)(PPh,),] (16)[RuBr,{N(OH)=CHPh)(NCPh)(PPh,),] - [RuBr,(NCPh),(PPh,),] + H,O (slow) (17)From a comparison of the apparent speed with whichorganic products are formed in the reactions under CO withthose under N, or ethylene, it seems that the role of CO is tofacilitate the liberation of the nitrosobenzyl derivatives withoutgenerating compounds which are themselves significantlyreactive.Indeed, the original intention of using CO was todeactivate [RuBr(NO)(PPh,),] which, we thought, might beformed in the reaction after elimination of PhCH,NO. Indeed,it has been suggested that in related reactions between[Ru(NO),(PPh,),] and halogens, in which [Ru(NO)-(PPh,),X,] is the final product, a likely intermediate is[Ru(NO)(PP~~),X].'~ We reasoned that the ability of such aspecies to undergo oxidative addition with PhCH,Br wouldcomplicate the intended nitrosylation processes.Anothersignificant point is that, under CO, no dibenzyl is formed,suggesting that, unlike the reactions in the absence of CO,radical processes are unimportant in the overall mechanism.Finally, we may conclude that the reaction between gaseousNO and PhCH,Br in solution is inefficient in comparison tothat when the NO is co-ordinated by ruthenium, and that thenature of the products is significantly modified by that co-ordination.ExperimentalThe complexes [RuCl(NO)(PPh,),], [RuX(CO)(NO)(PPh,),](X = Cl or Br), [RuX,(NO)(PPh,),] (X = Cl or Br),[RhCl,(NO)(PPh,),) and [Co(NO)(P(OEt),} ,] were preparedby methods readily available in the literature.CO and NO gaswere supplied by Air Products Ltd., and passed through H2S04,CRW"JO)2(dPPe)I, CRu(NO)2(P(OPh)3) 21, CRh(NO)(PPh,),I,KOH pellets, and molecular sieves. The ally1 and aryl halideswere distilled over CaBr, and stored under argon overanhydrous MgSO,. Infrared spectra were obtained usingPE-257, -457, and -180 spectrophotometers. 'H N.m.r. spectrawere obtained using a Varian H A 1 0 spectrometer. Analyticalvapour pressure chromatographic (v.P.c.) separations wereperformed by a PEFll gas chromatograph fitted with a flameionization detector. Glass columns (183 cm x 3 mm internaldiameter) were packed with free fatty acid phase with 5% w/wloading on Chromasorb G (80-100 mesh) acid-washedSiHClMe,.The carrier gas (N,) flow rate was 30 cm3 min-'and column temperature varied from 60-230°C with aprogrammed rise of 6 "C min-'. Quantitative measurementswere made by comparison with standard V.P.C. runs usingpredetermined concentrations of known compounds. Massspectra (m.s.) and gas chromatographic (g.c.) m.s. measurementswere made using an AEMS12 instrument fitted with a BiemannSeparator. For g.c.m.s., the carrier gas was helium, and columnconditions were as for conventional V.P.C. For conventionalmass spectrometry the ionising voltage was 70 eV(eV M 1.60 x lo-'' J) but for g.c.m.s, 30 eV.Reaction conditions are as described in Tables 1-9.Themetal compounds formed were separated, and characterised bymicroanalysis (C, H, N, halogen) and i.r. spectral studies. Theorganic compounds were determined by V.P.C. (comparison withauthentic compounds) and g.c.m.s.Typical Reactions: Treatment of [ Ru(NO),( PPh,) ,] withBenzyl Bromide in Toluene under C0.-[Ru(NO),(PPh,),] (0.7g ) and PhCH,Br (0.25 cm3) (1:2 mole ratio) were heated at90°C in CO-saturated dry toluene (50 cm3) for 48 h. Themixture was stirred and CO passed continuously through thetoluene to maintain saturation. The pale yellow solution whichformed was evaporated in uacuo to ca. 5 cm3, cooled to 0 "C andtreated with cold EtOH. The [RuBr,(CO),(PPh,),] whichprecipitated was filtered off and the filtrate evaporated in vucuoto leave an organic residue analysed by V.P.C.and g.c.m.s.(Found: C, 54.4; H, 3.3; Br, 19.6. C,,H,,Br,O,P,Ru requires C,54.2; H, 3.6; Br, 19.0%). 1.r. (KBr disc): 2070, 1990 cm-'.When the reaction was stopped after 12 h, the solid filteredoff contained [RuBr(CO)(NO)(PPh,),] and [RuBr,(CO),-(PPh,),], identified by i.r. spectroscopy. The former wasseparated from the latter by recrystallisation from CH,Cl,-MeOH mixtures: [RuBr(CO)(NO)(PPh,),] (Found: C, 48.6; H,3.4; Br, 10.3; N, 1.8. C,,H,,BrNO,P,Ru requires C, 48.5; H, 3.9;Br, 10.5; N, 1.8%). 1.r. (KBr disc): 1 925 (vco), 1 595 cm-' (vNo).Treatment of [Ru(NO),(PPh,),] with PhCH,Br in Tolueneunder Nitrogen.-[Ru(NO),(PPh,),] (0.5 g) and PhCH,Br(0.25 g) (1 : 2 mole ratio) were refluxed in toluene (80 cm3) underN, for 5 h.A yellow powder was precipitated and was collectedand recrystallised from toluene-n-hexane to give [RuBr,-(NCPh),(PPh,),] (Found: C, 61.9; H, 4.2; Br, 16.7; N, 2.8.C,,H4,Br,N,P,Ru requires C, 62.3; H, 4.2; Br, 16.6; N, 2.9%).1.r. (KBr disc): 2 223 cm-' (vCN).Concentration of the filtrate and addition of n-hexaneafforded a brown solid, identified as [RuBr,(NO)(PPh,),](Found: C, 48.9; H, 3.7; Br, 26.9; N, 1.9. C,,H,,Br,NOP,Rurequires C, 48.2; H, 3.3; Br, 26.8; N, 1.6%). 1.r. (KBr disc): 1 870cm-' (vNo).After removal of all solvents, the organic residue wassubjected to V.P.C. and g.c.m.s analysis.AcknowledgementsWe are grateful to Monsanto, U.S.A. (C. W. N.) and to theS.E.R.C. (I. W.) for financial support, to the Polish Academy oJ. CHEM. SOC. DALTON TRANS. 1986 749Sciences for leave of absence for I. W., and to the ChemistryDepartment, University of Shefieid for the provision oflaboratory facilities and technical assistance. We also thankJohnson Matthey PLC for the loan of ruthenium and rhodiumtrichloride. One of us (J. A. McC.) is grateful to theDipartimento di Chimica, Universita della Calabria, Rende(Cosenza), Italy, for provision of facilities to complete thisreport.References1 J. A. McCleverty, Chem. Rev., 1979,79,53.2 R. A. Clement, V. Klabunde, and G. W. Parshall, J. Mol. Cutal., 1978,3 M. Foa and L. Cassar, J. Organomet. Chem., 1971,3, 123.4 W. P. Wiener, M. A. White, and R. G. Bergman, J. Am. Chem. SOC.,1981, 103, 3612; M. P. Weiner and R. G. Bergman, ibid., 1983, 105,3922.4, 87.5 A. J. Shortland and G. Wilkinson, J. Chem. SOC., Dalton Trans., 1973,872; A. R. Middleton and G. Wifkinson, ibid-, 1980,1888 1981,1898.6 M. D. Seidler and R. G. Bergman, J. Am. Chem. Soc., 1984,106; 61 10.7 A. P. Gaughan, B. J. Corden, R. Eisenberg, and J. A. Ibers, Inorg.Chem., 1974, 13, 786; G. Doletti, 0. Gandolfi, M. Ghedini, andN. W. Hoffman, Znorg. Synzh., 1976, 16 32.8 J. A. McCleverty, C. W. Ninnes, and I. Wdochowin, J. Chem. Soc..Chem. Commun., 1976, 1061.9 B. Giovannitti, 0. Gandolfi, M. Ghedini, and G. Dolcetti, J.Organomet. Chem., 1977, 129,207.10 J. A. Kaduk and J. A. Ibers, Inorg. Chem., 1975, 14,3070.11 M. W. Schoonover, E. C. Baker, and R. Eisenberg, J. Am. Chem. SOC,12 C. G. Pierpont and R. Eisenberg, Znorg. Chem, 1972, 11, 1088.13 M. A. Bennett and T. Yoshida, J. Am. Chem. SOC., 1973, %, 3030.14 K. R. Grundy, K. R. Laing, and W. R. Roper, Chem. Commun., 1970,1979, 101, 1880.1500.Received 20th June 1985; Paper 5/104

ISSN:1477-9226    

DOI:10.1039/DT9860000743

出版商:RSC    

年代:1986

数据来源: RSC