New, ready degradation reactions of bisphosphines

摘要

1976 1205New, Ready Degradation Reactions of BisphosphinesBy S. Martin Nelson,Maxwell Perks, and Brian J. Walker," Department of Chemistry, David Keir Building,Queen's University of Belfast, Belfast BT9 5AG, Northern Ireland2-Bis(diphenylphosphino)methyl-6-methylpyridine ( l a ) and 2-bis(diphenylphosphino)methylpyridine ( l b )undergo ready degradation to monophosphine derivatives on aerial oxidation, quaternisation, reaction with bromine,or warming with acetic acid. Similar reactions take place with the corresponding palladium (11) complexes.Oxidation with manganese dioxide and reaction with sulphur lead to bisphosphine oxides and sulphides, respec-tively. Bis(dipheny1phosphino)methane (1 3b), 1 .I -bis(diphenylphosphino)ethane (1 3a), and cca-bis(dipheny1-phosphino)toluene (1 3c) generally do not undergo a similar loss of phosphorus, although treatment of (1 3c) withmethyl iodide under more vigorous conditions gave benzylmethyldiphenylphosphonium iodide.A mechanism involving an increase in co-ordination at one phosphorus atom, followed by nucleophilic attackat the other is suggested, and the importance of the stability of the leaving carbanion is discussed.THE 2-pyridyl-substituted bisphosphine (la) (ppn') is anexcellent chelating ligand exhibiting two types of bi-dentate behaviour.lB2 During investigations of the sitesR 0 ' CH(PPh,),(1) a ; R = Me( 2 )M = Con o r Ni'X = CI,Br,or I( 3 )of co-ordination in (la), neutral complexes of type (2)were treated with glacial acetic acid and gave 2 a newseries of complexes (3).The breaking of carbon-phosphorus bonds, especially in phosphines, generallyrequires vigorous conditions and/or transition metalcomplex formation.s In view of this it seemed likelythat the novel degradation of (2) under such mild con-ditions was assisted by co-ordination to the metal ion.We report a study of this reaction which shows that thepresence of metal ions is not a necessary condition fordegradation. A number of other degradation reactionsare described, the common factor throughout being theunprecedented ease of phosphorus-carbon bond breaking.( 4 ) a ; R = Me I51 a ; R = Meb ; R = H b ; R = H0I 1P h 2P - CH (OH) R( 6 ) R = Ph, PhCH,, or p - MeC6HtThe bisphosphine (la) reacted with a variety of re-agents to give, in most cases, derivatives of 2-diphenyl-phosphinomethyl-6-methylpyridine (4a).Refluxing a1 W. V. Dahloff, T. R. Dick, G. euro;3. Ford, W. S. J. Kelly, and* W. V. Dahloff, T. R. Dick, and S. M. Nelson, J . Chem. SOC.S. M. Nelson, J . Chem. SOC. ( A ) , 1971,3495.( A ) , 1969, 2919.methanolic solution of (la) in air gave the monophosphineoxide (5a) and diphenylphosphine oxide; the presence ofthe secondary phosphine oxide had been suggested by theisolation of a-hydroxy-phosphine oxides (6) from thereaction of (la) with various aldehydes. The bisphos-phine dioxide (7) could be obtained from (la) by reactionwith manganese dioxide in anhydrous methanol and wasstable to refluxing in methanol in the presence of oxygen.A stable disulphide (8a) could be prepared by treat-ment of (la) with sulphur in carbon disulphide; in nocase was any evidence found for monophosphine deriv-atives. The disulphide (8a) did not react with mangan-ese dioxide and, more surprisingly, was recovered un-changed from attempted reduction with lithium(7 1 (8) a ; R = Meb ; R = H" AcO-19)aluminium hydride.Recryst allisat ion from glacialacetic acid gave the pyridinium acetate (9). Howeverreactions of (la) with acetic acid, bromine, and methyliodide, under various conditions, gave, respectively,compounds (lo), (ll), and (12a), indicating the loss ofone phosphinyl group in each case. Protonation at Nrather than P in (10) is supported by the strong ab-sorption at 2 500 cm-1.The structures (5a) and (12a)were confirmed by synthesis from 2-diphenylphosphino-methyl-6-methylpyridine (4a). No evidence was ob-tained for either degradation or deuterium exchangeafter prolonged refluxing of (la) in methan2H01 or indeuterium oxide.2-Bis(diphenylphosphino)methylpyridine (lb) reacteda G. van Koten and J. G. Noltes, J.C.S. Chem. Comm., 1972,462; W. C. Kasba, D. K. Mitchell, R. F. Reichelderfer, andW. D. Korte, J . Amer. Chem. SOG., 1974,96,2847; J. R. Blickens-derfer and H. D. Kalsz, ibid., 1975, 97, 2681, and referencestherein1206 J.C.S. Perkin Iin a similar way with oxygen, methyl iodide, and sulphurto give compounds (5b), (12b), and (8b) respectively.( 1 a)R o + N/ CH2*PMePh2 I -(12) o ; R = Meb ; R = HAnalogous reactions with the bisphosphines (13a andb) did not involve loss of phosphorus, and dioxides, di-sulphides, and diphosphonium salts were obtained.The4.RCH IPPh,), Ph P-C H Ph.P Me Ph,113) a ; R = Me I-( 1 4 )b ; R = Hc ; R = Phphenyl-substituted diphosphine (13c) also formed a di-phosphine dioxide (the m.p. of our sample differs con-siderably from that previously reported) and a disulphide,and refluxing in benzene with 1 mol. equiv. of methyliodide for 15 min gave the phosphonium salt (14), identi-fied on the basis of its n.m.r. spectrum. The structure(14) was confirmed by oxidation to (a-diphenylphos-phinoylbenzy1)methyldiphenylphosphonium iodide (16),which in turn was prepared from benzyldiphenylphos-phine oxide by phosphinoylation to give (15), followed byquaternisation with methyl iodide.The salt (16) wasI: 1,Buli 8 Me I !Ph2P *CH,Ph - Ph,P.CHPh* + Ph,P*CHPhZ,Ph2PCI I IPPh 2 Me PPh, *(1 5 )0J/ Na2C031-(16)IIPh,P -CPh=PMe P h( 1 7 )recovered unchanged from refluxing in methanol, methyliodide, or acetic acid; however, treatment with sodiumcarbonate gave the corresponding phosphonium ylide(17). Loss of phosphorus from (13c) to give benzyl-methyldiphenylphosphonium iodide did occur on reflux-ing with an excess of methyl iodide.Reactions with the palladium(r1) complex (18) of ppnrsquo;(la) generally gave results similar to those obtained withthe free ligand. On the basis of analysis and massspectra, oxidation with manganese dioxide under an-hydrous conditions probably gives the bisphosphinedioxide complex (19) rather than the mono-oxide com-plex, and refluxing in an excess of methyl iodide gave thedegraded monophosphoniopalladium(11) complex (20).However, Pd(ppnrsquo;) X, was recovered unchanged fromtreatment with 1 mol.equiv. of methyl iodide, and noproduct could be isolated from reaction with glacialacetic acid.The presence of water in the reaction mixture appearedto be crucial for degradation to take place during oxidationsof (la) and (lb). The dioxide (7) is not an intermediatein the degradation since it is recovered unchanged fromrefluxing in absolute methanol. However, degradation(21) f8blsquo;PPh,1-3SCHEME( 2 2 )+ PhzPIdoes not precede oxidation since the bisphosphine (la) isalso stable in refluxing methanol in the absence ofoxygen.In view of this a reasonable mechanism foroxidative degradation involves the bisphosphine mono-oxide (21). The second stage of the reaction is presum-ably hydrolysis of (21) and here attack at tervalentphosphorus is preferred since (a) diphenylphosphineoxide is an isolated product, while no significant amoun1976 1207of phosphinic acid was detected, (b) phosphites aregenerally hydrolysed much faster than the correspondingpentavalent analogue~,~15 and (c) tetrahedral pentavalentphosphorus is more effective than tervalent phosphorusat stabilising adjacent negative charge. An analogousmechanism, involving iodide as nucleophile (see Scheme),can be written for degradative methylation.No evi-dence for the phosphonium ylide (22) was found, althoughdiphenylphosphine oxide was obtained after the additionof water.The importance of the stability of the leaving carb-anion is further evidenced by the absence of degradationof (13a and b) . The case of (13c) is presumably inter-mediate, since a full positive charge on phosphorus andforcing conditions are required for degradation. In viewof this the reported stability of the bisphosphines (23)and bisphosphonium salts (24) to mild degradative con-ditions is predictable. The degradations of (la and b) inR ,P CH Z-CH 2*PR 2 P h * P F P h * 2x-( 2 3 ) w 01241acetic acid presumably rely on stabilisation of the carb-anion by the pyridinium system, since the phosphine (10)is the isolated product.The absence of degradation during sulphurisation ismore difficult to explain, but may be due to inferiorcarbanion stabilisation in the sulphur case.Alter-natively, the addition of a second sulphur atom, to givethe stable disulphide (S), may be fast.EXPERIMENTALI.r., mass, and n.m.r. spectra were obtained with a Perkin-Elmer 457, an A.E.I. MS902, and a Varian HA-100 spectro-meter (tetramethylsilane as internal reference), respectively,unless otherwise stated. All experiments involving phos-phines, and other air-sensitive compounds, were carried outunder dry, oxygen-free, nitrogen, unless otherwise stated.Prepamtion of Bisphosphines .-Z-Bis (diphenylphosphino) -niethyl-6-methylpyridine (la), m.p.78-80", z (CDCl,)2.4-2.9 (21 H, m), 3.26 (1 H, d, JHH 4.0 Hz), 3.40 (1 H, d,Jm 3.8 Hz), 5.22 (1 H, t, JPH 2.2 Hz), and 7.77 (3 H, s), wasprepared from 2,6-lutidine by the method previouslydescribed.l A similar procedure starting from cc-picolinegave 2-bis (di~l2enylphosphino)methyZpyridine (lb), vmx. (KBr)1585 and 1570 cm-l (Found: C, 77.8; H, 5.2; N, 2.9.C,,H,,NP, requires C, 78.1 ; H, 5.4; N, 3.0). 2-Diphenyl-phosphinomethyl-6-methylpyridine (4a), vmX. (CHCl,) 1 586and 1 572 cni-l (the absence of appreciable phosphine oxideimpurities was confirmed by the lack of a strong absorptiona t 1180 cm-l); m/e 291 (Mi-); T (CDC1,) 2.P-2.9 (11 H,m), 3.22 (1 H, d, J H H 4.0Hz), 3.40 (1 H, d, JHH 3.9Hz), 6.40( 2 H, d , JPH 0.5 Hz), and 7.59 (3 H, s), was prepared fromJ .Michalski and T. Modro, Bull. Acad. polon. Ssi., SLY. Sci.chim., 1962,10, 327; M. Leplawy, J. Michalski, and J. Zabrocki,Chem. and Ind., 1964, 835.C;. Aksnes and D. Aksnes, Acta Chem. Scand., 1964, 18,1623 : 9. S. Noyce and J. A. Virglio, J. Org. Chern., 1972, 37,1052.2,6-lutidine by using a 1 : 1 molar ratio of butyl-lithium andchlorodiphenylphosphine.ccu-Bis(di~henylphos~hino)toZuene (1 3c). 2w-Butyl-lith-ium (10 ml, 0.02 mol) was added to benzyldiphenylphos-phine (5.4 g, 0.02 mol) in ether (200 ml). After stirring for4 h, chlorodiphenylphosphine (4.4 g, 0.02 mol) in ether(30 ml) was added and stirring was continued for 30 min,during which time the mixture became colourless. Anequal volume of water was added and the organic layer wasseparated, dried, and evaporated to give cccc-bis (diphenyl-phos9hino)toluene (5.6 g, 62), m.p.93-95'; vmx. (KBr)1496, 1482, 1456, and 1436 cm-l; z (CDCl,) 2.0-2.8(25 H, m) and 5.57 (1 H, t, JPH 3.5 Hz) (Found: C, 80.6;H, 5.7. C,,H,,P, requires C, 80.9; H, 5.7).1, 1-Bis(diphenylj5hosphino)ethane (13a) was prepared from1,l-dichloroethane by a modification of the general methodof Issleib * t o give crystals, m.p. (from ethanol) 106-108";7 (CDC1,) 2.P-2.8 (20 H, m), 6.81 (1 H, q, JHH 7 Hz), and9.02 (3 H, dt, ,JHH 7, 3JpH 10.5 Hz) (Found: C, 78.7 ; H, 5.8.C,,H,*P, requires C, 78.4; H, 6.1).Reactions of 2-Bis (diphenylphosphino) metJ~yl-6-nzetli y lpyr-idine (la).-(a) Oxidation. (i) The phosphine (la) (4.78 g,0.01 mol) was refluxed in benzene (25 ml) in air for 30 min.On cooling a white precipitate formed, m.p.52", identicalwith an authentic sample of diphenylphosphine oxide.,The filtrate was evaporated to give (6-methyl-2-pyridylmeth-yE)difJzenylphosphine oxide (5a) (2.5 g, 82) as a pale yellowoil, vDx. (film) 1 180 cm-l; rn/e 307 (M+) ; z (CDC1,) 2.9-3.4(13 H, m), 6.25 (2 H, d, JPH 12.0 Hz), and 7.68 (3 H, s)(Found: C, 74.6; H, 6.2; P, 4.8. C,,H,,NOP requiresC , 74.3; H, 5.9; N, 4.6).(ii) The phosphine (la) (0.47 g, 0.001 mol) and manganesedioxide (0.53 g, 0.006 mol) in dry tetrahydrofuran (30 ml)were refluxed under nitrogen for 12 h. The white preci-pitate which formed upon cooling was filtered off andvacuum dried a t room temperature to give 6-bis(diphenyl-~hos~hino)methyZ-2-methyZ~yridine PP'-dioxide (7) (0.34 g,60y0), m.p. 213-214"; vmx.(KBr) 1205 cni-l; 7 (CDCl,)2.5-3.5(23H,m),4.76(lH,t,JpH13.0Hz),and7.76(3H,s) (Found: C , 73.0; H, 4.9; N, 2.6. C,,H2,N02P2 requiresC, 73.3; H, 5.3; N, 2.8). The dioxide (7) was unchangedafter refluxing for 1 h in oxygenated methanol.(b) With bromine. Bromine (0.16 g) in chloroform (10ml) was added to the phosphine (la) (0.5 g) in chloroform(10 ml) and the mixture stirred at room temperature for 2 h.The solvent was removed under vacuum and the residuetaken up in hot benzene. Cooling gave (6-nzethyl-2-pyridyZ-nzethyZ)diphenyZphosphine oxide hydrobromide (1 1) (0.15 g,40), m.p. 184-185'; vmaZ (KBr) 2 500br, 1620, 1608,and 1 180 cm-l; z (CDCl,) 1.7-2.7 (14 H, m), 5.26 (2 H, d,Jp~14Hz),and7.24(3H,s)(Found: C,58.2; H,4.9; Br,20.6. C,,H,,BrNOP requires C, 58.7; H, 4.9; Br, 20.6).(c) With methyl iodide. (i) The phosphine (la) (1.1 g)and methyl iodide (25 ml) were refluxed for 30 min undernitrogen.The excess of methyl iodide was distilled off andthe oily residue taken up in ethanol. Careful addition ofether gave (6-methyl-2-py~idylmethyl)methyldipI1enylphos-phonium iodide (12a) (0.4 g), m.p. 193-19.5"; wz/e 306;z (CDCI,) 2.0-2.5 (11 H, m), 2.80 (1 H, d, JnH 3.5 Hz), 2.88R. B. King and P. R. Heckley, Phosphovus, 1974,4,209.T. A. Mastryukova, Kh. A. Suerbaev, P. V. Petrovskii, E. I.Fedin, and M. I. Kabachnik, Zhur. obslzchei Khivz., 1974,44, 2398(Chem. Abs., 1975, 82, 98057q).K.Issleib and D. Muller, Chem. Bey., 1959, 92, 3175.R. C. Miller, J . Org. Chenz., 1959, 24, 20131208 J.C.S. Perkin I(1 H, d, J H H 3.7 Hz), 5.12 (2 H, d, Jpn 16.0 Hz), 7.19 (3 H,d, Jpg: 14 Hz), and 7.70 (3 H, s) (Found: C, 54.9; H, 4.8;I, 29.0. C,,H,,INP requires C, 55.5; HI 4.8; I, 29.3).The filtrate was evaporated to give diphenylphosphineoxide, identical with an authentic sample.(ii) The phosphine (la) (2.4 g, 0.005 mol) in benzene (30ml) was added to methyl iodide (0.7 g, 0.005 mol) and themixture was refluxed for 1 h. Cooling and addition of ethergave a precipitate of (6-methyl-2-pyridylmethy1)methyldi-phenylphosphonium iodide (12a).The phosphine (4.8 g, 0.01 mol) indeoxygenated glacial acetic acid (25 ml) was refluxed for 15min.The excess of acetic acid was removed under vacuumand the residue dissolved in methanol. Addition of watergave 2-(di~henylphosphinomethyl)-6-methyl~yridinium acet-ate (10) as a yellow oil, vmX (KBr) 2 560, 1 720, 1 600, 1 580,and 1 250 cm-l; m/e 292 (Found: C, 72.0; H, 6.4; N, 3.8.C,lH,,NO,P requires C, 71.8; H, 6.3; N, 4.0). Theacetate (10) (3.51 g, 0.01 mol) in deoxygenated ethanol (50ml) was added to a filtered solution of nickel(r1) bromidetrihydrate (1.93 g, 0.01 mol) in ethanol (25 ml). Thesolution was refluxed for 5 min and cooled to give blue-greencrystals of the pyridinionickel(I1) tribromide,, m.p. 208-210', identical with an authentic sample (i.r.).The phosphine (4.8 g, 0.01 mol) wasadded to a deoxygenated solution of sulphur (0.96 g, 0.03mol) in carbon disulphide (50 ml).The solution was re-fluxed for 16 h and filtered hot. Cooling gave 2-bis(di-~henylphos~hino)methyZ-6-methylpyridine PP'-disulphide (8a)(3.5 g, 62), m.p. 211-213'; vmX. (KBr) 625 cm-1; wz/e539; z (CDCl,) 1.9-2.9 (21 H, m), 3.28 (1 H, d, JEH. 2.0Hz),3.36 (1 H, d, JEH 2.0 Hz), 4.10 (1 H, t, JPH 13.0 Hz), and 7.78(3 H, s) (Found: C, 68.5; H, 5.0; N, 2.4. C31H27NP2S2requires C, 69.0; H, 5.0; N, 2.6).(i) The phosphine (4.8 g, 0.01 mol)was added to a solution of benzaldehyde (2.12 g, 0.02 mol) inacetic anhydride (50 ml). The solution was refluxed for24 h and cooled to give whydroxybenzyldiphenylphosphineoxide, m.p. 174-176' (1it.,lo 178-179.5') ; v- (IIBr)3 410, 1 625, and 1 165 cm-1.(ii) Phenylacetaldehyde gave, under similar conditions,l-hydroxy-2-phenylethyldiphenylphosphine oxide, m.p.164-166', vmK (KBr) 3 410, 1610, and 1 152 cm-l (Found: C,74.15; H, 5.7. C,,H,,O,P requires C, 74.55; H, 5.9).(iii) p-Tolualdehyde gave, under similar conditions,a-hydroxy-p-methylbenzyldiphenylphosphine oxide, m.p.149-150' (1it.,l1 152-155').(g) Attempted deuteriation. The phosphine (10 solutionin CDC1,) was shaken with an equal volume of deuteriumoxide for 4 h; the n.m.r. spectrum of the resulting solutionwas identical with that of an untreated sample. The n.m.r.spectrum of a solution of the phosphine in methan2Holsuggested that no deuterium exchange had occurred evenafter several days.Reactions of 2-Bis(di~henyl~hos~hino)methyl-6-methyl~y~-idine PP'-Disulphide (8a) .-(a) Reduction.(i) The disul-phide (5.4 g, 0.01 mol) was added to a solution of lithiumaluminium hydride (1.9 g, 0.05 mol) in dry tetrahydrofuran(150 ml) and the mixture was refluxed for 24 h. Theproduct was filtered through kieselguhr and evaporated togive unchanged disulphide (8a) (84), m.p. 211-213O.(ii) The disulphide (5.4 g, 0.01 mol) was added to a sus-lo R. C. Miller, W. Rogers, L. A. Hamilton, and C. D. Miller,l1 D. S. Marmor and D. Seyferth, J . Org. Chew., 1969, 34, 748.(d) With acetic acid.(e) W i t h sulphur.(f) W i t h aldehydes.J . Amer. Chem. SOC., 1957, 79, 424.pension of copper powder (6.4 g, 0.1 mol) in dry ethanol(300 ml) and the mixture was refluxed for 2 days.Theproduct was filtered through kieselguhr and evaporated togive unchanged disulphide (8a) (89), m.p. 211-213'.The disulphide (0.54 g, 0.001 mol) wasadded to a suspension of manganese dioxide (0.44 g, 0.005mol) in ethanol (150 ml). The mixture was refluxed withstirring for 2 days and filtered through kieselguhr. Evapor-ation of the resulting solution gave unchanged disulphide(92), m.p. 211-213'.(c) W i t h acetic acid. A solution of the disulphide (0.54 g,0.001 mol) in deoxygenated acetic acid (50 ml) was refluxedfor 2 h; it was then evaporated to ca. 20 ml and slowlydeposited crystals of 2-bis(diphenylphosphino)methyl-6-methylpyridinium PI?'-disulphide acetate (9) (80) ; v-(KBr) 2 560, 1 708, 1601, 1580, and 1275 cm-l; m/e 540;z (CDCl,) 1.8-3.3 (24 H, m), 4.03 (1 H, t), 7.80 (3 H, s), and7.88 (3 H, s) (Found: C, 65.9; H, 5.1; S, 10.2.Camp;31-NO,P,S, requires C, 66.1; H, 5.2; S, 10.7).Reactions of 2-(Diphenylphosphinomethyl)-6-methylpyr-idine (4a) .-(a) Oxidation. The corresponding oxide (5a)was obtained by refluxing the phosphine (0.5 g) in unpmifiedmethanol (25 ml) for 10 min.The phosphine (2.91 g, 0.01 mol) wasadded to a solution of sulphur (0.32 g, 0.01 mol) in oxygen-free benzene (25 ml) and the mixture was refluxed for 12 h.Filtration and evaporation gave 2-(diphenylphosphino-methyl) 6-methylpyridine P-sulphide (2.4 g, 74) ; vmaK (KBr)620 cm-l; m/e 323; T (CDCl,) 2.0-3.2 (13 H, m), 5.89 (2 H,d, Jp= 14.0Hz), and 7.69 (3 H, s) (Found: C, 70.4; H, 5.5;N, 4.2; S, 9.6.C1,H18NPS requires C, 70.6; H, 5.6; N,(c) W i t h methyl iodide. The phosphine (0.58 g, 0.002mol) and methyl iodide (25 ml) were refluxed for 8 h.Evaporation and crystallisation of the resulting oil fromethanol-ether gave 2-( diphenylphosphinomethyl)-6-methyl-pyridine methiodide (0.5 g), m.p. 193-195'.Reactions of 2-Bis(di~henyl~hos~hino)methyl~y~idine.-(a) Oxidation. The phosphine (0.46 g, 0.001 mol) in meth-anol (25 ml) was refluxed in air for 10 min. Cooling anddropwise addition of water gave diphenyl-2-pyridylmethyl-phosphine oxide (5b), vmx. (KBr) 1185 cm-l; m/e 293;z (CDC1,) 2.3-3.3 (14 H, m) and 6.12 (2 H, d, 2 J p ~ 13.0 Hz)(Found: C, 73.3; H, 5.1. C,,H,,NOP requires C, 73.7;H, 5.4).(b) W i t h methyl iodide.The phosphine (0.46 g, 0.001mol) in methyl iodide (25 ml) was refluxed for 8 h. Themethyl iodide was removed under reduced pressure to leavean oil which was dissolved in ethanol. Addition of ethergave methyldiphenyl-(2-pyridyl.lnethyl)phosphonium iodide(12b) (0.3 g ) , m.p. 162-164'; T (CDC1,) 1.8-2.9 (14 H, m),4.88 (2 H, d, JPH 14.0 Hz), and 7.06 (3 H, d, JPH 14.0 Hz)(Found: C, 54.0; H, 4.3; I, 29.9. C,,H,,INP requires C,54.4; H, 4.5; I, 30.3).The phosphine (4.6 g, 0.01 mol) wasadded to a solution of sulphur (0.32 g, 0.01 mol) in oxygen-free carbon disulphide (25 ml) and the mixture refluxed for12 h. Filtration and evaporation under reduced pressuregave 2-bis(diphenylphosphino)methylpyridine PP'-disulphide(8b) (82y0), m.p. 215-216'; vmaX (KBr) 620 cm-1; 7(CDC1,) 1.7-3.2 (24 H, m) and 4.06 (1 H, t, 2 J p ~ 13.0 Hz)(Found: C, 68.3; H, 4.4.C,,H,,NP2S2 requires C, 68.6;H, 4.8).Reactions of 1,l-Bis (diphenylphosphino) ethane.-(a) Oxid-ation. The phosphine (3.98 g, 0.01 mol) in methanol (50 ml)(b) Oxidation.(b) With sulphur.4.3; s, 9.9).(c) W i t h sulphur1976was added to manganese dioxide (0.1 mol). The mixture H, 4.7; I, 30.0. C2,H2,1P requires C, 57.4; H, 4.8; I,was refluxed for 12 h, allowed to cool, and filtered through 30.4).kieselguhr, and the filtrate was evaporated to ca. 15 ml. (ii) The phosphine (4.6 g, 0.01 mol) was added to methylThis solution slowly deposited crystals of 1,l-bis(diphenyl- iodide (1.4 g, 0.01 mol) in benzene (30 ml) and the mixturephosphino)ethane PP'-dioxide (78), m.p.178-180"; vmX. was refluxed for 10 min. Careful addition of ether to the(KBr) 1 180 cm-1 (Found: C, 73.0; H, 5.9; P, 14.1. cooled mixture gave (a-di~henyZ~hosphinobenzyZ)methyZ-C2,H,,0,P, requires C, 72.6; H, 5.6; P, 14.4). The diphenylphosphonium iodide (la), m.p. 107-109"; -ccorresponding mono-oxide 1 2 could be converted into 1,l- (CD,),SO 2.2-3.0 (25 H, m), 3.77 (1 H, q, 2 J p ~ 16.0, 2 J p ~bis(dipheny1phosphino)ethane PP'-dioxide by treatment 1.0 Hz), and 7.48 (3 H, d, 2 J p ~ 14 Hz) (Found: C, 63.7;with hydrogen peroxide. H, 4.6; I, 22.0. C32H291P2 requires C, 63.8; H, 4.8; I,(b) With sulphur. The phosphine (3.98 g, 0.01 mol) was 21.2).added to sulphur (0.96 g, 0.03 mol) in deoxygenated carbon Reactions of 2-Bis(diPhenylPhosphino)rp.leth~z-6-me~hylpyr-disulphide (40 ml).The solution was refluxed for 12 h, then idinepalladium Dihalides (18).-(a) Oxidation. The com-filtered hot through kieselguhr and cooled to give crystals of plex Pd(ppn')Br, (18; X = Br) was refluxed in dichloro-1,l-bis(diphenylphosPhin1zo)ethane PP'-disulphide (3.8 g), m.p. ethane for 1 h with a five-fold excess of manganese dioxide.182-184"; vmx. (KBr) 579 cm-1; mle 462; (CDC1,) The mixture was filtered through kieselguhr and on cooling1.8-2.8 (20 H, m), 5.87 (1 H, dq, 2JHH 7.0, 2JHp 14.0 Hz), gave a brown precipitate of the PP'-dioxide (19; S = Br);and 8.61 (3 H, dt, 2JHH 7, 2JpH 17 Hz) (Found: C, 67.4; m/e 507 (low intensity) (Found: c , 48.5; H, 3.7; N, 1-7;H, 5.0; S, 13.6.C2,H,,P2S, requires C, 67.5; H, 5.2; S, Br, 21.2. C31H2,Br2N02P2Pd requires c, 48-75; H, 3.5;13.9). N, 1.8; Br, 20.95). The corresponding dichlorideThe phosphine (3.98 g, 0.01 mol) (x = c1) and di-iodide (x = I) were obtained under similarin methyl iodide (25 ml) was refluxed for 0.5 h. The excess conditions.of methyl iodide was removed under reduced pressure and The complex Pd(PPn')I2 (18;the residual oil recrystallised from ethanol-ether to give x = 1) in a 1O-fold molar excess of methyl iodide Was re-l,l-bis(diphenylphosphino)ethane bismethiodide (4.2 g), m.p. fluxed for 1 he The lnethYl iodide Was removed under248-2500; m/e 428; (CD,),SOJ 1 . 6 2 . 8 (20 H, m), reduced pressure and the residue was dissolved in hot di-4.04br (1 H, s), 6.87 (6 H, d, 2JpH 13 Hz), and 8.34 (3 H, dt, chloroethane. This solution gave on cooling orange crystals2JEH 7.0, 2JpH 16 Hz) (Found: C, 49.0; H, 4.4; I, 36.8.of methY~-(6~et~Y~-2-PYridY~me~hYl)di~henY~~hosPhoniqP~~-C,,H,,I,P, requires C, 49.3; H, 4.4; I, 37.2). ladiurn tri-iodide (20; X = I) (Found: C, 30.9; H, 2.6;N, 1.3; 1, 47.7. C20H2113NPPd requires C, 30.3; H, 2.6;after refluxing for 5 h in glacial acetic acid. N, 1.7; I, 48.0).a-(Diphenylphosphino) benzyldiphenylp~osphine Oxide (1 5).(c) Witit methyl iodide.(b) With methyl iOdide.(d) With acetic acid. The phosphine was unchangedReactions of aa-Bis(dipheny1phospFzino)toluene (13c) .-(a) Oxidation. The phosphine (4.6 g, 0.01 mol), added toethanol (25 ml), was refluxed in air until all the solid haddissolved.Filtration and cooling gave white crystals of in ether (250 ml)* After chlorodiPhenYIPhosPhineara-bis(diphenylphosphino)toluene PP'-dioxide (3 g), m.p. g, in ether ml) was added and stirring wasand the organic layer was separated, dried, and evaporatedto give the phosphine Oxide (15) (5*8 g), m*p. 135-138"*-2M-Buw1-1ithium (lo ml, mol) was added to a stirredOf benzyldiphenylphosphine Oxide (5'84 g,continued for 2 h. An equal volume of water was added 211-213" (lit.,13 306-307"); vmx. (KBr) 1 180 cm-l; rn/e492; (CDC1,) 2.0-3.0 (25 H, m) and 5-02 (1 H, t, 2JPH16 Hz) (Found: C, 75.6; H, 5.6. C,,H,,02P, requires C, u-Diphenylphosphinoylbenzylidenernethyldipheny~phosphor-ane (1 7) .-a-(Diphenylphosphino) benzyldiphenylphosphineoxide (4.76 g, 0.01 mol) and methyl iodide (1.42 g, 0.01 mol)in benzene (40 ml) were refluxed for 1 h.Cooling gavewhite crystals of a-diphenylj5hosphinoylbenzylmethyZdiphenyZ-9hosphoniunz iodide (16) (4.5 g), m.p. 204-206"; v-.(KBr) 1 160 cm-1; -c (CD,),SO 2.0-3.1 (25 H, m), 3.60(1 H, q, 2 J p ~ 16, 2 J p ~ 17 Hz), and 7.01 (3 H, d, 2 J p ~ 14 Hz)62.1; H, 4.7; P, 10.0). Thephosphonium salt (16) (3.1 g,0.005 mol) in ethanol (100 ml) was treated with az-sodiumprecipitated u-diphenyl~hos~hinoylbenzylidenemethyldi~hen-cm-~; -c (CDC1,) 2.15-3.0 (25 H, m) and 6-34 (3 H, d, 2~~~14 H ~ ) (Found: C, 78.0; H, 5.6; p, 12.4. c,,H,,oP, re-quires C, 78.3; H, 5.7; p , 12.7yo).5/2183 Received, lOtlz November, 1976113 M. I. Kabachnik, T. Ya. Medved, Yu. M. Polikarpov, andK. S. Yudina, Izvest. Akad. Nauk S.S.S.R., Ser. khim., 1967, 691(Chem. Abs., 1968, 68. 39743~).l4 S. Trippett, J. Chem. SOL, 1961, 2813.75.6; H, 5.3).(b) With suzphur' The phosphine (2.3 g J O*Oo5 mol) wasadded to sulphur (0.32 g, 0.01 mol) dissolved in deoxygen-ated carbon disulphide (50 ml). The solution was refluxedfor 24 h, filtered, and evaporated under reduced pressure togive acc-his(diphenylphosphino)toluene PP'-disulphide (2.4 g),m.p. (from ethanol) 196-199'; vm (KBr) 604 cm-l;(Found: C, 70.7; H, 5.2; S, 11.9. C,,H,,P,S, requires C,71.0; H, 5.0; S, 12.2).refluxing for 10 h in glacial acetic acid.iodide (25 ml) was refluxed for 0.5 h. The excess of methyliodide was removed under reduced pressure and the residualoil was crystallised from ether-ethanol to give benzylmethyl-diphenylphosphonium iodide (0.5 g), m.p. 241-244' (lit.,14243-245'); -c (CD,),SO 2.2-3.0 (15 H, m), 5.40 (2 H, d,2JPH 15-71, and 7-51 (3 H, d~ 2JPH 13.5 Hz) (Found: c , 57e2;l2 S. 0. Grim, L. C. Satek, C. A. Tolman, and J. P. Jesson,' (CDC13) 1*8-3'2 (25 H, m, and 4'68 ( l H, t, 2JpH l4 Hz) (Found: C, 61.9; H, 4.6; p. 9.7. C3,H,,IOp2 requires C,(') Wit'z acid* The PhosPhine was unchanged after carbonate (5 ml; 0.005 mol). The resulting solution slowly(dl With iodide* (i) The phosphine ( l g) in ylphosphorane (3.9 g), m.p. 189-191"; vm. (KBr) 1 180Inorg. Chem., 1975, 14, 656