JOURNALOFTHE CHEMICAL SOCIETYDALTON TRANSACT1Inorganic ChemistryAzomethine Derivatives. Part XV11.1s2ONSSome New Methyleneamino-derivatives of Silicon, Germanium, and TinBy Jane Keable, David G. Othen, and Kenneth Wade,' Chemistry Department, University Science Labora-tories, South Road, Durham DH1 3LEThe new hydrolytically sensitive yellow methyleneamino-derivatives M(N:CPh,)* (M = Ge or Sn), Ge(N:CR2)4,SiMe(N:CR,),, and SiMe2(N:CR2), (R = p-tolyl) and GeBr,(N:CBut,). GeX,(N:CBut,), (X = CI or Br), andGeCI( N:CBut,), have been prepared from Group 4 halides and methyleneaminolithium derivatives. Features oftheir Lr., l H n.m.r., and mass spectra, and of the structures of the compounds M(N:CPh,),.arereported and discussed.THIS paper describes some new methyleneamino-derivatives of silicon, germanium, and tin, which wereprepared in order to obtain further information on themode of attachment of imino-groups, R,C:N, to Group4 elements.Earlier studies on M(N:CR,),X, derivativesof the Group 2 or 3 elements Be,3 B,4-s or A1 had showntheir i.r. and lH n.m.r. spectra to be useful guides to theshapes (linear or bent) of their C=N-M skeletons, whereassimilar studies on met hyleneamino-derivatives of sili-con,1s8'10-1* germaniurn,ll-l3 and tin 11*1%1%1fj afforded littlestructural information. While the ' high ' azomethinestretching frequencies and singlet lH t-butyl resonancesof di-t - bu t ylmet h yleneaminosilanes Si ( N:CBut,) X, maysignify that these compounds have the linear C=N-Siskeletons that would allow maximum N _L Si x bond-ing,l the electronic l1 and lH n.m.r.spectra 13 of diaryl-methyleneamino-derivatives of these Group 4 elementssupport structures with bent C=N-M skeletons. Wehave accordingly prepared some new methyleneamino-derivatives, explored their spectra for further structuralinformation, and obtained a series of crystalline deriva-Part XVI, J. B. Farmer, R. Snaith, and K. Wade, J.C.S.Dalton, 1972, 1501.For a preliminary account of some of this work see N. W.Alcock, M. Pierce-Butler, G. R. Willey, and K. Wade, J.C.S.Chem. Comm., 1976, 183.a C. Summerford, K. Wade, and B. K. Wyatt, J . Chem. SOC.( A ) , 1970, 2016.I. Pattison and K. Wade, J . Chem. SOG. ( A ) , 1967, 1098;1968, 842.J. R. Jennings, I.Pattison, and K. Wade, J . Chem. SOC. ( A ) ,1969, 565.C. Summerford and K. Wade, J . Chem. SOG. ( A ) , 1970, 2010.M. R. Collier, M. F. Lappert, R. Snaith, and K. Wade, J.C.S.Dalton, 1972, 370.tives suitable for X-ray crystallographic study, a pre-liminary account of which has already appeared.2RESULTS AND DISCUSSIONThe new compounds are Listed in the Table. The di-phenylmethyleneamino-derivatives M(N:CPh,), (M =Ge or Sn) were prepared to provide, with the previouslyprepared silicon compound Si(N:CPh,),,lO a series ofcrystalline compounds suitable for X-ray crystallographicstudy . The di-9- t olyl- and di- t- bu t y l-met hyleneamino-compounds were prepared to see whether their lH n.m.r.spectra, by demonstrating the equivalence or non-equiv-alence of their tolyl or butyl groups, would establishtheir shapes.They were prepared by adding suitableproportions of the Group 4 chloride or bromide tofrozen (-196 "C) solutions of the appropriate lithiumderivative Li(N:CR,) in diethyl ether-hexane or -pen-tane mixtures, and allowing the mixture to warm toroom temperature, when reaction was normally com-plete. Attempts to prepare the di-t-butylmethylene-aminogermanes GeBr(N:CBut,), and Ge(N:CBut,), fromC. Summerford and K. Wade, J . Chew SOC. ( A ) , 19G9, 1487.R. Snaith, C. Summerford, K. Wade, and B. K. Wyatt, J .lo C. Summerford, K. Wade, and B. K. Wyatt, J . Chem. Soc.l1 L. H. Chan and E. G. Rochow, J . Organometullic Chem.,12 M. F. Lappert and D. E. Palmer, J.C.S.Dalton, 1973, 157.l3 R. J. Cook and K. Mislow, J . Amer. Chem. SOG., 1971, 98,l4 M. F. Lappert, J. McMeeking, and D. E. Palmer, J.C.S.l5 P. G. Harrison, J.C.S. Perkin I, 1972, 130.Chem. SOG. ( A ) , 1970, 2635.( A ) , 1969, 1487.1967, 9, 231.6703.Dalton, 1973, 1512GeBr, and Li(N:CBut2) (3 or 4 mol equivalents) wereunsuccessful. Three di-t-butylmethyleneamino-groupscould be attached to the same germanium atom, however,by use of GeC1, as the starting material, though heatingto ca. 70 "C was needed to attach the third methylene-amino-group, and the product was still GeC1(N:CBut,),,not Ge(N:CBut,),, even when an excess of Li(N:CBut,)was used. Greater difficulty in attaching But,C:Ngroups as opposed to Ph,C:N groups has also been foundin studies on silicon and boron l 6 systems, the differencebeing attributable to steric factors.In this connection,it appears significant that whereas only one But,C:Ngroup could be attached to a silicon atom,l three suchM.P., e,pc1b.p.. O,/"CCompound (PlmmHg)lSiMe,[N:C(C,H,Me-P) 2]SiMe[N:C(C,H,Me-+) 2]aGe(N:CPh,), 188(decomp.) 8Ge [ N:C (C,H,Me-p) 2] , 60(decomp.)GeC1( N :But2)GeC1,(N:CBut2) [120 (0.6)]GeBr2( N:But2) [120 (0.2)]GeBr,(N:CBut2) 48Sn(N:CPhd, 170-180(decomp.) {O I H N.m.r. data relate to benzene solutions.J.C.S. Daltondi-+-tolylmethyleneaminosilicon chlorides Sick - n-[N:C(C6H4Me-$)& and related germanium chloridesand bromides after preliminary experiments ledto products of variable composition.The di-t-butylmethyleneaminogermanium halides GeCh- x-(N:CBut,), (x = 1-3) and GeBr,(N:CBut,), by con-trast proved surprisingly stable to disproportionation.The dihalides, for example, are oils which can be purifiedby distillation under low pressure at 120-150 "C (Table),and their mass spectra contained no peaks attributable toproducts of disproportionation. The fragmentation ofGeX,(N:CBut,), (X = C1 or Br) in the mass spectro-meter+(C=N) +(M-N)cm-11 643 8601642 8671601 7OOeJ1 6984 707e1662 7311646 74 11646 7361 624 7311 690 6 664led to-no Ge(N:CBut2), or GeX, units, and no7(Me) a7.837.838.438.738.768.708.81' c79.9(81.0)80.4(82.8)77.6(78.9)79.6(79.6)61.9(61.4)60.1(61.0)41.3(42.1)23.6(23.9)76.6(76.3)Analysis b( % )H N Clor Br7.4 6.8(7.2) (6.9)7.0 6.6(6.8) (6.3)6.0 7.1(6.1) (7.1)6.3 6.0(6.2) (6.2)10.7 7.6 6.88.7 17.1(8.6) (6.6) (16.8)7.4 6.6 31.2(7.0) (6.6) (31.2)3.7 2.9 63.8(4.0) (3.1) (63.0)6.2 7.0(4.8) (6.7)A 3(10.2) (;:go) (6.7)b Calculated values a= given in parentheses. c Determined by cryoscopy inbenzene solutions.Recrystallised from toluene-hexane. 6 Nujol mull; the remaining i.r. data relate t o liquid films. f Tenta-tive assignment, obscured by phenyl absorption. From light petroleum. h From toluene-light petroleum. 6 From toluene.9 Not soluble enough in benzene t o allow cryoscopic determination of M.groups can be attached to the slightly larger germaniumatom.The identities of the new derivatives were confirmed byelemental analyses (Table), and their monomeric stateof association in benzene was established by cryoscopy.All nine compounds are yellow moisture-sensitive sub-stances which need to be manipulated and stored i.nvacuo, or under a dry atmosphere: their reaction withmoist air can be followed by the rapid fading of theyellow colour, by fuming in the case of the halides,and by the appearance of new absorptions, attributableto hydrolysis products, in their i.r.spectra. For ex-ample, Nuj ol mulls of the diarylmethyleneamino-derivatives, after brief exposure to air, characteristicallyabsorb in the range 3 220-3 280 [v(N-H)] and 1 650-1 660 cm-l [v(C=N)].Diarylmethyleneaminosilicon halides SiX4-,[N:C-(aryl)J, tend to disproportionate readily, e.g.as in2 SiMe,(Cl) (NzCPh,) +SiMe,(N:CPh,), + SiMe,Cl, (1)equation (1) .a* l1 Problems with similar disproportion-ations caused us to abandon the synthesis oflo E. A. Petch, R. Snaith, and K. Wade, unpublished work.l7 F. A. Miller and G. L. Carlson, Spectrochim. Acta, 1961, 17,977.Ge(N:CBut,), or GeBr, units were detected in the massspectrum of GeBr,(N:CBut,) . Fragmentation followedthe usual pattern for such derivatives: progressivecleavage of M-N and M-X bonds; loss of substituents Rfrom methyleneamino-groups R,CN ; and occasionalmigration of substituents R from the azomethine carbonatom to the metal.An X-ray crystallographic study of the compoundsM(N:CPh,), (M = Si,l0 Ge, or Sn) has shown theirC=N-M units to be bent, the angle at nitrogen averaging137" for M = Si, 127" for Ge, and 121" for Sn, indicatinga decreasing degree of N _L.M x bonding in this se-quence. Their ' short ' M-N bonds [Si-N, 172(1);Ge-N, 187(1); and Sn-N, 206(4) pm] also indicate sig-nificant N __L M x bonding, at least in the case of thesilicon and germanium compounds ; the uncertainty inthe length of the Sn-N bond is too great to allow firmconclusions to be drawn about its order.These structures may usefully be compared with thoseof isocyanate, isothiocyanate, and carbodi-imide deriva-tives of these same elements. The following GN-141angles have been found in structural studies on Group 4isocyanates, etc. : Si(NCO),, 180,17 146; l6 Si(NCS),, 180; l9la K.E. Hjortaas, Acta Chem. Sand., 1967, 21, 1381.lo G. L. Carlson, Spectrochim. Acta, 1962, 18, 16291976 3SiH,(NCO), SiH,(NCS), 180; SiMe,(NCO), 150; 22SiMe,(NCS) , 154; SiF,(NCO) , 161 ;:% SiCIz(NC0)4-,ca. 140; 24 GeH,(NCO), H,GeNCNGeH,, ca. 140 ; 25SnMe,(NCS), 173; 26 SnMe,(NCS),, 164; 27928 Me3-SnNCNSnMe,, 118; 29 and {[(SCN)Me,Sn],O}, 170".30These bond angles, and the M-N bond lengths in thesecompounds, are suggestive of N =+t M x bonding inmost cases, especially when it is borne in mind that thebent structures found by electron-diff raction studies onthe silyl pseudohalides 18,22-24 may really reflect the easeof deformation of floppy linear Si(NCX) ~ n i t s . ~ l ' ~ lThe structures of the methyleneamino-derivatives mayalso be compared with those of similar derivatives ofneighbouring elements.The phosphorus compoundP(NXPh,), has bent C=N-P units (average CNP angle,123") ,32 indicating little if any dative x bonding, whereasapproximately linear C=N-M units have been foundattaching the terminal imino-groups of (Be(N:CBut2),),to three-co-ordinate beryllium (CNBe angle, 161"),%of B(C6H,Me,-2,4,6),(N:CPh2) to three co-ordinate boron(CNB angle, 173"),% and of Li[A1(N:CBut,),] to four-co-ordinate aluminium (CNA1 angle, 167") .35We believe that the di-9-tolylmethyleneamino-com-pounds SiMe,( NXR,), , SiMe( NXR,),, and Ge(N:CR,),(R = 9-tolyl) , like the diphenylmethyleneamino-com-pounds M(N:CPh,),, contain bent C=N-M units, althoughwe have been unable to confirm this by our spectro-scopic studies.Their lH n.m.r. spectra contain onlysinglet absorptions (see Table for T values) attributableto the tolyl methyl groups, even at -80 "C, the lowesttemperature at which satisfactory spectra could be ob-tained. When Cook and Mislow l3 demonstrated thebent C=N-Ge unit of the compound GeMe,(N:CPh-(C,H,CF,-$)} by the overlapping doublet structure of itsGeJie, resonance they found it necessary to cool theirsolutions to -110 "C. Clearly, whether the preferredstructure is linear or bent, the barrier to inversion atnitrogen in many of these C=N-M systems is low. ThelH n.m.r. spectra of the new di-t-butylmethyleneamino-germanes GeX4-,(N:CBut,), contained only singlet t-butylabsorptions at or above -80 "C.(The parent imine,But,C:NH, gives a well resolved doublet at -60 "C.s)Again, structures with bent C=N-Ge units invertingrapidly at nitrogen appear likely.The i .r. spectra of the new methyleneamino-derivativesalso appear consistent with bent C=N-M structures in* For details see Notice to Authors No. 7, J.C.S. Dalton, 1974,Index issue (items less than 10 pp, are supplied as full-size copies).2o D. R. Jenkins, R. Kewley, and T. M. Sugden, Trans. FaradaySoc., 1962, 58, 1284.21 C. Glidewell, A. G. Robiette, and G. M. Sheldrick, Chem.Phys. Letters, 1972, 16, 526.22 K. Kimura, K. Katada, and S. H. Bauer, J . Amer. Chem.Soc., 1966, 88, 416.23 W. Airey, C. Glidewell, A. G. Robiette, and G. M. Sheldrick,J . Mol. Stvucture, 1971, 8, 435.24 R.L. Hilderbrandt and S. H. Bauer, J . Mol. Structure, 1969,3, 326.25 J . D. Murdoch and D. W. H. Rankin, J.C.S. Chem. Comm.,1972, 748.26 R. A. Forder and G. M. Sheldrick, J . Organometallic Chem.,1970, 21, 115.27 R. A. Forder and G. M. Sheldrick, J . Organometallic Chem.,1970, 22, 611.that the azomethine stretching absorptions have fre-quencies (Table) little different from those of the parentimines [Ph,C:NH has v(C=N) at 1 607, ($-MeC,H,),C:NHat 1610, and Bue2C:NH at 1610 ~ m - l ] . ~ ~ Coupling ofthe C=N and N-M vibrations of linear C=N-M units wouldbe expected to cause a marked increase in v(C=N) rela-tive to the parent imine, as has been found for derivativesof beryllium: aluminium? and gallium ,37 al-though this effect decreases as the mass of M increases.Detailed interpretation of the azomethine stretchingfrequencies in the Table is complicated by the varyingnumber of imino-groups present.Coupling of the azo-methine stretching vibrations is to be expected for deriva-tives with more than one imino-group attached to thesame central Group 4 atom [i.e. for all the compounds inthe Table except GeBr,(N:CBut,)] , and the frequencieslisted in the Table relate to the relatively sharp maximumof what in many cases is a broad absorption with pro-nounced shoulders ca. 10-30 cm-l to either side, furthercomplicated, in the case of the species with aryl sub-stituents, by the presence of the characteristic ringmode at ca. 1 575 cm-l.In the Table, we also list the frequencies of bandsassignable to M-N stretching vibrations.Lappert andPalmer,12 in their study of compounds MMe4-.[N:C-(CF3)2]z (M = Si, Ge, or Sn) assigned absorptions at ca.950-960 cm-l to the M-N stretching vibrations, thefrequencies surprisingly not varying significantly withM.38 Our own assignments, which must be regarded astentative in view of the complexity of the spectra in the500-950 cm-l region, relating to only one of the two M-Nstretching absorptions expected for most of these com-pounds, show the expected variation with M, and appear tobe in line with the frequencies of other M-N absorptions.%EXPERIMENTALThe methods used t o prepare the methyleneaminolithiumreagents, and the manipulative techniques used for themoisture-sensitive products, were as described in earlierparts of this series.' 1.r. spectra were recorded on a Perkin-Elmer 457 instrument. lH N.m.r. spectra were obtainedat 60 MHz on a Varian A56/60D spectrometer.Details of the i.r. spectra of the new compounds are inSuppIementary Publication No. SUP 21594 (4 pp.).*We thank Brian Hall for experimental assistance, and theS.R.C. for research grants (to J. K. and D. G. 0.).[4/860 Received, 30th April, 1974128 Y. M. Chow, Inorg. Chem., 1970, 9, 794.29 R. A. Forder and G, M. Sheldrick, J . Chem. SOC. ( A ) , 1971,30 Y. M. Chow, Inorg. Chem., 1971, 10, 673.31 B. Beagley, Chem. SOC. Specialist Periodical Report, 1973, 1,32 J . Keable, H. M. M. Shearer, and K. Wade, unpublished33 J . B. Farmer, H. M. M. Shearer, D. B. Sowerby, and K.34 G. J. Bullen, J.C.S. Dalton, 1973, 858.35 H. M. M. Shearer, R. Snaith, J. D. Sowerby, and K. Wade,36 B. Samuel, R. Snaith, C. Summerford, and K. Wade, J.37 J. B. Farmer and K. Wade, unpublished work.38 S. R. Stobart, Chem. SOC. Specialist Periodical Repovt, 1976,1107.123; 1974, 2, 28.work.Wade, unpublished work.Chem. Comnz., 1971, 1275.Chem. SOC. ( A ) . 1970, 1029.7, 283