Formation of germanium–nitrogen double bonds in reactions of the electron-rich germylene bis[bis(trimethylsilyl)amido]germanium(II) with a range of diazo-compounds

Abstract

The electron-rich germylene Ge[N(SiMe₃)₂]₂ reacts with the diazo-compounds R¹CH₂COC(N₂)R²[R¹= H, R²= CO(OEt), SO₂C₆H₄Me-p, or COPh; R¹, R²=–CMe₂CH₂C(O)–], which contain an enolisable function, to yield the heterocycles [graphic omitted]; the weakly acidic diazo-compounds ethyl diazoacetate and diazoacetophenone yield bis-adducts Ge[N(SiMe₃)₂]₂[C(N₂)COR][NHNC(H)COR](R = OEt or Ph). Diazo-compounds containing two non-enolisable substituents yield mono-adducts with Ge[N(SiMe₃)₂]₂ which can be hydrolysed to yield the diol Ge(OH)₂[N(SiMe₃)₂]₂ and, in one example, the corresponding hydrazone H₂NNC(COPh)CO(OEt). These adducts appear to be thermodynamically stable in an aprotic solvent, but can be trapped by addition of ethanol, to yield Ge[N(SiMe₃)₂]₂(OEt){NHNC[CCO(OMe)]₂}, or of diazoacetophenone to yield Ge[(SiMe₃)₂]₂[C(N₂)COPh]{NHNC[CO(OMe)]₂}. All the reactions of the germylene with diazo-compounds can be rationalised in terms of the initial formation of a germyleneazine [(Me₃Si)₂N]₂GeN–NC(X)Y, which readily adds any available protic species to give a germane derivative. MNDO calculations on model systems are in accord with the experimental findings and also explain their differences from results previously obtained using the simpler germylene GePh₂.