Reactivity of a germa-alkyne: Evidence for a germanone intermediate in the hydrolysis and alcoholysis processes

The formation of a new transient germa-alkyne Ar-Gepartial double bond, top dashedC–SiMe3 [Ar = 2,4-di-tert-butyl-6-(diisopropylaminomethyl)phenyl] is achieved by photolysis of the corresponding trimethylsilyldiazomethylgermylene ArGeC(N2)SiMe3 (2). The germa-alkyne is characterized by trapping reactions with H2O and an equimolar mixture of tert-butanol and water. The respective adducts, the gem-germanediol 5 and the alkoxygermanol 4 have been fully characterized by spectroscopic methods. A study of the mechanism is proposed and in both cases, the addition involves the transient formation of a germanone. The structures of 2 and 5 are determined by single-crystal X-ray diffraction.