Formation of germenes from bis(germavinylidene)

A series of germenes have been synthesized from the bis(germavinylidene) [(Me3SiNPPh2)(2)CGe -> GeC(PPh2NSiMe3)(2)] (1). The reaction of 1 with 2,2,6,6-tetramethylpiperidine N-oxide afforded [(Me3SiNPPh2)(2)CGe(ONCMe2C3H6CMe2)(2)] (2). Germavinylidene, the dissociation derivative of 1, underwent [1 + 4] cycloaddition with azobenzene, followed by a 1,3-H shift to give [(Me3SiNPPh2)(2)CGe(o-C6H4NHNPh)] (3). Treatment of 1 with benzil afforded the [1 + 4] cycloaddition compound [(Me3SiNPPh2)(2)CGe{O(Ph)CC(Ph)O}] (4). The results showed that the germavinylidene moiety dissociated from 1 acts as a synthon for the preparation of various germenes by addition to the germanium(II) center. The molecular structures of 2-4 have been determined.