Preparation, Structure, and Reactivity of Discrete Branched Oligogermanes

The hydrogermolysis reaction of PhGeH3 serves in the synthesis of discrete branched oligogermanes. Treatment of PhGeH3 with 3 equiv of the α-germyl nitriles R3GeCH2CN (R3 = Ph3 or Bu2CH2CH2OEt), which are generated in situ from the corresponding amides R3GeNMe2 and CH3CN, furnishes the tetragermanes PhGe(GePh3)3 and PhGe(GeBu2CH2CH2OEt)3 in excellent yield. The crystal structure of PhGe(GePh3)3 was determined. This compound is the first branched oligogermane to be structurally characterized. Reaction of the tetragermane PhGe(GeBu2CH2CH2OEt)3 with Bui2AlH generated the intermediate hydride PhGe(GeBu2H)3. Subsequent treatment of PhGe(GeBu2H)3 with the synthons R2Ge(NMe2)CH2CH2OEt (R = Bu, Et, Ph) in CH3CN solution furnished the heptagermanes PhGe(GeBu2GeR2CH2CH2OEt)3 (R = Bu, Et, Ph). The latter process also proceeds through the in situ formation of the α-germyl nitriles R2Ge(CH2CN)CH2CH2OEt.