Hydroalumination of dialkynylgermanes—synthesis of alkenyl–alkynylgermanes with intramolecular aluminium–carbon interactions

Abstract

Reactions of dialkylaluminium hydrides, R₂AlH [R = CH₂CMe₃, CMe₃, CH(SiMe₃)₂], with di(phenylethynyl)germanes, R₂Ge(CC–C₆H₅)₂ [R = CH₃ (1), C₆H₅ (2)], afforded mixed alkenyl–alkynylgermanes, R₂Ge(CC–C₆H₅)[C(AlR₂)C(H)–C₆H₅] (3 to 7), by hydroalumination of one of the CC triple bonds. In all cases the cis-arrangement of the Al and H atoms across the resulting CC double bond was observed. Crystal structure determinations revealed relatively strong intramolecular bonding interactions between the coordinatively-unsaturated aluminium atoms and the α-carbon atoms of the intact triple bonds bearing a partial negative charge. This interaction is only prevented by application of the very bulky bis(trimethylsilyl)methyl substituent.