Hydroalumination of dialkynylgermanes-synthesis of alkenyl-alkynylgermanes with intramolecular aluminium-carbon interactionsDedicated to Prof. Pascal Le Floch. This article is part of a themed issue on Main Group chemistry.CCDC reference numbers CCDC 762758-762762. For crystallographic data in CIF or other electronic format see DOI: 10.1039/c0nj00050g

Reactions of dialkylaluminium hydrides, R 2 AlH [R = CH 2 CMe 3 , CMe 3 , CH(SiMe 3 ) 2 ], with di(phenylethynyl)germanes, R 2 Ge(C&z.tbd;C-C 6 H 5 ) 2 [R = CH 3 ( 1 ), C 6 H 5 ( 2 )], afforded mixed alkenyl-alkynylgermanes, R 2 Ge(C&z.tbd;C-C 6 H 5 )[C(AlR 2 )&z.dbd;C(H)-C 6 H 5 ] ( 3 to 7 ), by hydroalumination of one of the C&z.tbd;C triple bonds. In all cases the cis -arrangement of the Al and H atoms across the resulting C&z.dbd;C 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. Hydroalumination of R 2 Ge(C&z.tbd;C-Ph) 2 (R = Me, C 6 H 5 ) affords alkenyl-alkynylgermanes which show an intramolecular interaction between the coordinatively-unsaturated aluminium atom and the α-carbon atom of the triple bond.