Facile Synthesis of an Unsaturated Spiro Germane by Hydroalumination and Intramolecular 1,1-Carbalumination

Treatment of the tetraethynylgermanium compound Ge(CCC6H5)4 4 with 2 equiv of H−Al[CH(SiMe3)2]2 yielded the addition product Ge(CCC6H5)2[C{AlR2}C(H)C6H5]2 (5, R = CH(SiMe3)2) by reduction of two of its CC triple bonds. Heating of 5 to 260 °C for 10 min gave a unique rearrangement reaction which via intramolecular 1,1-carbalumination afforded the spiro germane 6 (a 3,7-bis[1-phenylmeth-(Z)-ylidene]-4-germaspiro[3,3]hepta-1,5-diene derivative). The molecular structure of 6 comprises two unsaturated 1-germacyclobut-2-ene heterocycles with a joint germanium atom and two exocyclic CC double bonds.