Reactions of β-diketiminatoaluminum hydrides with tert-butyl hydrogenperoxide – Facile formation of dialuminoxanes containing Al–O–Al groups

Treatment of diphenyl-β-diketiminatoaluminum dihydride, LAlH2 [1, L = {H5C6–Ndouble bond; length as m-dashC(Me)}2CH] with neopentyl- or trimethylsilylmethyllithium afforded the corresponding alkylderivatives LAlH(R) [R = CH2–SiMe3 (2), CH2–CMe3 (3)] by the precipitation of lithium hydride. Deprotonation of a methyl group instead of salt elimination occurred by the similar reaction of the more basic alkyllithium compound LiC(SiMe3)3. The reactions of the hydrides 1–3 with tert-butyl hydrogenperoxide did not yield the expected peroxo derivatives, instead the dialuminoxanes LAl(R)–O–Al(R)L [R = OCMe3 (5), CH2SiMe3 (6), CH2CMe3 (7)] were isolated in high yields. Their Al–O–Al bridges deviated from linearity and had Al–O–Al bond angles of about 155° on average.