mu-Hydroxo organo aluminium and gallium compounds

Tetrakis [bis(trimethylsilyl)methyl] dialane(4) (1) with an aluminium-aluminium bond reacts with dimethyl sulfoxide (DMSO) and water under formation of a dialkyl hydroxo aluminium compound (2) which forms a trimer probably via Al-OH-Al bridges ([R(2)Al(mu- OH)](3); R = CH(SiMe(3))(2)) as detected by mass spectroscopy. A similar compound (5) is directly formed by the reaction of DMSO with the corresponding digallium(4) compound (4) containing a Ga-Ga bond without the addition of water. In contrast to 2, the gallium derivative 5 is an OH bridged dimer as shown by cryoscopic molar mass determination in benzene and crystal structure analysis (C28H78Ga2O2Si8, monoclinic, P2(1)/n; a = 960.1(1), b = 1474.7(2), c = 1699.4(2) pm, beta = 90.12(2)degrees; Z = 2; R(1) = 0.071). Treatment of the mu-hydroxo aluminium derivative 2 with the base isobutyl lithium does not give a deprotonation reaction, instead, compound 3 is quantitatively formed showing a six-membered Al2LiO3 heterocycle with three hydroxo groups bridging one lithium and two aluminium atoms (C34H91O3LiAl2N3Si8 . 0.50(C2H5)(2), monoclinic, P2(1)/c; a = 1553.25(6), b = 1519.88(7), c = 2647.6(1) pm, beta = 106.61(4)degrees; Z = 4; R(1) = 0.062).