Water- and O-sensitive compds. (tBu3SiEX2)2, tBu3SiEX2.Do, and (tBu3Si)2EX (E = Al, Ga, In; X = (F), Cl, Br; Do = OR2, NR3) were synthesized by reaction of EX3 with tBu3SiNa in the absence or presence of donors. In addn., (tBu3Si)AlBr2, (tBu3Si)2InF, and tBu3SiInBr2 were prepd. by reaction of AlBr3 with (tBu3Si)2Zn or of (tBu3Si)2InIn(SitBu3)2 with AgF2 and HBr, resp. The adduct [tBu3SiAlBr2.AlBr3.1/2MgBr2]2 is formed from AlBr3 and (tBu3Si)2Mg(THF)2. Thermal decompn. of the compds. in soln. or in the gas phase leads to the formation of tBu3SiEX2 (from the dimers or the donor adducts) and of tBu3SiX. The Lewis acidity of tBu3SiEX2 against donors increases in the direction Do = Et2O < THF < NEtMe2. Dehalogenation of (tBu3Si)2ECl with tBu3SiNa(THF)2 in pentane at room temp. leads to clusters (tBu3Si)4Al2, (tBu3Si)3Ga2.bul., (tBu3Si)4In2, and (tBu3Si)3Ga2Na(THF)3, redn. of tBu3SiGaCl2 with Na or K in heptane at 100 Deg to the tetrahedral (tBu3Si)4Ga4. The structures of (tBu3SiGaCl2)2, (tBu3Si)2GaCl, and [tBu3SiAlBr2.AlBr3.1/2MgBr2]2 were detd. by x-ray structure anal. [on SciFinder (R)]