The reaction of the trialkylalane (Me 3 Si) 3 CAlMe 2 × THF (1) (µ-SeMe)] 2 (7, M = Al; 8, M = Ga). The compounds exhibit a high thermal stability and can not be converted to the with H 2 S in toluene at room temperature results in the formation of the dimeric sulfido compound [(Me 3 Si) 3 CAl(µ-corresponding selenides [(Me 3 Si) 3 CM(µ 3 -Se)] n (M = Al, Ga) upon heating. In contrast, the trialkylalane 1 does not react S)] 2 × 2 THF (3), while the reaction of the homologous gallane (Me 3 Si) 3 CGaMe 2 (2) with H 2 S under similar with tellurium metal in refluxing toluene at all, while the trialkylgallane 2 affords the tellurolate [(Me 3 Si) 3 CGaMe(µ-conditions affords the heterocubane [(Me 3 Si) 3 CGa(µ 3 -S)] 4 (4). Heating of compound 3 in vacuo gives a mixture of the TeMe)] 2 (9) under similar conditions. Compounds 3-9 have been characterized by 1 H-and 29 Si-NMR, mass, and IR symmetrically substituted [(Me 3 Si) 3 CAl(µ 3 -S)] 4 (5) and the unsymmetrically substituted heterocubane [{(Me 3 Si) 3 CAl(µ 3 -spectroscopy. Furthermore, the molecular structures of compounds 3 • C 6 H 6 , 4 • 1.5 C 6 H 6 , 6, 7 • C 6 H 6 and 9 have S)} 3 MeAl(µ 3 -S)] (6). Reaction of the trialkylmetalanes 1 and 2 with elemental selenium in refluxing toluene results in the been determined by X-ray crystallography. formation of the corresponding selenolates [(Me 3 Si) 3 CMMe-