Reaction of the thiurams [R2NC(=S)S](2) (R = Me, Et, Bz) with the trimethylamine complexes of alane (AlH3) and gallane (GaH3) results in the high yield production of the tris-dithiocarbamate complexes [M(S2CNR2)(3)] (M = Al, Ga) formed via the reductive cleavage of the S-S bond. Transmetallation reactions of [(Et2O)(k). AlH3](n) with [M'(S2CNEt2)(n)] (M' = As, Sb, n = 3, M' = Se, n = 2) also result in the synthesis of [Al(S2CNEt2)(3)] in high yield. A number of these complexes have been structurally characterised: [Al(S2CNEt2)(3)] (1), isomorphous with its chromium(III) analogue, belonging to the monoclinic P2(1)/n, Z=4, form of the [M(S2CNEt2)(3)] family; Al-S are 2.377(6)-2.390(6) Angstrom, similar to values previously established for [Al(S2CNMe2)(3)]. CH2Cl2, which is isostructural with its Ga analogue, 3, (triclinic P1, Z = 2), for which Ga-S are 2.418(2)-2.449(2) Angstrom; solvent... tris-dithio-carbamate interactions in these species appear to be of negligible significance. Al-S are anomalously long cf. Ga-S in counterpart complexes ca. 2.37, 2.44 Angstrom, Al, Ga-OH2 in their alums being 1.877(3), 1.944(3) Angstrom. These observations are reinforced by studies of [M(S(2)CNBz(2))(3)], M = Al, Ga, 2, 5, monoclinic P2(1), Z = 4, isomorphous with previously reported M = Fe, Co, Ir complexes, and of orthorhombic Fdd2 [Ga(S2CNEt2)(3)]. 2CHCl(3), 4, in which the molecule lies on a crystallographic 2-axis, the hydrogen atoms of the chloroform molecules being wedged between the sulfur atoms of the pairs of ligands. (C) 2000 Elsevier Science S.A. All rights reserved.