Dithiocarbamate complexes of trivalent aluminium and gallium via metal hydrides

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 P21/n, Z=4, form of the [M(S2CNEt2)3] family; AlS are 2.377(6)–2.390(6) Å, similar to values previously established for [Al(S2CNMe2)3]·CH2Cl2, which is isostructural with its Ga analogue, 3, (triclinic P, Z=2), for which GaS are 2.418(2)–2.449(2) Å; solvent⋯tris-dithiocarbamate 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 Å, Al, GaOH2 in their alums being 1.877(3), 1.944(3) Å. These observations are reinforced by studies of [M(S2CNBz2)3], M=Al, Ga, 2, 5, monoclinic P21, Z=4, isomorphous with previously reported M=Fe, Co, Ir complexes, and of orthorhombic Fdd2 [Ga(S2CNEt2)3]·2CHCl3, 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.