Strukturen der Dimethylerdmetallphenylchalkogenolate [(Me ₂MEPh)_n] withM = Ga, In, Tl and e = S, Se, Te

The reaction of main group III trimethyls, Me₃M, with phenylchalcogenols HEPh leads to dimethyl earthmetal phenylchalcogenolates [(Me₂MEPh)_n] with M = Ga and E = S (1), Se (2), Te (3), M = In and E = S (4), Se (5), Te (6) and M = Tl and E = S (7), Se (8), Te (9). Alternatively, reaction between Me₃M and Me₃SiEPh with elimination of SiMe₄ is possible for E = Se, Te if a polar solvent is applied, in order to stabilize the initial adduct [Me₃M-E(Ph) SiMe₃]. Additionally, for M = Tl and E = S the dimeric adduct [{Me₂TlSPh(TlMe₃)}₂] (10) was isolated and structurally characterized. Single crystals and microcrystalline samples of compounds 1 to 9 were examined by X-ray crystallography and polymeric as well as dimeric structures were found. Depending on the size of main group III and VI atoms, sterically shielded polymeric chains or layer-like structures are obtained. The smaller metal atoms M = Ga, In are fourfold coordinated and these compounds exhibit polymorphism. This observation is consistent with quantum chemical calculations that show the syn- and anti-orientation of phenyl groups in a dimer to be energetically nearly equivalent. For M = Tl the coordination number is increased to 5 or 6 by additional coordination of chalcogen atoms with relatively long Tl-E bonds. Variable temperature NMR spectroscopy and molecular weight measurements indicate fast exchange and the presence of several different molecular structures in solution.