Bidentate N-heterocyclic carbene complexes of Group 13 trihydrides and trihalides

Abstract

Treatment of the potentially chelating bis-carbene, 1,2-ethylene-3,3′-di-tert-butyl-diimidazole-2,2′-diylidene, EtIBu^t, with [MH₃(NMe₃)], M = Al, Ga, In, in a 1 ∶ 1 or 1 ∶ 2 stoichiometery led to good yields of the metal rich 2 ∶ 1 adducts, [(MH₃)₂(μ-EtIBu^t)]. These complexes have been spectroscopically characterised and the X-ray crystal structures of two (M = Al or In) obtained. In contrast, the 1 ∶ 1 or 1 ∶ 2 reactions of EtIBu^t with MX₃, M = In or Tl, X = Br or Cl, led to the 1 ∶ 1 adducts, [MX₃(EtIBu^t)]. The X-ray crystal structure of one of these, [InBr₃(EtIBu^t)], shows the ligand to act in a chelating mode, taking up equatorial positions of an trigonal bipyramid. The reactions of EtIBu^t with MCl₃, M = Al or Ga, led to decomposition and in the aluminium reaction the major product of the decomposition process was the bis-imidazolium salt, [EtIBu^tH₂][Cl]₂, which has also been crystallographically characterised. Several related reactions are described.