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

Treatment of the potentially chelating bis-carbene, 1,2-ethylene-3,3'-di-tert-butyl-diimidazole-2,2'-diylidene, EtIBut, 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)(mu-EtIBut)]. 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 EtIBut with MX3, M = In or Tl, X = Br or Cl, led to the 1 : 1 adducts, [MX3(EtIBut)]. The X-ray crystal structure of one of these, [InBr3(EtIBut)], shows the ligand to act in a chelating mode, taking up equatorial positions of an trigonal bipyramid. The reactions of EtIBut 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, [(EtIBuH2)-H-t][Cl](2), which has also been crystallographically characterised. Several related reactions are described.