Synthesis and characterisation of stable carbene-indium(III) halide complexes

The reaction of the stable carbene, :CN(Pr')C2Me2NPr', with InX3, X = Cl or Br, yielded either the 1:1 or 1:2 complexes, [InX3{CN(PR')C2Me2NPr'}] and [InX3{CN(Pr')C2Me2NPr'}(2)], depending upon the stoichiometry employed. X-Ray crystallography showed one of the 1 : I adducts, X = Br, to be monomeric and tetrahedral. The 2: I adducts have a trigonal-bipyramidal geometry with two halides axial and one equatorial. Conductivity and NMR studies suggested all these complexes retain their neutrality in solution. Treatment of InX3 with 1 equivalent of CN(Pr')C2Me2NPr' and half an equivalent of water afforded the ionic compounds [HCN(Pr')C2Me2NPr'][InX4{CN(Pr')C2Me2NPr'}] which are fluxional in solution at room temperature. The crystal structures of both compounds show the anion to be trigonal bipyramidal with two axial and two equatorial halides.