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

Abstract

The reaction of the stable carbene, >:>[upper bond 1 start]CN(Prⁱ)C₂Me₂ [upper bond 1 end]NPrⁱ, with InX₃, X = Cl or Br, yielded either the 1∶1 or 1∶2 complexes, [InX₃{[upper bond 1 start]CN(Prⁱ)C₂Me₂N[upper bond 1 end]Prⁱ}] and [InX₃{[upper bond 1 start]CN(Prⁱ)C₂Me₂N[upper bond 1 end]Prⁱ}₂], depending upon the stoichiometry employed. X-Ray crystallography showed one of the 1∶1 adducts, X = Br, to be monomeric and tetrahedral. The 2∶1 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 [upper bond 1 start]CN(Prⁱ)C₂Me₂N[upper bond 1 end]Prⁱ and half an equivalent of water afforded the ionic compounds [H[upper bond 1 start]CN(Prⁱ)C₂Me₂N[upper bond 1 end]Prⁱ] [InX₄{[upper bond 1 start]CN(Prⁱ)C₂Me₂N[upper bond 1 end]Prⁱ}] 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.

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