Synthesis, crystal structures and dynamic NMR studies of novel trinuclear copper(I) halide complexes with 2,5-bis[(diphenylphosphino)methyl]thiophene

Abstract

Novel trinuclear copper(I) halide complexes with 2,5-bis[(diphenylphosphino)methyl]thiophene (dpmt), [Cu₃(µ₃-X)(µ-X)₂(µ-dpmt)₂] (X = I 1, Br 2 or Cl 3), have been synthesized and structurally characterised. They have unusual three-runged ladder structures with one triple-bridging and two double-bridging halide atoms. Two of the Cu^I are tetrahedrally co-ordinated and one, in the middle of the structure unit, has trigonal co-ordination geometry. The trinuclear Cu₃(µ₃-X)(µ-X)₂ framework shows some changes with halide anion X due to the size effect and intramolecular non-bonding Cu· · ·Cu and X· · ·X interactions. The NMR studies showed that the trinuclear framework is retained in solution for 1 (X = I), is in equilibrium with Cu₃(µ-X)₃ for 2 (X = Br) and changes to Cu₃(µ-Cl)₃ for 3 (X = Cl), an effect attributable to the decrease of halide size from iodide to chloride. The frameworks in the solutions of 2 and 3 exhibit fluxional behaviour involving bromine and chlorine mobility respectively.