Trinuclear Heterobimetallic Complexes by Stepwise Metalation of a Macrocyclic Tetraimidazolium Salt

Schulte to Brinke C., Hahn F.

Abstract

A series of trinuclear heterobimetallic AuI/M2 (M = RhIII, IrIII, RuII) complexes were prepared by the stepwise and selective metalation of a rigid cyclic tetraimidazolium salt. Reaction of the tetraimidazolium salt with exactly 1 equivalent of silver oxide and transmetalation of the dicarbene ligand to AuI yielded selectively a mononuclear AuI complex. This complex features an CNHC-Au-CNHC unit obtained by coordination of two N-heterocyclic carbene (NHC) donors placed in diagonal positions within the macrocycle and two non-metalated imidazolium moieties. Subsequent metalation of these imidazolium groups yielded heterobimetallic complexes (AuI/RhIII2, AuI/IrIII2, and AuI/RuII2) with Au···M separations shorter than 5.5 Å. The selective stepwise metalation of a rigid macrocyclic tetraimidazolium salt gives rise to trinuclear heterobimetallic tetracarbene complexes (AuI/RhIII2, AuI/IrIII2, AuI/RuII2) with M···M distances of less than 5.5 Å in the solid state.