Pyridine vs. Bipyridine Coordination in PtCl₂ Complexes of 4-^tButyl-4'-(4-pyridinyl)-2,2'-bipyridine

Abstract

The reaction of the new terpyridine ligand 4-tbutyl-4'-(4-pyridinyl)-2, 2'-bipyridine L with various sources of “PtCl2” selectively yields either trans-[PtCl2(L)2] (1) with L bonded in a monodentate fashion via its pendant 4-pyridyl ring or cis-[PtCl2(L)] (2), where L coordinates in a bidentate fashion through its 2,2'-bipyridine subunit. The molecular structures of L and of complex 1 were determined by X-ray crystallography and exhibit intra- and intermolecular hydrogen bonding. We have also converted the dichloro complex 2 into the bis(coumarin thiolate) complex 3. Owing to their free imine coordination sites, complexes 1–3 constitute interesting building blocks for multimetal structures in a “complexes as ligands” approach. The reductive behaviour of L and of complexes 1–3 has been investigated by cyclic and square wave voltammetry.