Preparative Aspects of One-Dimensional Transition Metal Coordination Compounds

Abstract

The results of a chemical and physical investigation of known linear chain metal compounds with direct metal-to-metal contacts can be successfully used as a guideline in the directed synthesis of new linear chain transition metal complexes with strong intermolecular interactions. One-dimensional metallic behaviour of crystallized four-coordinate planar transition metal compounds with 8 d electrons is expected if small and strongly π electron-accepting equatorial ligands like carbon monoxide are used. I.r., ¹H-n.m.r., ¹⁹⁵Pt-n.m.r., e.s.r., u.v. and ¹⁹³Ir-Mößbauer spectra show that increasing bulkiness and increasing electron donating properties of the (mostly organic) ligands considerably decrease the strength of the intermolecular metal interactions in all compounds. Planar transition metal complexes with less than 8 d electrons per metal seem to be far better suited for the formation of 1d metals. But because of the strong Lewis acid activity of the individual molecules in solution, the axial positions in the coordination sphere are blocked by donating solvent molecules. The self-association reaction necessary for the building of linear chains is prevented for this reason. Preparative procedures to overcome these problems are proposed. One of the “mixed valence” solids obtained contains a linear I-₃chain in addition to the linear metal chain.