A novel titanium–oxygen ladder structure supported by calix[4]arene ligands, characterised by synchrotron crystallography

Abstract

Reaction of an excess of TiCl₄ with p-tert-butylcalix[4]arene (H₄L¹) in toluene led to [{Ti₂(µ₃-O)Cl₂L¹}₂] 1, presumably via a fortuitous oxidation reaction. The crystal structure of the toluene disolvate, determined using synchrotron radiation single-crystal diffraction facilities, revealed a four-runged Ti₄O₄ planar ladder core terminated by chloro ligands on the outer titanium atoms. Each of the two calix[4]arene ligands is involved in co-ordination to three of the four titanium atoms, with one oxygen atom in a bridging mode between two metal atoms. This co-ordination enforces an unusual conformation on the ligand, with two opposite aromatic rings almost parallel and the other two splayed widely apart.