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

Reaction of an excess of TiCl4 with p-tert-butylcalix[4]arene (H4L!) in toluene led to [{Ti-2(mu(3)-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 coordination enforces an unusual conformation on the ligand, with two opposite aromatic rings almost parallel and the other two splayed widely apart.