A facile route to hetero-bimetallic Ti(IV)-alkali metal calix[4]arene complexes

Deprotonation of calix[4]arenes by alkali metal in methanol using simple benchtop procedures is effective in the formation of novel monomeric and dimeric titanium(IV) complexes. For the larger alkali metal cations, K+ and Cs+, favourable complexation within the (pi)-basic calix[4]arene cavity facilitates the formation of monomeric titanium(IV) complexes when oligomer formation is inhibited by an acetylacetonate ligand. In contrast, the smaller Li+ and Na+ ions preferentially form dimeric complexes with exo-bridging alkali and titanium(IV) metal centres. A dimeric complex is also obtained for potassium in the absence of acetylacetonate. The solid state structures of the K–Ti and Na–Ti calix[4]arene dimer complexes show different structural characteristics depending on the nature of the alkali metal.