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 π-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.