Deprotonation of calixarenes 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 calixarene 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 calixarene dimer complexes show different structural characteristics depending on the nature of the alkali metal.
Petrella, A. J., Craig, D. C., Lamb, R. N., Raston, C., & Roberts, N. K. (2003). A facile route to hetero-bimetallic Ti(IV)-alkali metal calixarene complexes. Dalton Transactions, 2003(24), 4590-4597. https://doi.org/10.1039/b310635g