Calcium fluoride incorporated in soluble organometallics: adduct formation and solution dynamics

Abstract

The recrystallization of [{Ti(C₅Me₅)F₃}₄CaF₂] 1 and [{Ti(C₅Me₄Et)F₃}₄CaF₂] 2 in the presence of an excess of hmpa (hexamethylphosphoramide) resulted in the formation of [{Ti(C₅Me₅)F₃}₄(CaF₂)(hmpa)] 3 and [{Ti(C₅Me₄Et)F₃}₄(CaF₂)(hmpa)] 4, respectively. The adducts 3 and 4 were spectroscopically characterized and the molecular structure of 4 was determined, showing a co-ordination of calcium by eight fluorine atoms from two [Ti₂(C₅Me₄Et)₂F₇]^– moieties and by an oxygen atom of an hmpa ligand. Adduct formation and solution behavior of 2 in different solvents was studied by ¹H and ¹⁹F NMR and variable-temperature NMR. A temperature dependent equilibrium between 2 and a solvated form 2·solv (solv = solvent molecule) is proposed. With increase of the temperature the equilibrium between 2 and 2·solv was observed to be entropy-shifted to the non-solvated form.