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

The recrystallization of [{Ti(C5Me5)F-3}(4)CaF2] 1 and [{Ti(C5Me4Et)F-3}(4)CaF2] 2 in the presence of an excess of hmpa (hexamethylphosphoramide) resulted in the formation of [{Ti(C5Me5)F-3}(4)(CaF2)(hmpa)] 3 and [{Ti(C5Me4Et)F-3}(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 [Ti-2(C5Me4Et)(2)F-7](-) moieties and by an oxygen atom of an hmpa ligand. Adduct formation and solution behavior of 2 in different solvents was studied by H-1 and F-19 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.