Observed hydrolysis of fluorine substituted bis(β-diketonato)-dichlorotitanium(iv) complexes

Abstract

Novel fluorine substituted mononuclear Ti(β-diketonato)₂Cl₂ complexes have been synthesised and shown to be involved in a partial hydrolysis reaction in solution, in which the hydrolyzed dinuclear {Ti(β-diketonato)₂Cl}₂(μ-O) is in equilibrium with the monomer. This is in contrast to the solution behaviour of the non CF₃-containing Ti(CH₃COCHCOCH₃)₂Cl₂, Ti(PhCOCHCOCH₃)₂Cl₂ and Ti(PhCOCHCOPh)₂Cl₂ complexes, under the same conditions. Variable temperature (¹H and ¹⁹F) NMR spectra and X-ray structure analyses reveal that the partially hydrolyzed dinuclear complex exists both in solution and in solid state, bridging through a single μ-oxo bridge and having one labile chloro-ligand per titanium center. Inclusion of electron-withdrawing CF₃ groups into the already electron-deficient Ti complexes, led to the formation of {Ti(CF₃COCHCOCF₃)₂Cl}₂(μ-O) (dinuclear) and [Ti(CF₃COCHCOCF₃)₂(μ-O)]₄ (tetranuclear) complexes in CDCl₃ containing trace amounts of water. DFT calculated free energies of hydrolysis support the existence of Ti(CH₃COCHCOCH₃)₂Cl₂ as a monomer and Ti(CF₃COCHCOCF₃)₂Cl₂ as a equilibrium mixture of the monomer and partially hydrolyzed dinuclear {Ti(β-diketonato)₂Cl}₂(μ-O) in CDCl₃ solution.