Structure, substitution and hydrolysis of Bis(trifluorobenzoylacetonato-O,O')dichloro titanium(IV): An experimental and computational study

The chlorine coordinated ligands in [Ti(tfba)(2)Cl-2] (Htfba = 4,4,4-trifluoro-1-(phenyl)-1,3-butanedione = PhCOCH2COCF3) are very susceptible to hydrolysis and even with trace amounts of water, the formation of hydrolysed complexes, dinuclear {Ti(tfba)(2)Cl}(2)(mu-O) or tetranuclear [Ti(tfba)(2)(mu-O)](4), take place, whereas with an excess of water, decomposition to TiO2 occurs. Substitution of the chloroligands in [Ti(tfba)(2)Cl-2] with H(2)biphen (H(2)biphen = 2,2'-dihydroxybiphenyl or biphenol) leads to [Ti (tfba)(2)biphen] with enhanced water stability. Experimentally, two steps were observed for the substitution [Ti(tfba)(2)Cl-2] + H(2)biphen. Computational chemistry calculations reveal that each step involves several transition states, with formation of a 7-coordinated intermediate in the first reaction half. Location of this intermediate is dependent on inclusion of empirical dispersion-corrections in the functional. The three geometrical cis-isomers of [Ti(tfba)(2)biphen] were observed in solution using low temperature H-1 and F-19 NMR, whereas in the solid state, two of the isomers, cis-cis-trans and cis-trans-cis, crystallized in the same unit cell. The crystal structure of the hydrolysed tetranuclear complex [Ti(tfba)(2)(mu-O)](4) is composed of four identical cis-cis-trans isomers of [Ti(tfba)(2)Cl-2 ]. The eight beta-diketonato backbones and the four bridging oxygens have a S-4 molecular symmetry. (C) 2016 Elsevier B.V. All rights reserved,