Reactions of titanium tetrachloride with carboxylic acids. Crystal and molecular structure of the dinuclear titanium oxo compound [{TiCl2(O2CBut)(ButCO2H)}2O

Abstract

Reaction of TiCl4(1 mol) with 2,2-dimethylpropanoic acid (2.5 mol) at room temperature yields the dinuclear oxo-bridged species [{TiCl2(O2CBut)(ButCO2H)}2O]1 which has been fully characterised by an X-ray crystal structure analysis. The two metal atoms are bridged by the oxo and two carboxylate groups, which with a co-ordinated acid molecule and two chlorine atoms on each titanium gives a slightly distorted octahedral environment around each metal centre. At 40 °C compound 1 decomposes to the trinuclear species [Ti3Cl3(O2CBut)5O2], and at higher temperatures (100–120 °C) to another dinuclear oxo derivative [{TiCl(O2CBut)2}2O] which can also be obtained from the action of 2,2-dimethylpropanoic anhydride on TiCl4 in refluxing toluene. Acetic acid produces a similar, but less soluble, species to 1. Aromatic acids react differently; para-substituted aryl acids generally yield trinuclear compounds [Ti3Cl3(O2CC6H4X-p)5O2](X = Cl or Br) although the p-But acid forms [{TiCl(O2CC6H4But-p)2}2O]. In contrast the ortho-and meta-substituted acids react to give either [Ti3Cl4(O2CR)4O2](R = C6H4Cl-o or -m) or [Ti4Cl5(O2CR)7O2](R = C6H4Me-o) derivatives.