Evidence for five-coordination in titanium(IV) complexes. A nuclear magnetic resonance investigation

Abstract

Diketonato complexes of titanium(IV), (X3Ti(dik))2 (X = Cl, Br; dik = anions of dipivaloylmethane and benzoylacetone), of apparent five-coordinate stoichiometry have been prepared and investigated in nitrobenzene solutions using the variable temperature nuclear magnetic resonance technique. The nmr spectra reveal the existence of two equilibrium species; a five-coordinate X3Ti(dik) and a six-coordinate X2Ti(dik)2 complex. The data are interpreted in terms of a symmetric dissociation of the six-coordinate titanium(IV) dimer, (X3Ti(dik))2, into two five-coordinate monomers which then undergo a disproportionation reaction to the four-coordinate titanium tetrahalide and the six-coordinate X2Ti(dik)2 species.