Electron spin resonance studies of electron addition to bis(cyclopentadienyl)titanium(IV) dichloride and cyclopentadienyltitanium(IV) trichloride

Abstract

Exposure of [Ti(cp)2Cl2](cp = cyclopentadienyl) in various media to 60Co γ-rays at 77 K gives the correponding titanium(III) complex, [Ti(cp)2Cl2]–, characterised by its e.s.r. spectrum. On warming glassy solutions in methanol, this species changes irreversibly into a second titanium(III) complex, thought to be [Ti(cp)2Cl]. This identification has been confirmed by comparison with the e.s.r. spectrum of authentic [Ti(cp)2Cl] in methanol. The structures of these complexes are discussed with particular reference to [V(cp)2Cl2]. Similar treatment of [Ti(cp)Cl3] gives the anion [Ti(cp)Cl3]–. The e.s.r. features for this complex suggest a major contribution from a dx2–y21 configuration rather than a dz21 configuration as found for the previous complexes. Again, on annealing above 77 K, chloride ions are lost and the [Ti(cp)Cl2] complex was detected. This was formed directly at 77 K in methanol glasses. A brief study of TiCl4 in the pure state at 77 K suggested the formation of [TiCl4]+ ions, having an e.s.r. spectrum comparable with that for Cl2–, together with [TiCl4]– ions, which have a distorted structure with the extra electron in a predominantly dz2 orbital.