Thermalisation of TiCl4 and phenol (1∶1) in toluene gave [TiCl3(OC6H5)] 1. The more soluble complex [TiCl3(OC6H4CMe3-4)] 2 is monomeric in benzene and reacts with 4,4′-dimethyl-2,2′-bipyridyl (dmbipy) to give mer-[TiCl3(OC6H4CMe3-4)(dmbipy)] 3 and the disproportionation product [TiCl2(OC6H4CMe3-4)2(dmbipy)]. The complex [TiCl3(OC6H2Me3-2,4,6)] 4 is monomeric in benzene whereas [TiCl3(OC6H3Pri2-2,6)] 5 partially disproportionates in solution into [TiCl2(OC6H3Pri2-2,6)2] and reacts with dmbipy to give mer-[TiCl3(OC6H3Pri2-2,6)(dmbipy)] 6 and [TiCl2(OC6H3Pri2-2,6)2(dmbipy)]. Thermalisation of 2,6-di-tert-butyl-4-methylphenol and TiCl4 in toluene caused debutylation but [TiCl3{OC6H2(CMe3)2-2,6-Me-4}] 7 forms in light petroleum (bp range 40–60 °C). Complex 7 is monomeric in benzene and does not form adducts with dmbipy or other sigma donors. A crystal structure determination of 7 showed a monomer with distorted tetrahedral co-ordination, a Ti–O bond length of 1.750(2) Å and Ti–Cl bonds longer than in TiCl4 but shorter than in [TiCl3(C5H5)] or [TiCl3{C5H3(CMe3)2-1,3}]. 2,4,6-Tri-tert-butylphenol debutylates when thermalised with TiCl4 in toluene giving [TiCl3{OC6H4(CMe3)2-2,4} ] 8. The complexes [TiCl3{OC6H2(CMe3)2-2,6-OMe-4}] 9, [TiCl3(OC6H3CMe3-2-Me-4)] 10, [TiCl3(OC6H4Ph-2)] 11 and the 1-naphthoxide complex [TiCl3(OC10H7)] 12 were also prepared. Density functional calculations performed on the models 4 and [TiCl3(OMe)] showed both lone pairs on oxygen donate electron density to titanium but O(2p)-to-C
C (π*) donation weakens the Ti–O interaction in the phenoxide complex; Cl(2p)-to-Ti(3d) donation is much reduced in the methoxide complex. The system [TiCl3(OC6H4CMe3-4)]/AlMe3 is 280 times more active than [TiCl3Cp] (Cp = cyclopentadienyl)/AlMe3 for low pressure (6 psi) ethylene polymerisation but
1//3 less active than TiCl4/AlMe3.