Mixed Titanium–Hafnium Chloridometallate Complexes

The addition of either NEt 3 BzCl or [Ph 3 PNPPh 3 ]Cl (1 equiv. chloride per metal) to a 1:1 mixture of HfCl 4 and TiCl 3 in SOCl 2 results in Ti oxidation and leads to the corresponding salts of the [TiHfCl 10 ] 2– ion. A solution IR investigation in the ν(M–Cl) region indicates that this ion is in equilibrium with the homodimetallic [Ti 2 Cl 10 ] 2– and [Hf 2 Cl 10 ] 2– ions. An X‐ray study of the NEt 3 Bz + salt reveals an edge‐sharing bioctahedral dianion sitting on a crystallographic inversion centre. The crystal is a solid solution of different species with compositional disorder at the metal site, each metal position having the occupancy Ti 0.685 Hf 0.315 . The M–M and M–Cl distances have intermediate values between those of the homodimetallic analogues. The results of DFT calculations rationalize the structural, energetic and M–Cl bonding differences. An electrochemical investigation, in comparison with that of [Ti 2 Cl 10 ] 2– and the parallel IR studies, provides further information on the solution equilibria. Adventitious hydrolysis during the crystallization of the [Ph 3 PNPPh 3 ] + salt affords crystals of [Ph 3 PNPPh 3 ] 2 [Cl 3 Ti(μ‐O)HfCl 5 ], whose dianion contains a tetrahedral Ti IV centre and an octahedral Hf IV centre bridged by an oxygen atom. A bond‐length analysis allows the description of this dianion as containing the hitherto unknown [Ti(O)Cl 3 ] – complex, which acts as an oxygen‐based donor ligand to [HfCl 5 ] – . (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)