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RESEARCH PRODUCT

Mixed Titanium–Hafnium Chloridometallate Complexes

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description

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 v(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 ) - .