Di-l-chloro-bis[(N-tert-butylimido)chlorobis- (pyridine-jN)titanium(IV)] perdeuterobenzene disolvate

Over the last 15 years, the chemistry of titanium±imido complexes has received considerable attention (Wigley, 1994). It has been shown that these complexes can be utilized in a wide variety of stoichiometric and sometimes catalytic coupling reactions with unsaturated substrates (Gade & Mountford, 2001, and references therein). A general entry point to new titanium±imido chemistry is gained via the readily prepared synthons [Ti(NR)Cl2(py)3] (R = Bu or aryl) (Mountford, 1997). During the course of our studies, we reported that prolonged exposure of [Ti(NBu)Cl2(py)3] to vacuum results in the loss of the trans pyridine ligand (Blake et al., 1997). We report here the solid-state structure of [Ti2( Cl)2(N Bu)2Cl2(py)4] crystallized as its perdeuterobenzene disolvate, (I).

The title compound, [Ti 2 (C 4 H 9 N) 2 Cl 2 (C 5 H 5 N) 4 ]Á2C 6 D 6 , possesses a dinuclear structure featuring two six-coordinate pseudo-octahedral titanium(IV) centres with bridging Cl atoms. The complex is located on a crystallographic inversion centre.

Comment
Over the last 15 years, the chemistry of titanium±imido complexes has received considerable attention (Wigley, 1994). It has been shown that these complexes can be utilized in a wide variety of stoichiometric and sometimes catalytic coupling reactions with unsaturated substrates (Gade & Mountford, 2001, and references therein). A general entry point to new titanium±imido chemistry is gained via the readily prepared synthons [Ti(NR)Cl 2 (py) 3 ] (R = t Bu or aryl) . During the course of our studies, we reported that prolonged exposure of [Ti(N t Bu)Cl 2 (py) 3 ] to vacuum results in the loss of the trans pyridine ligand (Blake et al., 1997). We report here the solid-state structure of [Ti 2 ("-Cl) 2 (N t Bu) 2 Cl 2 (py) 4 ] crystallized as its perdeuterobenzene disolvate, (I).
Molecules of (I) adopt a dinuclear structure in the solid state, possessing crystallographically imposed C i molecular symmetry. The solid-state structure is entirely consistent with the previously reported solution 1 H and 13 C NMR data (Blake et al., 1997). The two pseudo-octahedral six-coordinate titanium(IV) centres are bridged by two Cl atoms. The bridging ClÐTi bond lengths [Ti1ÐCl2 = 2.4600 (4) A Ê and Ti1ÐCl2A = 2.7438 (4) A Ê ] are longer than the terminal TiÐCl bond length [Ti1ÐCl1 = 2.3898 (4) A Ê ]. The bridging ClÐTi bond distance of the Cl atom trans to the imido group is considerably longer than the bridging TiÐCl bond distance of the Cl atom cis to the imido group [difference between Ti1ÐCl2 and Ti1ÐCl2 i = 0.2838 (6) A Ê ; symmetry code as in Table 1]. This is a re¯ection of the strong trans in¯uence exercised by the imido group. The near linearity of the Ti N t Bu linkage [Ti1 N1Ð C1 = 170.9 (2) ] is consistent with the imido ligand acting as a four-electron donor to the titanium centre (Wigley, 1994).

Experimental
The title compound was prepared according to the previously described procedure (Blake et al., 1997) and authenticated by comparison of its solution 1 H NMR spectrum with that previously reported. Crystallization from C 6 D 6 afforded crystals of (I) as airsensitive yellow blocks.
All H atoms were positioned geometrically after each cycle of re®nement. A three-term Chebychev polynomial weighting scheme was applied: (Prince, 1983;Watkin, 1994).

Figure 1
View of the molecular structure of (I). The displacement parameters are drawn at the 20% probability level and H atoms have been omitted for clarity. The solvent of crystallization has been omitted and the minor orientation of the disordered tert-butyl group is not shown. Atoms carrying the suf®x A are related to their counterparts by the symmetry code (1 À x, 1 À y, 1 À z).  Special details Refinement. Geometric similarity restraints were applied to the C-C bond lengths (su 0.02 Å) and to the N-C-C anf C-C-C angles (su 2 °) of the disordered tert-butyl group C1-C54