Titanium complexes mixed metal compounds

The mixed metal compounds,react to form a titanium C complex that is the true catalyst for the polymerization. An alkyl group is transferred from aluminium to titanium in exchange for a chloride. 

The synthesis of a mixed Ti(iv) complex based on Gp and the small carborane ligand C2B42 has been reported. The compounds Gp[2,3-R2-2,3-G2B4H4]TiCl are prepared by reduction of Cp2TiCl2 with /aw-m -Li-l-Li[2,3-R2-2,3-C2B4H4] and subsequent chemical oxidation with anhydrous TiCl4 in THF (Scheme 740). The crystal structure shows a distorted tetrahedral environment about the metal center similar to those of bis-Cp titanium derivatives (Figure 31). 

As a representative example, the solid state structure of the corresponding ethylene-bridged complex is shown in Scheme 2.2 and exhibits the special role of one lithium counter ion that stabilizes the helicate in concert with two molecules of water as a template. Later, bisimine-bridged ligands were also used to examine this class of coordination compounds. In this case, the helicates can be formed by simply mixing a diamine, 2,3-dihydroxybenzaldehyde, a source of titanium(IV) ions, and an alkali metal carbonate as a base. This procedure in principle resembles a hierarchical process with an initial imine condensation followed by helicate self-assembly, although the order of events cannot be predicted definitively. 

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