Titanium complexes with unsymmetrically substituted imidazolin-2-iminato ligands.

The reaction of the unsymmetrical N-heterocyclic carbenes 1-(2,4,6-trimethylphenyl)-3-(adamantyl)imidazolin-2-ylidene (IAdMes, 1a) and 1-(2,6-diisopropylphenyl)-3-(adamantyl)imidazolin-2-ylidene (IAdDipp, 1b) with trimethylsilyl azide furnished the 2-(trimethylsilylimino)imidazolines 2a (ImNSiMe) and 2b (ImNSiMe). Desilylation by stirring in methanol gave the corresponding imidazolin-2-imines 3a (ImNH) and 3b (ImNH). 2a and 2b were treated with [TiCl(THF)] (THF = tetrahydrofuran) and [CpTiCl] (Cp = η-CH) to form the mono- and bis(imidazolin-2-iminato) titanium(IV) complexes [(ImN)TiCl] (4, R = Mes, Dipp), [Cp(ImN)TiCl] (5, R = Mes, Dipp), and [(ImN)TiCl] (6, R = Mes, Dipp). The crystal structures of all compounds except 2b were determined by X-ray diffraction analysis.