A study of ortho- and para-siloxyanilines for the synthesis of mono-, bi-, and tetra-nuclear early transition metal–imido complexes

The siloxyanilines o-Me3SiOC6H4NH2 (1) and p-RMe2SiOC6H4NH2 (R=H (2); R=Me (3)), and their N-silylated derivatives p-Me3SiOC6H4NHSiMe3 (4) and p-Me3SiOC6H4N(SiMe3)2 (5) have been prepared from ortho- or para-aminophenol and used in the synthesis of imido complexes. Thus, binuclear [{Ti(η5-C5H5)Cl}{μ-NC6H4(p-OSiMe3)}]2 (6) and mononuclear [TiCl2{NC6H4(p-OSiMe3)}(py)3] (7) imido complexes have been obtained from the reaction of 3 and [Ti(η5-C5H5)Cl3] or [TiCl2(NtBu)(py)3], respectively. In contrast, the reaction of 1 with TiCl4 and tBupy affords the titanocycle [TiCl2{OC6H4(o-NH)N,O}(tBupy)2] (8). Compound 5 has also been used to prepare the niobium imide complex [NbCl3{NC6H4(p-OSiMe3)}(MeCN)2] (9), by its reaction with NbCl5 in CH3CN. These findings have been applied to the synthesis of polynuclear systems. Thus, chlorocarbosilane Si[CH2CH2CH2Si(Me)2Cl]4 (CS–Cl) has been functionalized with the ortho- and para-aminophenoxy groups to give 10 and 11, respectively. The use of 11 has allowed the formation of the tetranuclear compound 12. Attempts to synthesize terminal imido titanium complexes from 10 and TiCl4 in the presence of tBupy and Et3N, give complex 8 and carbosilane CS–Cl.