Cationic Methyl- and Chlorotitanium Phosphinimide Complexes
摘要:
A variety of donor-stabilized cationic complexes of the form [Cp(NPt-Bu-3)TiMe(L)] [MeB(C6F5)(3)] and [Cp(NPt-Bu-3)TiMe(L)] [B(C6F5)(4)] (L = Py, 4-EtPy, 4-t-BuPy, NC5H4NMe2, PMe3, Pn-Bu-3, PPh3, P(p-MeC6H4)(3)) have been prepared and characterized. Prolonged storage in CH2Cl2 solution resulted in chloride for methyl exchange to afford species of the form [CpTi(NPt-Bu-3)Cl(L)] [B(C6F5)(4)], [{CpTi(NPt-Bu-3)Me}(2)(mu-Cl)] [B(C6F5)(4)], and [CpTi(NPt-Bu-3)(mu-Cl)](2)[MeB(C6F5)(3)](2). The byproduct salt [(o-MeC6H4)(3)PCH2Cl] [B(C6F5)(4)] was obtained from reactions employing the sterically demanding donor phosphine P(o-MeC6H4)(3), suggesting transient generation of the cation [CpTi(NPt-Bu-3)Cl(CH2Cl2)](+). Analogous reactivity was not seen in C6H5Cl, although the species [{CpTi(NPt-Bu-3)Me}(2)(mu-Me)] [B(C6F5)(4)] could be formed in this solvent. The isolated zwitterionic complex TiCp(NPt-Bu-3)Me(mu-MeB(C6F5)(3)) readily performs insertion chemistry into the Ti-methyl bonds with diisopropylcarbodiimide and diphenylacetylene substrates to afford the cationic species [CpTi(NPt-Bu-3)((Ni-Pr)(2)CMe)] [MeB(C6F5)(3)], [TiCp(NPt-Bu-3)(PhCCPh(Me))] [MeB(C6F5)(3)], and [TiCp(NPt-Bu-3)(PhCCPh(Me))(PMe3)] [MeB(C6F5)(3)]. The implications of this chemistry are considered.