Alkylation, Cation Formation, and Insertion Reactions in Titanium Tris(ketimide) Complexes

Ti(NCtBu2)3Cl (1) reacts with TlPF6 in acetonitrile to afford [Ti(NCtBu2)3(N⋮CCH3)]PF6 (2), which proved to be unstable and decomposed at room temperature either in solution or in the solid state. Attempts to recrystallize 2 from a CH2Cl2/hexane mixture led to [Ti3(NCtBu2)6(μ2-F)3(μ3-F)2][PF6] (3). Treatment of 1 with LiMe and PhCH2MgCl gave the compounds Ti(NCtBu2)3CH2Ph (4) and Ti(NCtBu2)3Me (5), respectively. 4 was treated with B(C6F5)3 to afford [Ti(NCtBu2)3(CH2Ph)B(C6F5)3] (6), which exists in solution as a mixture of two species, the zwitterion [Ti(NCtBu2)3][(μ-CH2Ph)B(C6F5)3] (6A) and the solvate cation [Ti(NCtBu2)3(Solv)][(CH2Ph)B(C6F5)3] (6B). Above 60 °C, C6F5 is transferred to the metal center and Ti(NCtBu2)3(C6F5) (9) forms. This compound participates in a dynamic process in solution involving Ti···F interactions. The fluxional process observed for 6 can be stopped upon addition of 1 equiv of C⋮NMes, giving [Ti(NCtBu2)3(C⋮NMes)][(CH2Ph)B(C6F5)3] (7). C⋮NMes does not insert into Ti−N bonds, but it readily inserts into the Ti−C bond of Ti(NCtBu2)3(Me) (5) to afford [Ti(NCtBu2)3{η2-C(CH3)NMes}] (8).