Preparation of scandium complexes with benzamidinate ligands: Synthesis and reactivity of alkyl and hydride derivatives

A range of new scandium complexes incorporating N,N'-bis(trimethylsilyl)benzamidinato ligands has been prepared. Addition of [PhC(NSiMe(3))(2)]Li(TMEDA) to ScCl3(THF)(3) in THF gives [PhC(NSiMe(3))(2)]Sc-2(mu-CL)(2)Li(TMEDA) in moderate yield. Alternatively, the use of [RC(NSiMe(3))(2)]Na(Et(2)O)(N) (R = Ph, Tol) gives good yields of the lithium-free halide [RC(NSiMe(3))(2)]2ScCl(THF). The latter is a useful starting material for the preparation of a number of derivatives, including [PhC(NSiMe(3))(2)](2)ScR' (R' = CH(2)SiMe(3), Mes), [PhC(NSiMe(3))(2)](2)ScMe(THF), [TolC(NSiMe(3))(2)]Sc-2(BH4)(THF), and [PhC(NSiMe(3))(2)]2ScNHC6H3-2,6-Pr-2(i), which were obtained by salt metathesis reactions from the corresponding alkali-metal reagents. Reaction of [PhC(NSiMe(3))(2)](2)ScCH(2)SiMe(3) with Me(3)SiCCH gives the sigma-alkyne [PhC(NSiMe(3))(2)]2ScCC-SiMes and Me(4)Si. [PhC(NSiMe(3))(2)](2)ScCH(2)SiMe(3) reacts readily with H-2 to form {[PhC(NSiMe(3))(2)]2ScH}(2). The hydride reacts with Ph(2)C(2) in refluxing benzene to give the mono-insertion pro duct [PhC(NSiMe(3))(2)]2ScC(Ph)=C(Ph)H. Two derivatives have been crystallo graphically characterized: [PhC(NSiMe(3))(2)]Sc-2(mu-Cl)(2)Li(TMEDA) and {[PhC(NSiMe(3))(2)]2ScH}(2).