Preparation of Scandium Complexes with Benzamidinate Ligands:  Synthesis and Reactivity of Alkyl and Hydrido 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 ScCl 3 (THF) 3 in THF gives [PhC(NSiMe 3 ) 2 ] 2 Sc(μ-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 ] 2 ScCl(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 ] 2 Sc(BH 4 )(THF), and [PhC(NSiMe 3 ) 2 ] 2 ScNHC 6 H 3 -2,6-Pr i 2, 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 σ-alkyne [PhC(NSiMe 3 ) 2 ] 2 ScCCSiMe 3 and Me 4 Si. [PhC(NSiMe 3 ) 2 ] 2 ScCH 2 SiMe 3 reacts readily with H 2 to form {[PhC(NSiMe 3 ) 2 ] 2 ScH} 2 . The hydride reacts with Ph 2 C 2 in refluxing benzene to give the monoinsertion product [PhC(NSiMe 3 ) 2 ] 2 ScC(Ph) C(Ph)H. Two derivatives have been crystallographically characterized: [PhC(NSiMe 3 ) 2 ] 2 Sc(μ-Cl) 2 Li(TMEDA) and {[PhC(NSiMe 3 ) 2 ] 2 ScH} 2 .