No abstract

No abstract

No abstract

Amine elimination of scandium tris(silylamide) complex Sc[N(SiHMe 2 ) 2 ] 3 (THF) with 1 equiv of the amidine [PhC(N-2,6-i Pr 2 C 6 H 3 ) 2 ]H in toluene afforded the neutral mono(amidinate) scandium bis(silylamide) complex [PhC(N-2,6-i Pr 2 C 6 H 3 ) 2 ]Sc[N(SiHMe 2 ) 2 ] 2 (1) in 93% isolated yield. When 1 was activated with 1 equiv of [Ph 3 C][B(C 6 F 5 ) 4 ] in the presence of THF, the unexpected cationic amidinate scandium amide complex [{PhC(N-2,6-i Pr 2 C 6 H 3 ) 2 }ScN{SiHMe 2 }-{SiMe 2 N(SiHMe 2 ) 2 }(THF) 2 ][B(C 6 F 5 ) 4 ] (2) was generated. Treatment of 1 with excess AlMe 3 gave the Sc/Al heterometallic methyl complex [PhC(N-2,6-i Pr 2 C 6 H 3 ) 2 ]Sc[(μ-Me) 2 AlMe 2 ] 2 (3). All these complexes were well-characterized by elemental analysis, NMR spectroscopy, and X-ray crystallography. The combination 1/[Ph 3 C][B(C 6 F 5 ) 4 ] in toluene showed activity toward isoprene polymerization. Addition of excess AlMe 3 to the 1/[Ph 3 C][B(C 6 F 5 ) 4 ] catalyst system switched the regioselectivity of isoprene polymerization from 3,4-specific to cis-1,4-selective.