π-Carbazolyl supported bis(alkyl) complexes of Sc, Y and La for α-olefin polymerization and hydrogenation.

A series of new half-sandwich bis(alkyl) rare-earth metal complexes coordinated by a sterically demanding 1,3,6,8-tetra- tert -butyl-carbazol-9-yl ligand [ t Bu 4 Carb]La(CH 2 C 6 H 5 ) 2 (THF) (1-La), [ t Bu 4 Carb]Ln( o -NMe 2 C 6 H 4 CH 2 ) 2 (Ln = Sc (2-Sc), Y (2-Y), La (2-La), [ t Bu 4 Carb]Ln(CH 2 SiMe 3 ) 2 (THF) (Ln = Sc (3-Sc), Y (3-Y)), were synthesized. 1-La, 2-La, and 2-Y were prepared by an alkane elimination protocol, while 2-Sc, 3-Sc, and 3-Y became accessible only when salt metathesis reactions of t Bu 4 CarbK with R 2 Ln(THF) n + [BPh 4 ] - were employed. X-ray analysis revealed that in all complexes the carbazolyl ligand exhibits π-coordination with metal ions. 2-Sc and 3-Sc when activated with [Ph 3 C][B(C 6 F 5 ) 4 ] demonstrate excellent activity in α-olefin (octene-1, nonene-1, decene-1 and 1,1-diphenyl-but-1-ene) polymerization. When H 2 was used as a chain transfer agent (1 bar, rt) in the presence of 3-Sc/[Ph 3 C][B(C 6 F 5 ) 4 ] or 2-Y, 2-La olefin hydrogenation occurred with quantitative conversion.