Bis(alkyl) Sc and Y Complexes Supported by Tri‐ and Tetradentate Amidinate Ligands: Synthesis, Structure, and Catalytic Activity in α‐Olefin and Isoprene Polymerization

Bis(alkyl) complexes [(2,6‐Me 2 C 6 H 3 )NC(tBu)N(C 6 H 4 −2‐OMe)]M(CH 2 C 6 H 4 −2‐NMe 2 ) 2 (M=Sc ( 4 ), Y ( 5 )), [(2‐OMe−C 6 H 4 N) 2 C(tBu)]Y(CH 2 SiMe 3 ) 2 (THF) 2 ( 6 ), supported by N,N,O‐tridentate ( 4 , 5 ) and N,N,O,O‐tetradentate ( 6 ) amidinate ligands were synthesized by the alkane elimination approach reacting tris(alkyl) rare‐earth species M(R) 3 X n (R=Me 3 SiCH 2 , X=THF, n=2; R=CH 2 C 6 H 4 −2‐NMe 2 , n=0) with one equivalent of amidine (2,6‐Me 2 C 6 H 3 )N=C(tBu)−NH(C 6 H 4 −2‐OMe) ( 1 ) or (2‐MeO−C 6 H 4 )N=C(tBu)−NH(C 6 H 4 −2‐OMe) ( 2 ). The reaction of amidine 2 with equimolar amount of Y(CH 2 C 6 H 4 −2‐NMe 2 ) 3 in toluene unexpectedly results in the addition of N,N‐dimethylaminobenzyl group to C=N bond of one amidinate fragment, ligand disproportionation and the formation of novel bis(amide)amidinate complex [(2‐OMe−C 6 H 4 N) 2 C(tBu)CH 2 C 6 H 4 −2‐NMe 2 ]Y[(2‐OMe−C 6 H 4 N) 2 C(tBu)] ( 7 ). Complexes 4 – 6 were evaluated as catalysts for α‐olefins and isoprene polymerization.