Sc and Y bis(alkyl) complexes supported by bidentate and tridentate amidinate ligands. Synthesis, structure and catalytic activity in polymerization of isoprene and 1-heptene.

A series of bis(alkyl) complexes {( t Bu)C[N(2,6-Me 2 C 6 H 3 )] 2 }Ln(CH 2 SiMe 3 ) 2 (THF) n (Ln = Y, n = 1 (1); Ln = Sc, n = 1 (2)), {2-[Ph 2 P(O)]C 6 H 4 NC( t Bu)N(2,6-Me 2 C 6 H 3 )}Sc(CH 2 SiMe 3 ) 2 (3), {2-[Ph 2 P(NPh)]C 6 H 4 NC( t Bu)N(2,6-Me 2 C 6 H 3 )}Sc(CH 2 SiMe 3 ) 2 (4) coordinated by bidentate (N,N) and tridentate (N,N,O; N,N,N) amidinate ligands are synthesized using an alkane elimination approach. Yttrium complex 1 demonstrated a half-life of ∼2.5 days at room temperature in benzene-D6 (C 6 D 6 ) solution, whereas scandium complexes proved to be much more stable (25 d (2), 30 d (3) and 42 d (4)). Complexes 1-4 as a part of ternary catalytic systems 1-4/TB, HNB/AlR 3 (AlR 3 = AliBu 3 , AliBu 2 H; TB = [Ph 3 C][B(C 6 F 5 ) 4 ], HNB = [PhNHMe 2 ][B(C 6 F 5 ) 4 ]) demonstrated high catalytic activity in isoprene polymerization and enable 80%-100% conversion of 1000 equivalents of monomer into polymer at 25 °C within 3-180 min. The isolated polyisoprenes feature predominantly cis -1,4-regularity (69.2%-87.3%) and polydispersities M w / M n = 2.26-8.92. Moreover, the binary (2/TB) and ternary (1-4/TB/10 AliBu 3 ) systems initiate 1-heptene polymerization providing 40%-100% conversion of 500 equivalents of monomer in 24 h at 25 °C giving polymer samples with M n = 1.55-190.2 × 10 3 and M w / M n = 1.55-3.87.