Bis(alkyl) scandium and yttrium complexes coordinated by an amidopyridinate ligand: Synthesis, characterization and catalytic performance in isoprene polymerization, hydroelementation and carbon dioxide hydrosilylation

New neutral bis(alkyl) Sc and Y complexes [N,N,N]Ln(CHSiMe)(THF) [n = 0, Ln = Sc (1), Y (1); n = 1, Ln = Y (1)] stabilized by a tridentate monoanionic amidopyridinate ligand were straightforwardly prepared by alkane elimination, upon mixing ligand [N,N,N]H and metal precursor Ln(CHSiMe)(THF) in toluene at 0 °C. Depending on the work-up conditions, yttrium bis(alkyl)s were isolated as either a pentacoordinate Lewis base free complex [N,N,N]Y(CHSiMe) (1) or as a hexacoordinate THF adduct [N,N,N]Y(CHSiMe)THF (1). For the smaller Sc ion the only solvent-free complex [N,N,N]Y(CHSiMe) (1) was isolated as a pentacoordinate species irrespective of the reaction/work-up/crystallization conditions applied. Complexes 1 (Ln = Y, Sc) and 1 were scrutinized as pre-catalysts in ternary catalytic systems Ln/borate/AlBu (borate = [HNMePh][B(CF)] or [PhC][B(CF)]), applied to isoprene (IP) polymerization, providing moderate activity albeit high selectivity with predominant formation of 1,4-cis polyisoprene (up to 99%). The same complexes proved to be effcient catalysts also for the intermolecular hydrolelementation of styrene with various EH sustrates (pyrrolidine, morpholine, PhPH, PhPH, PhSH) affording linear anti-Markovnikov addition products exclusively. After a preliminary activation by B(CF), selected bis(alkyl) complexes from this series have been finally used as valuable pre-catalysts for the CO hydrosylilation to CH in the presence of organosilanes as reducing agents (PhMeSiH, PhSiH, EtMeSiH).