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

• Published in: Dalton transactions : an international journal of inorganic chemistry 2020-01, Vol.49 (3), p.638-65
• Main Authors: Gurina, G. A, Kissel, A. A, Lyubov, D. M, Luconi, L, Rossin, A, Tuci, G, Cherkasov, A. V, Lyssenko, K. A, Shavyrin, A. S, Ob'edkov, A. M, Giambastiani, G, Trifonov, A. A
• Format: Article
• Language: English
• Subjects: Alkanes; Carbon dioxide; Catalysts; Chemical synthesis; Crystallization; Crystallography; Hydrosilylation; Isoprene; Lewis base; Ligands; Morpholine; Polymerization; Reducing agents; Scandium; Selectivity; Toluene; Yttrium
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c9dt04338a

New neutral bis(alkyl) Sc and Y complexes [N,N py ,N − ]Ln(CH 2 SiMe 3 ) 2 (THF) n [ n = 0, Ln = Sc ( 1 Sc ), Y ( 1 Y ); n = 1, Ln = Y ( 1 Y THF )] stabilized by a tridentate monoanionic amidopyridinate ligand were straightforwardly prepared by alkane elimination, upon mixing ligand [N,N py ,N − ]H and metal precursor Ln(CH 2 SiMe 3 ) 3 (THF) 2 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 py ,N − ]Y(CH 2 SiMe 3 ) 2 ( 1 Y ) or as a hexacoordinate THF adduct [N,N py ,N − ]Y(CH 2 SiMe 3 ) 2 THF ( 1 Y THF ). For the smaller Sc ion the only solvent-free complex [N,N py ,N − ]Y(CH 2 SiMe 3 ) 2 ( 1 Sc ) was isolated as a pentacoordinate species irrespective of the reaction/work-up/crystallization conditions applied. Complexes 1 Ln (Ln = Y, Sc) and 1 Y THF were scrutinized as pre-catalysts in ternary catalytic systems Ln/borate/Al i Bu 3 (borate = [HNMe 2 Ph][B(C 6 F 5 ) 4 ] or [Ph 3 C][B(C 6 F 5 ) 4 ]), 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, Ph 2 PH, PhPH 2 , PhSH) affording linear anti-Markovnikov addition products exclusively. After a preliminary activation by B(C 6 F 5 ) 3 , selected bis(alkyl) complexes from this series have been finally used as valuable pre-catalysts for the CO 2 hydrosylilation to CH 4 in the presence of organosilanes as reducing agents (PhMe 2 SiH, PhSiH 3 , Et 2 MeSiH). Highly versatile and robust organolanthanides as catalysts or catalyst precursors for a variety of challenging transformations.