Electronic vs. Steric Hindrance Effects in Amine Ligands to Ru-Based Initiators for ROMP

• Autor(a) principal: Silva,Tiago B.
• Data de Publicação: 2014
• Outros Autores: Camargo,Ricardo S., Lima-Neto,Benedito S.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Journal of the Brazilian Chemical Society (Online)
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532014001202425
• topic: ancillary ligands; amines; ruthenium; olefin metathesis; ROMP

[RuCl2(PPh3)2(amine)x]-type complexes, with NH2Ph (1; x = 2), NH2Bz (2; x = 2) and NHBuPh (3; x = 1) in the presence of ethyldiazoacetate (EDA), were investigated for ring opening metathesis polymerization (ROMP) of norbornene (NBE), norbornadiene (NBD) and dicyclopentadiene (DCPD). Quantitative yields of polyNBE were obtained at 50 °C for 30 min with 1 and for 5 min with 2, whereas this occurred at 25 °C for 5 min with 3. Polydispersity index (PDI) values ranged from 3.5 to 1.6 (Mw = 104-105 g mol-1). Complex 3 was active for ROMP of NBD and DCPD, as well as for copolymerizations of NBE with either NBD or DCPD. The high σ-donor character of NH2Bz favored the reactivity of the six-coordinated complex 2, contrary to complex 1. The large cone angle of NHBuPh defined the fivecoordination in 3 and the best reactivity for ROMP, in spite of the low σ-donor character as in NH2Ph.