Electronic synergism in [RuCl2(PPh3)(2)(amine)] complexes differing the reactivity for ROMP of norbornene and norbornadiene

Autor(es)

Carvalho, Jr., Valdemiro P. ^[1] ; Ferraz, Camila P. ^[1] ; Lima-Neto, Benedito S. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Quim Sao Carlos, BR-13560970 Sao Carlos, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL; v. 333, n. 1-2, p. 46-53, DEC 1 2010.
• Citações Web of Science: 22

Resumo

The reactivity of the new complex {[}RuCl(2)(PPh(3))(2)(3,5-Me(2)piperidine)], complex 1, was investigated for ring opening metathesis polymerization (ROMP) of norbornene (NBE) and norbornadiene (NBD) in the presence of ethyl diazoacetate (EDA) in CHCl(3). The aim is to observe the combination of PPh(3) and an amine as ancillary ligands concerning the steric hindrance and the electronic perturbation in the properties of the N-bound site when replacing the amines. Thus, the results with 1 were compared to the results obtained when the amine is piperidine (complex 2). Reaction with 1 provides 70% yield of isolated polyNBE (M(n) =8.3 x 10(4) g/mol; PDI = 2.03), whereas 2 provides quantitative reaction (M(n) = 1.2 x 10(5) g/mol; PDI = 1.90) with {[}NBE]/{[}Ru] = 5000, {[}EDA]/{[}Ru] = 48 and 1.1 mu mol of Ru for 5 min at 25 degrees C. The resulting polymers showed c.a. 62% of trans-polyNBE, determined by (1)H NMR, and T(g) = 32 degrees C, determined by DSC and DMTA. For ROMP of NBD, 1 showed quantitative yield with PDI =2.62 when {[}NBD]/{[}Ru] = 5000 for 20 min at 25 degrees C, whereas the reaction with 2 reached 55% with PDI = 2.16 in the same conditions. It is concluded that the presence of the two methyl groups in the piperidine ring provides an increase in the induction period to produce the Ru-carbene species justifying better polyNBE results with 2, and a greater amine(sigma)-> Ru(pi)-> monomer synergism which contributed to the best activation of less tensioned olefin as NBD. (C) 2010 Elsevier B.V. All rights reserved. (AU)

• Processo FAPESP: 06/57577-4 - Uso de combinações de ligantes ancilares de P(III), N(III), e S(II ou IV) no desenvolvimento de catalisadores de Ru(II) para polimerização via metátese de olefinas
• Beneficiário: Benedito dos Santos Lima Neto
• Modalidade de apoio: Auxílio à Pesquisa - Regular