Mechanistic Investigation on the Polymerization of Phenylacetylene by 2-Diphenylphosphinopyridine Rhodium(I) Catalysts: Understanding the Role of the Cocatalyst and Alkynyl Intermediates

Angoy, M. ; Jimenez, M.V. (Universidad de Zaragoza) ; Modrego, F.J. (Universidad de Zaragoza) ; Oro, L.A. (Universidad de Zaragoza) ; Passarelli, V. ; Perez-Torrente, J.J. (Universidad de Zaragoza)

Resumen: The mono- and dinuclear rhodium(I) complexes featuring 2-(diphenylphosphino)pyridine ligands, [Rh(cod)(Ph2PPy)(+) and [Rh(nbd)(mu-Ph2PPY)(2)(2+) (cod = 1, 5-cyclooctadiene, nbd = 2, 5-norbornadiene), have been prepared in order to be evaluated as phenylacetylene (PA) polymerization catalysts. In contrast with compound [Rh(nbd){Ph2P(CH2)(2)Py}(+), featuring a 2 -(2-(diphenylphosphino)ethyl)pyridine ligand, that showed a moderate catalytic activity, both [Rh(diene)(Ph2PPy)](n)(n+) (n = 1, cod; n = 2, nbd) complexes showed no catalytic activity due to the formation of unusual dinuclear species [Rh-2(diene)(2)(mu-Ph2PPy)(mu-C=C-R))+, supported by a Ph2PPy bridging ligand and an alkynyl ligand coordinated in a mu-eta(1):eta(2) fashion, which are inactive in PA polymerization. However, compounds [Rh(diene)(Ph2PPy)](n)(n+) efficiently polymerize PA in the presence of a cocatalyst as iPrNH(2) affording highly stereoregular poly(phenylacetylene) (PPA) of My, = 3.42 X 10(5) (cod) and 2.02 X 10(5) (nbd) with polydispersities of 1.39 and initiation efficiencies of 4-7%. NMR studies on the polymerization reaction have allowed identification of the alkynyl species [Rh(C equivalent to CPh)(cod)(Ph2PPy)] as the likely initiating species involved in the generation of the rhodium-vinyl species responsible for the propagation step. The iPrNH(2) cocatalyst is possibly involved in the efficient proton transfer from the coordinated PA to iPrNH(2) that allows for a significant concentration of the key initiating species [Rh(C-CPh)(cod)(Ph2PPy)]. The distinct behavior of compounds [Rh(diene)(Ph2PPy)](n)(n+) as PA polymerization catalysts is a consequence of the binucleating ability of the Ph2PPy ligand in combination with the low basicity of the pyridine fragment which allows for the stabilization of the inactive alkynyl-bridge dinuclear species.

Idioma: Inglés

DOI: 10.1021/acs.organomet.8b00430

Año: 2018

Publicado en: Organometallics 37, 16 (2018), 2778-2794
ISSN: 0276-7333

Factor impacto JCR: 4.1 (2018)

Categ. JCR: CHEMISTRY, ORGANIC rank: 11 / 57 = 0.193 (2018) - Q1 - T1
Categ. JCR: CHEMISTRY, INORGANIC & NUCLEAR rank: 5 / 45 = 0.111 (2018) - Q1 - T1

Factor impacto SCIMAGO: 1.473 - Inorganic Chemistry (Q1) - Physical and Theoretical Chemistry (Q1) - Organic Chemistry (Q1)

Financiación: info:eu-repo/grantAgreement/ES/MINECO-FEDER/CTQ2013-42532-P
Financiación: info:eu-repo/grantAgreement/ES/MINECO-FEDER/CTQ2016-75884-P

Tipo y forma: Article (PostPrint)

Área (Departamento): Área Química Inorgánica (Dpto. Química Inorgánica)