doi:10.1021/acs.organomet.8b00430engAngoy, M.Jimenez, M.V.Modrego, F.J.Oro, L.A.Passarelli, V.Perez-Torrente, J.J.Mechanistic Investigation on the Polymerization of Phenylacetylene by 2-Diphenylphosphinopyridine Rhodium(I) Catalysts: Understanding the Role of the Cocatalyst and Alkynyl IntermediatesART-2018-107933The 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.2018http://zaguan.unizar.es/record/12787910.1021/acs.organomet.8b00430http://zaguan.unizar.es/record/127879oai:zaguan.unizar.es:127879info:eu-repo/grantAgreement/ES/MINECO-FEDER/CTQ2013-42532-Pinfo:eu-repo/grantAgreement/ES/MINECO-FEDER/CTQ2016-75884-POrganometallics 37, 16 (2018), 2778-2794by-nc-ndhttp://creativecommons.org/licenses/by-nc-nd/3.0/es/info:eu-repo/semantics/openAccess