title: Reaction of [TpRh(C2 H4 )2 ] with Dimethyl Acetylenedicarboxylate: Identification of Intermediates of the [2+2+2] Alkyne and Alkyne-Ethylene Cyclo(co)trimerizations.
abstract: The reaction between the bis(ethylene) complex [TpRh(C2 H4 )2 ], 1, (Tp=hydrotris(pyrazolyl)borate), and dimethyl acetylenedicarboxylate (DMAD) has been studied under different experimental conditions. A mixture of products was formed, in which TpRh(I) species were prevalent, whereas the presence of trapping agents, like water or acetonitrile, allowed for the stabilization and isolation of octahedral TpRh(III) compounds. An excess of DMAD gave rise to a small amount of the [2+2+2] cyclotrimerization product hexamethyl mellitate (6). Although no catalytic application of 1 was achieved, mechanistic insights shed light on the formation of stable rhodium species representing the resting state of the catalytic cycle of rhodium-mediated [2+2+2] cyclo(co)trimerization reactions. Metallacyclopentene intermediate species, generated from the activation of one alkyne and one ethylene molecule from 1, and metallacyclopentadiene species, formed by oxidative coupling of two alkynes to the rhodium centre, are crucial steps in the pathways leading to the final organometallic and organic products.
authors.affiliation: Instituto de Investigaciones Químicas, Departamento de Química Inorgánica, Centro de Innovación en Química Avanzada (ORFEO-CINQA), Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Sevilla, Avenida Américo Vespucio 49, 41092, Sevilla, Spain.
authors.forename: Giovanni
authors.identifier: http://orcid.org/0000-0001-8392-2649
authors.initials: G
authors.lastname: Bottari
authors.affiliation: Instituto de Investigaciones Químicas, Departamento de Química Inorgánica, Centro de Innovación en Química Avanzada (ORFEO-CINQA), Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Sevilla, Avenida Américo Vespucio 49, 41092, Sevilla, Spain. laura@iiq.csic.es.
authors.forename: Laura L
authors.initials: LL
authors.lastname: Santos
authors.affiliation: Instituto de Investigaciones Químicas, Departamento de Química Inorgánica, Centro de Innovación en Química Avanzada (ORFEO-CINQA), Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Sevilla, Avenida Américo Vespucio 49, 41092, Sevilla, Spain.
authors.forename: Cristina M
authors.initials: CM
authors.lastname: Posadas
authors.affiliation: Instituto de Investigaciones Químicas, Departamento de Química Inorgánica, Centro de Innovación en Química Avanzada (ORFEO-CINQA), Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Sevilla, Avenida Américo Vespucio 49, 41092, Sevilla, Spain.
authors.forename: Jesús
authors.identifier: http://orcid.org/0000-0002-5155-1262
authors.initials: J
authors.lastname: Campos
authors.affiliation: Department of Chemistry, Vienna University of Technology, Getreidemarkt 9/164SC, 1060, Vienna, Austria.
authors.forename: Kurt
authors.initials: K
authors.lastname: Mereiter
authors.affiliation: Instituto de Investigaciones Químicas, Departamento de Química Inorgánica, Centro de Innovación en Química Avanzada (ORFEO-CINQA), Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Sevilla, Avenida Américo Vespucio 49, 41092, Sevilla, Spain. paneque@iiq.csic.es.
authors.forename: Margarita
authors.identifier: http://orcid.org/0000-0002-8055-2491
authors.initials: M
authors.lastname: Paneque
keywords: alkynes; cycloadditions; cyclotrimerization; rhodium; scorpionate ligands