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Updated: May 28, 2026

Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization
Published on: November 27, 2015
Experimental and theoretical studies on the (co)cyclotrimerization of alkynes (and ethylene) in a TpRh compound
Giovanni Bottari1, Juan José Moreno1, Verónica Salazar2
1Instituto de Investigaciones Químicas, Departamento de Química Inorgánica, and Centro de Innovación en Química Avanzada (ORFEO-CINQA), Consejo Superior de Investigaciones Científicas (CSIC) and Universidad de Sevilla, Av. Américo Vespucio 49, Isla de la Cartuja, 41092 Sevilla, Spain. joaquin.lopez@iiq.csic.es.
Abstract:
The reactions between the Rh(I) ethylene complex TpRh(C2H4)2 (1; Tp = hydrotris(pyrazolyl)borate), and the alkynes di-tert-butylacetylene dicarboxylate (DTBAD), acetylene, phenylacetylene, and methyl propiolate (MP) have been studied, and the results compared with those obtained previously for dimethylacetylene dicarboxylate (DMAD). Electron withdrawing groups (DTBAD) at both termini of the triple bond stabilize η4-diene-Rh(I) species, while terminal alkynes (acetylene, phenylacetylene) easily lead to η3-allyl-Rh(III) species. The terminal alkyne methyl propiolate, with only one electron withdrawing substituent, exhibits an intermediate behavior, forming both η4-diene-Rh(I) and η3-allyl-Rh(III) species. Two types of intermediate octahedral TpRh(III) rhodacycles have been detected and characterized by NMR. Mechanistic investigations by DFT are also in agreement with the intermediate role of these types of species, which form via oxidative coupling of compounds of type [TpRh(C2H4)(C2R2)] and [TpRh(C2R2)2]. Ligand exchange reactions to form these species from 1 are instrumental in the outcome of the reactions.
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