Formation of phosphaethyne dimers: A mechanistic study

Tibor Höltzl, Dénes Szieberth, Minh Tho Nguyen, Tamás Veszprémi

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

High-level ab initio (CCSD(T), CBS-QB3 and CASSCF, CASPT2, MR-ACPF, MR-ACPF-2) and density functional theory (B3LYP) calculations were carried out to study the dimerization of phosphaacetylene or phosphaethyne (HCP). Seventeen low energy closed-shell and five openshell phosphaacetylene dimers were found on the potential energy surface. Two head-to-head, one head-to-tail and three other dimerization reaction pathways were determined, all with high activation barriers, suggesting that closed-shell minima are usually kinetically stable. An open-shell head-to-head reaction pathway has also been found with moderate initial barrier (95.0 kJ mol-1) leading to 1,2- and 1,3diphosphacyclobutadiene, suggesting that polymerization of HCP and oligomerization of its derivatives have open-shell mechanism. Formation of 1,2-di-phosphacyclobutadiene is both thermo-dynamically and kinetically favored over 1,3-diphosphacyclobutadiene. A head-to-head reaction involving LiBr as a catalyst was also studied. It has been pointed out that LiBr catalyze the closed-shell mechanism. All the four possible reaction channels of this reaction yield 1,4-diphosphatriafulvene with a fairly low activation Gibbs-free energy (44.8 kJ mol-1), suggesting that this compound could be synthesized. This finding fully supports the experimental results.

Original languageEnglish
Pages (from-to)8044-8055
Number of pages12
JournalChemistry - A European Journal
Volume12
Issue number31
DOIs
Publication statusPublished - Oct 25 2006

Keywords

  • Ab initio calculations
  • Dimerization
  • Phosphaacetylene
  • Phosphaethyne
  • Triafulvenes

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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