Mechanism of the [RhF(PPh3)3] to cis-[RhPh(PPh 3)2(PFPh2)] interconversion: P-C activation and F/Ph exchange via a metallophosphorane pathway

Stuart A. Macgregor, Tebikie Wondimagegn

Research output: Contribution to journalArticle

33 Citations (Scopus)

Abstract

Density functional calculations have been carried out to model various pathways for F/Ph exchange in [RhF(PPh3)3]. Calculations on the full experimental system showed this process to occur via a novel pathway involving initial attack of fluoride on phosphine. This results in the formation of a metallophosphorane intermediate featuring a 5-coordinate phosphorus center. From this species P-Ph activation is very facile and leads to the F/Ph-exchanged product, cis-[RhPh(PPh3)2(PFPh 2)]. The computed activation energy of 22.3 kcal/mol is in excellent agreement with the experimental value. Alternative pathways based on initial Ph group transfer are significantly higher in energy. A key factor favoring the metallophosphorane route is the reduction in coordination number at the metal center that occurs in the initial fluoride transfer step; in contrast Ph group transfer creates a more sterically encumbered metal center. The metallophosphorane pathway indicates that "hard" donor species such as fluoride can induce facile P-C bond activation. This novel mechanism of phosphine ligand disruption may have general significance for the stability of transition metal-phosphine complexes in the presence of such species. © 2007 American Chemical Society.

Original languageEnglish
Pages (from-to)1143-1149
Number of pages7
JournalOrganometallics
Volume26
Issue number5
DOIs
Publication statusPublished - 26 Feb 2007

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