The mechanism of formation of cyclic triphosphenium ions; detection of transient intermediates in solution

Dillon, K.B.; Monks, P.K.

Abstract

The mechanism of formation of cyclic triphosphenium ions [–(CH2)nP(R2)PP(R2)–]+ 3 from diphosphanes R2P(CH2)nPR2 and phosphorus(III) halides PX3 (X = Cl or Br) has been unequivocally established for the six-membered heterocycles with R = Et, iPr or c-Hex, n = 3, and for five-membered rings with R = Et, n = 2. The initial stage is the formation of an acyclic species, [R2P(CH2)nP(R2)- PX2]+X− 1. The cation of this species cyclises to a symmetrical dication [–R2P(CH2)nP(R2)P(X)−]2+ 2 by loss of halide, where the middle P atom has an X group attached and is still formally P(III). The rate-determining step is then a redox reaction to form the final cyclic monocationic product 3, with a ‘bare’ middle P atom. Several transient intermediate species, including the precursor cyclic dication 2 in each case, have been identified by means of 31P NMR solution-state spectroscopy.

Citation

Dillon, K., & Monks, P. (2007). The mechanism of formation of cyclic triphosphenium ions; detection of transient intermediates in solution. Dalton Transactions, 2007(14), 1420-1424. https://doi.org/10.1039/b617935e

• Journal Article Type: Article
• Acceptance Date: Feb 8, 2007
• Online Publication Date: Feb 22, 2007
• Publication Date: 2007
• Deposit Date: Sep 21, 2007
• Journal: Dalton Transactions
• Print ISSN: 1477-9226
• Electronic ISSN: 1477-9234
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 2007
• Issue: 14
• Pages: 1420-1424
• DOI: https://doi.org/10.1039/b617935e
• Public URL: https://durham-repository.worktribe.com/output/1536422