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Radical-initiated P,P-metathesis reactions of diphosphanes: evidence from experimental and computational studies

Branfoot, Callum, Young, Tom A., Wass, Duncan F. and Pringle, Paul G. 2021. Radical-initiated P,P-metathesis reactions of diphosphanes: evidence from experimental and computational studies. Dalton Transactions 50 (20) , pp. 7094-7104. 10.1039/D1DT01013A

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Abstract

By combining the diphosphanes Ar2P–PAr2, where Ar = C6H5, 4-C6H4Me, 4-C6H4OMe, 3,5-C6H3(CF3)2, it has been shown that P,P-metathesis generally occurs rapidly under ambient conditions. DFT calculations have shown that the stability of unsymmetrical diphosphanes Z2P–PZ′2 is a function of the difference between the Z and Z′ substituents in terms of size and electronegativity. Of the mechanisms that were calculated for the P,P-metathesis, the most likely was considered to be one involving Ar2P˙ radicals. The observations that photolysis increases the rate of the P,P-metatheses and TEMPO inhibits it, are consistent with a radical chain process. The P,P-metathesis reactions that involve (o-Tol)2P–P(o-Tol)2 are anomalously slow and, in the absence of photolysis, were only observed to take place in CHCl3 and CH2Cl2. The role of the chlorinated solvent is ascribed to the formation of Ar2PCl which catalyses the P,P-metathesis. The slow kinetics observed with (o-Tol)2P–P(o-Tol)2 is tentatively attributed to the o-CH3 groups quenching the (o-Tol)2P˙ radicals or inhibiting the metathesis reaction sterically.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Cardiff Catalysis Institute (CCI)
Publisher: Royal Society of Chemistry
ISSN: 1477-9226
Funders: EPSRC
Date of First Compliant Deposit: 13 May 2021
Date of Acceptance: 27 April 2021
Last Modified: 22 Jun 2021 13:07
URI: http://orca.cardiff.ac.uk/id/eprint/141281

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