What accounts for the difference between singlet phenylphosphinidene and singlet phenylnitrene in reactivity toward ring expansion?

John Morrison Galbraith; Peter P Gaspar; Weston Thatcher Borden

doi:10.1021/ja0269892

What accounts for the difference between singlet phenylphosphinidene and singlet phenylnitrene in reactivity toward ring expansion?

J Am Chem Soc. 2002 Oct 2;124(39):11669-74. doi: 10.1021/ja0269892.

Authors

John Morrison Galbraith¹, Peter P Gaspar, Weston Thatcher Borden

Affiliation

¹ Department of Chemistry, University of Washington, Box 351700, Seattle, WA 98195-1700, USA.

PMID: 12296732
DOI: 10.1021/ja0269892

Abstract

(8/8)CASSCF and (8/8)CASPT2 calculations have been performed in order to investigate the potential surface for the ring expansion of the (1)A(2) state of phenylphosphinidene (1c) to 1-phospha-1,2,4,6-cycloheptatetraene (3c). Unlike the comparable ring expansion of the (1)A(2) state of phenylnitrene (1b) to 1-aza-1,2,4,6-cycloheptatetraene (3b), ring expansion of 1c to 3c is computed to be quite endothermic. Nevertheless, cyclization of 1c, to form the bicyclic intermediate 2c in the ring expansion reaction, is computed to be only slightly more endothermic than the comparable cyclization reaction of 1b to 2b. The origins of these differences between the ring expansion reactions of 1b and 1c have been elucidated through the calculation of the energies of relevant isodesmic reactions.