Radical cations of bis(diphenylphosphino) derivatives (Ph2P-R-PPh2): the formation of localized, cyclic, and dimeric configurations; an ESR and quantum chemical study

Abstract

de, B. F. M. (1991). Radical cations of bis(diphenylphosphino) derivatives (Ph2P-R-PPh2): the formation of localized, cyclic, and dimeric configurations; an ESR and quantum chemical study. Journal of Physical Chemistry, 95(23), 9256-9263. DOI: 10.1021/j100176a042 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Phys. Chem. 1991, 95, 9256-9263 binations and overtones) of a free pseudorotor can become very complicated. ConclusionsWe have carried out calculations to provide a descriptive picture of the energy level patterns expected for the ring-puckering vibrations of spiro compounds. Since the spectra of these molecules are expected to be complicated, it is necessary to have a basic understanding of how these levels will change as a function of the interaction between the two rings (Le., the magnitude of the c coefficient).Since the vapor pressures of most spiro compounds are quite low, it is necessary in most cases to heat the samples in order to record their vapor-phase far-infrared spectra. We have constructed a special sample cell to do this and are initiating this work. 5600 MB Eindhoven, The Netherlands (Received: March 19, 1991) A matrix ESR study on radiogenic radical cations of Ph2P-R-PPh, derivatives with various linkers (R) is presented. The experiments show that in a frozen dichloromethane solution the radical cations can adopt localized (Ph2PR+), cyclic (Ph2P-R-PPh2'+), and dimeric (Ph2RP:PRPh2+) configurations, depending on the nature of the linker. The cyclic and dimeric products are formed in the reaction of a localized cation with a second free-electron pair, resulting in an intra-or intermolecular three-electron PLP u* bond, respectively. The formation of the cyclic structure, with a strongly bent PLP u* bond, requires a specific proximate position of the two phosphine moieties in the precursor molecule. The mutual orientation of the two free-electron pairs of the precursors is assessed by NMR via the nJpp spin-spin coupling constant. Ab initio UHF quantum chemical calculations at the 3-21G*/SCF level support the assignments. Acknowledgment

The Generation of Organic Radical Cations: A Guide to Current Practice for EPR Spectroscopic Studies

“…[109][110][111] This should cause little confusion with compounds of simple structure if the possibility is recognized and the spectra are strong, but it can cause difficulties with more complex compounds such as those containing two phosphorus centers, when the association may be intra-or inter-molecular. 112 Arene radical cations may form dimer (and sometimes higher order) complexes with their parents, and these may go on to give dehydrodimers. For example, the EPR spectrum of monomeric benzene has not been observed in fluid solution, but in CFCl 3 at 100 K (eirradiation) it shows a(6H) 0.43 mT.…”