The structure of diphosphine radical cations |
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| Affiliation: | 1. University of Leicester, University Road, Leicester LE1 7RH UK;2. Université de Provence, CNRS URA 1412, av. Normandie Niemen, 13397 Marseille Cedex 13 France;1. Taras Shevchenko National University of Kyiv, Chemistry Department, 64/13 Volodymyrs''ka str., Kyiv, 01601, Ukraine;2. Laboratoire de Chimie Physique Macromoléculaire, ENSIC, Université de Lorraine, 1 rue Grandville, BP 451, 54001 Nancy, France;1. Key Laboratory for Utility of Environment-Friendly Composite Materials and Biomass in University of Gansu Province, College of Chemical Engineering, Northwest Minzu University (Northwest University for Nationalities), Lanzhou, Gansu 730000, PR China;2. College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou, Gansu 730070, PR China |
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| Abstract: | When R2NNR2 molecules lose an electron to give (R2NNR2)+· radical cations, the whole unit becomes planar, with a(π1)2(π2)1 configuration. However, because R3P molecules are far more strongly pyramidal than R3N molecules, this flattening on electron loss is less, and phosphorous centred radical cations do not achieve planarity. This is clearly so for (R2PPR2)+ centres, whose liquid and solid state spectra analysed herein in terms of two equivalent 31P hyperfine couplings, show ca. 9% 3s character. This indicates considerable bending at each phosphorous centre. Furthermore, the form of the spectra, with no x — y splitting of the ‘perpendicular’ lines, suggests that each 31P coupling shares a common axis. This means that a trans conformation is required, as expected because this relieves steric strain and favours “π” type orbital overlap. |
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