Phosphorus ionization potentials

Ionic dissociation of carbon-carbon a-bonds in hydrocarbons and the formation of authentic hydrocarbon salts, 30, 173 Ionization potentials, 4, 31 Ion-pairing effects in carbanion reactions, 15, 153 Ions, organic, charge density-NMR chemical shift correlations, 11,125 Isomerization, permutational, of pentavalent phosphorus compounds, 9, 25 Isotope effects, hydrogen, in aromatic substitution reactions, 2,163... 

The valence MO energies and Mulliken populations for H3PCH2 at various theory levels are shown in Table 6. The low HOMO energy is consistent with the first ionization potentials determined for substituted ylides which are in the range 6-7 eV (Section II.B.l.f). The Mulliken populations show that there is a build-up of electron density on carbon, also reflected in the integrated spatial electron population (ISEP) value of 9.2 at the 3-21G level 65, with a corresponding decrease in electron density of phosphorus. The semiquantitative approach of Jardine et a/.190 gives a similar result. 

Alkylphosphines have been studied (99, 231), as have cyclopolyphos-phines (120). The reaction products of phosphorus with various olefins were investigated using mass spectral methods (108), and a large number of phospholines have been reported (181, 237). The mass spectrum of the trimer of tetramethylphosphinoborine showed that B—P, C—B, and C—P bonds were broken first, and with the pentamer of the dimethyl compound, B—H, B—P, and C—P bonds were broken (101, 232). The spectra of thiophosphorustri-A -methylimide and its arsenic analog were reported by Holmes and Forstner (130). Ionization potentials have been recorded for many perfluoroalkylarsines and some of the related alkyl compounds (79). 

The optimum geometry of tri-t-butylphosphine has been determined by CNDO/2 calculations,234 and the CNDO/S method has been extended to include second-row elements.235 The results for phosphorin (15) satisfactorily explain the observed u.v. transitions, dipole moment, and ionization potentials. An X-ray structure of 1-benzylphosphole (16) points to the presence of a non-planar ring with a mean P—C(ring) distance of 1.783 A 236 the shortening of the latter over the sum of the single-bond radii is consistent with some delocalization of the phosphorus lone pair. A number of new cyclic phosphides of carboxylic acids such as (17) can be... 

The extreme bond system of phosphorus-carbon yhdes, indicated in Eq. (1), is reflected in outstandingly low first ionization potentials (Tab. 1.1). 

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