The Thermochemistry of Phosphorus Tetrahalide Anions

Abstract

The Br 3 P-Brand I 3 P-Ibond strengths have been determined by measuring thresholds for collision-induced dissociation in a flowing afterglow-tandem mass spectrometer. The results are combined with previously determined values for the PF 4and PCl 4systems to determine the effect of the terminal atom on hypervalent bond strengths. The bond strengths correlate very well with the difference in the electronegativities of phosphorus and the halogen atoms. Computational results at the B3LYP/6-311+G(d) level indicate that PCl 4and PBr 4have seesaw geometries and are good examples of three-center, four-electron bonding. PF 4has a similar geometry, but the bonding is more ionic, whereas PI 4is tetrahedral, consistent with greater steric crowding.

Effect of Substituents on the Strength of Hypervalent Phosphorus−Halogen Bonds

“…[14][15][16] The bond energy in POF 4was measured to be 32 kJ/mol higher than that in PF 4 -, and this relative number is unaffected by difficulties with the overall scale. The values D(PF 3 -Cl -) ) 65 kJ/mol 9 and D(PCl 3 -Cl -) ) 90 kJ/mol 11 have also been reported.…”

“…These anions are hypervalent, − because their electron dot structures show 10 electrons around the P atom. The X 3 P−X - bond strengths have now been measured in the gas phase for all four halogens, − and several bond strengths in 15 mixed-group tetrahalides are also known. There is a linear correlation between the bond strengths and the difference in the electronegativities of the central atom and the halogen.…”

Structure and properties of intrinsic and extrinsic defects in black phosphorus

“…This is in good agreement with the strength of P-I bond in PI 3 . 38 The neutral charge state was found to be lowest in energy for all Fermi level positions throughout the bandgap and no bandgap states were created upon forming this defect. Bader analysis shows almost no charge transfer between iodine and the BP lattice, indicative of a covalent bond between P and I.…”

The bond dissociation energies of SO3—X– (X = F, Cl, Br, and I)

“…Caldwell and Kebarle (11,43) collected an extensive set of measurements of the binding energies of three or four halide ions to different ligands, and other studies have added to this work (44)(45)(46). Representative experimental data are shown in Table 5.…”