Pseudopotential SCF–MO studies of hypervalent compounds. I. XeF2 and XeF4

The (ab initio) effective potential theory developed by Ewig et al. has been applied to a series of hypervalent compounds with a view to elucidating the anomalous properties of several of the higher fluorides of xenon and iodine. In this initial paper the development of a minimal basis set substantially better than an STO‐4G atom‐optimized set is described. Calculations carried out on XeF2 and XeF4 give valence orbital energies in fair agreement with those obtained with the more flexible, all‐electron SCF–MO calculations by Basch et al. Equilibrium structures of XeF2 and XeF4 provided by the effective potential calculations possess the correct symmetries. Bond lengths, although too long by 0.09 Å, correctly reproduce the contraction observed experimentally upon fluorination of XeF2. Calculated bending and stretch–stretch interaction force constants are in pleasing agreement with experiment, as is the stretching anharmonicity. Stretching frequencies evaluated at the experimental bond length, however, are 25% high. Overall, the ability of the present treatment to give a reasonable account of the structures and force fields of XeF2 and XeF4 justifies its application to the higher fluorides where interpretations of observations are more speculative.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70823/2/JCPSA6-73-1-367-1.pd

Pseudopotential SCF–MO studies of hypervalent compounds. II. XeF+5 and XeF6

New evidence bearing upon the anomalous properties of xenon hexafluoride has been obtained via the ab initio molecular orbital approach applied successfully to the di‐ and tetrafluorides in paper I. Structures of both XeF+5 and XeF6 are governed by a stereochemically active lone pair. In the case of the square–pyramidal cation the Fax–Xe–Feq angle calculated for the bare ion is within 2° of the value observed in the crystalline complex. For the hexafluoride, however, the calculated deformation from Oh symmetry is appreciably greater than that deduced from electron diffraction intensities. Nevertheless, the results of calculations are in sufficient conformity with the Bartell–Gavin, Pitzer–Bernstein interpretation and at variance with the ’’electronic‐isomers’’ interpretation to leave little doubt about the answer. With increasing fluorination in the XeFn series the HOMO–LUMO energy difference decreases and the second‐order Jahn–Teller effect is enhanced. Increasing fluorination (and increased positive charge on Xe) also shortens bond lengths; calculated shortenings parallel observed shortenings. The deformation of XeF6 from Oh is along t1u bend and stretch coordinates to a C3v structure with long bonds adjacent to the lone pair, as expected according to the valence‐shell–electron‐pair‐repulsion model. Pure t2g deformations are destabilizing but anharmonic t1u–t2g coupling significantly stabilizes the deformation. Steric aspects of the structure and force field are diagnosed and found to be minor. Values for the force constants f44, f55, f̄4444, f̄444′4′, and f̄445 are derived and found to be of the magnitude forecast in the Bartell–Gavin and Pitzer–Bernstein treatments except that the calculations do not reproduce the delicate balances believed to lead to almost free pseudorotation in XeF6.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69894/2/JCPSA6-73-1-375-1.pd

Phosphorus And Its Compounds

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Phosphorus and its compounds

Mode of access: Internet

Atomic Energy Commission Report AECD-4152

The following report is meant to be used as a guide for planning and interpreting future distribution experiments of tubanyl salts between organic solvents and aqueous solutions

Atomic Energy Commission Report AECD-3950

Abstract: "This report suggests using methyl acetate extraction of charge material as a means of determining the non-volatile residue. It is shown that the volatile constituents of charge material are all extremely soluble in methyl acetate whereas the non-volatile materials are quite insoluble. Percent NVH on several samples of charge material by this method are reported and discussed.