Mutual influence of axial and equatorial P-Cl bonds in the molecular forms of pentachlorophosphorane,their lengths in gaseous and crystalline states

The quantum-chemical calculations by RHF/6-31G(d), MR2/6-31G(d) and MP2/6-31+G(d) methods of molecular forms of pentachlorophosphorane with the complete geometry optimization at the different lengths of P-Cl bonds are performed. The results of the calculations are used for estimation of respective ³⁵Cl NQR frequencies. The lengths of axial (2.05 Å) and equatorial (2.01 Å) P-Cl bonds are found, when the calculated NQR frequencies of Cl atoms practically coincide with the obtained experimentally at 77 K. These bonds are a little shorter than in the gaseous state of the matter. In contrast to the ratio of the lengths of the experimental P-Cl bonds and NQR frequencies of respective Cl atoms, at the use of increased lengths of these bonds in the quantum-chemical calculations of the molecule, the ³⁵Cl NQR frequencies of Cl atoms calculated from the results of these calculations, increase. Therewith, the change in the length of the equatorial P-Cl bonds with unchanged length of axial bonds leads to a significantly greater change in the NQR frequencies of axial chloroine atoms than of the equatorial, and vice versa.