Microwave spectrum of tungsten pentafluoride chloride

Abstract

The microwave spectrum of tungsten pentafluoride chloride has been observed and measured. The spectrum is of the symmetric top type, exhibiting tungsten isotope effects, which have not previously been observed by microwave spectroscopy, and chlorine isotope effects. The rotational constants for the various isotopic species in the vibrational ground state are: B₀= 1387.664, 1387.597, 1387.539 and 1387.413 MHz for ³⁵Cl¹⁸²WF₅, ³⁵Cl¹⁸³WF₅, ³⁵Cl¹⁸⁴WF₅ and ³⁵Cl¹⁸⁶WF₅; and B₀= 1354.459, 1354.385, 1354.312 and 1354.160 MHz for the corresponding tungsten isotopes of ³⁷ClWF₅.

The W—Cl bond length is determined directly from the data as r(W—Cl)= 2.252 ± 0.002 Å. The determination of the other structural parameters in terms of a model with C_4ν symmetry is discussed, and if all five W—F bonds are assumed equal in length the result is: r(W—F)= 1.836 ± 0.001 Å; angle(F—W—F_axial)= 88°41′± 10′.

The rotational spectrum in the ν₁₁ vibrational state has been assigned and gives the rotation-vibration constant α₁₁= 0.830 ± 0.005 MHz for the four ³⁵ClWF₅ isotopic species.