Rotational spectrum of (CH3)3P⋯HCl and a comparison of properties within the series of axially symmetric dimers R3Y⋯HCl, where Y = N or P and R = H or CH3

Abstract

The rotational spectra of two symmetric-top isotopomers of the trimethylphosphine–hydrogen chloride dimer have been observed by pulsed-nozzle, Fourier-transform microwave spectroscopy and analysed to give the following ground-state spectroscopic constants: [graphic omitted] The Cl nuclear quadrupole coupling constant χ(³⁵Cl) is used to establish that the description (CH₃)₃P⋯HCl rather than (CH₃)₃[graphic omitted]H⋯Cl is more appropriate, although a very small extent of proton transfer cannot be ruled out. The former model is used to obtain r(P⋯Cl)= 3.6131(2)Å and k_σ= 10.48(7) N m^–1. A comparison of χ(³⁵Cl) and k_σ among members of the series R₃Y⋯HCl, where Y = N or P and R = H or CH₃, allows the conclusion that the dimers (R = H, Y = P), (R = H, Y = N) and (R = CH₃, Y = P) are of a different nature from (R = CH₃, Y = N). These conclusions are discussed in the light of estimates of the energetics of the process R₃ Y⋯HCl = R₃[graphic omitted]H⋯Cl.