Rotational spectrum and molecular properties of the dinitrogen–chlorine monofluoride complex

The ground-state rotational spectra of the three isotopomers ¹⁴N₂³⁵ClF, ¹⁵N₂³⁵ClF and ¹⁵N₂³⁷ClF of a complex formed by dinitrogen and chlorine monofluoride have been observed with a pulsed-nozzle, Fourier-transform microwave spectrometer. The spectroscopic constants B₀, D_J, χ_aa(A)(A =¹⁴N_i, ¹⁴N_o or Cl) and M_bb(Cl) are reported. The complex is shown to have a linear (or nearly linear) arrangement N_oN_iClF of the nuclei in the equilibrium conformation with r(N_iCl)= 2.920(2)Å. The intermolecular stretching force constant, k_σ= 5.00(5) N m^–1, is implied by the centrifugal distortion constant D_J. Interpretation of the nuclear quadrupole coupling constants χ_aa(A) leads to the oscillation angles θ_av= cos^–1〈cos²θ〉^1/2= 17.8(5)° and ϕ_av= cos^–1〈cos²θ〉^1/2= 10(3)° for the N₂ and ClF subunits, respectively. Additionally, the diffence χ_aa(N_i)–χ_aa(N_o) leads, on the basis of a simple model, to the conclusion that the polarisation of N₂ attending complex formation is equivalent to the transfer of a fraction δ≈ 0.02 of an electronic charge from N_o to N_i. A comparison of the properties of four related complexes N₂YF and OCYF, where Y = Cl or H, is presented.