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

The ground-state rotational spectra of the three isotopomers ¹⁴N₂⋯³⁵ClF, ¹⁵N₂⋯³⁵ClF and ¹⁵N₂⋯³⁷ClF 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_i⋯ClF of the nuclei in the equilibrium conformation with r(N_i⋯Cl) = 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. Intepretation of the nuclear quadrupole coupling constants χ_aa(A) leads to the oscillation angles θ_av = cos^-1〈cos² θ〉^1/2 = 17.8(5)° and φ_av = cos^-1〈cos² θ〉^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 N₂⋯YF and OC⋯YF, where Y = Cl or H, is presented.