Are B…ClF bonds linear? The angular geometry of a pre-reactive complex of oxirane and chlorine monofluoride from rotational spectroscopy

A pre-reactive complex formed by oxirane and ClF was characterised through the ground-state rotational spectra of the isotopomers (CH2)2O…35ClF and (CH2)2O…37ClF. The complex has Cs symmetry, with the O…ClF nuclei confined to the symmetry (ac) plane. Determination of the complete Cl nuclear quadrupole coupling tensor χaa, χbb-χcc and χac led to the equilibrium angle αaz between the ClF axis (z) and the a-axis directions. By fitting the observed rotational constants A0, B0 and C0 under the assumption of unchanged monomer geometries and with αaz fixe the geometrical parameters r(O…Cl) = 2.437(2) Å, f = 112.7(1)° and the deviation θ = 2.91(3)° from collinearity of the O…ClF nuclei were established.