SOME INDO CALCULATIONS OF NITROGEN-NITROGEN SPIN-SPIN COUPLING-CONSTANTS

Sum-over-states perturbation calculations, within the INDO framework, are reported for some one- and two-bond nitrogen-nitrogen coupling constants. Overall, the agreement between the calculated and observed couplings is satisfactory. Least-squares values are obtained for the integral products (SN2(0))2 and 〈r-3〉N2, which are 38.408 and 23.447 a. u.-6, respectively, for 1J(NN); the corresponding values for 1J(N=N) are 33.790 and 20.392 a.u.-6, respectively. With the exception of the Z isomer of β-acetylphenylhydrazine all of the one-bond coupling constants are predicted to be negative in sign. In most cases both the contact and orbital contributions to the couplings are significant. The presence of valence shell s lone-pair electrons produces negative contact contributions, and valence shell p lone pairs give rise to positive contact terms as previously predicted. © 1979.