Some INDO calculations of the dependence of one-bond phosphorus-phosphorus coupling upon molecular geometry

Some INDO parameterized SCPT calculations of ¹J(P? P) and ¹J(P?P) are reported as a function of geometry. At structures corresponding to the gas-phase equilibrium configuration of diphosphine, all of the substituted diphosphines considered are predicted to have negative values of ¹J(P? P). Both contact and non-contact contributions to ¹J(P? P) are significant, whereas the angular variation of ¹J(P? P) is mainly due to the contact term. The non-contact interactions are dominant in determining the value of ¹J(P?P).