Ab initio calculations have been carried out in a systematic investigation of pnicogen homodimers (PH 2 X) 2 , for X=F, OH, NC, NH 2 , CCH, CN, CH 3 , H, and BH 2 . Complex binding energies range from 7 to 34kJmol −1 , which is within the range observed for neutral hydrogen-bonded complexes. One-bond spin–spin coupling constants across the pnicogen interaction 1p J(P–P) exhibit a quadratic dependence on the P–P distance, similar to the dependence of 2h J(X–Y) on the X–Y distance for complexes with X–H⋯Y hydrogen bonds. Thus, computed values of 1p J(P–P) could be used to extract P–P distances from experimentally measured coupling constants.