Conformational stability, structural parameters, and vibrational frequencies from ab initio calculations for biphosphine

Ab initio calculations have been carried out utilizing various basis sets up to MP2/6-311++G** to determine the conformational stability and structural parameters of biphosphine, P2H4. A very shallow minimum is found at the trans position without bound vibrational states and an energy difference of about 400 cm(-1) (1.14 kcal mol(-1)) above the stable gauche conformer. Additionally, infrared intensities, Raman activities and vibrational frequencies have been determined using the RHF/6-31G*, MP2/6-31G* and/or MP2/6-311G** basis sets. These theoretical quantities are compared to the corresponding experimental values and several reassignments of the fundamentals are proposed. The results are compared to those obtained for some related molecules.