Analysis of diborane X-ray diffraction data utilizing structure factors calculated from molecular wave functions

Crystal unit-cell structure factors for diborane, B₂H₆, have been calculated for four possible molecular geometries, using densities obtained from self-consistent field molecular wavefunctions. These structure factors were fitted for various B-H distances to the experimental X-ray data for B₂H₆ by varying the parameters of several thermal vibration models. B-H bond lengths so determined have values about 0.05 Å longer than those determined by the usual spherical atom analysis of the X-ray data. Consideration of additional factors, such as the X-ray B-H bond shortening due to rigid rotation of the molecule in the crystal, leads to the conclusion that the bond length correction given by this treatment accounts for about two-thirds of the observed discrepancy between X-ray and electron diffraction values for the B-H bond lengths in diborane.