The Vibrational Spectra of Diborane and Some of its Isotopic Derivatives

Abstract

The infrared spectra of ordinary diborane, of B210H6, and of B210D6 have been determined in the vapor state over the spectral range 250–3800 cm−1. The Raman spectra of ordinary diborane and B210D6 have been measured in the liquid at −130°C. Qualitative depolarization measurements have been made on nearly all observed Raman lines. The vibrational spectra have been interpreted with the help of the various selection rules and the product rule for isotope shifts. The fundamental frequencies obtained from this interpretation differ considerably from those previously published, but are in agreement with a large amount of spectroscopic data, including much not hitherto available. It is concluded that the nonplanar bridge model (D2h symmetry) fits the spectroscopic data best, although the unsymmetrical C2h form cannot be definitely excluded. The theoretical and observed vapor heat capacities agree satisfactorily over the temperature range 100–300°K.