Raman Spectroscopy, X-ray Diffraction, and Hydrogenation Thermochemistry of N,N,N,N-Tetramethylcyclotriborazane under Pressure

Abstract

The novel hydrogen-rich BN materials Me2NHBH3 and c-N2B2H4Me4 have been studied by a combination of vibrational spectroscopy and single crystal X-ray diffraction over the pressure range 0–40 GPa. Assignments of Raman-active vibrational modes were made for c-N2B2H4Me4 on the basis of a combination of gas-phase predictions and previous assignments for similar compounds. The Raman spectrum of single crystals were found to have excellent signal-to-noise for pressures over the 0–40 GPa range, making it an ideal method for in situ analysis of high pressure reactions involving c-N2B2H4Me4. The enthalpy of the reaction c-N2B2H4Me4 + 2 H2 → 2 Me2NHBH3 was estimated to be 2.9 kcal/mol endothermic at ambient pressure. The corresponding pressure dependence of ΔGrxn was estimated from the P–V equations of state (EOS) measured for Me2NHBH3, c-N2B2H4Me4, and H2 over the 0–12 GPa range. Using the EOS for fluid hydrogen, the reaction is estimated to have a favorable ΔΔGrxn of 10 kcal/mol over the 0–2 GPa pressure range. A...