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Compound 1 (Mg(H2O)6B10H10·4H2O) was synthesized and characterized using NMR, IR, XRD, and elemental analysis. Its thermal decomposition behavior was studied using Simultaneous Thermogravimetric Modulated Beam Mass Spectrometry (STMBMS), TGA, DSC, IR, and 11B NMR. The crystal structure of 1reveals multiple dihydrogen and hydrogen bonding interactions that form a 3D extended structure. A reaction network characterizing the thermal decomposition of 1and its secondary products over a temperature range from 20 to 1000 °C has been developed. Thermal decomposition of 1is primarily controlled by two competing branches in the reaction network, where coordinated water evolves as either H2O (dehydration) or H2(dehydrogenation). The extent of reaction to form H2depends on the fraction of the coordinated water remaining in the sample when its temperature is between 160 and 225 °C. The evolution of coordinated water is reversible and controlled by dissociative sublimation. For the release of coordinated water between 160 and 215 °C, the vapor pressure of water is given by LogeP(Torr) = 30.4561 – 12425.2/T(K) and ΔHs= 103.3 ± 0.3 kJ/mol. The nature of the condensed phase secondary product remaining after all coordinated water is removed by either dehydration and/or dehydrogenation depends strongly on the extent of reaction to form Mg(OH)xB10H10–x. Results of STMBMS experiments where xvaries from 0.2 to ∼4 are used to develop the reaction network that characterizes the thermal decomposition process. Heating of 1at 205 °C resulted in the formation of water-soluble Mg(OH)x(H2O)2–xB10H10–x, while prolonged heating of 1at 270 °C and heating up to 1000 °C led to decomposition.

DADB synthesis: The diammoniate of diborane (DADB) was synthesized in a new metathesis reaction between the diammoniate of monochloroborane and potassium borohydride in liquid ammonia (see scheme). 1H and 11B NMR spectra of DADB are reported. The stability in THF was examined by variable‐temperature 11B NMR spectroscopy.

Unsolvated NaB3H8is prepared by reaction of Na/Hg amalgam with THF·BH3at room temperature for 3 d (<70% yield).

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