Consecutive methane activation mediated by single metal boride cluster anions NbB4−.

Cleavage of all C–H bonds in two methane molecules by gas-phase cluster ions at room temperature is a challenging task. Herein, mass spectrometry and quantum chemical calculations have been used to identify one single metal boride cluster anions NbB₄⁻ that can activate eight C–H bonds in two methane molecules and release one H₂ molecule each time under thermal collision conditions. In these consecutive reactions, the loaded Nb atoms and the support B₄ units play different roles but act synergistically to activate CH₄, which is responsible for the interesting reactivity of NbB₄⁻. Moreover, there are some mechanistic differences in these two reactions, including the mechanisms for the first C–H bond activation steps, dihydrogen desorption sites, and major electron donors. This study shows that non-noble metal boride species are reactive enough to facilitate thermal C–H bond cleavages, and boron-based materials may be one kind of potential support material facilitating surface hydrogen transport. [ABSTRACT FROM AUTHOR]