Transition Metal-Free Alkyne Hydrogenation Catalysis with BaGa2, a Hydrogen Absorbing Layered Zintl Phase

• Published in: Journal of the American Chemical Society 2019-12, Vol.141 (51), p.19969-19972
• Main Authors: Hodge, Kelsey L, Goldberger, Joshua E
• Format: Article
• Language: English
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.9b09856

Inexpensive, transition metal-free intermetallic compounds have received almost no attention as heterogeneous catalysts. Here, we show that BaGa2, a Zintl–Klemm compound composed of honeycomb sheets of Ga– anions separated by Ba2+ cations and known to react with H2 under moderate conditions to form a layered polyanionic hydride BaGa2H2, effectively catalyzes the hydrogenation of phenylacetylene into styrene and ethylbenzene under modest conditions (1–50 bar H2, 40–100 °C). Remarkably, the catalytic activity of BaGa2 (surface specific activities up to 8390 h–1) is on the same order of magnitude as commercial Pd-based catalysts. In contrast, BaGa2H2 shows negligible catalytic activity, thereby indicating that the unsaturated Ga– framework is necessary for phenylacetylene and styrene adsorption. These findings open up future explorations of utilizing and optimizing the long-term stability of transition metal-free intermetallic hydrogen absorbing compounds for hydrogen-based catalysis.