Fabrication of atomically dispersed barium hydride catalysts for the synthesis of deuterated alkylarenes

Marvelous natures of alkali and alkaline earth metal hydrides in catalyzing chemical transformations are being discovered. However, the synthesis of (sub)nanostructured metal hydrides, critically important to enhance their catalytic performances, is yet a very challenging task. Herein, we develop a highly reactive heterogeneous catalyst comprising atomically dispersed barium hydrides on MgO support with an ultrahigh barium loading of up to 20 wt% via a convenient preparation method involving liquid-ammonia impregnation followed by hydrogenation. The surface barium hydride species not only exhibits extraordinary reactivity toward H2 activation at room temperature, but also enables the highly efficient hydrogen isotope exchange (HIE) of both sp3 C–H and sp2 C–H bonds in nonactivated alkylarenes using D2 as the deuterium source under mild conditions. The deuteration rate at benzylic site is two orders of magnitude higher than that of bulk BaH2. This study offers an alternative synthetic route for the manufacture of deuterium-labeled compounds using a heterogenous transition metal-free hydride catalyst beyond the widely studied molecular metal complexe catalysts. Hydrogen isotope exchange is essential for the synthesis of deuterium-labeled compounds but remains challenging under mild conditions. This study demonstrates the selective deuteration of alkylarenes at room temperature using atomically dispersed surface barium hydride.