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

Abstract

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.