Catalytic N−H Bond Activation and Breaking by a Well‐Defined CoII1O4 Site of a Heterogeneous Catalyst

Abstract Catalytic N−H bond activation and breaking by well‐defined molecular complexes or their heterogeneous analogues is considered to be a challenge in chemical science. Metal(0) nanoparticles catalytically decompose NH 3 ; they are, however, ill defined and contain a range of contiguous metal sites with varying coordination numbers and catalytic properties. So far, no well‐defined/molecular M n + ‐containing materials have been demonstrated to break strong N−H bonds catalytically, especially in NH 3 , the molecule with the strongest N−H bonds. Recently, noncatalytic activation of NH 3 with the liberation of molecular H 2 on an organometallic molybdenum complex was demonstrated. Herein, we show the catalytic activation and breaking of N−H bonds on a singly dispersed, well‐defined, and highly thermally resistant (even under reducing environments) Co II 1 O 4 site of a heterogeneous catalyst for organic (ethylamine) and inorganic (NH 3 , with the formation of N 2 and H 2 ) molecules. The single‐site material serves as a viable precursor to ultrasmall (2.7 nm and less) silica‐supported cobalt nanoparticles; thus, we directly compare the activity of isolated cationic cobalt sites with small cobalt nanoparticles. Density functional theory (DFT) calculations suggest a unique mechanism involving breaking of the N−H bonds in NH 3 and N−N coupling steps taking place on a Co 1 O 4 site with the formation of N 2 H 4 , which then decomposes to H 2 and N 2 H 2 ; N 2 H 2 subsequently decomposes to H 2 and N 2 . In contrast, Co 1 N 4 sites are not catalytically active, which implies that the ligand environment around a single atom of a heterogeneous catalyst largely controls reactivity. This may open a new chapter for the design of well‐defined heterogeneous materials for N−H bond‐activation reactions.