A series of polymer‐supported cooperative PC(sp3)P pincer catalysts was synthesized and characterized. Their catalytic activity in the acceptorless dehydrogenative coupling of alcohols and the transfer hydrogenation of aldehydes with formic acid as a hydrogen source was investigated. This comparative study, examining homogeneous and polymer‐tethered species, proved that carefully designing a link between the support and the catalytic moiety, which takes into consideration the mechanism underlying the target transformation, might lead to superior heterogeneous catalysis.

High‐valent metal complexes are viable candidates for hydrogenation catalysts: The domain of catalytic hydrogenation is traditionally dominated by low‐valent metals; however, the heterolytic bond‐splitting mechanism does not require an electron‐rich metal. Here we report a structurally well‐defined ruthenium(IV) catalyst capable of hydrogen activation at room temperature and the efficient hydrogenation of carbonyl and carboxyl compounds under molecular hydrogen. More information can be found in the Research Article by D. Gelman and co‐workers (DOI: 10.1002/chem.202201098). Artwork: Shrouq Mujahed.

In this communication, we report on the successful application of a high‐valent RuIV bifunctional catalyst (1) for mild hydrogenation of cyclic and acyclic carbonates. Our experimental and theoretical studies suggest that the hydrogenation mechanism is operated by an unusual formally zwitterionic RuIV complex. According to our hypothesis, the positively charged high‐valent metal center is responsible for stronger hydrogen coordination. On the other hand, the proximate negatively charged ligand site facilitates heterolytic H2 bond activation, which leads to efficient catalysis.

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Low-valent metals traditionally dominate the domain of catalytic hydrogenation. However, metal-ligand cooperating (MLC) catalytic systems, operating through heterolytic HÀ H bond splitting by a Lewis acidic metal and a basic ligand site, do not require an electron-rich metal. On the contrary, high-valent metals that induce weaker back donation facilitate heterolytic bond activation. Here we report, for the first time, the efficient hydrogenation of carbonyl and carboxyl compounds under molecular hydrogen catalyzed by a structurally well-defined Ru IV catalyst bearing a bifunctional PCP pincer ligand. The catalyst exhibits reactivity toward molecular hydrogen superior to that of the low-valent analog and allows hydrogen activation even at room temperature.