Cationic cobalt complexes enable unprecedented cobalt-catalyzed C-H/C-C functionalizations with unique selectivity features. The versatile cobalt catalyst proved broadly applicable, enabled efficient C-H/C-C cleavage at room temperature, and delivered Z-alkenes with excellent diastereocontrol.

The transition metal catalyzed amide bond forming reaction of esters with amines has been developed as an advanced approach for overcoming the shortcomings of traditional methods. The broad scope of substrates in transition metal catalyzed amidations remains a challenge. Here, a manganese­(I)-catalyzed method for the direct synthesis of amides from a various number of esters and amines is reported with unprecedented substrate scope using a low catalyst loading. A wide range of aromatic, aliphatic, and heterocyclic esters, even in fatty acid esters, reacted with a diverse range of primary aryl amines, primary alkyl amines, and secondary alkyl amines to form amides. It is noteworthy that this approach provides the first example of the transition metal catalyzed amide bond forming reaction from fatty acid esters and amines. The acid–base mechanism for the manganese­(I)-catalyzed direct amidation of esters with amines was elucidated by DFT calculations.

C-H activations with challenging arylacetamides were accomplished by versatile ruthenium(II) biscarboxylate catalysis. The distal C-H functionalization offers ample scope-including twofold oxidative C-H functionalizations and alkyne hydroarylations-through facile base-assisted internal electrophilic-type substitution (BIES) C-H ruthenation by weak O-coordination.

Evaluation of the hemilability of hybrid ligands provides a key to understand the metal–ligand cooperation in transition metal catalysis. Here, we design and synthesize a type of RuII complexes based on the hemilability of N-heterocyclic carbenes (NHCs), pyridine, and pyrazole, to compare their activity with other reported Ru catalysts in benzylic C–H oxidation. The RuII catalysts showed ultrastrong catalytic activity in water at room temperature and achieved a turnover frequency (TOF) of 114 h–1, which is the highest TOF value ever reported for Ru-catalyzed benzylic C–H oxidation. The addition of tridentate hybrid ligands in the Ru central position has two beneficial effects: NHCs with a stronger donor ability stabilize the Ru center; however, nitrogen ligands with a relatively weaker donor ability release from the Ru center, so that they induce a reaction. UV–vis, high-resolution electrospray ionization mass spectrometry (ESI-MS), electron paramagnetic resonance (EPR) spectrometry, the trapping of radicals, and the density functional theory calculations (DFT) suggested that a cation catalyst L–RuII– t BuO2H is formed via the reaction between starting RuII catalysts and tert-butyl hydroperoxide, which further undergoes a cleavage of the O–O bond to generate a radical and a cation L–RuIII–OH active intermediate.