Metal−ligand cooperation, in which metal and ligand participate in bond cleavage and formation, is gathering great attention in recent years. In contrast to the classical bond cleavage by active metal centers with spectator ligands, metal−ligand cooperation has enabled unprecedented reactivities. Especially, metal−ligand cooperative H−H bond cleavage has been extensively studied and applied to various catalysts. On the other hand, there are substantial efforts to expand the scope of the bond to be cleaved other than the H−H bond. This review summarizes the recent progress in the metal−ligand cooperative cleavages of Si−H, B−H, and C−H bonds and their catalytic applications.

C–H bond cleavage and formation is one of the most essential elementary reactions in organic chemistry. Herein, a heterolytic sp3 C–H bond reductive elimination from hydroxyCp dimethylplatinum­(IV) B is reported. Protonation of cyclopentadienone dimethylplatinum­(II) A afforded B via the protonation of the ligand. Successive C–H bond formation from the C anion of the methyl group and the H cation of the hydroxyCp group was observed in the presence of carboxylic acids or hydrogen chloride. The reaction was accompanied by the concurrent reduction of Pt­(IV) to Pt­(II). Experimental and theoretical investigations suggested that the mechanism for the C–H bond formation was acid-mediated metal–ligand cooperative outer-sphere reductive elimination.

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In contrast to conventional metal–ligand cooperative cleavage of a B−H bond, which provides a B cation on the ligand and an H anion on the metal, we report herein the umpolung of B−H bonds by novel cyclopentadienone iridium complexes. The B−H bonds of 4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolane (HBpin) and 1,8‐naphthalenediaminatoborane (HBdan) were cleaved to give a B anion on the metal and an H cation on the phenolic oxygen atom of the ligand. Mechanistic investigation by DFT calculations revealed that the alkoxycarbonyl‐substituted cyclopentadienone ligand facilitated deprotonation from Ir−H after oxidative addition of the B−H bond to give the umpolung product. The generated boryliridium complex was found to undergo borylation of an allyl halide in the presence of base, thus showing the nucleophilic nature of the boron atom.

The cleavage of silicon−hydrogen bonds to generate silicon-containing metal complexes has played an essential role in the preparation of organosilicon compounds. Herein, we report the reaction of cyclopentadienone iridium complex 1 with hydrosilanes to afford hydroxycyclopentadienyl iridium silyl complexes 4 via the umpolung of the Si−H bond. The nucleophilicity of the Ir−Si bond in the resulting complex was demonstrated in the reaction with an allyl halide and ethyl acrylate. Furthermore, a silylene complex was formed from hydroxycyclopentadienyl silyliridium complex 4 via the formal reductive elimination of the C−H bond at the silicon center to release benzene. The silylene complex synthesized from tricarbylsilane showed ambiphilic reactivities, which are consistent with the classical reactivities of silylenes.