Cleavage of Si–H, B–H, and C–H Bonds by Metal–Ligand Cooperation

Abstract

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.

Umpolung of B−H Bonds by Metal–Ligand Cooperation with Cyclopentadienone Iridium Complexes

“…One way to activate B−H bonds by transition metal complexes is the oxidative addition, that is the homolytic cleavage of a B−H bond on the central metal to generate a B anion and an H anion. Alternatively, metal–ligand cooperative heterolytic cleavage has been attracting emerging attention in the last decade [7–9] . Figure 1 summarizes the representative reports for B−H bond cleavage by metal–ligand cooperation: a) ruthenium thiolate by Ohki, Tatsumi, and Oestreich, [10] b) N,O‐chelated phosphoramidate by Schafer, Love, and Weller, [11] c) palladium carbene by Iluc, [12] and d) cyclopentadienone ruthenium dimer by Casey and Clark [13] .…”

“…Figure 1 summarizes the representative reports for B−H bond cleavage by metal–ligand cooperation: a) ruthenium thiolate by Ohki, Tatsumi, and Oestreich, [10] b) N,O‐chelated phosphoramidate by Schafer, Love, and Weller, [11] c) palladium carbene by Iluc, [12] and d) cyclopentadienone ruthenium dimer by Casey and Clark [13] . In all of these precedents, each B−H bond is cleaved into an H anion on the metal and a B cation on the electronegative atom of the ligand, which is inheriting the polarization in the parent B−H bonds [9] . To the best of our knowledge, there is no report for the cleavage of a B−H bond with a metal‐ligand bifunctional complex to give a B anion on the metal and an H cation on the ligand [14]…”

Element‐Ligand Cooperativity with p‐Block Elements

“…A key feature is the cooperative H 2 ‐formation from the ligand‐based H δ + and the Ru‐H δ – in a cis ‐arrangement. Besides, MLC has found broad application in the activation of Si–H, B–H, and C–H bonds and their catalytic transformations . Most often, the ligand acts as a nucleophile and the metal as an electrophile.…”

Umpolung of B−H Bonds by Metal–Ligand Cooperation with Cyclopentadienone Iridium Complexes

“…[13] In all of these precedents, each B À H bond is cleaved into an H anion on the metal and a B cation on the electronegative atom of the ligand, which is inheriting the polarization in the parent BÀH bonds. [9] To the best of our knowledge, there is no report for the cleavage of a BÀH bond with a metal-ligand bifunctional complex to give a B anion on the metal and an H cation on the ligand. [14] Here in this study, we report the first umpolung cleavage of the BÀH bond by cyclopentadienone iridium hydride complex (Figure 1 e).…”

“…Alternatively, metal-ligand cooperative heterolytic cleavage has been attracting emerging attention in the last decade. [7][8][9] Figure 1 summarizes the representative reports for BÀH bond cleavage by metal-ligand cooperation: a) ruthenium thiolate by Ohki, Tatsumi, and Oestreich, [10] b) N,O-chelated phosphoramidate by Schafer, Love, and Weller, [11] c) palladium carbene by Iluc, [12] and d) cyclopentadienone ruthenium dimer by Casey and Clark. [13] In all of these precedents, each B À H bond is cleaved into an H anion on the metal and a B cation on the electronegative atom of the ligand, which is inheriting the polarization in the parent BÀH bonds.…”