Multimetallic-Catalyzed C–C Bond-Forming Reactions: From Serendipity to Strategy

Abstract

The use of two or more metal catalysts in a reaction is a powerful synthetic strategy to access complex targets efficiently and selectively from simple starting materials. While capable of uniting distinct reactivities, the principles governing multimetallic catalysis are not always intuitive, making the discovery and optimization of new reactions challenging. Here, we outline our perspective on the design elements of multimetallic catalysis using precedent from well-documented C–C bond-forming reactions. These strategies provide insight into the synergy of metal catalysts and compatibility of the individual components of a reaction. Advantages and limitations are discussed to promote further development of the field.

Cooperative Bimetallic Catalysis via One‐Metal/Two‐Ligands: Mechanistic Insights of Polyfluoroarylation‐Allylation of Diazo Compounds

“…Besides these advances, Buchwald, [48] Peters and Fu, [49] Hartwig, [50] Stahl, [51] Hong [52] and Ngai [53] et al also disclosed cooperative bimetallic mechanisms in their catalytic reactions using one single metal precursor. Although cooperative bimetallic catalysis has emerged as a powerful approach for reaction engineering, [54][55][56][57][58][59][60] multiligand systems that are based on a single metal is still underdeveloped. For the current catalytic system comprised of a single Pd precursor and two distinct ligands, a series of control experiments were performed subsequently, along with the independent synthesis of catalysis-relevant species, stoichiometric reactions, and kinetic measurements, as delineated in the following sections.…”

Rh(II)/Pd(0) Dual-Catalyzed Regio-Divergent Three-Component Propargylic Substitution

“…The combined use of two or even more metal catalysts to construct new C–C and C–X bonds in a single operation has attracted widespread attention since novel reactivity and selectivity might be achieved together with a bonus of simplified workup procedures. − In particular, bimetallic and tandem catalysis has emerged as an efficient and reliable method to enable a series of new transformations, − which might offer potential opportunities to achieve the difunctionalization of diazo compounds together with propargylation in MCRs. Herein, we report a dirhodium­(II)/palladium(0) dual-catalyzed ligand-controlled regio-divergent three-component propargylic substitution, which uses an α-diazo ester and an amine to generate a nucleophilic intermediate in situ, followed by a regio-divergent propargylic substitution via Pd catalysis (Scheme d).…”

Catalytic C–H Trifluoromethylation of Arenes and Heteroarenes via Visible Light Photoexcitation of a Co(III)–CF3 Complex

“…Whereas early transition metal M–CF 3 bonds readily undergo α-fluoride abstraction to generate difluoromethyl carbene complexes, − M–CF 3 bonds to low-valent later 3d metals are often thermodynamically robust and kinetically inert . Accordingly, recent successes in the development of metal-mediated trifluoromethylations activate M–CF 3 bonds via formation of, for instance, high formal oxidation state complexes, which are prone to C–CF 3 reductive elimination. − In this context, photoredox activation of organometallic catalysts, termed multimetallic or metallaphotoredox catalysis, , has received considerable attention for C–C bond formation, including radical alkylations from homolysis of Co­(III)–alkyl complexes . Typically, these processes separate the light-harvesting species from the transition metal catalyst.…”

“…reductive elimination. 24−26 In this context, photoredox activation of organometallic catalysts, termed multimetallic or metallaphotoredox catalysis, 19,27 has received considerable attention for C−C bond formation, including radical alkylations from homolysis of Co(III)−alkyl complexes. 28 Typically, these processes separate the light-harvesting species from the transition metal catalyst.…”