Selectivity Effects in Bimetallic Catalysis

Abstract

An emerging area of homogeneous catalysis is the use of catalysts featuring two closely associated metal sites. This approach complements the traditional focus on single-site catalysts and makes available new parameters with which to optimize catalytic behavior. Single-site catalysts are optimized through changing 1) the identity of the metal, and 2) the steric and electronic properties of the ligands. Bimetallic catalysts introduce new optimization parameters such as 3) catalyst nuclearity (mononuclear vs. binuclear), and 4) bimetallic pairing (relative compatibility of two metal sites). In order to harness these new optimization parameters in developing systems, it is necessary to first understand the origin of bimetallic selectivity effects that already have been documented. This Concept article highlights bimetallic effects on the chemo-, regio-, and stereoselectivity of catalytic transformations, using selected case studies from the recent literature as illustrative examples.

Leveraging molecular metal–support interactions for H2 and N2 activation

“…The manner in which a metalmetal bonded (M A −M B ) complex activates a substrate with an X−Y bond can be divided broadly into three categories ( bonds between disparate metals, such as the pairing of a late transition metal with an early or main-group metal, often leads to heterolytic substrate activation. Cooperative substrate activation by early-late heterobimetallics [21][22][23][24][25][26][27] has been more generally reviewed, as has the reactivity of metalloradicals formed in situ from metal-metal bonded precursors [28][29][30]. Rather, we focus on the case in which a single active metal binds and activates substrate, while the supporting metal tunes the electronic coordination environment of the active metal via a metal-metal bond.…”

Dinuclear Metal Synergistic Catalysis Boosts Photochemical CO2‐to‐CO Conversion

“…[1][2][3][4][5] Compared with mononuclear metal catalysts,t he dinuclear ones has more parameters with which to optimize its catalytic performances,n ot only by changing the metal and ligand, but also varying the bimetallic pairing. [1][2][3][4][5] Compared with mononuclear metal catalysts,t he dinuclear ones has more parameters with which to optimize its catalytic performances,n ot only by changing the metal and ligand, but also varying the bimetallic pairing.…”

A New Domain of Reactivity for High‐Valent Dinuclear [M(μ‐O)2M′] Complexes in Oxidation Reactions

“…[1] Moreover, such studies can lead to the discovery of novel species [2] exhibiting reactivity patterns different from their homodinuclear counterparts. The illustrative example (Scheme 1 inset) is the recently reported [L 1 Ni(μ-O) 2 Cu(MeAN)] + ( 1; L 1 = [HC(CMeNC 6 H 3 ( i Pr) 2 ) 2 ]; MeAN = N,N,N ′ ,N ′ ,N ″-pentamethyl dipropylenetriamine), [3] complex which, in sharp contrast to the presence of electrophilic oxido groups in symmetric [M 2 (μ–O) 2 ] n+ (M = Ni, Co, Fe and Mn) analogues, [4] possesses nucleophilic oxido ligands and deformylates aldehydes.…”

“…The synthesis and investigation of heterobimetallic bis(moxido) complexes with [M(m-O) 2 M'] n+ cores are of particular interest for modeling the structures and reactivities of active sites in chemically related metalloenzymes containing two different metal ions. [1] Moreover,such studies can lead to the discovery of novel species [2] exhibiting reactivity patterns different from their homodinuclear counterparts.T he illustrative example (Scheme 1i nset) is the recently reported [L 1 Ni(m-O) 2 Cu(MeAN)] + (1; L 1 = [HC(CMeNC 6 H 3 ( i Pr) 2 ) 2 ]; MeAN = N,N,N',N',N''-pentamethyl dipropylenetriamine) [3] complex, which, in sharp contrast to the presence of electrophilic oxido groups in symmetric [M 2 (m-O) 2 ] n+ (M = Ni, Co, Fe and Mn) analogues, [4] possesses nucleophilic oxido ligands and deformylates aldehydes.…”