Heterometallic complexes, tandem catalysis and catalytic cooperativity

Abstract

This minireview reports the most recent advances in the use of heterometallic catalysts based on singleframe N-heterocyclic carbene ligands. The article describes the synthetic strategies for the preparation of heterometallic catalysts, and their applications in the design of tandem processes by combining the catalytic properties associated with the two (or more) different metal centers. Several examples are discussed in which the use of heterometallic complexes results in a clear enhancement of the catalytic outcome compared to the results provided by mixtures of related homometallic complexes. The field constitutes a research area that is full of potential and is at its very earliest stage.

A Nanosized Janus Bis-N-heterocyclic Carbene Ligand Based on a Quinoxalinophenanthrophenazine Core, and Its Coordination to Iridium

“…Among poly--NHCs, 4 those featuring geometrically isolated carbenes bound by rigid polyaromatic systems have constituted a particularly interesting family, because they can give access to bis(NHC) structurally dynamic homopolymers, 5 and polymetallic catalysts whose properties are fundamentally different from those given by their monometallic ana--logues. 6 Besides their applications in catalysis and materi--als science, this type of compounds have found a promi--nent space in the field of metallosupramolecular chemis--try, in which a number of poly NHC--based molecular rectangles, 7 cylinders, 8 and organometallic polymers 9 are known. Metallorganic assemblies with cavities are espe--cially interesting because cage--like structures can be used for purely cage--catalyzed chemical transformations, 10 in which the substrate adapts to the shape of the cavity giv--ing rise to increased reactivity and selectivity.…”

Formal Gold‐to‐Gold Transmetalation of an Alkynyl Group Mediated by Palladium: A Bisalkynyl Gold Complex as a Ligand to Palladium

“…Recently, the use of two transition metal complexes in catalytic reactions, the so called bimetallic catalysis, is opening new avenues for the synthesis of molecules. [1][2][3][4] These processes rely on the efficient exchange of organic fragments between metal co-catalysts along with a fast and efficient final coupling step that drives the reaction to completion. Among the first examples, the coupling of alkynyl groups has used the cooperative role of two metals, generally a group 11 metal and palladium as, for example, in the Sonogashira reaction.…”

High Catalytic Activity of Heterometallic (Fe₆Na₇and Fe₆Na₆) Cage Silsesquioxanes in Oxidations with Peroxides

“…First of all, the use of different metal ions is known as a key to controlled design of high-nuclearity complexes of picturesque molecular architecture [1][2][3][4][5]. Also, acting together, different metal ions provide catalytic activity in a wide range of processes [6][7][8] as well as intriguing magnetic properties [9]. The most popular synthetic approaches to such complexes involve use of organic ligands as well as application of "complex-as-ligand" tactics [10][11][12][13].…”