Single Atom and Metal Cluster Catalysts in Organic Reactions: From the Solvent to the Solid

Abstract

The supporting of pre‐formed soluble metal catalysts on solids is a typical methodology to transform soluble but unrecoverable metal complexes into recoverable and reusable solid catalysts. However, this methodology has been barely implemented for ligand‐less, bare single metal atoms (SMAs) and nanoclusters (NCs) in organic synthesis, despite these ultrasmall species can be formed in‐situ during reaction and be the truly catalytic species. The aim of this review is to explore how to speciate active single metal atoms and clusters during homogeneous catalysis (in solution), without ligands, and to prepare them independently, to be transferred to solid supports and catalyze organic reactions. In many cases, the translation to solids gives single atom catalysts (SACs). Supporting of ultrasmall metal aggregates gives more stable, reusable and, sometimes, chemoselective catalysts for representative organic reactions.

Soluble individual metal atoms and ultrasmall clusters catalyze key synthetic steps of a natural product synthesis

“…The eruption during the last ten years of single atoms catalysts (SACs) 1 and catalytic few-atom metal clusters 2 with exceptional catalytic activity (thousand to millions of turnover numbers) for different reactions have brought the organic synthetic community to adopt them for a variety of transformations [3][4][5][6][7][8] , including biologically active compounds 3,4,9 , since the metal efficiency of these ultrasmall catalytic species can in many cases be higher than classical organometallic complexes 9 . Significant progresses have been achieved in single and few-atom metal-catalyzed hydrogenation, oxidation, hydroaddition and cross-coupling reactions, to name a few, covering also from mild click chemistry to harsh radical C-H activation reactions 10 .…”