Development of Nickel-on-Charcoal as a ‘‘Dirt-Cheap’’ Heterogeneous Catalyst: A Personal Account

A personal account tracing the origins and continuing evolution of nickel-on-charcoal (Ni/C) as a practical, alternative, group 10 metal catalyst is presented. Discussed are applications to several ‘‘name reactions’’ which lead to both carbon−carbon and carbon−nitrogen bond constructions utilizing inexpensive aryl chlorides as substrates. Reductions of chloroarenes are also catalyzed by Ni/C, a process which may be worthy of consideration in terms of environmental cleanup of PCBs and dioxins. Collaborative efforts are also mentioned aimed at probing the surface structure of Ni/C, with the goal of enhancing catalyst activity. Future directions for development of heterogeneous nickel catalysts are proposed. 1 Introduction: Nickel-on-Charcoal? Never Heard of It… 2 Mixing a Ni(II) Salt with Charcoal: Getting It to ‘Stick’ and Reduction to Ni(0) 3 First Results: Negishi-Like Couplings with Functionalized Zinc Reagents 4 Is Ni/C Compatible with Grignard Reagents? Kumada-Like Couplings 5 Suzuki Couplings with Aryl Chlorides: Ni/C Takes the Challenge 6 Aminations of Aryl Chlorides: and the ‘Magic’ Phosphine Ligand is… 7 Reductive Dechlorinations of Aryl Chlorides: Searching for a Mild Source of Hydride 8 What Does “Ni/C” Really Look Like? Surface Science to the Rescue 9 Summary… and a Look Ahead