Mono- and Dinuclear α-Diimine Nickel(II) and Palladium(II) Complexes in C-S Cross-Coupling

The usefulness of transition metal catalytic systems in C-S cross-coupling reactions is significantly reduced by air and moisture sensitivity, as well as harsh reaction conditions. Herein, we report four highly air- and moisture-stable well-defined mononuclear and bridged dinuclear alpha-diimine Ni(II) and Pd(II) complexes for C-S cross-coupling. Various ligand frameworks, including acenaphthene- and iminopyridine-based ligands, were employed, and the resulting steric properties of the catalysts were evaluated and correlated with reaction outcomes. Under aerobic conditions and low temperatures, both Ni and Pd systems exhibited broader substrate scope and functional group tolerance than previously reported catalysts. Over 40 compounds were synthesized from thiols containing alkyl, benzyl, and heteroaryl groups. Also, pharmaceutically active heteroaryl moieties are incorporated from thiol and halide sources. Notably, the bridged dinuclear five-coordinate Ni complex has outperformed the remaining three mono four- or six-coordinate complexes by giving almost quantitative yields across a broad substrate scope.

Automated summary

In this study, highly air- and moisture-stable transition metal catalytic systems for C-S cross-coupling reactions were reported. These systems exhibited broader substrate scope and functional group tolerance than previously reported catalysts, with over 40 compounds synthesized from thiols. The five-coordinate bridged dinuclear Ni complex outperformed other complexes by giving almost quantitative yields across a broad substrate scope.