Taking Nickel To The Next Level

If chemists had a nickel for every time nickel catalysts were used in the synthesis of pharmaceuticals, natural products, or polymers, they’d have a hefty chunk of change. Although its group 10 cousin palladium generally gets most of the attention for cross-coupling chemistry, nickel-catalyzed cross-coupling reactions are growing in popularity because they’re more economical and sustainable. Plus, nickel can do things that are challenging for palladium, such as cross-couple tertiary alkyl halides. In all of those reactions, nickel adopts the 0, +1, +2, or +3 oxidation states. Now, University of Michigan, Ann Arbor, chemists Melanie S. Sanford and Nicole M. Camasso report a new nickel complex in the rare +4 oxidation state (Science 2015, DOI: 10.1126/science.aaa4526). The Michigan chemists make the unusual complex, which is stable for three days at room temperature, through the reaction of nickel(II) precursors with the oxidant S-(trifluoromethyl)dibenzothiophenium triflate. The resulting nickel(IV) complex can undergo highly selective carbon-heteroatom coupling reactions, wedding sp³ carbons to oxygen, nitrogen, and sulfur (example shown). The complex has the potential for direct applications in the development of nickel-catalyzed carbon-heteroatom coupling reactions, Sanford and Camasso note.