A nickel catalyst in the rare +4 oxidation state has been created by UM Chemistry graduate student Nicole M. Camasso and Professor Melanie S. Sanford. The report appears in Science online on February 5, 2015, "Design, synthesis, and carbon-heteroatom coupling reactions of organometallic nickel(IV) complexes." Nickel catalysts are commonly used in the synthesis of pharmaceuticals, natural products, and polymers, but most have been in the 0, +1, +2, or +3 oxidation states.
The report caught the attention of C&EN News, "Taking Nickel to the Next Level."
Abstract from Science:
Homogeneous nickel catalysis is employed for the synthesis of pharmaceuticals, natural products, and polymers. These reactions generally proceed via nickel intermediates in the Ni0, NiI, NiII, and/or NiIII oxidation states. In contrast, NiIV intermediates are rarely accessible. We report herein the design, synthesis, and characterization of a series of organometallic NiIV complexes, accessed by the reaction of NiII precursors with the widely used oxidant, (S-(trifluoromethyl)dibenzothiophenium)triflate. These NiIV complexes undergo highly selective carbon(sp3)-oxygen, carbon(sp3)-nitrogen, and carbon(sp3)-sulfur coupling reactions with exogenous nucleophiles. The observed reactivity has the potential for direct applications in the development of nickel-catalyzed carbon-heteroatom coupling reactions.
(Science 2015, DOI: 10.1126/science.aaa4526)