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Design, synthesis, and carbon-heteroatom coupling reactions of organometallic nickel(IV) complexes

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Science  13 Mar 2015:
Vol. 347, Issue 6227, pp. 1218-1220
DOI: 10.1126/science.aaa4526

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Taking advantage of four for a nickel

Metal atoms change their oxidation state—i.e., lose or gain electrons—relatively easily. This is a major reason why metal compounds accelerate so many chemical reactions. Camasso and Sanford now report a straightforward way to prepare complexes of nickel in the +4 oxidation state, based on careful tuning of the coordination environment around the metal center (see the Perspective by Riordan). These complexes could prove useful in coupling carbon to oxygen, nitrogen, or sulfur, and complement more traditional nickel catalysts that operate in lower oxidation states.

Science, this issue p. 1218; see also p. 1203

Abstract

Homogeneous nickel catalysis is used 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.

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