A Five-Coordinate Nickel(II) Fluoroalkyl Complex as a Precursor to a Spectroscopically Detectable Ni(III) Species

Mechanistic proposals for nickel-catalyzed
coupling reactions often
invoke five-coordinate alkyl- or aryl-bound Ni­(II) and/or high-valent
nickel­(III) species, but because of their reactive nature, they have
been difficult to study and fingerprint. In this work, we invoked
the stabilizing properties of fluoroalkyl ligands to access such nickel
species bearing ligands that are commonplace in organic coupling reactions.
We show that five-coordinate Ni­(II) complexes containing nickel–carbon
bonds can readily be prepared given the appropriate precursor, and
we also present evidence for the formation of Ni­(III) species upon
chemical and electrochemical oxidation of the five-coordinate complexes.