Nickel(I)–Phenolate Complexes: The Key to Well-Defined Ni(I) Species

Phosphine-stabilized monovalent nickel complexes play
an important
role in catalysis, either as catalytically active species or as decomposition
products. Most routes to access these complexes are highly ligand
specific or rely on strong reducing agents. Our group recently disclosed
a path to access nickel(I)–phenolate complexes from bis(1,5-cyclooctadiene)nickel(0)
(Ni(cod)2). Herein, we demonstrate this protocol’s
broad applicability by ligating a wide range of mono- and bidentate
phosphine ligands. We further show the versatility of the phenolate
fragment as a precursor to nickel(I)–alkyl or aryl species,
which are relevant to Ni catalysis or synthetically useful nickel(I)–chloride
and hydride complexes. We also demonstrate that the chloride complex
can be synthesized in a one-pot procedure starting from Ni(cod)2 in good yield, making this protocol a valuable alternative
to current procedures. Single-crystal X-ray diffraction, IR, and EPR
(or NMR) spectroscopy were employed to characterize all of the synthesized
nickel complexes.