Nickel(II) Pincer Carbene Complexes: Oxidative Addition of an Aryl C–H Bond to Form a Ni(II) Hydride

The
synthesis and characterization of a series of nickel­(II) pincer
complexes of the meta-phenylene-bridged bis-N-heterocyclic DIPPCCC ligand framework are reported. Characterization of
the Ni­(II)Cl complex revealed a square planar species with Cl– and the anionic carbon trans to one another. Formation
of Ni­(II) alkyl complexes derived from complex 1 was
accomplished by addition of LiR [R = CH3 (2); CH2SiMe3 (3)]. Furthermore,
we report a synthetic pathway to access the catalytically relevant
Ni­(II)H species (DIPPCCC)­NiH (4), by direct
oxidative addition of an aryl C–H bond across a Ni(0) center.
Complexes 1–4 have been characterized
by 1H and 13C NMR and electronic absorption
spectroscopies as well as X-ray crystallography.