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 H-1 and C-13 NMR and electronic absorption spectroscopies as well as X-ray crystallography.