Accessing Pincer Bis(carbene) Ni(IV) Complexes from Ni(II) via Halogen and Halogen Surrogates

This communication describes the two electron oxidation of ((CCC)-C-DIPP)NiX ((CCC)-C-DIPP = bis-(diisopropylphenyl-benzimidazol-2-ylidene)phenyl); X = Cl or Br) with halogen and halogen surrogates to form ((CCC)-C-DIPP)NiX3. These complexes represent a rare oxidation state of nickel, as well as an unprecedented reaction pathway to access these species through Br-2 and halogen surrogate (benzyltrimethylammonium tribromide). The Ni-IV complexes have been characterized by a suite of spectroscopic techniques and can readily reduce to the Ni-II counterpart, allowing for cycling between the Ni-II/Ni-IV oxidation states.