Formal Nickelate(-I) Complexes Supported by Group 13 Ions

Formal nickelate(-I) complexes bearing Group 13 metalloligands (M = Al and Ga) were isolated. These 17 e(-) complexes were synthesized by one-electron reduction of the corresponding Ni-0 -> M-III precursors, and were investigated by single-crystal X-ray diffraction, EPR spectroscopy, and quantum chemical calculations. Collectively, the experimental and computational data support: 1) the strengthening of the Ni-M bond upon one-electron reduction, and 2) the delocalization of the unpaired spin across the Ni and M atoms. An intriguing electronic configuration is revealed where three valence electrons occupy two sigma-type bonding interactions: Ni(3d(z2))(2)-> M and sigma-(Ni-M)(1). The latter is an unusual Ni-M sigma-bonding molecular orbital that comprises primarily the Ni 4p(z) and M np(z)/ns atomic orbitals.