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 →M 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 σ-type bonding interactions: Ni(3dz2 ) →M and σ-(Ni-M) . The latter is an unusual Ni-M σ-bonding molecular orbital that comprises primarily the Ni 4p and M np /ns atomic orbitals.