EPR study of mono-o-iminobenzosemiquinonato nickel(II) complexes with Ni-C σ-bond

New four-coordinate nickel(II) complexes of (Ph3P)Ni(o-Tolyl)(ISQ) species with 4,6-di-tert-butyl-N-aryl-o-iminobenzosemiquinonate anion-radical ligands (ISQ) have been prepared and characterized. Complexes contain σ-bound o-tolyl and neutral donor ligand PPh3. The sterical hindrances of N-aryl in o-iminobenzosemiquinonate ligands lead to the tetrahedral distortion of square-planar configurations of complexes. Complexes are able to exchange of PPh3 on some neutral donor ligands.