An unusual dichromium(II,II) compound bearing di-2-pyridyl ketone oximate ligands and prepared by the ligand-assisted reduction of a trichromium(III,III,III) complex in air

The reaction of the oxide-centred triangular, trichromium(III,III,III) complex [Cr3O(O2CCMe3)6(H2O)3](O2CCMe3) with di-2-pyridyl ketone oxime, (py)2CNOH, in MeCN under aerobic and refluxing conditions yields the pivalate-free, dichromium(II,II) complex [Cr2{(py)2CNO}4] · 2H2O (1 · 2H2O). The dinuclear complex can also be prepared by the reaction of [Cr(CO)6] with (py)2CNOH in refluxing MeCN/H2O in air. The two high-spin CrII atoms are doubly bridged by two 2.1110 oximate ligands, while a chelating 1.0110 (py)2CNO− ion completes distorted trigonal bipyramidal coordination at each metal centre. The dimers are stabilized by intramolecular stacking interactions between the terminal (py)2CNO− ligands, and the structural effects of these interactions are discussed.