Five-coordination in complexes of 2-(3,5-Dimethylpyrazol-1-yl)quinoline, a sterically hindered diimine system

Abstract

The bidentate diimine-type ligand 2-(3,5-dimethylpyrazol-1-yl)quinoline forms mono complexes with the bivalent chlorides of iron, cobalt, nickel and copper. These complexes are magnetically dilute, but electronic spectral data indicate that, except for the cobalt complex which is tetrahedral, the metal atoms are five-coordinate and hence a chloro-bridged structure is proposed. The cobalt(II) complex readily adds a water molecule, and structure determination by X-ray diffraction shows that the complex aquadichloro[2-(3,5-dimethylpyrazol-1-yl)quinoline]cobalt(II) is monomeric and five-coordinate, the coordination environment approximating trigonal bipyramidal.