Transition-metal complexes of the 2,3-dipyridylquinoxalines. Part IV. Cobalt(II), nickel(II), and copper(II) halide derivatives of 6-methyl-2,3-di-(6-methyl-2-pyridyl)quinoxaline and 6,7-dimethyl-2,3-di-(6-methyl-2-pyridyl)quinoxaline

Abstract

The cobalt(II), nickel(II), and copper(II) halide complexes of 6-methyl-2,3-di-(6-methyl-2-pyridyl)quinoxaline (dpq) and 6,7-dimethyl-2,3-di-(6-methyl-2-pyridyl)quinoxaline (dmpq) are described, and the structures are interpreted on the basis of magnetic and spectral data. For cobalt and nickel, the complexes MX₂(dpq)(M = Co, Ni; X = Cl, Br, I) and MX₂(dmpq)(M = Co; X = Cl, Br, I; M = Ni; X = Br, I) were isolated and shown to be essentially tetrahedral. NiCl₂(dmpq), which has a distorted octahedral structure, was also isolated. The complexes CuCl₂(dpq) and Cu₂Cl₄(dmpq) have square planar structures, but the data for CuBr₂(dpq) do not allow conclusive structural assignments to be made. The solution properties of the complexes are described and interpreted.