Transition-metal complexes of pyrrole pigments. Part VI. Some bivalent metal complexes of 3,3′,4,4′-tetrachloro-5,5′-diethoxycarbonyldipyrromethene

Abstract

The cobalt(II), nickel(II), copper(II), and zinc(II) complexes of 3,3′,4,4′-tetrachloro-5,5′-diethoxycarbonyldipyrro-methene were investigated by means of electronic, vibrational, and e.s.r. spectroscopy as well as X-ray diffraction measurements of powdered samples. I.r. and visible spectral data proved the distorted tetrahedral co-ordination of M–N₄ type for the cobalt(II) and zinc(II) complexes. The nickel(II) and copper(II) complexes showed two kinds of carbonyl bands in their i.r. spectra, and the d→d transition bands were consistent with the distorted octahedral (C₂) co-ordination. E.s.r. spectra of the copper complex were characteristic of rhombic co-ordination, showing g₁≃g₂ > g₃ and A₃ > A₂≃A₁. Both nickel and copper complexes consequently possess a distorted octahedral configuration of M–N₄O₂ type around the central metal atoms. The characteristic features of X-ray diffraction patterns for the four metal complexes were consistent with these structural assignments.