Dipyrromethene complexes of transition metals. Part II. Stereochemistry of complexes of cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), mercury(II), and palladium(II) and crystal structure analysis of the palladium complex

Complexes have been formed between bivalent ions of cobalt, nickel, copper, zinc, mercury, and palladium and the the ligands 4,4′-dicarboxyethyl-3,3′,5,5′-tetramethyldipyrromethene (mpmH) and 3,4′-dicarboxyethyl-5-chloro-3′,4,5′-trimethyldipyrromethene (cpmH). The stereochemistry of these complexes has been investigated by measurement of magnetic susceptibility, and 1H n.m.r. spectra, and u.v. visible spectra. An X-ray determination of the crystal and molecular structure of the complex Pd(mpm)2 is reported. The palladium atom lies on a crystallographic centre of symmetry and is necessarily coplanar with the four co-ordinated nitrogen atoms of the ligand. The unique bidentate ligand is not planar.