Dithiooxamides as ligands: crystal structures and vibrational analyses of bis(N,N'-dicyclohexyldithiooxamidato)palladium(II) bis(N,N'-dibenzyldithiooxamide)copper(II) diperchlorate, and dichloro(N,N'-dimethyldithiooxamide)zinc(II) and the carbon-13 nuclear magnetic resonance spectra of related compounds.