The nature of coordination in metal monothiocarbamates is shown to depend on the hardness or softness of the metal ton. Thus, the monothiocarbamate ion acts as a monodentate ligand with metal-sulphur bending when the metal ion is a soft acid while it acts as a bidentate ligand when the metal ion is a hard acid; it can exhibit either behaviour when the metal ion is a borderline acid. In dialkyltin and dialkylmonocholorotin complexes, the monothiocarbamate ion acts as a bidentate ligand with strong Sn-S bonding while in trialkyl-or triaryl-tin complexes it acts essentially as a monodentate ligand. Thus, R₃Sn(I) seems to be a soft or borderline acid while R₂Sn(II) is a hard acid.

The electrochemical behaviour of the adducts Cr(TPP)·Cl·L, whereTPP = tetraphenylporphyrin;L = pyridine, 2-picoline, 2,6-lutidine, 4-cyanopyridine, morpholine or 4-picoline is reported and the relationship between reduction potentials, the electron band I transition and the binding energy of the Cr2p_3/2 level examined.

Based on criteria for the differences in oxidation potentials determined in acetonitrile by cyclic voltammetry and reduction potentials determined inDMSO, it is concluded that the adducts behave as normal metalloporphyrins. Further, variations for the different adducts are attributed primarily to different inductive effects from the heterocyclic axial groups. The adduct formed from 2,6-lutidine, however, shows anomalous behaviour which is attributed to a marked steric effect between the ligand and the porphinato-nitrogen atoms.