TIN AND LEAD DERIVATIVES OF A SCHIFF-BASE BIS(ORTHOQUINONE) LIGAND

The condensation of two molecules of 3,5-di-tert-butylcatechol (dbc) w ith ammonia under oxidizing conditions is believed to proceed via a ke to-imine radical. Further condensation, and subsequent reaction with t in(II) or lead(II) halides, yields complexes of identical composition, M[dbqdi](2), where dbqdi is quinone-1-(2-hydroxy-3,5-di-tert-butylphe nyl)imine anion; this name is used without prejudice as to the actual structure of the ligand. The two compounds differ in crystallographic and magnetic properties, and ESR measurements show that the tin compou nd has a triplet ground state. Both involve six-coordination of the me tal in a distorted environment; tin is in the +IV state, but lead is II, and there are corresponding differences in the form of the ligand. For Sn-IV(dbqdi)(2), the crystal parameters are orthorhombic, space g roup C222(1), a = 19.597(4), b = 24.375(4), c = 23.755(6) Angstrom, Z = 8, and R = 0.073 for 1405 unique reflections. For Pb-II(dbqdd)(2), m onoclinic, space group P2(1)/n, a = 14.56(1), b = 25.967(9), c = 15.13 (1) Angstrom, beta = 99.81(7)degrees, Z = 4, R = 0.065 for 4911 unique reflections. The different complexation behaviour is shown to be a co nsequence of the redox properties of the two metallic elements.