Tin and lead derivatives of a Schiff base – bis(orthoquinone) ligand

Abstract

The condensation of two molecules of 3,s-di-tert-butylcatechol (dbc) with ammonia under oxidizing conditions is believed to proceed via a keto-imine radical. Further condensation, and subsequent reaction with tin(I1) or lead(I1) halides, yields complexes of identical composition, M [dbqdi],, where dbqdi is 3,5-di-tertbutyl-1,2-quinone-1-(2-hydroxy-3,5-di-tert-butylphenyl)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 compound has a triplet ground state. Both involve six-coordination of the metal 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 snIv(dbqdi),, the crystal parameters are orthorhombic, space group C222,, a = 19.597(4), b = 24.375(4), c = 23.755(6) A, Z = 8, and R = 0.073 for 1405 unique reflections. For pbU(dbqdi),, monoclinic, space group P2,ln, a = 14.56(1), b = 25.967(9), c = 15.13(1) A, P = 99.81(7)', Z = 4, R = 0.065 for 491 1 unique reflections. The different complexation behaviour is shown to be a consequence of the redox properties of the two metallic elements.Key words: tin, lead, ESR, coordination chemistry, electron transfer.Resume : On croit gtntralement que la condensation de deux moltcules de 3,s-di-tert-butylcattchol (dbc) avec de I'ammoniac, dans des conditions oxydantes, se produit par le biais d'un radical ctto-imine. Une condensation substquente, avec rtaction ulterieure avec des halogenures d1Ctain(II) ou de plomb(II), fournit des complexes de composition identique, M(dbqdi),, dans lesquels dbqdi est l'anion 3,s-di-tert-butyl-1.2-quinone-1-(2-hydroxy-3,s-di-tert-butylphtny1)imine; on utilise ce nom sans tgard B la structure rtelle du coordinat. Les proprietts cristallographiques et magnetiques des deux composts sont differentes et les mesures de RPE indiquent que le derive de l'ttain possbde une ttat fondamental triplet. Les deux impliquent un niveau de coordination de six pour le metal, avec un environnement dtformt; l'ttain est dans un &tat +IV alors que pour le plomb il est de +I1 et on peut observer des differences correspondantes dans le forme du coordinat. Pour le snIv(dbqdi),, les cristaux sont orthorhombiques, groupe d'espace C222,, avec a = 19,597(4), b = 24,375(4) et c The reactions of substituted orthobenzoquinones with main group elements, or the low oxidation state derivatives of such elements, have been the subject of a number of recent papers from this laboratory. In general, the products of these processes are the appropriate catecholate or semiquinone derivatives, which have been characterized by spectroscopic and crystallographic methods. An important feature of these results is that the redox reactions in question have been shown to be one-electron transfer processes (1).We have now extended this research to an investigation of the structure of the compounds formed when tin or lead in the +I1 state react with a ...

New avenues for ligand-mediated processes – expanding metal reactivity by the use of redox-active catechol, o-aminophenol and o-phenylenediamine ligands

“…44 Preliminary mechanistic investigations suggest that (at least) one of the o-phenylenediamine ligands of complex 38 is excited upon UV-irradiation at B298 nm (via species 39), resulting in N-H bond homolysis to give an H-atom and an o-aminoanilino radical (40). A second H-atom abstraction from the ligand may generate H 2 .…”

Two new dibenzobicyclic penta‐ and hexacoordinated tin compounds

“…The ligand may chelate the tin atom in different charged forms [11][12][13]. The ligand may chelate the tin atom in different charged forms [11][12][13].…”

“…A reaction was reported recently of tin(II)chloride with the ligand LH 3 that afforded the hexacoordinated tin compound of type C bonded to two identical ligands with a very distorted octahedral symmetry due to the constraints produced by the ligand geometry [13] (Figure 1). …”

“…The structure of this paramagnetic compound is a delocalized frame; one localized form can be de- scribed as one ligand being a diradical monoanion and the other a monoanion [13]. In order to avoid the introduction of two ligands, reactions with mono-and dialkyl tin compounds were performed with the aim to introduce only one 4,6-di-tert-butyliminophenolate ligand and to find out which coordination a tin center may achieve and which behavior of the ligand can be induced, depending on the tin substitution [11][12][13].…”

Pb(II) Complexes of Schiff Bases Derived from Benzoylhydrazine as the Antibacterial Agents

“…El-ajaily et al [13] prepared Pb(II) complex with Schiff base derived from the reaction of salicylaldehyde and urea. Condensation and subsequent reaction with Pb(II) halides yielded complex of composition Pb [DBQDI], where DBQDI is 3,5-di-tertbutyl-1,2-quinone-1-(2-hydroxy-3,5-di-tert-butylphenyl) imine anion [14]. Liu et al [15] 2 ] adopts 2-coordinate geometry, which is different from the 4-coordinate geometry of isonicotinato lead(II) complex [20].…”