'Double redox-activity' in azobenzene-quinonoid palladium(II) complexes: a combined structural, electrochemical and spectroscopic study.
Reactions of [(az(-H))Pd(μ-Cl)(2)Pd(az(-H))] (az = azobenzene) with the zwitterionic, p-benzoquinonemonoimine-type ligands 4-(n-butylamino)-6(n-butylimino)-3-oxocyclohexa-1,4-dien-1-olate (Q(1)) or 4-(isopropylamino)-6(isopropylimino)-3-oxocyclohexa-1,4-dien-1-olate) (Q(2)) in the presence of a base leads to the formation of the mononuclear complexes [(az(-H))Pd(Q(1)(-H))] (1) and [(az(-H))Pd(Q(2)(-H))] (2) respectively. Structural characterization of 2 shows an almost square planar coordination geometry around the Pd(II) centre, a short Pd-C bond, a slight elongation of the N=N double bond of the az(-H) ligand and localization of the double bonds within the Q(2)(-H) ligand. Additionally, intermolecular N-H-O interactions exist between the uncoordinated N-H and O groups of two different molecules. Cyclic voltammetry of the complexes reveals an irreversible oxidation and two reversible reduction processes. A combination of electrochemical and UV-vis-NIR and EPR spectroelectrochemical studies are used to show that both coordinated ligands participate successively in the redox processes, thus revealing their non-innocent character.
Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550, Stuttgart, Germany.
Naina
N
Deibel
David
D
Schweinfurth
Ralph
R
Huebner
Pierre
P
Braunstein
Biprajit
B
Sarkar