Reactions of [(az-H)Pd(μ-Cl)2Pd(az-H)] (az = azobenzene) with the
zwitterionic, p-benzoquinonemonoimine-type ligands
4-(n-butylamino)-6(n-butylimino)-3-oxocyclohexa-1,4-dien-1-olate (Q1) or
4-(isopropylamino)-6(isopropylimino)-3-oxocyclohexa-1,4-dien-1-olate) (Q2) in
the presence of a base leads to the formation of the mononuclear complexes
[(az-H)Pd(Q1-H)] (1) and [(az-H)Pd(Q2-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[double bond, length as m-dash]N double bond of the az-H ligand and
localization of the double bonds within the Q2-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
