Diastereomerically Pure Heterodi- and Heterotetrametallic (Pd and Pt) Compounds: A Study of the Effect Induced by the Binding Mode of a Ferrocene-Containing Ligand on Their Electrochemical Properties.

Abstract

The reaction of (1S,2R)-[(η5-C5H5)Fe{(η5-C5H4)-CH=NCH(Me)-CH(OH)(C6H5)}] (1) with Na2[PdCl4] in the presence of Na(OAc)·3H2O produced three diastereomerically pure tetrametallic cyclopalladated complexes (6bI-6bIII). In two of them (6bI and 6bII), the imine 1 adopts the [C(sp2,ferrocene), N]- mode of binding, but they differ in the planar chirality of the 1,2-ferrocenyl unit (Sp in 6bI and Rp in 6bII), whereas ligand 1 in 6bIII acts as a [C(sp2,phenyl),N]- group. Treatment of 6bI-6bIII with PPh3 gave [Pd{κ2-C,N{(η5-C5H3)-CH=N-CH(Me)-CH(OH)(C6H5)}Fe(η5-C5H5)}Cl(PPh3)] (7bI,7bII) and [Pd{κ2-C,N{(C6H4)-CH(OH)-CH(Me)-N=CH-(η5-C5H4)}Fe(η5-C5H5)}Cl(PPh3)] (7bIII). The PtII compounds [Pt{κ2-C,N{(η5-C5H3)-CH=NCH(Me)CH(OH)(C6H5)}Fe(η5-C5H5)}Cl(PPh3)] [(Sp,1S,2R) and (Rp,1S,2R) diastereomers, 7aII and 7aII, respectively)] have also been prepared. The results of electrochemical studies of 6bI-6bIII, 7bI-7bIII, 7aI, 7aII and related PtII complexes with 1 acting as an (N) or (N,O)- ligand are also reported. Comparison of the results provides conclusive evidence for the relative influence of the mode of binding of the ligand, the nature of the MII atom, the type of metallated atom C(sp2,phenyl or ferrocenyl), the ancillary ligands and their relative disposition on the electrochemical properties of this type of compound.