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

摘要

The reaction of (1S,2R)-[(η~5-C_5H_5)Fe{(η~5-C_5H_4)-CH=NCH (Me)-CH(OH)(C_6H_5)}] (1) with Na_2[PdCl_4] in the presence of Na(OAc)·3H_2O produced three diastereomerically pure tetrametallic cyclopalladated complexes (6b_I-6b_(III)). In two of them (6b_I and 6b_(II)), the imine 1 adopts the [C(sp~2,ferrocene), N]~- mode of binding, but they differ in the planar chirality of the 1,2-ferrocenyl unit (S_p in 6b_I and R_p in 6b_(II)), whereas ligand 1 in 6b_(III) acts as a [C(sp~2,phenyl),N]~- group. Treatment of 6b_I-6b_(III) with PPh_3 gave [Pd{κ~2-C,N{(η~5-C_5H_3)- CH=N-CH(Me)-CH(OH)(C_6H_5)}Fe(η~5-C_5H_5)}Cl(PPh_3)] (7b_I, 7b_(II)) and [Pd{κ~2-C,N{(C_6H_4)-CH(OH)-CH(Me)-N=CH-(η~5- C_5H_4)}Fe(η~5-C_5H_5)}Cl(PPh_3)] (7b_(III)). The Pt~(II) compounds [Pt{κ~2-C,N{(η~5-C_5H_3)-CH=NCH(Me)CH(OH)(C_6H_5)}Fe(η~5- C_5H_5)}Cl(PPh_3)] [(Sp,1S,2R) and (R_p,1S,2R) diastereomers, 7a_I and 7a_(II), respectively)] have also been prepared. The results of electrochemical studies of 6b_I-6b_(III), 7b_I-7b_(III), 7a_I, 7a_(II) and related Pt~(II) 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 M~(II) atom, the type of metallated atom C(sp~2,phenyl or ferrocenyl), the ancillary ligands and their relative disposition on the electrochemical properties of this type of compound.