Influence of Co-ordination Number on Copper(I)-Copper(II) Redox Interconversions. Part 3. Reduction of a Sterically Constrained Bis-(substituted phenanthroline) Complex of Copper(II) by Iron(II) and Ruthenium(II) Complexes

Article abstract of DOI:10.1039/DT9820000927

Further kinetic studies are reported for reduction of the copper(II) complex. ^2-, containing the ligand L^2- = 2,9-dimethyl-4,7-bis-1,10-phenanthroline.The methyl susbstituents in the 2,9 positions create a steric hidrance which limits the extent of co-ordination to Cu^II (bis and not tris complexes are formed) and five- and four-(tetrahedral) co-ordinate complexes are believed to be present.With ^4-, ^2- (edta = ethylenediaminetetra-acetate), ^3-, and ²⁺ (pyz = pyrazine) as reductants (abbreviation Red) limiting kinetics are observed, and a self- consistent interpretation is possible in terms of the sequence: Cu^II --->^<*>Cu^II (k₁,k_-1); Red + ^<*>Cu^II ---> products (k2), and Red + Cu^II ---> products (k₃).In this sequence Cu^II and Cu² are the five- and four-co-ordinate forms respectively.The step k₃ is additional to the sequence previously proposed for ^4- the results for which have been modified accordingly.Contributions from k₃ are not apparent with 3- and ²⁺, whereas with ²⁺ (py = pyridine) reaction via k₃ appears to be dominant.Possible explanations of the balance between k₂ and k₃ in terms of different E^<*> values and ability to inner-sphere are cnsidered.

Full text of DOI:10.1039/DT9820000927

View Article Online / Journal Homepage / Table of Contents for this issue

View Article Online

View Article Online

View Article Online