26 



F. P. DWYER 



more negative. In some of these couples, however, the electronic states are 

 different. It is questionable whether comparisons between the spin-free 

 protoporphyrin and the spin-paired Z)/5(pyridine) and dicyano complexes can 

 be made on the same basis as the electronically equivalent ruthenium 

 complexes. 



Table 1, Redox potentials of ruthenium complexes in 



SULPHURIC ACID (1 N) 



(py = pyridine, en = ethylenediamine). 



SUMMARY 



The metal-porphyrins have been discussed as typical strongly interacting 

 metal complexes in respect to such properties as the vacant co-ordination 

 positions about the metal, the peripheral charge distribution and the oxidation 

 state. A series of mono- and Z)zXbipyridine) ruthenium complexes has been 

 proposed as model systems. The importance of the whole complex unit is 

 emphasized in opposition to the concept of metal with attached ligand. 



REFERENCES 



Basolo, F. & Pearson, R. G. (1958). Mechanisms of Inorganic Reactions, 34-90; 177-210 



John Wiley, New York. 

 Blau, F. (1889). Mh. Chem. 10, 367. 



Brandt, W. W., Dwyer, F. P. & Gyarfas, E. C. (1954). Chem. Rev. 54, 959. 

 Cahill, a. E. & Taube, H. (1951). /. Amer. chem. Soc. 12,, 2847. 

 Chance, B. (1951). The Enzymes, 2, 428, Sumner and Myrback, Academic Press, New 



York. 

 Chatt, J., Duncanson, L. H. & Venanzi, L. M. (1955). J. chem. Soc, 4456. 

 Dwyer, F. P. & Goodwin, H. (1959). Unpublished work. 

 Dwyer, F. P., Gyarfas, E. C, Shulman, A. & Wright, R. D. (1957). Nature, Lond. 



179, 452. 

 Dwyer, F. P. & Gyarfas, E. C. (1950). Nature, Lond. 166, 1181. 

 Dwyer, F, P. & Sargeson, A. M. (1960). Nature, Lond. 186, 966. 

 Djordjevic, C, Lewis, J. & Nyholm, R. S. (1959). Chem. and Ind. 4, 122. 

 Falk, J. E. & Nyholm, R. S. (1958). Current Trends in Heterocyclic Chemistry, 130-139, 



Butterworths, London. 

 Gibson, J. F. & Ingram, D. J. (1956). Nature, Lond. 178, 871. 

 Itukani, Y., Okuda, T., Sato, M. & Akabori, S. (1959). Bull. chem. Soc. Japan 32, 203. 



