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Vol. 85
TABLE I11 Accordingly, zinc electrodes were electrolyzed in 3y0 potassium chloride and in 37" potassium sulfate a t 2.5' DEVIATIONSO F A T O M S IS COPPER TETRAPHESYLPORPHINE The FROM THE PLASEPARALLEL TO THE 001 PLASEAND PASSING employing a current density of 60 ma. cm.-*. results confirm the studies of Sorenson, et al.,that THROUGH THE ORIGIN Atom
cu N C1
cz
C1
C4
cs cs Cl
Deviation in
A.
0.00 04 .26 .24 - .09 - .24 - .42 - .76 - 1.42
The bond distances in the copper tetraphenylporphine and nickel etioporphyrin I agree to within the experimental errors. Both molecules have a nonplanar configuration of the porphyrin ring although the details of the non-planarity are different for the two molecules. The X-ray analysis of palladium tetraphenylporphine, which is isomorphous with copper tetraphenylporphine, is in progress, and both structures will be published in detail a t a future time. Acknowledgments.-The author wishes to thank W. Busing, K. Xartin, A. Levy and A. Zalkin for making available their computer programs. The author also wishes to thank A. Tulinsky for his initial encouragement in the determination of porphyrin structures.
anodic dissolution in non-oxidizing electrolytes involves only the formation of bipositive ions. Anodic dissolution of zinc in 3% potassium nitrate a t 25 and 38' results in valences of less than two (1.82-1.87 a t 23') considerably outside of experimental errors. This is in harmony with results obtained by Sorenson, et al., for zinc dissolving in sodium nitrate. However, when zinc amalgam is electrolyzed a t GO ma. ern.-* in nitrate solution, there is no evidence of univalent ions; the agreement between the faradaic equivalent obtained from the current based on bipositive ions compares excellently with the amount of zinc dissolved as determined by titration with EDTA, and confirmed by weight measurements of the electrode (Table I). TABLE I W t . zinc (calcd.), g.
W t . zinc (exptl.), g.
0.1262 ,1939 ,2851 ,2864 ,0892
0.1269 ,1951 ,2817 2734 ,0903
Temp., 'C.
25 3~ 0 . 2 25 25 58 58
Apparent valence
1.99 1.99 2.02 2.09 1.98
No mercury was detected in solution. A loosely adhering black film was observed on the zinc anode DEPARTMENT OF CHEMISTRY during electrolysis in potassium nitrate but was not UNIVERSITY OF CHICAGO present on the amalgam or on zinc in other electrolytes CHICAGO 37, ILLINOIS EVERLY B. FLEISCHER (sulfate and chloride). RECEIVED FEBRUARY 20, 1963 The value of 2.09 is higher than normal experimental error can account for and suggests the possibility of a competing electrolytic anode reaction which might VALENCE EXHIBITED BY ZINC AMALGAM ANODICALLY DISSOLVING IN NITRATE SOLUTIONS' conceivably compensate for a decrease in apparent Sir: valence arising from non-electrolytic oxidation of unipositive zinc ion by the electrolyte. However, the Sorenson, Davidson and Kleinberg* have proposed only possible competing electrolytic oxidation would that zinc and cadmium dissolve anodically in certain require oxygen evolution and no evolution was oboxidizing agents (chlorates and nitrates) with an initial served a t the anode. Furthermore, no nitrite ion was mean valence between one and two. Other investigadetectable in the anolyte after prolonged electrolysis. t o r ~ have ~ - ~ reported the anodic disintegration of such The results clearly show, inasmuch as the concept metals as Be, Mg, AI and Fe in salt solutions. In the of uncommon valence states is inadequate to explain case of Be and Mg "chunks" of metal have been obthe anodic dissolution of zinc in oxidizing electrolytes, tained as a residue and shown to have originated from that mechanisms involving breakdown of the anode into the electrode and not through n ~ c l e a t i o n . ~ There~~ atoms and/or atomic aggregates cannot be rejected. fore, any material dissolving in the electrolyte and not a part of the electrical circuit would not contribute to DEPARTMENT O F CHEMICAL ENGISEERING AND CHEMISTRY WILLIAMJ , JAMES SCHOOLOFMIXES AND METALLURGY the faradaic current, and could account for apparent GLESNE. STONER UNIVERSITY OF MISSOURI valencies of less than two. The presence of atomic ROLLA, MISSOURI aggregates of colloidal and sub-colloidal size also could RECEIVED FEBRUARY 16, 1963 account for the reducing properties of the anolyte. In July, 1962, Dr. T. P. Hoar (Cambridge, England) suggested that the mechanism of anodic dissolution of SOME CHARGE-TRANSFER SALTS OF lI2,3,4,5-PENTACARBOMETHOXYCYCLOPENTADIENYL zinc be studied by the use of a zinc amalgam electrode. ANION The amalgamation would prevent the disintegration of Sir : the electrode and the formation of films such as are obIn the cuurse of studving the chemistry of 1,2.3,4,3served on pure zinc (99.99%) electrodes in nitrate pentacarbomethoxycyclopentadiene' we found that its solutions. As the diffusion of zinc ions of any valence anion, I , will function as a planar donor in a series of would not be prevented by the amalgamation, one would organic charge-transfer salts, in which the isoelectronic expect the behavior of zinc amalgam to correspond planar cations tropylium, 2,4,G-trirnethylpprylium, to that of zinc in the same electrolyte as regards the pentaphenylpyrylium, N-methylpyridinium and Xinitial mean valence. methylquinolinium serve as acceptors. Good yields ( 1 ) This work supported by a research grant from O S K . of these stable salts? are obtained by stirring a suspen(2) 1). 1'.Sorenson, A . W. Ilavidson and J. Kleinberg, J . I n o v g . . Y t d C h e m . , lS, 64 (1960). ( 3 ) &I. E. Straumanis and 1). C. Mathis, J . Eleclrochem. Soc., 109, 434 (1902); J . Less-Common .Melds, 4, 213 (19G2). (1) W, J. James, M. E. Straumanis, B. K. Bhatia and J. W. Johnson, J . Elecfrochem. SOC.,109, 199C (1902). 67) B. Roald and M. A. Streicher, ibid., 97, 283 (1950). (6) G . A . Marsh and E . Schaschl, ibid., 107, 960 (1960) 17) h1. E. Straumanis and B. K . Bhatia, ibid., 110 (1903).
11) 0. Uiels, B e r , 7 6 , 14.52 19-12). .?) Salt formation ncr doubt is a result of the low nucleophilicity of I.
Less substituted cyclopentadienyl anions (thus, less delocalization of the negative charge) have been shown t o form covalent compounds with tropyliurn.3 pyryliuml and pyridium.' 3 ) 13' von E Doering and H. Krauch. A i r a m C h p m . , 68, 661 '1956); \ I B \.ol'pin. I . S. hkhrem and D. S . Kursanov, %h Obshch K h i i i i . , 28, ,4.30 19.58 , K Hafner. .-I?ZKPL Chrnf. 76, 43 '1903)
