1625reaction at [H' ] = 0.281 having the larger value. These qualitative results are in keeping with both reactants being of the same charge and not a reaction between a neutral Mn(VI1) species and a protonated Ru(1I) ion.The results of this study demonstrate that the various Ru(I1) ions present in acidic perchlorate media are considerably less reactive with Mn(VI1) than the corresponding Fe(I1) complexes. The observation that the unprotonated Ru(I1) ion is considerably less reactive that the monoprotonated Ru(I1) ion once again points to the importance of a proton in the activated complex in the conversion of Mn(VI1) to Mn(V1) when the Eo of the reductant ion is greater than 0.56 V.233313 Perhaps (13) F. M. Moore and K. W. Hicks, Inorg. Chem., 14, 413 (1975). the proton can more effectively reduce the repulsive charge between the negatively charged M n 0 4 and the smaller Fe(I1) ions than the larger Ru(I1) ions.Our results and those of Sutter indicate that the proton needed in the reaction of Mn04-with R u ( C N )~~-and Fe-(CN)6e is brought into the activated complex by the reductant ion rather than the oxidant. The other Mn04--inorganic reductant ion systems that have been investigated (MO(GN)~"-, W(CN)84-, VOz+) show the opposite trend, and the oxidant is the protonated species. Acknowledgment. The authors thank Mr. Stephen Bialkowski (University of Utah) for his computerization of the experimental [H+] results.The concentration-independent visible absorption spectrum and lack of electrical conductance of CuC12 in pyridine both indicate existence of a single solution complex, CuC12(py),, generally believed to be six-coordinate pseudooctahedral. However, the solubility data for the CuC12.2py solid compound in pyridine-aprotic diluent mixtures of varying composition can best be rationalized in terms of the equilibrium C~C l~( p y )~ * CuC1z(py)3 + py. At the same time the diluents exert but a very small effect on the visible absorption band of CuC12, indicating essential lack of changes in the coordination sphere of copper(I1) upon dilution. Exceptional in this respect is chloroform whose additions result in decreasing intensity and a blue shift of the band, consistent with the formation of a centrosymmetrical octahedral complex, except at low pyridine concentrations where the spectral changes become reversed. This effect agrees with the expected stabilization of the octahedral complex by the protic solvent due to its Hv-type interaction with the coordinated pyridine molecules enhancing the dielectron back-donation from the central metal atom. At the same time it shows existence of a different, less symmetrical environment of the Cu2+ cation in the CuClz solutions in pure pyridine or in mixtures thereof with the aprotic diluents. In an apparent contradiction to these inferences are the ESR spectra of frozen solutions showing axial symmetry of the complex as well as interaction of the unpaired electron with four equivalent nitrogen nuclei. An explanation is provided by the observation that decreasing temperature ...
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