alph X. Ewall and Daniel B. Iluchital
494 inorganic Chemistry, Vol. 14, No. 3, 1975
E. Ochiai and D.H. Busch, Inoig. Chem.. 8, 1798 (1969). L. F. Lindoy, X. E. Tokel, L.B. Anderson, and D. H. Busch, J. Coord. Chem., 1, 7 (1971). E. Ochiai and D.FI. Busch. Inorg. Ckem., 8. 1474 (!969). A preliminary report has appeared: P. 1-1. Merrell, V. 1. Goedken. D. H. Busch, arid J. A. Stone. J. Amer. Chem. Soc., 92, 7590 (1970). J . P. Collman and C. R. Reed, J . Amer. Chem. Sac., 95, 2048 (1971). S. L. Hoard and W. K.Scheidt, Proc. :\’or. Acad. S c i . U.S., 70, 3919
a high-spin six-coordinate iron(I1) derivative. The AEg for low-spin pseudooctahedral [Fe(ms-CRH)(NCS)2] (0.67 mm/sec) is typical of low-spin iron(I1) derivatives,2l~*3the low AEq value resuiting from the spherically symmetric filled t2g (Oh) orbitals. For the high-spin iron(II1) derivatives [Fe(ms-CRH)X2]BF4 the AEg values are typically sma112lJ3 because of the spherical symmetry of the half-filled 3d shell. ~ ~ ~ ~ o ~ These ~ e investigations d ~ ~ e were n ~supported . by U.S. Public Health Service Grant No. GM10040 from the National Institute of General Medical Sciences. Part of the informaiion contained in this article was developed during the course of work under Contract At(07-2)-1 with the U.S. Atomic Energy Commission.
(1973).
L. F. Lindoy. V. Katovic, and 0.IT. Busch, J . Ckem. Educ., 49, 117 (1972).
.4.C. Melnyk. Thesis. The Ohio Slate University, Columbus. Ohio 43210, 1973. J . L. Burnieister, Coord. Chem. Rev., 1, 205 (1966). J . S . Griffith and I,. E. Orgel, T t u n ~FUi*udUy . Soc., 53, 601 (1957): S. S.Dharmotti and C. R. Kanekur, J. Chem. Phys., 31, 1436 (1959). R . A, D. Wentworth and T. S. Piper, Inorg. Chem., 4. 709 (1965). J . C. Dabrowiak, P. H . Merrell, and D. 13. Busch. Inorg. Ckem., 11, 1979 ( 1 972). For typical conductance values see R.L.Dutta, D. W. Meek, and D. 11, Busch, Inorg. Chem., 9, 1215 (1970), and references therein B. N. Figgis. “Introduction to Ligand Fields,” Intersciencc, N e w York, London. and Svdneb. 1967. Chautcr 10. D. M. 1. Good~ame,’M.Goodgal&. LI.A. Hetchman. and M. J . Wcelts. Inorg. Chem., 5 , 6 3 5 (1966). V . L. Goedken. P. H . Merrell, and I).€3. Busch, J . Amer. Chem. Soc., 94, 3397 (1972). R’. E. Erickcon, Advan. Chem. Ser., IVQ~68, 86 (1967). E. Fluck, “Chemical Applications to .MOss!iauer Spectroscopy,” V . 1. Goldanskii and R. H. Herber, Ed., Academic Press, New York and London. 1968, p 286. 1.May. Advan. Chem. Ser., No. 68, 52 (!967). J. Danon, “Chemical Applications of Mossbauer Spcctroscopy,” V. I . Goldanskii and R. 1-1. Ilerbcr. Ed., .4cademic Press. N e w York arid London. 1968. pp 233-241. W. M.Reiff, Inorg. Chem., 13. 239 (1974).
Registry No. [Fe(ms-CRFI)CI]CI, 31 122-39-1; [Fe(ms-CRH)BrIBr, 31 122-40-4; [Fe(ms-CRH)I]I, 31 122-41-5; [Fe(ms-CRH)Cl]PF6, 53537-54-5: [Fe(nis-CRH)Br]PF6, 53537-56-7; [Fe(msCRH)I]PF6, 53537-58-9; [Fe(ms-CRH)(N3)z], 53432-27-2; [Fe(nzs-CRH)OAc]PFs, 53432-29-4; [Fe(ms-CRH)(NCS)z]. 5343230-7; [Fe(ms-CRH)Clz]ClOo, 53466-54-9; [Fe(ms-CRH)Clz]BF4, 53466-55-0; [Fe(ms-CRH)Brz]Cl04, 53466-57-2; [Fe(ms-CRH)BrzIBF4, 53466-58-3; [Ni(m.~-CRH)](ClO4)z,53537-60-3.
References and Notes (I) (a) Evans Chemical Laboratory, The Ohio State University. (h) Sa-
vannah River Laborator), E. l. du Pont de Nemours and Co. (2) ( a ) D. H. Busch, Helv. Chim.Acta (Fasciculus exrruordinarius Aifred Werner), 174 (1967); (b) V . F. Curtis. Coord. Cherrr. Rev., 3. 3 (1968). (3) L. F. Lindoy and D. H. Busch, Prep. Inorg. React., 6. I (1970). (4) J. L. Karn and D. H. Busch, inorg. Chem.. 8, 1149 (1969).
Contribution from the Department of Chemistry, Seton Hall University, South Orange. Kew Jersey 07079
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R A L P H X. EWALL and D A Y I E L H. HL‘CHITAL*
Received June 6, 1974
AIC40363M
A deep purple cyanide-bridged intermediate is formed between Co”EDTA and either Fe(CN)s3- or Fe(CN)5P(CsH5)32-.
The equilibrium and rate constants for the formation of the intermediate and the rate constarit for the decomposition of the intermediate at 30°, p H 6.00 (EDTA-NaOH), and I = 0.26 M (EDTA-NaC104) are 201 MI, 3.8 X I O 4 &-I sec-I, and 1.74 X 10-2 sec-’ for Fe(CN)63- and 1,490 M-1, 2.0 X 104 A!-1 sec-1, and 2.10 X 10-3 sec~1 for Fe(Cl”j)5P(C6H5)j2-.. Activation parameters and thermodynamic data are also reported. The resultcs indicate that the chargc and size of the substituent group and the net driving force all influencc the stability and rate of formation of the intermediates in these reactions.
The first example of the inner-sphere reaction of a cobalt(I1)-chelate complex was reported by Adamson and Gonickl in 1963. A purple intermediate was observed in the oxidation of ethylenediaminetetraacetatocobaltate(II), CoIIEDTA, with hexacyanoferrate(III), Fe(CN)63-. On the basis of magnetic and spectrophotometric measurements, it was concluded that the intermediate was the bridged-binuclear successor complex, viz.,a Colll-NC-FelI species. This intermediate was shown to decompose slowly to the products of the reaction. GoIIIEDTA and Fe(CN)64-. Huchital and Wilkins2 later reported results for the formation of the intermediate in this reaction using the more sophisticated stopped-flow and T-jump techniques. These workers found that a second intermediate could form via the oxidation of the first intermediate by excess Fe(CK)&, producing a Co[lI-NC-FeIlI species. The rate of formation of this intermediate was about 50-100 times slower than for the first intermediate. More recently Huchital and coworkers3 extended these studies to other cobalt(I1) -chelate systems. Rate and equilibria data were discussed with regard to the
stereochemisty o f the chelate and the effets of substitution on the chelate ring on the stability of the intermediate. In order to understand more fully thc factors at play in these redox reactions, we have investigated the oxidation reactions of CoIIEDTA in which the oxidants arc a monosubstituted ferricyanide ion, Fe(CN)j%2--. The cases in which X i s NH3, HzO, and P(Cd35)3 have been examined. Of primary int,erest here are the effects of the charge and size of the substituent group and the number of cyano groups available for bridge formation. We report here on the oxidation of CoIIEDTA by Fe(CN)jp(c6Hj)32- at I = 0.26 M and pH 6.00. Results are also presented for the CoIIEDTA reaction with ferricyanide ion, reexamined under the above solution conditions. ~ x ~ e Section ~ ~ ~ e ~ ~ a ~ Materials. NaCIQ4 (BDH Chemicals), 1
