Recent studies in our laboratories have been made to determine the formation constants for complexes of copper (II) and palladium (II) with potassium dithiooxalate. Earlier studies (1) have shown that nickel (II), palladium (II) and platinum (II) form square planar complexes with this ligand. Subsequent work (2) has shown that copper (II) also forms a planar complex with potassium dithiooxalate

Cell, Richard

Deskin, William A.

Lord, Gary

Worcester, Julie

University of Northern Iowa

Proceedings of the Iowa Academy of Science Volume 82 Number 3-4 Article 5 1976 Formation Constants for Dithiooxalate Complexes William A. Deskin Cornell College Julie Worcester Cornell College Richard Cell Cornell College Gary Lord Cornell College Let us know how access to this document benefits you Copyright ©1976 Iowa Academy of Science, Inc. Follow this and additional works at: https://scholarworks.uni.edu/pias Recommended Citation Deskin, William A.; Worcester, Julie; Cell, Richard; and Lord, Gary (1976) "Formation Constants for Dithiooxalate Complexes," Proceedings of the Iowa Academy of Science, 82(3-4), 156-157. Available at: https://scholarworks.uni.edu/pias/vol82/iss3/5 This Research is brought to you for free and open access by the Iowa Academy of Science at UNI ScholarWorks. It has been accepted for inclusion in Proceedings of the Iowa Academy of Science by an authorized editor of UNI ScholarWorks. For more information, please contact scholarworks@uni.edu. 156 Formation Constants for Dithiooxalate Complexes WILLIAM A. DESKIN,1 JULIE WORCESTER, RICHARD CELL AND GARY LORD DESKIN, WILLIAM A., JULIE WoRCESTER, RICHARD CELL and GARY LORD (Department of Chemistry, Cornell College, Mount Vernon, Iowa 52314). Formation Constants for Dithiooxalate Complexes. Proc. Iowa Acad. Sci. 82(3-4): 156-157, 1976. The formation constants have been determined for the dithiooxa-Recent studies in our laboratories have been made to de-tefmine the formation constants for complexes of copper (II) and palladium (II) with potassium dithiooxalate. Earlier studies (I) have shown that nickel (II), palladium (II) and platinum (II) form square planar complexes with this ligand. Subsequent work ( 2) has shown that copper (II) also forms a planar complex with potassium dithiooxalate. EXPERIMENTAL The metal salts used in this research were reagent grade. The solutions were prepared using distilled water which had been passed through a mixed bed ion exchange column. Solu-tions of the metal salts were analyzed by standard gravimet-ric methods. The ionic strength of all solutions was adjusted to 0.2 M by addition of the appropriate amount of sodium perchlorate. Ethylenediamine was purified by refluxing with zinc dust and distilled. Potassium dithiooxalate, K2dto (East-man Kodak) was purified by a published method ( 3). The salt bis-ethylene-diaminepalladium (II) p-toluenesulphonate, Pd (en) 2 (ts) 2, was prepared by a published method ( 4). Anal. calcd. for C18 H 30 N 40r;S2Pd: Pd, 18.7. Found: Pd, 18.4. Spectra All spectra were recorded on a Beckman DK-2A spectro-photometer. Formation Constants The f3 2 values of the metal dithiooxalate complexes were determined in water at 25° and an ionic strength of 0.2 M (sodium perchlorate) . The method ( 5) used was a competi-tive reaction between ethylenediamine and dithiooxalate for coordination sites on the metal ion. Concentrations of the species in the reaction were adjusted M (en) 22+ + 2 dto2- = M ( dto) 22- + 2 en ( 1) so that the equilibration reaction proceeded only part way. The pH of the solution was adjusted to 9.0 and the absorb-ance was measured. Spectra suggest that mixed ethylenedia-mine-dithiooxalate complexes are not formed. The solutions were assumed to contain the species M(en) 22+, Men2+, en, M ( dto) 22- and dto2-. The extinction coefficients of these spe-I Department of Chemistry, Cornell College, Mount Vernon, Iowa 52314. late complexes of copper (II) and palladium (II) at a constant ionic strength of 0.2 M (sodium perchlorate). The following values are reported: for the Cu(dto)22- complex log [3 2 = 20.0 ± 0.2, for the Pd(dto)22- complex log [3 2 = 28.9 ± 0.5. cies are known and the formation constants of M (en) n 2+ are available ( 6). This information, together with knowledge of the total concentration of metal, ethylenediamine, and dithio-oxalate, allows one to solve for the value of (32 for the dithio-oxalate complex. The calculations were made using a program written for the IBM 1130. RESULTS AND DISCUSSION The formation constant was determined for copper (II) with the dithiooxalate ligand. Spectral measurements were made at 396 nm for a series of solutions where the concen-trations of the ligands were varied over a five-fold range. The equilibration reaction Cu(en) 22+ + 2 dto2- = Cu(dto):?- + 2 en (2) was approached from both directions. The results of some 20 measurements gave for Cu ( dto) i-, log (32 = 20.0 ± 0.2. The extinction coefficient for Cu ( dto) 22- is 8900 1 mole-I cm-I. In the study of the palladium (II) complex with dithio-oxalate, it was found that we could only study the equilib-rium from one direction. The equilibrium Pd(en) 2 (ts) 2 + 2 dto2- = Pd(dto) 22- + 2 en+ 2 ts- (3) proceeded at a reasonable rate. The reverse reaction, in which the palladium (II) complex with dithiooxalate exchanges with ethylenediamine, did not proceed rapidly enough to make quantitative measurements for the formation constants. Some solutions were still changing in absorbance after 24 hours, and over this period of time the dithiooxalate ligand was decomposing. The results of some 20 solutions in which the potassium salt of dithiooxalate was added to the palladium (II) com-plex of ethylenediamine (equation 3) gave a log 132 for Pd ( dto) 22- = 29. The extinction coefficient at 380 nm for Pd(dto) 22- is 6700 1 mole-I cm-1 • However, it should be pointed out that this method is based on a reliable value for the formation constant of Pd (en) 22+. Some early work ( 7) re-ports a log {3 2 of 26.9. Subsequent research on the Pd(en) 22+ complex ( 4) sets a lower limit on log K1 of 20 and re-ports log K2 = 18.4. In our work we require a value for K2 and f32 • For the above calculation of log (3 2 for the Pd ( dto) 22-complex, we have used the value reported by Jprgensen (4) for K2 and the (3 2 of Mellor and Maley (7). Thus our value is certainly a lower limit. Using the values of Jprgensen to set a lower limit for (32 , our value would be greater than 40 1Deskin et al.: Formation Constants for Dithiooxalate ComplexesPublished by UNI ScholarWorks, 1975FORMATION COMPLEXES 157 for log f32 for the Pd ( dto) 22- complex. This is most interest-ing in that it is thermodynamically one of the most stable complexes which has been reported. ACKNOWLEDGMENT We wish to thank the Research Corporation for support of this work under a Cottrell College science grant. LITERATURE CITED (1) E. G. Cox, W. WARDLAW, and K. C. WEBSTER, ]. Chem. Soc., 1475 ( 1935). (2) D. CoucouvAN1s, J. Amer. Chem. Soc., 93, 1786 (1971). (3) R. G. PEARSON and P. ELLGEN, Inorg. Chem., 6, 1379 (1967). (4) L. RAsMUSSEN and C. K. Jf/lRGENSEN, Acta Chem. Scand., 22, 2313 (1968). ( 5) R. G. PEARSON and D. A. SWEIGART, Inorg. Chem., 9 1167 ( 1970). ( 6) A. E. MARTELL and L. G. SILLEN, "Stability Constants of Metal-Ion Complexes." 2nd ed. Special Publication No. 17, The Chemical Society, London, 1964, p. 372. (7) D. P. MELLOR and C. MALEY, Nature, 161, 436 (1948). 2Proceedings of the Iowa Academy of Science, Vol. 82 [1975], No. 3, Art. 5https://scholarworks.uni.edu/pias/vol82/iss3/5

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