Potentiometric Study of the Copper(II) Ions Complexation Process with Thiourea in Acidic Medium

Potentiometric titration method was used to study the copper(II) ions complexation process with thiourea in medium containing 1 mol/l of hydrochloric acid at a temperature of 298 K. It was found out that mononuclear (CuTM_n) and binuclear (Cu₂TM_n) complexes were observed in the copper(II) --- thiourea system depending on the copper ions concentration. It was determined that in acid medium with copper(II) ions concentration less than 5 · 10^--4 mol/l and mononuclear complexes of the composition are generated in the system, which constant is equal to lg β₃ = 11.9. With an increase in the copper(II) ions concentration (C_Cu⁺² > 5 · 10^--4 mol/l), binuclear thiourea complex dominates in the system. Stability constant logarithm of the Cu₂TM₆ composition binuclear complex is equal to 27.5 and was calculated using the modified Leden's method. Based on the constants, complexes existence regions were determined depending on the ratio C_TM/C_Cu⁺². With the C_TM/C_Cu⁺² ≥ 5 relations, existence of a dominant complex significantly depends on the copper(II) ions concentration. It turned out that fractions of all complex particles were growing with an increase in the copper(II) ions concentration in the system. It was found that stability of thiourea complexes in the CuL_i²⁺, AgL_i⁺, AuL_i⁺ rows was increasing

Литература

[1] Ozga P. Electrodeposition of Sn--Ag and Sn--Ag--Cu alloys from thiourea aqueous solutions. Arch. Metall. Mater., 2006, vol. 51, no. 3, pp. 413--421.

[2] Gomez E., Garcia-Torres J., Valles E. Study and preparation of silver electrodeposits at negative potentials. J. Electroanal. Chem., 2006, vol. 594, iss. 2, pp. 89--95. DOI: https://doi.org/10.1016/j.jelechem.2006.05.030

[3] Ahrland S., Chatt J., Davies N.R. The relative affinities of ligand atoms for acceptor molecules and ions. Q. Rev. Chem. Soc., 1958, vol. 12, iss. 3, pp. 265--276. DOI: https://doi.org/10.1039/QR9581200265

[4] Pearson R.G. Hard and soft acids and bases. J. Am. Chem. Soc., 1963, vol. 85, iss. 22, pp. 3533--3539. DOI: https://doi.org/10.1021/ja00905a001

[5] Fedorov V.A., Fedorova A.V., Nifantyeva G.G., et al. On complexing of lead(II) and cadmium ions with thiourea and some of its derivatives. Zhurn. neorg. khim., 1974, vol. 19, no. 4, pp. 990--994 (in Russ.).

[6] Krzewska S., Podsiadly H., Pajdowski L. Studies on the reaction of copper(II) with thiourea--III equilibrium and stability constants in Cu(II)--thiourea--HCIO₄ redox system. Inorg. Nucl. Chem., 1980, vol. 42, iss. 1, pp. 89--94. DOI: https://doi.org/10.1016/0022-1902(80)80050-9

[7] Doona C.J., Stanbury D.M., Equilibrium and redox kinetics of copper(II)--thiourea complexes. Inorg. Chem., 1996, vol. 35, iss. 11, pp. 3210--3216. DOI: https://doi.org/10.1021/ic9502077

[8] Mironov I.V., Tsvelodub L.D. Complexation of copper(I) by thiourea in acidic aqueous. J. Solution Chem., 1996, vol. 25, no. 3, pp. 315--325. DOI: https://doi.org/10.1007/BF00972529

[9] Nikolskiy B.P., Palchevskiy V.V., eds. Oksredmetriya [Oxredmetry]. Leningrad, Khimiya Publ., 1975.

[10] Azizkulova O.A., Davlatova Kh.S., Dzhurabekov U.M. Complexation of copper(II) with N-acetylthiourea with 3 mol/l НСL. Doklady AN Respubliki Tadzhikistan [Reports of the Academy of Sciences of the Republic of Tajikistan], 2014, vol. 57, no. 2, pp. 121--126 (in Russ.).

[11] Amindzhanov A.A., Bakhodurov Yu.F., Khasanov F.N., et al. Complexation with copper(II) 1-phenyl-2,3-dimetilpirazolin-5-tionnom in the 6 mol/l HCI at 298 K. Doklady AN Respubliki Tadzhikistan [Reports of the Academy of Sciences of the Republic of Tajikistan], 2014, vol. 57, no. 9-10, pp. 771--777 (in Russ.).

[12] Azizkulova O.A., Davlatova Kh.S., Dzhurabekov U.M. Coordination compounds of copper(II) with N-acetylthiourea. Doklady AN Respubliki Tadzhikistan [Reports of the Academy of Sciences of the Republic of Tajikistan], 2015, vol. 58, no. 5, pp. 403--407 (in Russ.).

[13] Hartley F.R., Burgess C., Alcock R.M. Solution equilibria. E. Horwood, 1980.

[14] Lukinskas P., Savickaja I., Sukiene V., et al. Potentiometric study of silver complexes with thiourea in acid media. J. Coord. Chem., 2008, vol. 61, iss. 16, pp. 2528--2535. DOI: https://doi.org/10.1080/00958970801947454

[15] Popova A.A. The effect of complexation on the anodic behavior of transition metals. Part I. Izvestiya vuzov. Severo-kavkazskiy region. Ser. Estestvennye nauki [Bulletin of Higher Educational Institutions. North Caucasus Region. Natural Sciences], 2007, no. 5, pp. 30--33 (in Russ.).

[16] Vasilyev V.P. Termodinamicheskie svoystva rastvorov elektrolitov [Thermodynamic properties of electrolyte solutions]. Moscow, Vysshaya shkola Publ., 1982.

[17] Krzewska S., Podsiadły H. Complexes of Ag(I) with ligands containing sulphur donor atoms. Polyhedron, 1986, vol. 5, iss. 4, pp. 937--944. DOI: https://doi.org/10.1016/S0277-5387(00)80133-3

[18] Mironov I.V., Makotchenko E.V. Transformations of the Bis(thiourea)gold(I) complex in alkaline medium and interaction of thiourea with HAuCl₄. Russ. J. Inorg. Chem., 2018, vol. 63, no. 12, pp. 1667--1672. DOI: https://doi.org/10.1134/S0036023618120161

[19] De Marco D. Complex formation equilibria between Ag(I) and thioureas in propan-2-ol. ISRN, 2013, vol. 2013, art. 189394. DOI: https://doi.org/10.1155/2013/189394