ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Kinetics of the substitution reactions of chromium(III) complexes. III. The solvation of the trans-dithiocyanatobis(ethyl-enediamine)chromium(III) ion

V. Holba

Komenský University, Bratislava

Abstract:  Kinetics of the solvation of trans-[Cr(SCN)₂-(en)₂]⁺ ion in 0.01M HNO₃ at 50° was studied by a spectro-photometric method. From the change of the absorption spectra at 520 mμ in relation to time (0-150 min.) and from the change of pH from 2.0 to 2.41, it was detd. that the solvation occurs in 2 steps. The reaction scheme may be expressed as: [Cr-(SCN)₂(en)₂]⁺ + 2H₂O k₁ → [Cr(SCN)₂(H₂O)₂en]⁺ + en (1) and [Cr(SCN)₂(H₂O)₂en]⁺ + H₂O k₂ → [CrSCN(H₂O)₃en]²⁺ + SCN^-(2), where k₁ > k₂. In reaction 1 there is a substitution of the ethylenediamine with H₂O, which is liberated. The velocity const. is k1 = 5.3 × 10^-3/min. The activation energy is EA = 24.4 kcal./mol. In reaction 2, SCN- is liberated and the velocity const. is k₂ = 2.4 × 10^-4/min.

Full paper in Portable Document Format: 196a441.pdf (in Slovak)

Chemical Papers 19 (6) 441–446 (1965)