Equilibria in aqueous solutions of some chromium(2+) complexes

Károly Micskei, Ferenc Debreczeni, István Nagypál

Research output: Contribution to journalArticle

25 Citations (Scopus)

Abstract

The stepwise formation constants of the complexes formed in the Cr2+-ethylenediamine (en), -malonate (mal), -glycinate (glyO), -β-alaninate (alaO), -iminodiacetate (imda), -nitrilotriacetate (nta), and -ethylenediaminetetra-acetate (edta) systems in aqueous 1 mol dm-3 KCl at 25 °C, determined pH-metrically, are as follows: log K1en = 5.48, log K2en = 4.15, log K1mal = 3.57, log K2mal = 1.92, log K1glyO = 4.21, log K2glyO = 3.06, log K1 alaO = 3.89, log K1 imda = 5.01, log K2imda = 3.17, log K1nta = 6.52, log K2nta = 3.14, log K 1edta = 12.70. The logarithm of the equilibrium constant for the Cr2+ = Cr(OH)+ + H+ process is -5.30; the formation of a protonated complex was detected in the Cr2+-malonate and -ethylenediaminetetra-acetate systems and the formation of a binuclear [Cr2(nta)]+ complex in the Cr2+ -nitrilotriacetate system. The log (K1/K2) values for the Cr2+ and Cu2+ complexes are roughly the same in the case of bidentate ligands, but they are much lower for Cr2+ than for Cu2+ in the case of multidentate ligands. The ratios of 'excess' stabilities of the Cr2+ and Cu2+ complexes are also roughly the same (0.54) in the case of bidentate ligands, but no excess stability (even destabilization) of the Cr2+ complexes was found in the case of the multidentate ligands. These phenomena are interpreted in terms of the difference in ionic radii of the two metal ions.

Original languageEnglish
Pages (from-to)1335-1338
Number of pages4
JournalJournal of the Chemical Society, Dalton Transactions
Issue number7
DOIs
Publication statusPublished - Jan 1 1983

ASJC Scopus subject areas

  • Chemistry(all)

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