Additional Aspects of Complexation of Gold(I) with Thiomalate

• Published in: Journal of solution chemistry 2018-03, Vol.47 (3), p.511-527
• Main Authors: Mironov, Igor V., Kharlamova, Viktoria Yu
• Format: Article
• Language: English
• Subjects: Acidic oxides; Chemistry; Chemistry and Materials Science; Condensed Matter Physics; Depolymerization; Geochemistry; Gold; Industrial Chemistry/Chemical Engineering; Inorganic Chemistry; Oceanography; Oxidation; Physical Chemistry; Protonation
• ISSN: 0095-9782; 1572-8927
• DOI: 10.1007/s10953-018-0735-y

Some equilibria involving gold(I) thiomalate (mercaptosuccinate, TM) complexes have been studied in the aqueous solution at 25 °C and I  = 0.2 mol·L −1 (NaCl). In the acidic region, the oxidation of TM by AuCl 4 - proceeds with the formation of sulfinic acid, and gold(III) is reduced to gold(I). The interaction of gold(I) with TM at n TM / n Au  ≤ 1 leads to the formation of highly stable cyclic polymeric complexes Au m TM m ∗ with various degrees of protonation depending on pH. In general, the results agree with the tetrameric form of this complex proposed in the literature. At n TM / n Au  > 1, the processes of opening the cyclic structure, depolymerization and the formation of Au TM 2 ∗ occur: Au 4 ( TM) 4 8 - + TM 3 - ⇌ Au 4 ( TM) 5 11 - , log 10 K 45  = 10.1 ± 0.5; 0.25 Au 4 ( TM) 4 8 - + TM 3 - ⇌ Au(TM) 2 5 - , log 10 K 12  = 4.9 ± 0.2. The standard potential of Au(TM) 2 5 - is E 1 / 0 ∘ = - 0.255 ± 0.030 V . The numerous protonation processes of complexes at pH