Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2021 Jun 16;27(34):8668-8672.
doi: 10.1002/chem.202101028. Epub 2021 May 17.

Cooperative Ligands in Dissolution of Gold

Eeva Heliövaara  1 , Henri Liljeqvist  1 , Mikko Muuronen  1   2 , Aleksi Eronen  1 , Karina Moslova  1 , Timo Repo  1
Affiliations

Cooperative Ligands in Dissolution of Gold

Eeva Heliövaara et al. Chemistry. .

Abstract

Development of new, environmentally benign dissolution methods for metallic gold is driven by needs in the circular economy. Gold is widely used in consumer electronics, but sustainable and selective dissolution methods for Au are scarce. Herein, we describe a quantitative dissolution of gold in organic solution under mild conditions by using hydrogen peroxide as an oxidant. In the dissolution reaction, two thiol ligands, pyridine-4-thiol and 2-mercaptobenzimidazole, work in a cooperative manner. The mechanistic investigations suggest that two pyridine-4-thiol molecules form a complex with Au0 that can be oxidized, whereas the role of inexpensive 2-mercaptobenzimidazole is to stabilize the formed AuI species through a ligand exchange process. Under optimized conditions, the reaction proceeds vigorously and gold dissolves quantitatively in two hours. The demonstrated ligand-exchange mechanism with two thiols allows to drastically reduce the thiol consumption and may lead to even more effective gold dissolution methods in the future.

Keywords: S ligands; gold; gold dissolution; ligand exchange; reaction mechanisms.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
The concept of 4‐PS‐assisted gold dissolution. The thione form of 4‐PS coordinates to the Au0 surface, and the formed bisliganded Au0 species assist the one‐electron oxidation and dissolution of AuI. The in situ formed sulfate anion balances the charge. [18]
Figure 2
Figure 2
Species found in high‐resolution ESI‐TOF mass spectra when dissolving Au0 with 4‐PS and 1.
Figure 3
Figure 3
CuI and AgI species found in high‐resolution ESI‐TOF mass spectra in dissolution experiments with 1.
Figure 4
Figure 4
(a) Schematic picture of the cooperative two‐ligand dissolution of Au0; Step I: Generation of Au0 bisliganded species, Step II: Oxidation of Au0(L1)2 to AuI(L1)2, Step III: Ligand‐exchange reaction and formation of mixed‐ligand species AuI(L1)(L2), Step IV: Formation of bisliganded AuI(L2)2. (b) Complexation free energies for Au0 and AuI and the corresponding oxidation potentials of 9, 11 and 12.
See this image and copyright information in PMC

References

    1. Doidge E. D., Carson I., Tasker P. A., Ellis R. J., Morrison C. A., Love J. B., Angew. Chem. Int. Ed. 2016, 55, 12436–12439; - PubMed
    2. Angew. Chem. 2016, 128, 12624–12627.
    1. Rao M. D., Singh K. K., Morrison C. A., Love J. B., RCS Adv. 2020, 10, 4300–4309. - PMC - PubMed
    1. Lahtinen E., Kivijärvi L., Tatikonda R., Väisänen A., Rissanen K., Haukka M., ACS Omega 2017, 2, 7299–7304. - PMC - PubMed
    1. Yue C., Sun H., Liu W.-J., Guan B., Deng X., Zhang X., Yang P., Angew. Chem. Int. Ed. 2017, 56, 9331–9335; - PubMed
    2. Angew. Chem. 2018, 129, 9459–9463.
    1. Wade L., Science 2013, 341, 1448–1449. - PubMed

LinkOut - more resources