Fully reduced and mixed-valent multi-copper aggregates supported by tetradentate diamino bis(thiolate) ligands

Wang, B., Barnes, J., Ferrara, S. J., Sproules, S. , Zhang, X., Mague, J. T. and Donahue, J. P. (2023) Fully reduced and mixed-valent multi-copper aggregates supported by tetradentate diamino bis(thiolate) ligands. Inorganic Chemistry, (doi: 10.1021/acs.inorgchem.3c00784)

Abstract

Tetradentate diamino bis(thiolate) ligands (l-N2S2(2−)) with saturated linkages between heteroatoms support fully reduced [(Cu(l-N2S2))2Cu2] complexes that bear relevance as an entry point toward molecules featuring the Cu2ICu2II(μ4-S) core composition of nitrous oxide reductase (N2OR). Tetracopper [(Cu(l-N2(SMe2)2))2Cu2] (l-N2(SMe2H)2 = N1,N2-bis(2-methyl-2-mercaptopropane)-N1,N2-dimethylethane-1,2-diamine) does not support clean S atom oxidative addition but undergoes Cl atom transfer from PhICl2 or Ph3CCl to afford [(Cu(l-N2(SMe2)2))3(CuCl)5], 14. When introduced to Cu(I) sources, the l-N2(SArH)2 ligand (l-N2(SArH)2 = N1,N2-bis(2-mercaptophenyl)-N1,N2-dimethylethane-1,2-diamine), made by a newly devised route from N1,N2-bis(2-fluorophenyl)-N1,N2-dimethylethane-1,2-diamine, ultimately yields the mixed-valent pentacopper [(Cu(l-N2SAr2))3Cu2] (19), which has 3-fold rotational symmetry (D3) around a Cu2 axis. The single CuII ion of 19 is ensconced within an equatorial l-N2(SAr)2(2−) ligand, as shown by 14N coupling in its EPR spectrum. Formation of 19 proceeds from an initial, fully reduced product, [(Cu(l-N2SAr2))3Cu2(Cu(MeCN))] (17), which is C2 symmetric and exceedingly air-sensitive. While unreactive toward chalcogen donors, 19 supports reversible reduction to the all-cuprous state; generation of [19]1– and treatment with S atom donors only return 19 because structural adjustments necessary for oxidative addition are noncompetitive with outer-sphere electron transfer. Oxidation of 19 is marked by intense darkening, consistent with greater mixed valency, and by dimerization in the crystalline state to a decacopper species ([20]2+) of S4 symmetry.

• Item Type: Articles
• Additional Information: The Louisiana Board of Regents (LEQSF-(2002-03)-ENH-TR-67) and the National Science Foundation (MRI-1228232 and 0619770) are thanked for funding of Tulane University’s X-ray crystallography and mass spectrometry instrumentation, and Tulane University is acknowledged for its ongoing assistance with operational costs for the X-ray diffraction facility. The authors gratefully acknowledge support for this project from the National Science Foundation (CHE-1800520 for B.W., J.B., and J.P.D.). Professor Robert A. Pascal of the Chemistry Department at Tulane University is thanked for helpful discussion regarding the synthesis of ligand 5.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Sproules, Dr Stephen
• Authors: Wang, B., Barnes, J., Ferrara, S. J., Sproules, S., Zhang, X., Mague, J. T., and Donahue, J. P.
• College/School: College of Science and Engineering > School of Chemistry
• Journal Name: Inorganic Chemistry
• Publisher: American Chemical Society
• ISSN: 0020-1669
• ISSN (Online): 1520-510X
• Published Online: 13 June 2023
• Copyright Holders: Copyright © 2023 The Authors.
• First Published: First published in Inorganic Chemistry 2023
• Publisher Policy: Reproduced under a Creative Commons license