Formation and Reactivity of Copper Acetylacetone Bis(Thiosemicarbazone) Complexes

The complexation reaction mechanism of acetylacetone bis‐thiosemicarbazone ligands (H2acacR) with CuII is explored using a variety of physical methods. The complexes form via a complicated multistep mechanism that is initiated by ring opening of the pyrazoline form of the ligand and leads, ultimatel...

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Bibliographic Details
Published in:European journal of inorganic chemistry 2018-11, Vol.2018 (43), p.4731-4741
Main Authors: Bilyj, Jessica K., Harmer, Jeffery R., Bernhardt, Paul V.
Format: Article
Language:English
Subjects:
Acetylacetone
Anaerobic conditions
Coordination compounds
Copper
Crystallography
Cyclic voltammetry
Electrochemistry
EPR
Imines
Inorganic chemistry
Ligands
Reaction mechanisms
Ring opening
Thiosemicarbazone
X ray spectra
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Summary:The complexation reaction mechanism of acetylacetone bis‐thiosemicarbazone ligands (H2acacR) with CuII is explored using a variety of physical methods. The complexes form via a complicated multistep mechanism that is initiated by ring opening of the pyrazoline form of the ligand and leads, ultimately in air, to an oxidised ketone form of the ligand. Tetradentate N2S2 coordinated forms of the intermediate [Cu(acacR)] are stable only under anaerobic conditions. Upon exposure to air these complexes are cleanly oxidised to the ketone complex [Cu(acacRO)] as shown by X‐ray crystallography, electrochemistry, UV/Vis and EPR spectroscopy. The behavior of these complexes contrasts with those of closely related bis‐dithiocarbazate Schiff bases which stabilise CuIII. The formation of copper(II) complexes of acetylacetone bis(thiosemicarbazone) ligands is a multistep process and in the presence of oxygen facile metal‐catalysed ligand oxidation is a feature.
ISSN:1434-1948
1099-0682
DOI:10.1002/ejic.201801002