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Rizzato S, Manca G, Lemée MH, Marchiò L, Cesare Marincola F, Guerri A, Ienco A, Serpe A, Deplano P. Halogen-Bonding-Mediated Radical Reactions: The Unexpected Behavior of Piperazine-Based Dithiooxamide Ligands in the Presence of Diiodine. Inorg Chem 2023; 62:694-705. [PMID: 36602377 PMCID: PMC9846695 DOI: 10.1021/acs.inorgchem.2c02340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
N,N'-Dialkylpiperazine-2,3-dithiones (R2pipdt) were recognized as a class of hexa-atomic cyclic dithiooxamide ligands with peculiar charge-transfer donor properties toward soft electron-acceptors such as noble metal cations and diiodine. The latter interaction is nowadays better described as halogen bonding. In the reaction with diiodine, R2pipdt unexpectedly provides the corresponding triiodide salts, differently from the other dithiooxamides, which instead typically achieve ligand·nI2 halogen-bonded adducts. In this paper, we report a combined experimental and theoretical study that allows elucidation of the nature of the cited products and the reasons behind the unpredictable behavior of these ligands. Specifically, low-temperature single-crystal X-ray diffraction measurements on a series of synthetically obtained R2pipdt (R = Me, iPr, Bz)/I3 salts, complemented by neutron diffraction experiments, were able to experimentally highlight the formation of [R2pipdtH]+ cations with a -S-H bond on the dithionic moiety. Differently, with R = Ph, a benzothiazolylium cation, resulting from an intramolecular condensation reaction of the ligand, is obtained. Based on density functional theory (DFT) calculations, a reasonable reaction mechanism where diiodine plays the fundamental role of promoting a halogen-bonding-mediated radical reaction has been proposed. In addition, the comparison of combined experimental and computational results with the corresponding reactions of N,N'-dialkylperhydrodiazepine-2,3-dithione (R2dazdt, a hepta-atomic cyclic dithiooxamide), which provide neutral halogen-bonded adducts, pointed out that the difference in the torsion angle of the free ligands represents the structural key factor in determining the different reactivities of the two systems.
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Affiliation(s)
- Silvia Rizzato
- Dipartimento
di Chimica, Università degli Studi
di Milano, Via Golgi 19, I-20133 Milano, Italy
| | - Gabriele Manca
- Istituto
di Chimica dei Composti Organometallici ICCOM-CNR, Via Madonna del Piano 10, I-50019 Sesto Fiorentino, Florence, Italy
| | - Marie-Hélène Lemée
- Institut
Laue-Langevin, 71 avenue des Martyrs, CS 20156, 38042 Grenoble Cedex 9, France
| | - Luciano Marchiò
- Dipartimento
di Chimica, Scienze della Vita e della Sostenibilità Ambientale, Università di Parma, 43124 Parma, Italy
| | - Flaminia Cesare Marincola
- Dipartimento
di Scienze Chimiche e Geologiche, Università
di Cagliari, 09042 Monserrato, Cagliari, Italy
| | - Annalisa Guerri
- Dipartimento
di Chimica “Ugo Schiff”, Università
di Firenze, Via della
Lastruccia 3, 50019 Sesto Fiorentino, Firenze, Italy
| | - Andrea Ienco
- Istituto
di Chimica dei Composti Organometallici ICCOM-CNR, Via Madonna del Piano 10, I-50019 Sesto Fiorentino, Florence, Italy,
| | - Angela Serpe
- Dipartimento
di Ingegneria Civile, Ambientale e Architettura (DICAAR) and Research
Unit of INSTM, Università di Cagliari, I-09042 Monserrato, Cagliari, Italy,Istituto
di Geologia Ambientale e Geoingegneria del Consiglio Nazionale delle
Ricerche (IGAG-CNR), Piazza d’Armi, 09123 Cagliari, Italy,
| | - Paola Deplano
- Dipartimento
di Scienze Chimiche e Geologiche, Università
di Cagliari, 09042 Monserrato, Cagliari, Italy,Dipartimento
di Ingegneria Civile, Ambientale e Architettura (DICAAR) and Research
Unit of INSTM, Università di Cagliari, I-09042 Monserrato, Cagliari, Italy
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