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Substitution reactions of cis-platinum(II) complexes containing bidentate N,N-donor pyridinecarboxamide ligands with different substituents

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dc.contributor.authorPapo, Tshephiso Rose
dc.contributor.authorJaganyi, Deogratius
dc.contributor.authorMambanda, Allen
dc.date.accessioned2024-06-20T07:05:24Z
dc.date.available2024-06-20T07:05:24Z
dc.date.issued2022-12-05
dc.description.abstractSubstitution reactions of [2-(pyridinecarboxamide)dichloride Pt(II)] [PtCl2], [N-phenyl-(2-pyridinecarboxamide)dichloride Pt(II)] [PhPtCl2], [N-(4-methylphenyl)-2-pyridinecarboxamide)dichloride Pt(II)] [CH3PhPtCl2], [N-(4-methoxyphenyl)-(2-pyridine-carboxamide)dichloride Pt(II)] [CH3OPhPtCl2] and [N-(4-fluorophenyl)-(2-pyridinecarboxamide)dichloride Pt(II)] [FPhPtCl2], with nucleophiles; thiourea (TU), N,N′-dimethylthiourea (DMTU) and N,N,N′,N′-tetramethylthiourea (TMTU) were studied under pseudo first-order conditions. The rates of substitution were investigated as a function of nucleophile concentration and temperature using stopped-flow and UV-visible absorption spectrophotometers. Substitutions of the two coordinated chloride ligands of the Pt(II) complexes occur consecutively, with the first substitution occurring opposite the coordinated pyridyl. The observed pseudo first-order rate constants regressed linearly with concentration of the incoming nucleophiles according to the equation kobs = k2[Nu]. The highest substitution rates were measured for PtCl2, which is attributed to the unsubstituted non-leaving carboxamide ligand. The Pt(II) center of this complex is the most electrophilic as a result of the strong withdrawal of electron density through π-resonance by the carboxamide group. The introduction of a 4′-substituted phenyl group on the amido N of the carboxamide reduces the reactivity of the complexes due to proportional electronic effects from the ancillary substituents on the phenyl ring as well as its conformational disposition with respect to the plane of the complex. The order of reactivity of studied nucleophiles is TU > DMTU > TMTU. The substitution is associatively activated as supported by the negative entropy of activation values for the reactions.
dc.identifier.citationTshephiso Papo, Deogratius Jaganyi & Allen Mambanda. Kinetics and mechanistic investigation of the substitution from dinuclear Pt(II) complexes bridged by N,N’-bis(2-pyridylcarboxamide)phenylenediamines. Journal of Coordination Chemistry 0:0, pages 1-15.
dc.identifier.issn2557–2573
dc.identifier.urihttps://doi.org/10.1080/00958972.2022.2149327
dc.identifier.urihttps://erepository.mku.ac.ke/handle/123456789/5912
dc.language.isoen
dc.publisherJournal of Coordination Chemistry
dc.titleSubstitution reactions of cis-platinum(II) complexes containing bidentate N,N-donor pyridinecarboxamide ligands with different substituents
dc.typeArticle
dspace.entity.typePublication
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