Hydrolysis of chlorido complexes of d8 metals: Old models, new facts

KOZELKA, Jiří. Hydrolysis of chlorido complexes of d8 metals: Old models, new facts. Inorganica Chimica Acta. Lausanne: Elsevier, 2019, vol. 495, SEP 1 2019, p. 1-8. ISSN 0020-1693. Available from: https://dx.doi.org/10.1016/j.ica.2019.05.045.

Basic information

• Original name: Hydrolysis of chlorido complexes of d8 metals: Old models, new facts
• Authors: KOZELKA, Jiří (203 Czech Republic, guarantor, belonging to the institution).
• Edition: Inorganica Chimica Acta, Lausanne, Elsevier, 2019, 0020-1693.

Other information

• Original language: English
• Type of outcome: Article in a journal
• Field of Study: 10402 Inorganic and nuclear chemistry
• Country of publisher: Netherlands
• Confidentiality degree: is not subject to a state or trade secret
• WWW: URL
• Impact factor: Impact factor: 2.304
• RIV identification code: RIV/00216224:14310/19:00110712
• Organization unit: Faculty of Science
• Doi: http://dx.doi.org/10.1016/j.ica.2019.05.045
• UT WoS: 000481728800015
• Keywords in English: Square-planar substitution; Hydrolysis; Aquation kinetics; Charge-separation effect; Cisplatin; d8 complexes
• Tags: rivok
• Tags: International impact, Reviewed

Abstract

The discovery of the antitumor activity of cisplatin in 1969 has accelerated research in platinum chemistry. In particular, cisplatin hydrolysis, the rate-determining process activating the drug for reaction with DNA, was extensively studied and discussions of the mechanism of square-planar substitutions were rekindled. One intriguing aspect of cisplatin hydrolysis is the fact that the rates of the two aquation steps are almost identical, in spite of the charge-separation effect which would be expected to slow down the second step. This result is analyzed here in the context of the more general observation made by Martin et al. that aquation of chloridoammine complexes of Pt(II) proceeds at similar rates, independently of complex charge. Ancient hypotheses put forward to explain this observation are confronted with recent data. The discussion is extended to aquation of chlorido-am(m)ine complexes of Pd(II) and Au(III), and to chloride substitutions by thiourea and pyridine. It is shown that the charge independence is not limited to chloride substitution by water. This new correlation of published data invalidates our recent hypothesis according to which non-conventional hydrogen bonding from the attacking water molecule to the Pt(II) center as acceptor counterbalances the charge separation effect. Recent data also show that the frequently used kinetic model for square-planar substitutions featuring a metastable five-coordinate intermediate does not apply to complexes involving only simple o-donating ligands such as amines, water, or chloride. By inference, the Martin-Basolo model, explaining the charge-independence of aquation rate constants with the mutual compensation between charge separation and charge neutralization in the transition state, remains the only model compatible with available data.