Further Insight into the Lability of MeCN Ligands of Cytotoxic Cycloruthenated Compounds: Evidence for the Antisymbiotic Effect Trans to the Carbon Atom at the Ru Center

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• 作者：Ana Soraya Lima Barbosa ; Christophe Werl茅 ; Claudia Olivia Oliva Colunga ; Cecilia Franco Rodr铆guez ; Ruben Alfredo Toscano ; Ronan Le Lagadec ; Michel Pfeffer
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：August 3, 2015
• 年：2015
• 卷：54
• 期：15
• 页码：7617-7626
• 全文大小：599K
• ISSN：1520-510X

文摘

The two MeCN ligands in [Ru(2-C₆H₄-2鈥?Py-魏C,N)(Phen, trans-C)(MeCN)₂]PF₆ (1), both trans to a sp² hybridized N atom, cannot be substituted by any other ligand. In contrast, the isomerized derivative [Ru(2-C₆H₄-2鈥?Py-魏C,N)(Phen, cis-C)(MeCN)₂]PF₆ (2), in which one MeCN ligand is now trans to the C atom of the phenyl ring orthometalated to Ru, leads to fast and quantitative substitution reactions with several monodentate ligands. With PPh₃, 2 affords [Ru(2-C₆H₄-2鈥?Py-魏C,N)(Phen, cis-C)(PPh₃)(MeCN)]PF₆ (3), in which PPh₃ is trans to the C 蟽 bound to Ru. Compound 3 is not kinetically stable, because, under thermodynamic control, it leads to 4, in which the PPh₃ is trans to a N atom of the Phen ligand. Dimethylsulfoxide (DMSO) can also substitute a MeCN ligand in 2, leading to 5, in which DMSO is coordinated to Ru via its S atom trans to the N atom of the Phen ligand, the isomer under thermodynamic control being the only compound observed. We also found evidence for the fast to very fast substitution of MeCN in 2 by water or a chloride anion by studying the electronic spectra of 2 in the presence of water or NBu₄Cl, respectively. An isomerization related to that observed between 3 and 4 is also found for the known monophosphine derivative [Ru(2-C₆H₄-2鈥?Py-魏C,N)(PPh₃, trans-C)(MeCN)₃]PF₆ (10), in which the PPh₃ is located trans to the C of the cyclometalated 2-phenylpyridine, since, upon treatment by refluxing MeCN, it leads to its isomer 11, [Ru(2-C₆H₄-2鈥?Py-魏C,N)(PPh₃, cis-C)(MeCN)₃]PF₆. Further substitutions are also observed on 11, whereby N^N chelates (N^N = 2,2鈥?bipyridine and phenanthroline) substitute two MeCN ligands, affording [Ru(2-C₆H₄-2鈥?Py-魏C,N)(PPh₃, cis-C)(N^N)(MeCN)]PF₆ (12a and 12b). Altogether, the behavior of the obtained complexes by ligand substitution reactions can be rationalized by an antisymbiotic effect on the Ru center, trans to the C atom of the cyclometalated unit, leading to compounds having the least nucleophilic ligand trans to C whenever an isomerization, involving either a monodentate or a bidentate ligand, is possible.