蟺-Complexes of Tropolone and Its N-Derivatives: Ambidentate [O,O]/[N,O]/[N,N]-Cycloheptatrienyl Pentamethylcyclopentadienyl Ruthenium Sandwich Complexes

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• 作者：Michael Pittracher ; Ulla Frisch ; Holger Kopacka ; Klaus Wurst ; Thomas M眉ller ; Luciano Oehninger ; Ingo Ott ; Evelyn Wuttke ; Stefan Scheerer ; Rainer F. Winter ; Benno Bildstein
• 刊名：Organometallics
• 出版年：2014
• 出版时间：April 14, 2014
• 年：2014
• 卷：33
• 期：7
• 页码：1630-1643
• 全文大小：610K
• 年卷期：v.33,no.7(April 14, 2014)
• ISSN：1520-6041

文摘

Tropolone and its N-derivatives isopropylaminotropone and diisopropylaminotroponimine react with [Cp*Ru(CH₃CN)₃]PF₆ as the source of the electron-rich Cp*Ru⁺ synthon in a simple 鈥渃apping reaction鈥?to the first cyclopentadienyl/cycloheptatrienyl sandwich complexes containing two vicinal oxo or amino substituents. These heteroleptic, cationic C₅/C₇ 蟺-complexes, [Cp*Ru(C₇H₅)O₂H]⁺ (4), [Cp*Ru(C₇H₅)O(NⁱPr)H]⁺ (5), and [Cp*Ru(C₇H₅)(NⁱPr)₂H]⁺ (6), are air-stable 18-electron metallocenes without precedence. In solution, NMR spectroscopy proves the principal 蟺-coordination of the substituted 畏⁷-cycloheptatrienyl ligands, whereas in the solid state a 畏⁵-cycloheptatrienyl coordination mode with bent oxo/imino moieties prevails, as shown by X-ray single-crystal structure analyses. Chemically, these compounds are the conjugate Br酶nsted acids of neutral [O,O]-, [N,O]-, or [N,N]-metalloligands. Reaction with metal acetates or acetylacetonates by in situ deprotonation and complex formation gives access to trimetallic (M = Cu²⁺, 10鈥?b>12) or tetrametallic (M = Fe³⁺, 13) complex cations. Their single-crystal structure analyses show square-planar or square-pyramidal (M = Cu²⁺) or octahedral (M = Fe³⁺) coordination motifs with peripheral, 畏⁵-coordinated Cp*Ru moieties. Electrochemical studies on the trorucenes 4鈥?b>6 showed a likely metal-based chemically reversible (4) or irreversible one-electron reduction (5, 6) as well as an irreversible one-electron oxidation for the N-substituted compounds 5 and 6. The behavior of the heterotri- and tetrametallic complexes 10, 11, and 13 was rationalized by a combination of cyclic and square-wave voltammetry as well as the combination of chronocoulometry and linear-sweep voltammetry and by comparison with the mononuclear copper or iron tropolone and topolonimine precursors 14鈥?b>16. These studies indicate that in 10 and 11 the trorucene moieties are reduced first in two coincident or slightly separated one-electron reductions with the Cu²⁺ reduction at very negative potential, whereas in 13 the central Fe(III)-tris(troponolato) moiety is reduced prior to the trorucene appendices. An in vitro anticancer screening in MDA-MB-231 breast adenocarcinoma and HT-29 colon carcinoma cell lines showed enhanced antiproliferative activity for the [O,O]-coordinated iron and copper complexes.