Mechanism of Alkyne Insertion into the Ru−C Bonds of Orthoruthenated Compounds Featuring Similarity of the Ru(II) and Pd(II) Reactions

Abstract

The pseudo-first-order rate constants k obs for the reaction between the ring-substituted orthoruthenated N,N-dimethylbenzylamines [RuII(η6-C6H6)(o-C6H3RCH2NMe2)Cl] (R = 4,5-(MeO)2, 5-Me, H, 5-F), and alkynes R‘C⋮CR‘‘ (R‘/R‘‘ = Ph/Ph, Ph/C6H4CF3-3, Ph/C6H4NO2-4, Et/Et, CO2Me/CO2Me) to afford the isoquinolinium cations coordinated to the [Ru0(η6-C6H6)] moiety are a linear function of [R‘C⋮CR‘‘] in methanol at 20.0−40.0 °C in accord with the rate-determining insertion of alkyne into the Ru−C bond. The latter was confirmed by the observation that the electron-donating groups R at the dimethylbenzylamine ruthenocycle favor the insertion and the slope of the corresponding Hammett plot equals −1.6 against σ+. The electron-poor alkynes react slower than the electron-rich ones. An X-ray structural investigation of the product of the MeO2CC⋮CCO2Me reaction with the related ruthenocycle [(3-MeC5H3N-2-C6H4)Ru(μ-I)(CO)2]2 demonstrates that the alkyne inserts into the Ru−C bond. Addition of LiCl retards the insertion markedly indicative of the importance of the ionization of the coordinated chloride. The major reaction pathway involves the solvento species [RuII(η6-C6H6)(o-C6H3RCH2NMe2)(MeOH)]+, the existence of which was confirmed by the spectrophotometric study of the starting compound in the presence of LiCl. All the observations reported show that the d6 system under study is very mechanistically similar to the insertion of alkynes into the dinuclear d8 PdII complexes [Pd(o-C6H3RCH2NMe2)(μ-Cl)]2, the key difference being the ways of creation of a coordinative site readily accessible by alkyne. These are the ionization of the Ru−Cl bond and the cleavage of the [Pd(μ-Cl)2Pd] bridge in the ruthenium and palladium cases, respectively.

The development of anticancer ruthenium(ii) complexes: from single molecule compounds to nanomaterials

“…219 The metal-to-ligand bond distances of Ru-C are significantly shorter than that of Ru-N, and the binding of cyclometallated ligands with Ru is very stable. 220,221 In addition, the cyclometalation can decrease the valence charge of the Ru(II) complexes, which contributes to an increase in the lipophilicity and cellular uptake of Ru(II) complexes.…”

Synthesis, Structure, Reactivity, and Catalytic Activity of Cyclometalated (Phosphine)‐ and (Phosphinite)ruthenium Complexes

“…[16] Besides, there were several reported cases about insertion reactions of alkynes into Ru-C bonds of similar five-membered cycloruthenated complexes, which generally afforded the corresponding seven-membered cycloruthenated complexes by means of the 1,2 insertion of an alkyne. [6,20] Therefore, we tried the reaction of cycloruthenated complex 2a with diphenylacetylene in methanol or 1,2-dichloroethane, and expected a similar product containing a seven-membered ring. However, the reaction surprisingly generated an organic product 10, and no ruthenium-containing products were isolated (Scheme 5).…”

Metallkomplexe mit biologisch wichtigen Liganden, CIV [1]. ortho-Palladierte Komplexe von N,N-Dimethyl-C-phenyl-glycinmethylester. Synthese von α-Aminosäure-Derivaten durch Insertion von Isocyaniden, CO, Alkenen und Alkinen in die Pd-C-Bindung / Metal Complexes of Biologically Important Ligands, CIV [ 1]. ortho-Palladated Complexes of N,N-Dimethyl-C-phenylglycine-methylester. Synthesis of α-Amino Acid Derivatives by Insertion of Isocyanides, CO, Alkenes, and Alkynes into the Pd-C Bond

“…Die Insertion von Alkinen in die Metall-C-Bindung orthometallierter Komplexe ist vielfach untersucht worden. Bei cyclopalladierten Verbindungen führt die Insertion von ein, zwei und drei Alkin-Einheiten in die Pd-C-Bindung häufig zu größeren Palladacyclen; in be stimmten Fällen wird eine Demetallierung zum or ganischen Produkt beobachtet [5]. Die Umsetzung von 2a -c mit vier Äquivalenten Diphenylacetylen liefert die metallorganischen Butadien-Derivate 9a -c (Schema 10).…”

“…Sie zeigen eine Reihe interessanter Reaktionen, durch die das metallierte Kohlenstoff-Atom gezielt funktionalisiert werden kann. Durch Umsetzung von cyclometallierten Verbindungen mit Alkenen [4], Al kinen [5], CO [6], 7], Halogenen, Acylchloriden etc. [3a] wurde eine Vielzahl von substituierten metallorganischen und organischen Verbindungen dargestellt.…”