Synergistic oxygen atom transfer by ruthenium complexes with non-redox metal ions

Abstract

Non-redox metal ions can affect the reactivity of active redox metal ions in versatile biological and heterogeneous oxidation processes; however, the intrinsic roles of these non-redox ions still remain elusive. This work demonstrates the first example of the use of non-redox metal ions as Lewis acids to sharply improve the catalytic oxygen atom transfer efficiency of a ruthenium complex bearing the classic 2,2'-bipyridine ligand. In the absence of Lewis acid, the oxidation of ruthenium(ii) complex by PhI(OAc)2 generates the Ru(iv)[double bond, length as m-dash]O species, which is very sluggish for olefin epoxidation. When Ru(bpy)2Cl2 was tested as a catalyst alone, only 21.2% of cyclooctene was converted, and the yield of 1,2-epoxycyclooctane was only 6.7%. As evidenced by electronic absorption spectra and EPR studies, both the oxidation of Ru(ii) by PhI(OAc)2 and the reduction of Ru(iv)[double bond, length as m-dash]O by olefin are kinetically slow. However, adding non-redox metal ions such as Al(iii) can sharply improve the oxygen transfer efficiency of the catalyst to 100% conversion with 89.9% yield of epoxide under identical conditions. Through various spectroscopic characterizations, an adduct of Ru(iv)[double bond, length as m-dash]O with Al(iii), Ru(iv)[double bond, length as m-dash]O/Al(iii), was proposed to serve as the active species for epoxidation, which in turn generated a Ru(iii)-O-Ru(iii) dimer as the reduced form. In particular, both the oxygen transfer from Ru(iv)[double bond, length as m-dash]O/Al(iii) to olefin and the oxidation of Ru(iii)-O-Ru(iii) back to the active Ru(iv)[double bond, length as m-dash]O/Al(iii) species in the catalytic cycle can be remarkably accelerated by adding a non-redox metal, such as Al(iii). These results have important implications for the role played by non-redox metal ions in catalytic oxidation at redox metal centers as well as for the understanding of the redox mechanism of ruthenium catalysts in the oxygen atom transfer reaction.

Directing transition metal-based oxygen-functionalization catalysis

“…54 Ruthenium imine complexes, like Ru(bpy) 2 Cl 2 (bpy ¼ 2,2 0 -bipyridine), are among the most distinguished ruthenium complexes oxidized to generate the Ru IV ]O intermediate. 55 Interestingly, the catalytic epoxidation efficiency of Ru(bpy) 2 Cl 2 was increased upon the incorporation of Lewis acid like Al(OTf) 3 (OTF: tri-uoromethanesulfonate), which led to the formation of more active species, the Ru IV ]O/Al III intermediate. Such results have highlighted the roles of non-redox metal ions, like Lewis acids, in regulating the reactivity of high-valent metal-oxo complexes.…”

“…74 e Ru(bpy) 2 Cl 2 (bpy ¼ 2,2 0 -bipyridine). 55 The rapid disappearance of the absorbance band at 490 nm following the addition of excess olen was primarily used as an evaluation point (Fig. 2d).…”

Transformation of Methyl Linoleate to its Conjugated Derivatives with Simple Pd(OAc)2/Lewis Acid Catalyst

“…In exploring non-redox metal ions serving as Lewis acids to improve the catalytic efficiency of redox metal complexes [27][28][29][30][31][32], we unexpectedly found that, in Wacker-type oxidations, the Lewis properties of copper(II) play significant Abstract With the rapid depletion of fossil resources, the exploitation of biomass to partly replace fossil resources as the source of carbon in the chemical industry constitutes a promising alternative for the near future. This work introduces catalytic transformation of vegetable oil, i.e., methyl linoleate, to its conjugated esters by a simple Pd(OAc) 2 /Sc(OTf) 3 catalyst, which has extensive applications in industry.…”

Καταλυτική Παραγωγή Η2 Από Νανοδομημένα Υβριδικά Υλικά Σε Χαμηλές Θερμοκρασίες

“…(Δ) [178] καθοριστικό στάδιο, η τιμή ln(TOF) ως προς (1/T) (K -1 ), δίνει γραμμική συνάρτηση, από όπου υπολογίζεται η E α [259]. Τα δεδομένα των διαγραμμάτων απεικονίζονται στους Πίνακες 9.3, 9.4 και 9.5.…”

“…Τα δεδομένα των διαγραμμάτων απεικονίζονται στους Πίνακες 9.3, 9.4 και 9.5. [184] (B) [192] αντίδραση είναι εξαρτώμενη της θερμοκρασίας η ενέργεια ενεργοποίησης (Ε α ), υπολογίζεται μέσω της κλίσης της εξίσωσης ευθείας, σύμφωνα με την εξίσωση (9.1) [258,259]:…”