Imidazolium Salts of Ruthenium Anionic Cyclopentadienone Complexes: Ion Pair for Bifunctional Catalysis in Ionic Liquids

Abstract

The reactivity of the dinuclear complex dicarbonyl[η4‐3,4‐bis(4‐methoxyphenyl)‐2,5‐diphenylcyclopenta‐2,4‐dienone] (2) with imidazolium salts has been studied using a library of variously functionalized imidazolium salts, and leading to a class of ruthenium anionic complexes of the type [dicarbonyl{η4‐3,4‐bis(4‐methoxyphenyl)‐2,5‐diphenylcyclopenta‐2,4‐dienone} (halide)Ru][1,3‐disubsittuted‐imidazolium] (4) in the form of ion pair with imidazolium. The reaction is clean, general and quantitative and the complexes formed are stable to air and moisture both in the solid state and in solution. The ionic complexes 4 show affinity for ionic liquids and represent stable precursors of a catalytic active species, likely similar to those generated from Shvo catalyst, a well‐established homogeneous bifunctional catalyst for hydrogen transfer. Our approach allows the use of green ionic liquids (IL) as solvents, providing better control of catalytic reactions involving 4, and easier catalyst recycle. IL‐supported ionic pair catalysts exhibit interesting catalytic activity (up to > 99 % of conversion) in the transfer hydrogenation of a model compound such as 4‐fluoroacetophenone. The IL‐supported redox catalysts can be also recycled exploiting the biphasic nature of the system. The synthetic method here discussed represents a novelty within the field of IL‐supportation and is potentially useful for the heterogenization of the catalysts.

Supported Ionic Liquids for the Efficient Removal of Acetylsalicylic Acid from Aqueous Solutions

“…imidazolium, pyridinium, pyrrolidium, tetraalkylammonium and tetraalkylphosphonium) paired with organic or inorganic anions (e.g. trifluoromethylsulfonate, bis(trifluoromethylsulfonyl)imide, hexafluorophosphate, trifluoroethanoate, tetrafluoroborate, Cl -, Brand I -) [22][23][24][25][26][27][28][29] . Amongst the interesting features of neat ILs, such as negligible volatility, high thermal stability and high polarity [22] , the most interesting characteristic is their tunability.…”

Advances in Catalytic Routes for the Homogeneous Green Conversion of the Bio‐Based Platform 5‐Hydroxymethylfurfural

“…Over the past decade, ILs have gained wide recognition in the field of green synthesis, where they can act as environmentally benign solvents and support various chemical processes, including catalysis. [78][79][80] In 2020, taking advantage of the work by Riisager and co-workers, [75] Hallett and co-workers [81] extended the oxidation of HMF to DFF using oxygen (1 atm) with a TEMPO/CuCl catalyst system and a range of imidazolium-based ILs as solvents in the presence of a base at different HMF substrate loadings (10-50 %). ILs could overcome drawbacks derived from the toxicity of acetonitrile, separation and purification problems (e. g., TEMPO removal), low substrate loadings, or high oxygen pressures.…”

“…A modern and elegant way to immobilize homogeneous catalysts for recovery and recycling is the use of ionic liquids (ILs) as solvents or for biphasic mixtures. Over the past decade, ILs have gained wide recognition in the field of green synthesis, where they can act as environmentally benign solvents and support various chemical processes, including catalysis [78–80] . In 2020, taking advantage of the work by Riisager and co‐workers, [75] Hallett and co‐workers [81] extended the oxidation of HMF to DFF using oxygen (1 atm) with a TEMPO/CuCl catalyst system and a range of imidazolium‐based ILs as solvents in the presence of a base at different HMF substrate loadings (10–50 %).…”

Mechanism and conformation changes for the whole regeneration process of cellulose in pyridinium-based ionic liquids

“…Ionic liquid (IL) is a kind of material that is wholly composed of cation and anion. ILs become widely available for catalysis, separation, electrochemistry and medicine, because of their excellent thermal and chemical stability, low vapour pressure and strong designability (Cesari et al, 2019;Friess et al, 2021;McNeice et al, 2021;Md Moshikur et al, 2020;Tiago et al, 2020;Xiong et al, 2019;Zhang and Pesic, 2021). The premise of utilization of cellulose is to dissolve cellulose in solvent.…”