Donor functionalized ruthenium N-heterocyclic carbene complexes in alcohol oxidation reactions

Abstract

N-Pyridyl, N'-amido functionalized imidazolium bromides were obtained in high yields as an N-heterocyclic carbene (NHC) precursor and used as bidentate or a pincer ligands to obtain ruthenium complexes via a silver NHC transmetallation route. The incorporation of a phenyl group as an amido-N substituent (R = Ph) results in a bidentate coordination mode through the C(NHC) and N(pyridyl) donors, whereas in its absence (R = H) a pincer coordination mode was observed through the N(pyridyl)^C(NHC)^O(amido) donors. The ruthenium complex featuring a pincer type NCO coordination mode with a protic NH function adjacent to the coordinating O(amido) atom was found to efficiently catalyse the oxidation of activated alcohols effecting quantitative conversions within 30 minutes. However the oxidation of deactivated alcohols required longer reaction times to effect the quantitative transformation.

Alcohol oxidation reactions catalyzed by ruthenium–carbonyl complexes of thioarylazoimidazoles

“…The catalytic oxidation properties of ruthenium(II) carbonyl complexes containing bidentate NN, NO, OO, tridentate NNN, ONO, ONS and tetradentate NNNN, NNOO donor ligands have been much studied . Ru―NHC complexes were recently described as useful catalysts in the alcohol oxidation process . Ru(II) carbonyl complexes of 2‐hydroxy‐1‐naphthylideneimine show conversion of alcohols of 28.5–93.5%, iodosylbenzene complexes of ruthenium show 28–100% conversion of alcohols, cycloruthenated carbonyl complexes of arylazo phenolate show 11–99% conversion and Ru/Os carbonyl diiodo/dichloro complexes of arylazo imidazoles show 51–96% conversion, which are comparable to the catalytic activity of Ru(II) carbonyl complexes of 1‐alkyl‐2‐{( o ‐thioalkyl)phenylazo}imidazole of 37–97% in this work.…”

Solvent-Free Microwave-Assisted Peroxidative Oxidation of Alcohols Catalyzed by Iron(III)-TEMPO Catalytic Systems

“…Many catalytic methods have been developed for the oxidation of alcohols, the most commonly utilizing homogeneous catalysts based on different transition metals, such as Co [3], Mn [4,5], V [6], Cu [7][8][9][10], Fe [11][12][13][14], Mo [14], Ru [16,17], and Pd [18]. Unfortunately, most of the Electronic supplementary material The online version of this article (doi:10.1007/s10562-015-1616-2) contains supplementary material, which is available to authorized users.…”

“…Moreover, they suffer from the usual separation and recycling difficulties inherent to homogenous catalytic system. To eliminate the harmful wastes, the development of catalytic oxidation procedures that involve green oxidants, in particular dioxygen or peroxides [H 2 O 2 , tert-butylhydroperoxide ( t BuOOH or TBHP)], is a matter of current interest [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19].…”

Photofunctional Platinum Complexes Featuring N‐heterocyclic Carbene‐Based Pincer Ligands

“…A large panel of transition metal complexes bearing N-heterocyclic carbene (NHC)-based pincer ligands in neutral CNC, [1] CNN, [2] PCP, [3] SCS, [4] CSC; [5] anionic CNC; [6] and dianionic OCO [7] or NCO [8] bonding modes are known. Organometallic architectures comprising poly-NHC frameworks were also obtained in the last few years.…”