Sequential Formation of [Ru(IPr)2(CO)H(OH2)]+ and [Ru(IPr)(η6-C6H6)(CO)H]+ upon Protonation of Ru(IPr)2(CO)H(OH) (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene)

Saker, Olly; Mahon, Mary F.; Warren, John E.; Whittlesey, Michael K.

doi:10.1021/om801150v

Cited by 23 publications

(7 citation statements)

References 40 publications

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“…However, recombination of pCy to cpxF leads to an even more stable Ru–hydride complex cpxD . Our spectroscopic studies support the presence of cpxD with in situ 1 H NMR spectroscopy detecting the hydride signal at −10.19 ppm. − Subsequently, hydride transfer to reduce the nitrobenzene could operate under two pathways (i.e., inner- or outer-sphere). The free energy barrier for inner-sphere hydride transfer through TS1-is is 31.9 kcal/mol while the outer-sphere via TS1-os is lower at 22.9 kcal/mol relative to intermediates cpxJ and cpxD , respectively.…”

Section: Resultssupporting

confidence: 64%

Half-Sandwich Ruthenium Phenolate–Oxazoline Complexes: Experimental and Theoretical Studies in Catalytic Transfer Hydrogenation of Nitroarene

et al. 2017

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In this work, five ruthenium complexes [Ru(p-cymene)LCl] containing phenolate-oxazoline ligands [ 4); and 2-(4,4-dimethyl-4,5-dihydrooxazol-2-yl)phenol ( 5)] were synthesized and characterized. The solid-state structures of all ruthenium complexes were determined by single-crystal X-ray diffraction. The catalytic activities of these complexes in the transfer hydrogenation reaction of nitroarene to aniline were investigated. Aniline and their derivatives were obtained in good to excellent yields with isopropanol as the hydride source. The present protocol provides an environmentally benign synthetic method for the reduction of nitroarenes to anilines without employing harsh reaction conditions. Theoretical studies employing density functional theory were carried with the aim to propose a feasible reaction mechanism and to draw insights into the reactivity of the half-sandwich ruthenium catalyst.

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Section: Resultssupporting

confidence: 64%

Half-Sandwich Ruthenium Phenolate–Oxazoline Complexes: Experimental and Theoretical Studies in Catalytic Transfer Hydrogenation of Nitroarene

et al. 2017

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“…We have previously communicated the reaction of 4a with SIMes to effect replacement of phosphine, yielding RuHCl(SIMes)(Im(OMe) 2 )(PPh 3 ) ( 7 ) . This is a rare example of a cis -bis-carbene Ru hydride complex; although several other Ru bis-carbene complexes are known to adopt a cis disposition, ,− the majority of such species adopt a trans- NHC geometry. ,− Dixneuf and co-workers prepared cis -carbene Ru derivatives using a sterically unencumbered carbene, while Whittlesey et al studied a series of Ru cis -bis-carbene complexes employing NHCs with N-bound isopropyl or cyclohexyl substituents.…”

Section: Resultsmentioning

confidence: 99%

Ruthenium Carbene–Diether Ligand Complexes: Catalysts for Hydrogenation of Olefins

et al. 2013

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A series of carbene–diether ligands were prepared and the corresponding Ag salts used to prepare the complexes RuHCl(PPh3)2(Im(OR)2) (Im(OR)2 = C3H2(NCH2CH2OR)2; R = Me (4a), t-Bu (4b), tert-hexyl (4c), Ph (4d), 2,6-i-Pr2C6H3 (4e)). In an analogous fashion the species RuHCl(PPh3)2(Y2Im(OMe)2) (Y2Im(OMe)2 = Y2C3(NCH2CH2OMe)2; Y2 = C6H4 (4f), Y = Cl (4g), Me (4h)) were also synthesized. Similarly RuHCl(CO)(PPh3)2(Im(OMe)2) (5) was prepared and readily converted to RuHCl(CO)(SIMes)(Im(OMe)2) (6) via treatment with SIMes. The reaction of 4a with SIMes afforded RuHCl(SIMes)(Im(OMe)2)(PPh3) (7), which reacts subsequently with Na[BPh4] to give [RuH(Im(OMe)2)(SIMes)][(η6-Ph)BPh3] (8). In a series of tests, the species 4a–h, 5, 6, and 8 were shown to catalyze the hydrogenations of 1-hexene, cyclohexene, and dimethyl itaconate. From the activity of 4a–h it is clear that the capability of the carbene–ether substituents to coordinate to the metal as well as electron-donating substituents on the carbene fragment enhances catalytic activity. Other variations such as in 5, 6, and 8 resulted in terminal-olefin-selective hydrogenation catalysts, although the zwitterionic species 8 showed significantly enhanced activity.

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“…This restriction largely originates from the high susceptibility of the M−C NHC bond toward reductive elimination under reducing conditions . Imidazolium elimination and heterogenization of the catalyst system are particularly pronounced in processes involving sufficiently stable intermediates that comprise metal-bound hydride, , alkyl, or aryl groups …”

Section: Introductionmentioning

confidence: 99%

Chelating NHC Ruthenium(II) Complexes as Robust Homogeneous Hydrogenation Catalysts

et al. 2009

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A series of ruthenium(II) complexes have been prepared by using bidentate chelating N-heterocyclic carbene (NHC) ligands that feature different donor groups E (E=olefin, thioether, carboxylate, and NHC). Rigid coordination of all donor sites was concluded from NMR spectroscopy, and the electronic impact of the donor group was evaluated by electrochemical analyses. The chelating donor group had a strong influence on the activity of the metal center in catalyzing direct hydrogenation of styrene. A thioether group or a second NHC donor site essentially deactivates the metal center. Complexes comprising a NHC tethered with an olefin or a carboxylate group showed appreciable activity, though only the carboxylate-functionalized system proved to be a precursor for homogeneous hydrogenation. According to in situ high-pressure NMR analyses, complexes featuring a carboxylate chelating group are remarkably resistant toward reductive elimination even under strongly reducing conditions and may, therefore, be used repeatedly.

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Sequential Formation of [Ru(IPr)₂(CO)H(OH₂)]⁺ and [Ru(IPr)(η⁶-C₆H₆)(CO)H]⁺ upon Protonation of Ru(IPr)₂(CO)H(OH) (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene)

Cited by 23 publications

References 40 publications

Half-Sandwich Ruthenium Phenolate–Oxazoline Complexes: Experimental and Theoretical Studies in Catalytic Transfer Hydrogenation of Nitroarene

Half-Sandwich Ruthenium Phenolate–Oxazoline Complexes: Experimental and Theoretical Studies in Catalytic Transfer Hydrogenation of Nitroarene

Ruthenium Carbene–Diether Ligand Complexes: Catalysts for Hydrogenation of Olefins

Chelating NHC Ruthenium(II) Complexes as Robust Homogeneous Hydrogenation Catalysts

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