85698-56-2Relevant articles and documents
Ruthenium(II)–Pyridylimidazole Complexes as Photoreductants and PCET Reagents
Pannwitz, Andrea,Prescimone, Alessandro,Wenger, Oliver S.
supporting information, p. 609 - 615 (2017/02/05)
Complexes of the type [Ru(bpy)2pyimH]2+[bpy = 2,2′-bipyridine; pyimH = 2-(2-pyridyl)imidazole] with various substituents on the bpy ligands can act as photoreductants. Their reducing power in the ground state and in the long-lived3MLCT excited state is increased significantly upon deprotonation, and they can undergo proton-coupled electron transfer (PCET) in the ground and excited state. PCET with both the proton and electron originating from a single donor resembles hydrogen atom transfer (HAT) and can be described thermodynamically by formal bond dissociation free energies (BDFEs). Whereas the class of complexes studied herein has long been known, their N–H BDFEs have not been determined even though this is important in view of assessing their reactivity. Our study demonstrates that the N–H BDFEs in the3MLCT excited states are between 34 and 52 kcal mol–1depending on the chemical substituents at the bpy spectator ligands. Specifically, we report on the electrochemistry and PCET thermochemistry of three heteroleptic complexes in 1:1 (v/v) CH3CN/H2O with CF3, tBu, and NMe2substituents on the bpy ligands.
Design of an Os Complex-Modified Hydrogel with Optimized Redox Potential for Biosensors and Biofuel Cells
Pinyou, Piyanut,Ruff, Adrian,P?ller, Sascha,Ma, Su,Ludwig, Roland,Schuhmann, Wolfgang
supporting information, p. 5319 - 5326 (2016/04/09)
Multistep synthesis and electrochemical characterization of an Os complex-modified redox hydrogel exhibiting a redox potential ≈+30 mV (vs. Ag/AgCl 3 m KCl) is demonstrated. The careful selection of bipyridine-based ligands bearing N,N-dimethylamino moieties and an amino-linker for the covalent attachment to the polymer backbone ensures the formation of a stable redox polymer with an envisaged redox potential close to 0 V. Most importantly, the formation of an octahedral N6-coordination sphere around the Os central atoms provides improved stability concomitantly with the low formal potential, a low reorganization energy during the Os3+/2+ redox conversion and a negligible impact on oxygen reduction. By wiring a variety of enzymes such as pyrroloquinoline quinone (PQQ)-dependent glucose dehydrogenase, flavin adenine dinucleotide (FAD)-dependent glucose dehydrogenase and the FAD-dependent dehydrogenase domain of cellobiose dehydrogenase, low-potential glucose biosensors could be obtained with negligible co-oxidation of common interfering compounds such as uric acid or ascorbic acid. In combination with a bilirubin oxidase-based biocathode, enzymatic biofuel cells with open-circuit voltages of up to 0.54 V were obtained.
Dehydrogenative Coupling of 4-Substituted Pyridines Catalyzed by a Trinuclear Complex of Ruthenium and Cobalt
Nagaoka, Masahiro,Kawashima, Takashi,Suzuki, Hiroharu,Takao, Toshiro
, p. 2348 - 2360 (2016/08/02)
The dehydrogenative coupling of 4-substituted pyridines catalyzed by a heterometallic trinuclear complex composed of Ru and Co, (Cp?Ru)2(Cp?Co)(μ-H)3(μ3-H) (1, Cp? = η5-C5Me5), was investigated. When the pyridine substrate contains an electron-donating group at the 4-position, complex 1 showed a high catalytic activity compared to di- and triruthenium complexes (Cp?Ru)2(μ-H)4 (4) and (Cp?Ru)3(μ-H)3(μ3-H)2 (5). The catalytic activity of 1 was also remarkably higher than the congeners of other group 9 metals, Ru2Rh (2) and Ru2Ir analogues (3). The distinctive reactivity of 1 was attributed to a paramagnetic intermediate, (Cp?Ru)2{(dmbpy)Co}(μ-H)(μ3-H)2 (12, dmbpy = 4,4′-dimethyl-2,2′-bipyridine), which was formed by the reaction of 1 with 4-picoline accompanied by the dissociation of the Cp? at the Co atom. The reaction of 12 with unsubstituted pyridine resulted in the elimination of 4,4′-dimethyl-2,2′-bipyridine, indicating that the Co atom in 12 acts as a dissociation site. In contrast to the reaction of 1 with 4-picoline, the reaction of 2 and 3 with 4-picoline afforded the corresponding μ3-pyridyl complexes (Cp?Ru)2(Cp?M)(μ-H)3(μ3-η2(||)-C5H3NCH3) (15, M = Rh; 16, M = Ir). 4-(Trifluoromethyl)pyridine was not dimerized by 1; however, a similar μ3-pyridyl complex, (Cp?Ru)2(Cp?Co)(μ-H)3(μ3-η2(||)-C5H3NCF3) (13), was obtained. The stability of the μ3-pyridyl complex is probably one of the reasons for the low catalytic activity of 2 and 3 in the coupling reaction.
Exchange of pyridine and bipyridine ligands in trimethylplatinum(iv) iodide complexes: Substituent and solvent effects
Ghosh, Biswa Nath,Schlecht, Sabine
, p. 101900 - 101909 (2015/12/08)
A series of mononuclear trimethylplatinum(iv) complexes of bipyridine ligands, [PtMe3(L-L)I] (L-L = bipy, 4-Mebipy, 4-MeObipy and 4-Me2Nbipy) has been synthesized by the reaction of trimethylplatinum(iv) iodide with bipyridine ligands L-L in an equimolar ratio. Also, treatment of mononuclear trimethylplatinum(iv) iodide complexes of pyridine ligands, [PtMe3L2I] (L = py, 4-Mepy, 4-MeOpy and 4-Me2Npy) with the corresponding bipyridine ligands leads to the exchange of the pyridines by the bipyridine ligands, thereby resulting in the formation of the more stable chelate bipyridine complexes. The ligand-exchange reactions have been studied by 1H NMR spectroscopy. The 1H NMR spectra of a 1: 1 mixture of mononuclear pyridine complexes [PtMe3L2I] and corresponding bipyridine ligands L-L reveal the formation of two chelate bipyridine complexes, [PtMe3(L-L)I] and [PtMe3(L-L)L]I, in solution. Speciation of the pyridine and bipyridine complexes in solution was found to be dependent on the substituent as well as on the nature of the solvent. Furthermore, crystal structures of three bipyridine complexes [PtMe3(L-L)I] (L-L = 4-Mebipy, 4-MeObipy and 4-Me2Nbipy) have also been investigated here.
Strongly blue luminescent cationic iridium(III) complexes with an electron-rich ancillary ligand: Evaluation of their optoelectronic and electrochemiluminescence properties
Ladouceur, Sebastien,Swanick, Kalen N.,Gallagher-Duval, Shawn,Ding, Zhifeng,Zysman-Colman, Eli
, p. 5329 - 5343 (2013/11/06)
Two strongly blue luminescent cationic heteroleptic iridium complexes 1b and 2b bearing a 4,4′-bis(dimethylamino)-2,2′-bipyridine (dmabpy) ancillary ligand and either 1-benzyl-4-(2,4-difluorophenyl)-1H-1,2,3-triazole (dFphtl) or 2-(2,4-difluorophenyl)-5-methylpyridine (dFMeppyH), respectively, have been synthesized and fully characterized. In comparison with other analogues, the interplay of the triazole unit with the dmabpy unit and methylation of the pyridine ring are discussed with respect to the photophysical, electrochemical, and electrochemiluminescent (ECL) properties of the complexes. The two complexes, 1b and 2b, are blue emitters with λmax = 495 and 494 nm, respectively. The nature of the excited states was established by various photophysical and photochemical experiments as well as DFT calculations. Both complexes emit from a ligand-centered state, however, the emission of 1b possesses significant charge-transfer character, which is absent in 2b. The presence of the methyl group on the cyclometalating ligand leads only to a modest increase in the radiative rate constant, k r, but otherwise does not appreciably influence the optoelectronic properties of the complex compared with the non-methylated analogue. In contrast, the efficacy of the ECL emission when scanning to 2.50 V is strongly influenced by the presence of the methyl group. ECL emission is also enhanced in complexes bearing dmabpy ancillary ligands compared with those containing dtBubpy ligands. The two complexes exhibit similar electrochemical behavior. Incorporation of the dmabpy ligand shifts both the oxidation and reduction cathodically. The combination of the dmabpy and dFphtl groups increases the redox potential difference and thus the HOMO-LUMO gap but the emission is not further blueshifted. Thus, the structural modification of the cyclometalating ligand, although only modestly tuning the emission energy, modulates the nature of the excited state and the efficiency of the ECL process. The synthesis, photophysical, electrochemical, and electrochemiluminescent properties of two highly emissive cationic blue-emitting Ir complexes are reported. Variation of the ligand results in a change in the nature of the emission. The decoration on both the cyclometalating and ancillary ligands strongly influences the ECL efficiencies. A detailed DFT/TDDFT study corroborates experiment. Copyright
Cu-catalyzed selective mono-N-pyridylation: Direct access to 2-aminoDMAP/sulfonamides as bifunctional organocatalysts
Isik, Murat,Tanyeli, Cihangir
supporting information, p. 1604 - 1611 (2013/03/28)
Direct and selective mono-N-pyridylation of trans-(R,R)-cyclohexane-1,2- diamine is described here. Facile preparation of a novel chiral 2-aminoDMAP core catalaphore via Cu catalysis has led to the development of various sulfonamide/2-aminoDMAPs as bifunctional acid/base organocatalysts (most in two steps overall), which have been shown to very effectively promote asymmetric conjugate addition of acetylacetone to trans-β-nitroolefins with good to excellent yields (87-93%) and enantioselectivites (up to 99%).
Synthesis of triruthenium complexes containing a triply bridging pyridyl ligand and its transformations to face-capping pyridine and perpendicularly coordinated pyridyl ligands
Takao, Toshiro,Kawashima, Takashi,Kanda, Hideyuki,Okamura, Rei,Suzuki, Hiroharu
experimental part, p. 4817 - 4831 (2012/10/08)
Unlike the reactions of carbonyl clusters with pyridine leading to the formation of μ-pyridyl complexes, the reaction of the triruthenium pentahydrido complex {Cp*Ru(μ-H)}3(μ3-H) 2 (Cp* = η5-C5Me5) (1) with pyridines provided μ3-η2(//)-pyridyl complexes, (Cp*Ru)3(μ-H)4(μ3- η2(//)-RC5H3N) (2a, R = H; 2b, R = 4-COOMe; 2c, R = 4-COOEt; 2d, R = 4-Me; 2e, R = 5-Me), in which the molecular plane of the pyridyl group was tilted with respect to the Ru3 plane. Electron-rich metal centers of the trimetallic core enabled back-donation to the pyridyl group, which caused the additional π-coordination of the C=N bond. The electron-rich metal centers of 2a-2c also promoted further transformation into face-capping pyridine complexes {Cp*Ru(μ-H)} 3(μ3-η2:η2: η2-RC5H4N) (3a, R = H; 3b, R = 4-COOMe; 3c, R = 4-COOEt) upon heating. In contrast, the thermolysis of 2d did not afford a face-capping picoline complex because of the poor electron-accepting ability of the picolyl moiety. Instead, the coordinatively unsaturated μ3- picolyl complex (Cp*Ru)3(μ-H)2(μ3- η2-4-Me-C5H3N) (4d) was obtained. Owing to its unsaturated nature, 4d can react with γ-picoline to yield 4,4′-dimethyl-2,2′-bipyridine. Although the reaction rate was slow, complex 1 catalyzed the dehydrogenative coupling of 4-substituted pyridines containing an electron-donating group. The protonation of 2a also afforded the coordinatively unsaturated pyridyl complex [(Cp*Ru)3(μ-H) 2(μ3-H)(μ3-η2: η2(⊥)-C5H4N)]+ (5a), but the coordination mode of the pyridyl group in 5a was completely different from that in 4d. The pyridyl moiety in 5a was coordinated on one of the Ru-Ru bonds in a perpendicular fashion. The methylation of the face-capping pyridine complex 3a, which led to the formation of the N-methyl pyridinium complex [(Cp*Ru)3(μ-H)3 (μ3- η2:η2:η2-C5H 5NMe)]+ (7b) was also examined. NMR studies on 7b as well as X-ray diffraction studies suggested enhanced back-donation to the pyridinium moiety because of the localized cationic charge on the nitrogen atom.
Dehydrogenative coupling of 4-substituted pyridines catalyzed by diruthenium complexes
Kawashima, Takashi,Takao, Toshiro,Suzuki, Hiroharu
, p. 11006 - 11007 (2008/03/13)
Coupling reaction of 4-substituted pyridines via direct C-H bond activation was achieved by the use of diruthenium complexes 1 and 2. These reactions provide a variety of functionalized bipyridines in a selective manner without the formation of terpyridines. Copyright
First direct C-2-lithiation of 4-DMAP. Convenient access to reactive functional derivatives and ligands
Cuperly, David,Gros, Philippe,Fort, Yves
, p. 238 - 241 (2007/10/03)
The first direct α-lithiation of 4-DMAP has been peformed via reaction with the BuLi-Me2N(CH2)2-OLi (BuLi-LiDMAE) reagent. This new methodology avoids the use of a activation-lithiation-regeneration sequence or halogen-met
Process for producing aldehydes by hydroformylation of olefins
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, (2008/06/13)
PCT No. PCT/EP97/00372 Sec. 371 Date Jul. 15, 1998 Sec. 102(e) Date Jul. 15, 1998 PCT Filed Jan. 28, 1997 PCT Pub. No. WO97/28113 PCT Pub. Date Aug. 7, 1997A process for the preparation of aldehydes or aldehydes and alcohols by hydroformylation of olefins containing more than 3 carbon atoms comprising a hydroformylation stage, in which the olefin is hydroformylated under a pressure of from 50 to 1000 bar and at a temperature of from 50 DEG to 180 DEG C. using a rhodium catalyst that is dissolved in a homogeneous reaction medium and by extraction of the rhodium catalyst, in which a) the hydroformylation is carried out in the presence of a rhodium complex, which exhibits, as ligand, a polydentate, organic nitrogen compound that is free from phosphorus and capable of forming complexes with Group VIII metals, which additionally contains at least one tertiary nitrogen radical that is capable of being protonized by a weak acid, b) the effluent of the hydroformylation stage is subjected to extraction with an aqueous solution of a distillable acid optionally following separation or partial separation of aldehydes and alcohols, (c) the aqueous acid extract is subjected to thermal treatment in the presence of an organic solvent or solvent mixture, which is inert under the hydroformylation conditions, with distillation of the aqueous acid, by means of which treatment the complex is deprotonized and transferred to the organic phase, and (d) the organic phase containing the catalyst complex is recycled to the hydroformylation stage.
