139-02-6Relevant articles and documents
Mononuclear Sulfido-Tungsten(V) Complexes: Completing the Tp*MEXY (M = Mo, W; E = O, S) Series
Sproules, Stephen,Eagle, Aston A.,George, Graham N.,White, Jonathan M.,Young, Charles G.
, p. 5189 - 5202 (2017)
Orange Tp*WSCl2 has been synthesized from the reactions of Tp*WOCl2 with boron sulfide in refluxing toluene or Tp*WS2Cl with PPh3 in dichloromethane at room temperature. Mononuclear sulfido-tungsten(V) complexes, Tp*WSXY {X = Y = Cl, OPh, SPh, SePh; X = Cl, Y = OPh; XY = toluene-3,4-dithiolate (tdt), quinoxaline-2,3-dithiolate (qdt); and Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate} were prepared by metathesis of Tp*WSCl2 with the respective alkali metal salt of X-/XY2-, or [NHEt3]2(qdt). The complexes were characterized by microanalysis, mass spectrometry, electrochemistry, and infrared (IR), electron paramagnetic resonance (EPR) and electronic absorption spectroscopies. The molecular structures of Tp*WS(OPh)2, Tp*WS(SePh)2, and Tp*WS(tdt) have been determined by X-ray crystallography. The six-coordinate, distorted-octahedral W centers are coordinated by terminal sulfido (WS = 2.128(2) - 2.161(1) ?), terdentate facial Tp*, and monodentate/bidentate O/S/Se-donor ligands. The sulfido-W(V) complexes are characterized by lower energy electronic transitions, smaller giso, and larger Aiso(183W) values, and more positive reduction potentials compared with their oxo-W(V) counterparts. This series has been probed by sulfur K-edge X-ray absorption spectroscopy (XAS), the spectra being assigned by comparison to Tp*WOXY (X = Y = SPh; XY = tdt, qdt) and time-dependent density functional theoretical (TD-DFT) calculations. This study provides insight into the electronic nature and chemistry of the catalytically and biologically important sulfido-W unit.
Structure and reactivity of sodium phenoxide - Following the course of the Kolbe-Schmitt reaction
Kunert, Michael,Dinjus, Eckhard,Nauck, Maria,Sieler, Joachim
, p. 1461 - 1465 (1997)
Solvent-free sodium phenoxide (NaOPh) crystallises as a polymer and forms a polymeric chain in the [001] direction. The low coordination of the sodium atoms, as evident in the crystal structure, is confirmed by the easy coordination of oxoligands (σ-donors). Hence, the four-membered ring chain of the solvent-free sodium phenoxide is separated by oxoligands, and forms partial structures as the polymer fragments. Thus, NaOPh crystallises in THF with the formation of an Na6O6 core, consisting of two face-fused heterocubes, and in N,N,N′,N′-tetrarnethyl urea (TMU) with the formation of a Na4O4 heterocubane. The solvent-free NaOPh-CO2 complex obtained from the addition of CO2 to a solution of sodium phenoxide is, when exposed to a temperature of 80 °C, subject to an irreversible phase transition, as demonstrated by FT-IR and DTA studies. The complex formed at 80 °C is, apparently, another intermediate of the Kolbe-Schmitt reaction. WILEY-VCH Verlag GmbH,.
Electrochemical reductive dehalogenation of ortho-halogenated phenols on Ag electrode by in situ FTIR
Yi, Jingmiao,Lu, Jinjin,Shi, Xiaohong,Song, Dandan,Zhao, Weijuan,Li, Meichao
, p. 3879 - 3882 (2014)
Electrochemical reductive dehalogenation reactions of ortho-halogenated phenols, namely, o-iodophenol (OIP), o-bromphenol (OBP) and o-chlorophenol (OCP) on Ag electrode in alkaline medium have been studied by in situ FTIR combined with cyclic voltammetry and computational calculations. The Ag electrode showed a high electrochemical activity for dehalogenation reactions of OBP and OIP in contrast with OCP under the similar conditions and the dehalogenation potential of OIP was more positive than OBP, reflecting more facile reduction of OIP on Ag electrode. On the basis of in situ FTIR of OCP on Ag electrode, it was not obvious and the electrochemical reduction reaction was quite weak. Therefore, the order of electrochemical reductive dehalogenation was OIP > OBP > OCP.
NHC-CDI Betaine Adducts and Their Cationic Derivatives as Catalyst Precursors for Dichloromethane Valorization
Sánchez-Roa, David,Mosquera, Marta E. G.,Cámpora, Juan
, p. 16725 - 16735 (2021/11/18)
Zwitterionic adducts of N-heterocyclic carbene and carbodiimide (NHC-CDI) are an emerging class of organic compounds with promising properties for applications in various fields. Herein, we report the use of the ICyCDI(p-Tol) betaine adduct (1a) and its cationic derivatives2aand3aas catalyst precursors for the dichloromethane valorization via transformation into high added value products CH2Z2(Z = OR, SR or NR2). This process implies selective chloride substitution of dichloromethane by a range of nucleophiles Na+Z-(preformed or generatedin situfrom HZ and an inorganic base) to yield formaldehyde-derived acetals, dithioacetals, or aminals with full selectivity. The reactions are conducted in a multigram-scale under very mild conditions, using dichloromethane both as a reagent and solvent, and very low catalyst loading (0.01 mol %). The CH2Z2derivatives were isolated in quantitative yields after filtration and evaporation, which facilitates recycling the dichloromethane excess. Mechanistic studies for the synthesis of methylal CH2(OMe)2rule out organocatalysis as being responsible for the CH2transfer, and a phase-transfer catalysis mechanism is proposed instead. Furthermore, we observed that1aand2areact with NaOMe to form unusual isoureate ethers, which are the actual phase-transfer catalysts, with a strong preference for sodium over other alkali metal nucleophiles.
Dehydrogenative Coupling of Aldehydes with Alcohols Catalyzed by a Nickel Hydride Complex
Eberhardt, Nathan A.,Wellala, Nadeesha P. N.,Li, Yingze,Krause, Jeanette A.,Guan, Hairong
, p. 1468 - 1478 (2019/04/17)
A nickel hydride complex, {2,6-(iPr2PO)2C6H3}NiH, has been shown to catalyze the coupling of RCHO and R′OH to yield RCO2R′ and RCH2OH, where the aldehyde also acts as a hydrogen acceptor and the alcohol also serves as the solvent. Functional groups tolerated by this catalytic system include CF3, NO2, Cl, Br, NHCOMe, and NMe2, whereas phenol-containing compounds are not viable substrates or solvents. The dehydrogenative coupling reaction can alternatively be catalyzed by an air-stable nickel chloride complex, {2,6-(iPr2PO)2C6H3}NiCl, in conjunction with NaOMe. Acids in unpurified aldehydes react with the hydride to form nickel carboxylate complexes, which are catalytically inactive. Water, if present in a significant quantity, decreases the catalytic efficiency by forming {2,6-(iPr2PO)2C6H3}NiOH, which causes catalyst degradation. On the other hand, in the presence of a drying agent, {2,6-(iPr2PO)2C6H3}NiOH generated in situ from {2,6-(iPr2PO)2C6H3}NiCl and NaOH can be converted to an alkoxide species, becoming catalytically competent. The proposed catalytic mechanism features aldehyde insertion into the nickel hydride as well as into a nickel alkoxide intermediate, both of which have been experimentally observed. Several mechanistically relevant nickel species including {2,6-(iPr2PO)2C6H3}NiOC(O)Ph, {2,6-(iPr2PO)2C6H3}NiOPh, and {2,6-(iPr2PO)2C6H3}NiOPh·HOPh have been independently synthesized, crystallographically characterized, and tested for the catalytic reaction. While phenol-containing molecules cannot be used as substrates or solvents, both {2,6-(iPr2PO)2C6H3}NiOPh and {2,6-(iPr2PO)2C6H3}NiOPh·HOPh are efficient in catalyzing the dehydrogenative coupling of PhCHO with EtOH.