- Gold(I) complexes with chloro(diaryl)silyl ligand. Stoichiometric reactions and catalysis for O-functionalization of organosilane
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An Au(I) complex with a chloro(diphenyl)silyl ligand [Au(SiPh2Cl)(PCy3)] (1a) is obtained from the reaction of Ph2SiH2 with [AuCl(PCy3)]. (4-FC6H4)2SiH2, (4-MeC6H4)2SiH2, and Ph2GeH2 react with [AuCl(PCy3)] to form complexes with the chlorodiarylsilyl ligand, [Au(SiAr2Cl)(PCy3)] (1b: Ar = C6H4-4-F, 1c: Ar = C6H4-4-Me) and with the chloro(diphenyl)germyl ligand, [Au(GePh2Cl)(PCy3)] (2a), respectively. Complex 1a reacts with H2O to form Ph2SiH(OH) and (Ph2SiH)2O, whereas the reaction of EtOH with 1a yields Ph2SiH(OEt) exclusively. Complex 1a catalyzes the hydrolysis of Ph2SiH2 ([Au]:[H2SiPh2]:[H2O] = 0.05:1.0:10.0) at 60 °C to yield Ph2SiH(OH) and (Ph2SiH)2O. The reaction of Ph2SiH2 with HOEt in the presence of a catalytic amount of 1a affords Ph2SiH(OEt). Both stoichiometric and catalytic reactions using 1a lead to the recovery of [AuCl(PCy3)] from the reaction mixture.
- Kanda, Atsushi,Osakada, Kohtaro,Tsuchido, Yoshitaka
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- Synthesis, characterization and catalytic oxidation of organosilanes with a novel multilayer polyoxomolybdate containing mixed-valence antimony
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Oxidation of organosilanes is one of the pivotal reactions in organic synthesis and the corresponding products of silanols are widely as raw materials in industrial processes. In this paper, a new type of polyoxomolybdate containing mixed-valence antimony, [SbVSbIII4Mo18O66]7? (1a), has been isolated as tetramethyl ammonium salt in aqueous solution. The compound was structurally characterized by FT-IR, XPRD, TG, XPS, ESI–MS etc. It is the first time that the containing mixed-valence antimony polyoxomolybdate was used as a heterogeneous catalyst to efficaciously catalyze the oxidation of organosilanes to silanols under mild reaction conditions. Furthermore, the catalyst was stable and maintained its catalytic activity after three reaction cycles.
- Wang, Yaping,Lu, Jingkun,Ma, Xinyi,Niu, Yanjun,Singh, Vikram,Ma, Pengtao,Zhang, Chao,Niu, Jingyang,Wang, Jingping
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p. 167 - 174
(2018/04/24)
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- Plasma-Assisted Synthesis of Monodispersed and Robust Ruthenium Ultrafine Nanocatalysts for Organosilane Oxidation and Oxygen Evolution Reactions
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We report a facile and general approach for preparing ultrafine ruthenium nanocatalysts by using a plasma-assisted synthesis at 2 supports. This gives robust catalysts with excellent activities in both organosilane oxidation and the oxygen evolution reaction.
- Gnanakumar, Edwin S.,Ng, Wesley,Co?kuner Filiz, Bilge,Rothenberg, Gadi,Wang, Sheng,Xu, Hualong,Pastor-Pérez, Laura,Pastor-Blas, M. Mercedes,Sepúlveda-Escribano, Antonio,Yan, Ning,Shiju, N. Raveendran
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p. 4159 - 4163
(2017/10/23)
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- Cu3(BTC)2 catalyzed oxidation of silane to silanol using TBHP or water as oxidants
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In the present work, a series of metal organic frameworks are examined for the conversion of Si-H to Si-OH using either t-butylhydroperoxide (TBHP) or water as oxidants. The reaction is optimized using dimethylphenylsilane (1) as a model substrate. It is observed that Cu3(BTC)2 (BTC: 1,3,5-benzenetricarboxylate) exhibits a comparable activity with Zr(BDC) (BDC: 1,4-benzenedicarboxylate) while the activity of Fe(BTC) is lower than Cu3(BTC)2 using TBHP as oxidant. On the other hand, the reaction of 1 with water in the presence of Cu3(BTC)2 as a catalyst showed complete conversion of 1 with 99% selectivity to the corresponding silanol, but other MOFs like Fe(BTC) and Zr(BDC) are inactive under identical reaction conditions. A series of control experiments indicate that Cu2+ is essential to convert 1 to 2 under the present experimental conditions. Further, Cu2+ in Cu3(BTC)2 acts as redox centre with TBHP whereas it behaves as a Lewis acid using water as oxidant. High conversion and selectivity is observed for all the silanes studied under the present experimental conditions. The catalyst stability is assessed by powder XRD, FT-IR and SEM images and observing no structural deterioration of Cu3(BTC)2 either in TBHP or water as oxidants. Furthermore, hot filtration test indicated the absence of copper under the present reaction conditions, thus confirming the stability of Cu3(BTC)2.
- Anbu, Nagaraj,Dhakshinamoorthy, Amarajothi
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p. 145 - 153
(2017/07/26)
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- Metal-free catalytic hydrogen production from a polymethylhydrosilane-water mixture
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Hydrogen gas is the most promising carbon-free energy carrier although its on-demand generation remains a formidable challenge. One of the potential pathways for generating hydrogen is through hydrolytic oxidation of organosilanes. Here, we demonstrate that the hydroxide ion OH- serves as a potent room-temperature metal-free catalyst in the hydrolytic oxidation of polymethylhydrosilane, PMHS to hydrogen gas and the corresponding silanol with a turnover number and turnover frequency in excess of 200 and 8 min-1 respectively. Kinetic studies suggest the hydrogen generation rate is first order with respect to PMHS and OH- but zero order with respect to water. The first step of the reaction, where the Si center of PMHS is attacked by the OH- ion, is believed to be the rate-determining step.
- Yap, Chew Pheng,Poh, Hwa Tiong,Fan, Wai Yip
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p. 5903 - 5906
(2016/02/05)
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- Kinetics and mechanisms of the reactions of transient silylenes with amines
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The N-H insertion reactions of dimethyl-, diphenyl-, and dimesitylsilylene (SiMe2, SiPh2, and SiMes2, respectively) with n-butylamine (BuNH2) and diethylamine (Et2NH) were studied in hexanes by steady-state and laser photolysis methods. The process begins with the formation of the corresponding Lewis acid-base complexes, which decayed with second-order kinetics at rates that show modest sensitivity to silylene and amine structures. The complexation process, which was also studied using triethylamine (Et3N), proceeds at rates close to the diffusion limit, but the rate constants vary systematically with steric bulk in the amine. Equilibrium constants were determined for the complexation of Et2NH and Et3N with SiMes2, which proceeds reversibly. The complexes of SiMe2 and SiPh2 with BuNH2 and Et2NH decayed with pseudo-first-order rate coefficients in the 104-105s-1 range. This is consistent with upper limits of about 106M-1s-1 for the rate constants for amine-catalyzed H-migration, which is thought to be the dominant mechanism for product formation from the complexes. The results are compared to published kinetic data for the O-H insertion reactions of these silylenes with alcohols, which also proceeds via initial complexation followed by catalytic proton transfer. The results indicate that catalyzed H-transfer in the amine complexes is at least 104 times slower than the analogous process in silylene-MeOH complexes. The experimental data are compared to the results of theoretical calculations of the SiMe2+NH2Me and SiMe 2+MeOH potential energy surfaces, carried out at the Gaussian-4 and B3LYP/6-311+G(d,p) levels of theory.
- Kostina, Svetlana S.,Singh, Tishaan,Leigh, William J.
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experimental part
p. 937 - 946
(2012/01/13)
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- Catalysis by cationic oxorhenium(v): Hydrolysis and alcoholysis of organic silanes
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The cationic [2-(2′-hydroxyphenyl)-2-oxazolinato(-2)]oxorhenium(v) complex 1 promotes oxidative dehydrogenation of organosilanes with water and alcohols in a catalytic manner to give excellent yields of silanols and silyl ethers, respectively. The reactions proceed conveniently under ambient and open-flask conditions with low catalyst loading (≤1 mol%). The scope of the reaction with water is quite broad and includes aliphatic, aromatic, tertiary, secondary and primary silanes. The rate of reaction depends on the catalyst and silane concentrations and kinetic isotope effect measurements demonstrate involvement of the Si-H bond in the activated complex. The most influential factor on the silane affecting reactivity is steric hindrance and a quantitative correlation with the Taft steric parameter (E) is presented. A combination of kinetic data and isotope labelling results are used to discuss plausible mechanisms for the oxidative dehydrogenation reaction pathway.
- Corbin, Rex A.,Ison, Elon A.,Abu-Omar, Mahdi M.
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experimental part
p. 2850 - 2855
(2009/06/27)
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- Hydrogen production from hydrolytic oxidation of organosilanes using a cationic oxorhenium catalyst
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We describe herein the novel application of a transition metal oxo complex, a cationic oxorhenium(V) oxazoline, in the production of molecular hydrogen (H2) from the catalytic hydrolytic oxidation of organosilanes. The main highlights of the reaction are quantitative hydrogen yields, low catalyst loading, ambient conditions, high selectivity for silanols, water as the only co-reagent, and no solvent requirement. The amount of hydrogen produced is proportional to the water stoichiometry. Thus, reaction mixtures of polysilyl organics such as HC(SiH3)3 and water contain potentially >6 wt % hydrogen. Kinetic and isotope labeling experiments have revealed a new mechanistic paradigm for the activation of Si-H bonds by oxometalates. Copyright
- Ison, Elon A.,Corbin, Rex A.,Abu-Omar, Mahdi M.
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p. 11938 - 11939
(2007/10/03)
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