- Optical properties of trinuclear metal chalcogenolate complexes-room temperature NIR fluorescence in [Cu2Ti(SPh)6(PPh3)2]
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The optical properties of four isostructural trinuclear chalcogenolato bridged metal complexes [Cu2Sn(SPh)6(PPh3)2], [Cu2Sn(SePh)6(PPh3)2], [Ag2Sn(SPh)6(PPh3)2] and [Cu2Ti(SPh)6(PPh3)2] have been investigated by absorption and photoluminescence spectroscopy and time-dependent density functional theory (TDDFT) calculations. All copper-tin compounds demonstrate near-infrared (NIR) phosphorescence at ~900-1100 nm in the solid state at low temperature, which is nearly absent at ambient temperature. Stokes shifts of these emissions are found to be unusually large with values of about 1.5 eV. The copper-titanium complex [Cu2Ti(SPh)6(PPh3)2] also shows luminescence in the NIR at 1090 nm but with a much faster decay (τ ~ 10 ns at 150 K) and a much smaller Stokes shift (ca. 0.3 eV). Even at 295 K this fluorescence is found to comprise a quantum yield as high as 9.5%. The experimental electronic absorption spectra well correspond to the spectra simulated from the calculated singlet transitions. In line with the large Stokes shifts of the emission spectra the calculations reveal for the copper-tin complexes strong structural relaxation of the excited triplet states whereas those effects are found to be much smaller in the case of the copper-titanium complex.
- Kühn, Michael,Lebedkin, Sergei,Weigend, Florian,Eichh?fer, Andreas
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- A simple and efficient room temperature silylation of diverse functional groups with hexamethyldisilazane using CeO2 nanoparticles as solid catalysts
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In this study, a mild and efficient method is developed for the silylation of diverse functional groups using CeO2 nanoparticles (n-CeO2) as solid catalysts with hexamethyldisilazane (HMDS) as silylating agent at room temperature. Alcohols, phenols and acids are silylated to their respective silyl derivatives with faster reaction rate while amines and thiols required relatively longer reaction time. Moreover, the solid catalyst is easily be separated from the reaction mixture and recycled more than five times without any obvious decay in its activity. Powder X-ray diffraction (XRD), transmission electron microscope (TEM), UV–vis diffuse reflectance spectra (UV-DRS) and Raman analyses revealed identical structural integrity, particle size, absorption edge and valence state for the reused solid compared to the fresh solid catalyst.
- Anbu, Nagaraj,Vijayan, Chellappa,Dhakshinamoorthy, Amarajothi
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- Indium Catalyzed Hydrofunctionalization of Styrene Derivatives Bearing a Hydroxy Group with Organosilicon Nucleophiles
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Hydrofunctionalization is one of the most important transformation reactions of alkenes. Herein, we describe the development of an indium-triiodide-catalyzed hydrofunctionalization of alkenes bearing a hydroxy group using various types of organosilicon nucleophiles. Indium triiodide was the most effective catalyst, whereas typical Lewis acids such as TiCl4, AlCl3, and BF3·OEt2 were ineffective. Many functional groups were successfully introduced, and these resulted in yields of 31-86%. Various styrene derivatives were also applicable to this reaction. Mechanistic investigation revealed that the present hydrofunctionalization proceeded through Br?nsted acid-catalyzed intramolecular hydroalkoxylation of alkenes followed by InI3-catalyzed substitution reaction of cyclic ether intermediates.
- Kita, Yuji,Yata, Tetsuji,Nishimoto, Yoshihiro,Yasuda, Makoto
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p. 740 - 753
(2018/01/28)
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- Reductive silylation of Cp?UO2(MesPDIMe) promoted by Lewis bases
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Functionalization of the uranyl moiety (UO22+) in Cp?UO2(MesPDIMe) (1-PDI) (MesPDIMe = 2,6-((Mes)NCMe)2C5H3N; Mes = 2,4,6-triphenylmethyl), which bears a reduced, monoanionic pyridine(diimine) ligand, is reported. Silylating reagents, R3Si-X (R = Me, X = Cl, I, OTf, SPh; R = Ph, X = Cl), effectively add across the strong OUO bonds in the presence of the Lewis base, OPPh3, generating products of the form (R3SiO)2UX2(OPPh3)2 (R = Me, X = I (2-OPPh3), Cl (3-OPPh3), SPh (5-OPPh3), OTf (6-OPPh3); R = Ph, X = Cl (4-OPPh3)). During this transformation, reduction to uranium(iv) occurs with loss of (Cp?)2 and MesPDIMe, each of which acts as a one-electron source. In the reaction, the Lewis base serves to activate the silyl halide, generating a more electrophilic silyl group, as determined by 29Si NMR spectroscopy, that undergoes facile transfer to the oxo groups. Complete U-O bond scission was accomplished by treating the uranium(iv) disiloxide compounds with additional silylating reagent, forming the family (Ph3PO)2UX4. All compounds were characterized by 1H NMR, infrared, and electronic absorption spectroscopies. X-ray crystallographic characterization was used to elucidate the structures of 2-OPPh3, 4-OPPh3, 5-OPPh3, and 6-OPPh3.
- Kiernicki,Harwood,Fanwick,Bart
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p. 3111 - 3119
(2016/02/20)
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- Novel protocol for the synthesis of organic ammonium tribromides and investigation of 1,1′-(Ethane-1,2-diyl)dipiperidinium bis(tribromide) in the silylation of alcohols and thiols
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A novel and efficient protocol for the synthesis of organic ammonium tribromides (OATBs) is developed by using inexpensive and eco-friendly periodic acid as an oxidant for the conversion of Br-to Br3-. The method does not use any mineral acid and metal oxidants. The protocol is utilized to synthesize a new bis(tribromide) viz., 1,1′-(ethane-1,2-diyl)dipiperidinium bis(tribromide) (EDPBT). EDPBT is investigated as a catalyst in the silylation of alcohols and thiols by HMDS (hexamethyldisilazane) under solvent-free conditions.
- Dey, Rupa R.,Paul, Bappi,Dhar, Siddhartha S.,Bhattacharjee, Sushmita
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supporting information
p. 1545 - 1547
(2015/02/19)
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- Synthesis and characterization of 2-carboxyethyltriphenyl phosphonium tribromide and its application as catalyst in silylation of alcohols and thiols under solvent-free condition
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A phosphonium-based catalyst, 2-carboxyethyltriphenyl phosphonium tribromide (CTPTB), has been synthesized by reacting triphenyl phosphine with acrylic acid and potassium bromide under solvent-free condition followed by oxidation of Br- to with KMnO4. This hitherto unknown tribromide reagent is characterized by ultraviolet-visible, Fourier transform-infrared, 1H NMR, and 31P NMR spectroscopy. Its efficacy as catalyst is established by investigating its catalytic activity in silylation of alcohols and thiols by hexamethyl disilazane (HMDS). It is found to be a very good catalyst and selectively and efficiently catalyzes the silylation reactions. Copyright
- Dey, Rupa Rani,Dhar, Siddhartha Sankar
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supporting information
p. 2355 - 2363
(2014/07/22)
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- Poly(N-bromobenzene-1,3-disulfonamide) and N,N,N′,N′-tetrabromobenzene-1,3-disulfonamide as novel catalytic reagents for silylation of alcohols, phenols, and thiols using hexamethyldisilazane
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Poly(N-bromobenzene-1,3-disulfonamide) [PBBS] and N,N,N′,N′-tetrabromobenzene-1,3-disulfonamide [TBBDA] are effective catalysts for the silylation of alcohols, phenols, and thiols in the presence of hexamethyldisilazane with, or without solvent, and also under microwave irradiation.
- Ghorbani-Vaghei, Ramin,Zolfigol, Mohammad Ali,Chegeny, Mahdieh,Veisi, Hojat
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p. 4505 - 4508
(2007/10/03)
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- Efficient Preparation of a Key Intermediate in the Synthesis of Roxifiban by Enzymatic Dynamic Kinetic Resolution on Large Scale
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Additional information is presented for the transformation of a kinetic resolution into a dynamic kinetic resolution of the isobutyl ester 5b to form the acid 2 in high yield and ee via the intermediacy of a thioester 6c, (Pesti, J. A.; Yin, J.; Zhang, L.-H; Anzalone, L. J. Am. Chem. Soc. 2001, 123, 11075-11076.). The development of optimized reaction conditions for the preparation of 6c, its dynamic kinetic resolution to 2, and the scale-up of both reactions into a pilot plant are described.
- Pesti, Jaan A.,Yin, Jinguao,Zhang, Lin-Hua,Anzalone, Luigi,Waltermire, Robert E.,Ma, Philip,Gorko, Edward,Confalone, Pat N.,Fortunak, Joseph,Silverman, Charlotte,Blackwell, John,Chung,Hrytsak, Michael D.,Cooke, Mary,Powell, Lakisha,Ray, Charles
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- A Novel Route to Efficient Inorganic Oxide Surface Modifications: Molecularly Self-assembled Linear and Conjugated Alkynyl Thin Film Materials
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Treatment of surface hydroxy groups on glass, quartz and single crystal silicon with commercially available group 14 chlorides, ECl4 (E = Si, Sn), and then NEt2H yields surface-anchored NEt2 moieties, which react with several organic molecules containing terminal acidic protons, including rigid-rod alkynes, via acid-base hydrolysis, leading to molecularly self-assembled chromophoric monolayers.
- Yam, Chi Ming,Kakkar, Ashok K.
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p. 907 - 910
(2007/10/02)
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- Polysulfonylamines, XXXVI, Trimethylsilyl Dimesylamine: Preparation, NMR-Spectroscopic Characterization, and Reactivity as a Silylating Agent
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(CH3)3SiN(SO2CH3)2 (1), m.p. 69-70 deg C, is obtained by metathesis of AgN(SO2CH3)2 with (CH3)3SiCl (improvement of a known procedure) or, more conveniently, by silylation of HN(SO2CH3)2 with 2NH.The (1)H, (13)C and (29)Si NMR solution spectra and the (29)Si NMR solid-state spectrum suggest the constitution of 1 in solution (CDCl3, CD2Cl2, CDCl2-CDCl2) to be an equilibrium mixture of the N-silylated form (CH3)3Si-N(SO2CH3)2 (I) and the O-silylated form (CH3)3Si-O-S(O)(CH3) = NSO2CH3 (II) in a molar ratio of 2:1 at room temperature, whereas in the known crystal structure of 1 only form I is present.The solid-state NMR experiment acted as a bridge between X-ray crystallography and solution-state NMR, enabling assignments of the resonances to be made with confidence to the tautomers.At room temperature, form II undergoes a rapid intramolecular 1.5-migration of silicon between oxygen centers of the two sulfonyl groups.As shown by kinetic measurements using (1)H NMR spectroscopy, 1 is a highly reactive agent for silylating ketones in the presence of triethylamine.Hydroxy and thiol functions, even when sterically hindered, are silylated by 1 in uncatalyzed reactions.It is further shown that HN(SO2CH3)2 is an efficient catalyst for silylations with 2NH. Key words: Polysulfonylamines, Trimethylsilyl Dimesylamine, N,O- and O,O-Silyl Migration, Silylation of Hydroxy and Thiol Functions, Solid State (29)Si NMR
- Blaschette, Armand,Wieland, Elke,Hamann, Thomas,Harris, Robin K.
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p. 1693 - 1700
(2007/10/02)
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- Highly Regioselective and Stereospecific Functionalization of 1,2-Proanediol with Trimethyl(X)silanes Employing the 1,3,2λ5-Dioxaphospholane Methodology
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The regioselective ring opening of (S)-4-methyl-2,2,2-triphenyl-1,3,2λ5-dioxaphospholanes (2) was initiated with several trimethylsilyl reagents (Me3SiX: X = PhS, I, Br; Cl, CN, and N3) to afford the regioisomeric (silyloxy)phosphonium salts.A stereospecific extrusion of triphenylphosphine oxide from these oxyphosphonium salts gave predominatly the thermodynamically less stable C-2-X-substituted derivatives with nearly complete inversion of stereochemistry at the C-2 stereogenic center (i.e., X = PhS).
- Mathieu-Pelta, Isabel,Evans, Slayton A.
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p. 3409 - 3413
(2007/10/02)
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- Improved Direct Preparation of O-Trimethylsilyl Monothioacetals from Thiols and Carbonyl Compounds
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Preparation of 1-alkylthio- or 1-phenylthio-1-trimethylsiloxyalkanes and -cycloalkanes directly from carbonyl compounds and thiols, is achieved using 1-trimethylsilylimidazole and trimethylsilyl triflate as a catalyst.
- Sassaman, Mark B.,Prakash, G.K.Surya,Olah, George A.
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p. 104 - 106
(2007/10/02)
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- Transformation of α-assisted carbanions into the corresponding trimethylsiloxy derivatives using bis(trimethylsilyl)peroxide
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The reaction of bis(trimethylsilyl)peroxide with tlithium derivatives of sulphides and nitriles is reported to give the corresponding O-trimethylsilyl hemithioacetals and cyanohydrins. From these products the carbonyl function can be exposed in acidic media or in the presence of fluoride ions. This methodology provides an attractive route to transform a CH2-X group (X = PhS, MeS or CN) into the corresponding CHO, allowing the preparation of aldehydes that can be considered difficult to prepare such as, for example, formyltrimethylsilane which was generated and trapped in situ using a Wittig reaction.
- Dembech,Guerrini,Ricci,Seconi,Taddei
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p. 2999 - 3006
(2007/10/02)
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- Reactivity of the Labile Silaethene Me2Si=C(SiMe3)2, Stored as Ph2C=NSiMe3 Adducts
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Silaethene Me2Si=C(SiMe3)2 (1), stored as Ph2C=NSiMe3 adducts and regenerated from the adducts at about 100 deg C as a reaction intermediate, combines with reactants a-b (e.g.HO-H, RO-H, RCOO-H, RS-H, RHN-H, Ph2CN-H, RO-SiR3, R2N-SiR3, Ph2CN-SiR3, Cl-GeR3, Cl-SnR3) with insertion into the a-b bond, with a=b (e.g.O=CPh2, Me3SiN=CPh2, CH2=CHOMe, cis-piperylene), a=b=c (e.g.RN=N=N, O=N=N), a=b-c=d (e.g. butadiene, isoprene, trans-piperylene, 2,3-dimethylbutadiene, cyclopentadiene, anthracene, benzophenone, N-trimethylsilylbenzophenoneimine) under -, - as well as -c ycloaddition and with a=b-c-H (e.g. propene, butenes, isoprene, 2,3-dimethylbutadiene, acetone) under ene reaction.According to relative reaction rates, insertion and -cycloadditions seem to proceed in two reaction steps, whereas -cycloadditions and ene reactions with organic dienes and enes obviously are one step reactions.For reactivities cf.Table I. - Key words: Silaethene Me2Si=C(SiMe3)2, Insertions, Cycloadditions, Relative Reactivities
- Wiberg, N.,Preiner, G.,Wagner, G.,Koepf, H.
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p. 1062 - 1074
(2007/10/02)
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- A Facile Synthesis of Sulfides Using S-Aryl-isothiuronium Intermediates
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A variety of sulfides were conveniently prepared by a treatment of aryl iodides with thiourea in the presence of nickel(0) catalyst, then with CaO, and finally with a variety of electrophiles such as alkyl, acyl, silyl, aryl, or alkenyl halides.
- Takagi, Kentaro
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p. 1379 - 1380
(2007/10/02)
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- Thioether complexes of tungsten hexacarbonyl
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The preparation of a series of organic and organometallic thioethers R3MSR' (M = C,Si,Ge, or Sn) is reported.From these, several new compounds of type 1 are synthesized, some of which contain para-substituted aryl functions for R and R'.In hexane solution in the carbonyl streching region of the ir the uv there is evidence for a degree of multiple bonding, at least in the M - S - WW - CO portion of these molecules.Multiple bonding extending into aromatic R or R'is small or non-existent and cannot be assessed precisely because of spontaneous decomposition of the complexes.All the complexes undergo a thermally initiated decomposition, the case of which depends on the nature of R, R', and M.The unusual W(I) thiolate cis-2 is the termal decomposition product.
- Lucas, C. Robert
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p. 1758 - 1763
(2007/10/02)
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- Reagents and synthetic methods. 31. Silylations with N-trimethylsilyl-2-oxazolidinone (TMSO)
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Silylation of ketones, alcohols, mercaptans, and carboxylic acids with N-trimethylsilyl-2-oxazolidinone (TMSO) and triflic acid as catalyst has been described from synthetic and mechanistic points of view.
- Aizpurua, Jesus M.,Palomo, Claudio,Palomo, Antonio L.
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p. 336 - 340
(2007/10/02)
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- Substitution Reactions of Thallous Thiophenoxide and Thallous Phenylselenide with Halogen-Bearing Substrates
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Thallous thiophenoxide (1) and thallous selenide (2) were prepared by the action of either thallous ethoxide or thallous pentoxide on thiophenol and benzeneselenol.The reagents 1 and 2 reacted readily with aroyl and acyl halides, imidoyl chlorides, α-halo ketones, α-halo esters, α-halo lactones, α-halo carboxylic acids, allyl halides, alkyl halides, chlorotrimethylsilane, chloroacetonitrile, and N-chlorosuccinimide to give substitution products and varying amounts of diphenyl disulfide and diphenyl diselenide.The reactions were run as heterogeneous mixtures in ether.The origin of the diphenyl disulfide and diphenyl diselenide was homolytic cleavage of the thallium-sulfur or thallium-selenium bond, on the basis of the products derived from the reactions of N-chlorosuccinimide with 1 and 2.
- Detty, Michael R.,Wood, Gary P.
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- Chemistry of Sulfenic Acids. 1. Synthesis of Trimethylsilyl Arenesulfenates (Arenesulfenic Acids)
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Trimethylsilyl arenesulfenates (5), masked sulfenic acids, are prepared in low yield by trapping the intermediate arenesulfenic acid generated by thermolysis of the corresponding N-benzylidenarenesulfinamide (4) with chlorotrimethylsilane-hexamethyldisilazane.Attempts to prepare 5 by oxidation of trialkyl(phenylthio)silanes (8) with 2-(benzenesulfonyl)-3-phenyloxaziridine (11), an aprotic oxidizing reagent, gave instead the previously unknown trialkylsilyl benzenesulfinates (12).These results are attributed to the enhabced nucleophilicity (α effect) of the intermediate trialkylsilyl arenesulfenate ester.
- Davis, Franklin A.,Rizvi, Syed Q. A.,Ardecky, Robert,Gosciniak, Donald J.,Friedman, Arthur J.,Yocklovich, Steven G.
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p. 1650 - 1653
(2007/10/02)
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