- Reactivity of lanthanide and yttrium hydrides and hydrocarbyls toward organosilicon hydrides and related compounds
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The reaction of lanthanide and yttrium hydrocarbyls {Cp*2Ln(μ-Me)}2 (Cp* = tBuC5H4 (Cp′), Ln = Y (1), Tb (2), Yb (3), Lu (4); Cp* = Me3SiC5H4 (Cp″), Ln = Lu (5)), one of which, 2, has been characterized by X-ray crystal analysis, with various organosilicon, -germanium, and -tin hydrides (as well as some organoaluminum and -gallium hydrides) in hydrocarbon solution was found to yield the corresponding unsolvated dimeric lanthanide and yttrium hydrides {Cp*2Ln(μ-H)}2 rather than compounds with lanthanide-element (Si, Ge, Sn) bonding. Thus, the reaction involves hydride transfer to Ln rather than the silyl transfer studied earlier for pentamethylcyclopentadienyllanthanide hydrocarbyls. Dimeric compounds Cp*2Ln(μ-H)(μ-Me)LnCp*2 with different bridging ligands were isolated; they are intermediates in this reaction. Dimeric lanthanide and yttrium hydrides catalyze the H/D exchange in silanes. This catalytic reaction is most correctly described by a mechanism involving nucleophilic substitution at the silicon atom. Yttrium and lutetium hydrocarbyls 1 and 4 react with various alkoxysilanes to produce the dimeric alkoxides {Cp′2Ln(μ-OR)}2 or the hydrocarbyl alkoxides Cp′2Ln(μ-Me)(μ-OR)LnCp′2 (R = Me, Et), depending on the reaction conditions. The reaction of 4 with (MeO)4Si provided Cp′2Lu(μ-Me)(μ-OMe)LuCp′2, which has been characterized by X-ray crystal analysis. This compound contains one methyl bridge (Lu-C 2.57(2) and 2.58(2) A?) and nonsymmetrically bonded μ-OMe ligand (Lu-O 2.20(2) and 2.12(2) A?). The reaction of 1 and 4 with Me3SiCl leads to the corresponding dimeric chlorides {Cp′2Ln(μ-Cl)}2 only. Thus, the reaction of lanthanide and yttrium hydrocarbyls with various heterosubstituted organosilanes R3SiX, where X = H, OR, or Cl, is a selective and convenient synthetic method in the chemistry of the group 3 elements. Complexes with Ln(μ-H)(μ-Me)Ln and Ln(μ-H)(μ-Cl)Ln bridging were prepared in high yield by the exchange reactions between the corresponding dimeric compounds {Cp*2Ln(μ-X)}2 (X = H, Me, Cl) in a hydrocarbon solution. The capacities of various bridging fragments to undergo reversible cleavage (dissociation) in the hydrocarbon solution increase in the sequence Ln-O(Me)-Ln ? Ln-Cl-Ln Ln-H-Ln Ln-Me-Ln.
- Voskoboynikov, Alexander Z.,Parshina, Inna N.,Shestakova, Alia K.,Butin, Kim P.,Beletskaya, Irina P.,KuZ'Mina, Lyudmila G.,Howard, Judith A. K.
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- Redox-Active-Ligand-Mediated Formation of an Acyclic Trinuclear Ruthenium Complex with Bridging Nitrido Ligands
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Coordination of a redox-active pyridine aminophenol ligand to RuIIfollowed by aerobic oxidation generates two diamagnetic RuIIIspecies [1 a (cis) and 1 b (trans)] with ligand-centered radicals. The reaction of 1 a/1 b with excess NaN3under inert atmosphere resulted in the formation of a rare bis(nitrido)-bridged trinuclear ruthenium complex with two nonlinear asymmetrical Ru-N-Ru fragments. The spontaneous reduction of the ligand centered radical in the parent 1 a/1 b supports the oxidation of a nitride (N3?) to half an equivalent of N2. The trinuclear omplex is reactive toward TEMPO-H, tin hydrides, thiols, and dihydrogen.
- Bagh, Bidraha,Broere, Dani?l L. J.,Siegler, Maxime A.,van der Vlugt, Jarl Ivar
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- Transformations of organosilanes by Pt(II) complexes with hemilabile P,N-chelating ligands
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The article reviews the author's own work to enhance the reactivity of Pt(II) complexes towards organosilanes by employing hemilabile chelating ligands R2N-R′-PPh2 (P∩N). Variation of the groups R and R′ allows to influence the react
- Schubert, Ulrich,Pfeiffer, Jürgen,St?hr, Frank,Sturmayr, Dietmar,Thompson, Susan
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- Thermodynamic, Kinetic, Structural, and Computational Studies of the Ph3Sn-H, Ph3Sn-SnPh3, and Ph3Sn-Cr(CO)3C5Me5 Bond Dissociation Enthalpies
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The kinetics of the reaction of Ph3SnH with excess ?Cr(CO)3C5Me5 = ?Cr, producing HCr and Ph3Sn-Cr, was studied in toluene solution under 2-3 atm CO pressure in the temperature range of 17-43.5 °C. It was found to obey the rate equation d[Ph3Sn-Cr]/dt = k[Ph3SnH][?Cr] and exhibit a normal kinetic isotope effect (kH/kD = 1.12 ± 0.04). Variable-temperature studies yielded ΔH? = 15.7 ± 1.5 kcal/mol and ΔS? = -11 ± 5 cal/(mol·K) for the reaction. These data are interpreted in terms of a two-step mechanism involving a thermodynamically uphill hydrogen atom transfer (HAT) producing Ph3Sn? and HCr, followed by rapid trapping of Ph3Sn? by excess ?Cr to produce Ph3Sn-Cr. Assuming an overbarrier of 2 ± 1 kcal/mol in the HAT step leads to a derived value of 76.0 ± 3.0 kcal/mol for the Ph3Sn-H bond dissociation enthalpy (BDE) in toluene solution. The reaction enthalpy of Ph3SnH with excess ?Cr was measured by reaction calorimetry in toluene solution, and a value of the Sn-Cr BDE in Ph3Sn-Cr of 50.4 ± 3.5 kcal/mol was derived. Qualitative studies of the reactions of other R3SnH compounds with ?Cr are described for R = nBu, tBu, and Cy. The dehydrogenation reaction of 2Ph3SnH → H2 + Ph3SnSnPh3 was found to be rapid and quantitative in the presence of catalytic amounts of the complex Pd(IPr)(P(p-tolyl)3). The thermochemistry of this process was also studied in toluene solution using varying amounts of the Pd(0) catalyst. The value of ΔH = -15.8 ± 2.2 kcal/mol yields a value of the Sn-Sn BDE in Ph3SnSnPh3 of 63.8 ± 3.7 kcal/mol. Computational studies of the Sn-H, Sn-Sn, and Sn-Cr BDEs are in good agreement with experimental data and provide additional insight into factors controlling reactivity in these systems. The structures of Ph3Sn-Cr and Cy3Sn-Cr were determined by X-ray crystallography and are reported. Mechanistic aspects of oxidative addition reactions in this system are discussed.
- Cai, Xiaochen,Majumdar, Subhojit,Fortman, George C.,Koppaka, Anjaneyulu,Serafim, Leonardo,Captain, Burjor,Temprado, Manuel,Hoff, Carl D.
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- Spectroscopic studies of tributylstannyl radical. Rates of formation, termination, and abstraction determined by transient absorption spectroscopy
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Transient absorption spectroscopy (TAS) was used to measure the rate of formation and the rate of self-termination of the main group metal hydride, tri-n-butyltin hydride (Bu3-SnH). Irradiation of di-tert-butyl peroxide in the presence of Busu
- Shaw, Wendy J.,Kandandarachchi, Pramod,Franz, James A.,Autrey, Tom
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- Convenient one-pot synthesis of hexa-n-butylditin from bis(tri-n-butyltin) oxide
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Hexa-n-butylditin is prepared in high yield (83%), by reduction of bis(tri-n-butyltin) oxide with sodium borohydride in ethanol. The first stage is reduction to tri-n-butyltin hydride (not isolated), which rapidly gives hexa-n-butylditin with the loss of hydrogen under the basic reaction conditions.
- McAlonan, Helena,Stevenson, Paul J.
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- Illuminating Stannylation
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We have developed photoboosted stannylation reactions of terminal alkynes (linear-selective hydrostannylation) and fluoroarenes (defluorostannylation), in which the stannyl anion is photoexcited to an excited triplet (T1) stannyl diradical species. This u
- Sakamoto, Kyoka,Nagashima, Yuki,Wang, Chao,Miyamoto, Kazunori,Tanaka, Ken,Uchiyama, Masanobu
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supporting information
p. 5629 - 5635
(2021/05/04)
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- Bis(pentafluorophenyl)phenothiazylborane-an intramolecular frustrated Lewis pair catalyst for stannane dehydrocoupling
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We synthesized a novel Lewis acidic aminoborane containing a phenothiazyl substituent and demonstrated its potential to catalytically promote the dehydrocoupling of tin hydrides. The observed reactivity would imply a homolytic frustrated Lewis pair type mechanism, however computational analysis suggests a heterolytic mechanism for this reaction. This result represents one of the first frustrated Lewis pair systems to dehydrocouple stannanes in a heterolytic fashion.
- Bentley, Jordan N.,Caputo, Christopher B.,Pradhan, Ekadashi,Zeng, Tao
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p. 16054 - 16058
(2020/12/03)
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- A Drastic Effect of TEMPO in Zinc-Catalyzed Stannylation of Terminal Alkynes with Hydrostannanes via Dehydrogenation and Oxidative Dehydrogenation
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With a system consisting of a catalytic zinc Lewis acid, pyridine, and TEMPO in a nitrile medium, terminal alkynes coupled with HSnBu3, providing alkynylstannanes with structural diversity. The resulting alkynylstannane, without being isolated, could be directly used for Pd- and Cu-catalyzed transformations to deliver internal alkynes and more intricate tin-atom-containing molecules. Mechanistic studies indicated that TEMPOSnBu3 formed in situ from TEMPO and HSnBu3 works to stannylate the terminal alkyne in collaboration with the zinc catalyst, and that both of dehydrogenation and oxidative dehydrogenation processes are uniquely involved in a single reaction. (Figure presented.).
- Kai, Yuichi,Oku, Shinya,Sakurai, Kyoko,Tani, Tomohiro,Tsuchimoto, Teruhisa
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supporting information
(2019/08/21)
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- Nickel-catalyzed decarbonylative stannylation of acyl fluorides under ligand-free conditions
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Nickel-catalyzed decarbonylative stannylation of acyl fluorides under ligand-free conditions was disclosed. A variety of aromatic acyl fluorides are capable of reacting with silylstannanes in the presence of cesium fluoride. A one-pot decarbonylative stannylation/Migita-Kosugi-Stille reaction of benzoyl fluoride, giving rise to the direct formation of the corresponding cross-coupled products, further demonstrated the synthetic utility of the present method. This newly developed methodology with a good functional-group compatibility via C-F bond cleavage and C-Sn bond formation under nickel catalysis opens a new area for the functionalization of acyl fluorides in terms of carbon-heteroatom bond formation.
- Wang, Xiu,Wang, Zhenhua,Liu, Li,Asanuma, Yuya,Nishihara, Yasushi
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- Copper-catalyzed α-selective hydrostannylation of alkynes for the synthesis of branched alkenylstannanes
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A variety of branched alkenylstannanes can directly be synthesized with excellent α-selectivity by the copper-catalyzed hydrostannylation using a distannane or a silylstannane, irrespective of the electronic and steric characteristics of terminal alkynes employed. Synthetic utility of the resulting branched alkenylstannane has been demonstrated by the total synthesis of bexarotene.
- Yoshida,Shinke,Kawano,Takaki
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supporting information
p. 10616 - 10619
(2015/06/30)
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- Sonochemical synthesis of bis(tri-n-butylstannyl) aromatic compounds via Barbier-like reactions
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This paper reports a study of the synthesis of aryltri-n-butylstannanes via a sonochemical Barbier reaction of aryl- and heteroaryl bromides with bis(tri-n-butyltin) oxide (2) in THF. Our results demonstrate that, despite previous reports on contrary, the aryltributylstannanes can also be obtained under the same reaction conditions via sonicated reactions between aryl monobromides and tri-nbutyltin chloride (2). A comparative study of the reactions of electrophiles 2 and 3 with bromobenzene, 2-bromopyridin, o- and m-bromoanisole, m-bromotoluene, 9-bromophenthrene, and 9-bromoanthracene, indicates that the corresponding aryl- and heteroaryl-tri-n-butylstannyl derivatives are obtained in about the sameyields. Best reaction conditions and the results obtained in the investigation of the sonicated reactions between several aromatic and heteroaromatic dibromides are also reported. It was found that the reactions using 1,2-, 1,3-, and 1,4-dibromobenzenes, 4,40-dibromobiphenyl, 1,4-dibromonaphthalene, 2,5-and 3,5-dibromopyridines, and 2,5-dibromothiophene lead to the corresponding bis(tri-n-butylstannylated) derivatives in many cases in very high yields. Also the excellent results obtained in the sonicated reactions of 1,3,5-tribromobenzene with 2 and 3 are reported.
- Gerbino, Darío C.,Fidelibus, Pablo M.,Mandolesi, Sandra D.,Ocampo, Romina A.,Scoccia, Jimena,Podestá, Julio C.
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- A catalyst-economic one-pot protocol for the synthesis and conversion of functionalized vinylstannanes
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A wide range of functionalized compounds can easily be obtained by a Pd-catalyzed one-pot hydrostannylation/elimination/distannylation/radical allylation sequence. The Pd catalyst used can be involved in up to five different reaction steps. A wide range of functionalized compounds can easily be obtained by a Pd-catalyzed one-pot hydrostannylation/elimination/ distannylation/radical allylation sequence. In this highly catalyst-economic protocol, the Pd catalyst can be involved in up to 5 different reactions. Copyright
- Klos, Manuel R.,Kazmaier, Uli
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p. 1726 - 1731
(2013/04/23)
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- Electrochemical cleavage of sulfonamides: An efficient and tunable strategy to prevent β-fragmentation and epimerization
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The electrochemical reduction of sensitive sulfonamides is described. The addition of a benzoyl group on the nitrogen atom facilitates the reductive cleavage of sulfonamides preventing β-fragmentation and epimerization. This strategy was successfully applied to the cyclopropylamine and to α-amino stannanes.
- Viaud, Pierre,Coeffard, Vincent,Thobie-Gautier, Christine,Beaudet, Isabelle,Galland, Nicolas,Quintard, Jean-Paul,Le Grognec, Erwan
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supporting information; experimental part
p. 942 - 945
(2012/03/26)
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- Regioselective catalytic conversion of hydrocarbons to versatile synthetic reagents via C-H bond functionalization
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The present invention provides a novel and improved method of functionalizing a C—H bond of an arene compound comprising the step of reacting an organometallic compound having a group 14 element with the arene compound having at least one hydrogen bonded to a carbon in the presence of a catalyst.
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Page/Page column 4-5
(2011/11/30)
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- A neutral, monomeric germanium(I) radical
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Stoichiometric reduction of the bulky β-diketiminato germanium(II) chloride complex [(ButNacnac)GeCl] (ButNacnac = [{N(Dip)C(But)}2CH]-, Dip = C6H 3Pri2-2,6) with either sodium naphthalenide or the magnesium(I) dimer [{(MesNacnac)Mg}2] ( MesNacnac = [(MesNCMe)2CH]-, Mes = mesityl) afforded the radical complex [(ButNacnac)Ge:]? in moderate yields. X-ray crystallographic, EPR/ENDOR spectroscopic, computational, and reactivity studies revealed this to be the first authenticated monomeric, neutral germanium(I) radical.
- Woodul, William D.,Carter, Emma,Mueller, Robert,Richards, Anne F.,Stasch, Andreas,Kaupp, Martin,Murphy, Damien M.,Driess, Matthias,Jones, Cameron
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p. 10074 - 10077
(2011/08/03)
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- A convenient route to distannanes, oligostannanes, and polystannanes
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The quantitative conversion of the tertiary stannane (ν;-Bu) 3SnH (2) into (ν-Bu)6Sn2 (4) was achieved by heating the neat hydride material under low pressure or under closed inert atmosphere conditions. A 31% conversion of Ph3SnH (3)to Ph6Sn 2 (5) was also observed under low pressure; however, under closed inert atmosphere conditions afforded Ph4Sn (6) as the major product. A mixed distannane, (ν-Bu)3SnSnPh3 (7), can also be prepared in good yield utilizing an equal molar ratio of 2 and 3 and the same reaction conditions used to prepare 4. This solvent-free, catalyst-free route to distannanes was extended to a secondary stannane, (ν-Bu)2SnH 2 (8), which yielded evidence (NMR) for hydride terminated distannane H(ν-Bu)2SnSn(ν-Bu)2H(9), the polystannane [(ν-Bu)2Sn] ' (10), and various cyclic stannanes [(ν- Bu)2Sn]ν=5,6=5,6 (11, 12). Further evidence for 10 was afforded by gel permeation chromatography (GPC) where a broad, moderate molecular weight, but highly dispersed polymer, was obtained (Mw = 1.8 × 104 Da, polydispersity index (PDI) = 6.9) and a characteristic UV-vis absorbance (1max)of ν370 nm observed.
- Khan, Aman,Gossage, Robert A.,Foucher, Daniel A.
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p. 1046 - 1052
(2011/02/16)
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- Rhodium and iridium amino, amido, and aminyl radical complexes
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The chlorido-bridged dimeric complex [Rh2(μ-Cl) 2(trop2-NH)2] [trop2NH = bis(benzo[a,d]cycloheptenyl)amine] or the acetonitrile complexes [Rh(trop 2NH)(MeCN)2]+ (CF3SO 3-) and [IrCl(MeCN)(trop2NH)] are well-suited precursor complexes for phenanthroline-type complexes [M(trop 2NH)(R,Rphen)]+A- (M = Rh, Ir; R = H, Me, Ph substituents in the 4,7- or 5,6-positions of the phen ligand, A- = CF3SO3-, PF6-). These complexes contain 18-valence-electron configured metal centers in a trigonal-bipyramidal coordination sphere with the amino (NH) group in an axial position and each of the olefinic C=Ctrop units is in an equatorial position. The cationic amino complexes [M(trop2NH)(R,R-phen)] + are sufficiently acidic (pKa in dmso: 18.2-19.0) to be quantitatively deprotonated by one equivalent of KOtBu to give neutral amido complexes [M(trop2N)(R,R-phen)] (M = Rh, Ir). These can be easily oxidized to give aminyl radical complexes [M(trop2N .)(R,R-phen)]+A-, which for M = Rh can be isolated as green crystals. The iridium complex [Ir(trop2N .)(phen)]+ is unstable. High-resolution pulse EPR spectroscopy was used to gain insight into the electronic structure of the aminyl radical complexes. Remarkably, the rhodium and iridium complexes have a very similar electronic structure, as revealed by their EPR parameters {[Rh(trop2N.)(phen)]+: g1,2,3 = 2.084(2), 2.049(2), 2.027(2); |Aiso| = 45.4 (N1), 10.4 (N2), 3.1 (N3) 27.0 (Rh) MHz; [Ir(trop2N.)(phen)]+: g 1,2,3 = 2.140(2), 2.107(2), 2.015(2); |Aiso| = 47 (N1), 7.9 (N2), 3.5 (N3), 26.8 (Ir) MHz} and these show that about 60% of the spin population is localized on the nitrogen center (N1) of the trop2N ligand. In reactions with stannanes (R3SnH) and thiols (RSH), H-atom transfer to the trop2N nitrogen atom is observed, [M(trop 2N.)(phen)]+ + EH → [M(trop 2NH)(phen)]+ + 1/2HE-EH. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Donati, Nicola,Stein, Daniel,Buettner, Torsten,Schoenberg, Hartmut,Harmer, Jeffrey,Anadaram, Sreekanth,Gruetzmacher, Hansjoerg
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p. 4691 - 4703
(2009/04/12)
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- Stereoselective radical tandem cyclohydrostannation of optically active di-unsaturated esters of TADDOL
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This paper reports the results obtained in a study on the radical addition of triorganotin hydrides, R3SnH (R = Me, n-Bu, Ph; Neophyl), to four TADDOL unsaturated diesters. It was found that diese reactions lead in high yields to products of cyclohydrostannation. It was also found that whereas the addition of these hydrides to TADDOL diacrylate and TADDOL dimethacrylate leads to the expected mixtures of two and four cycloundecane diastereoisomers, respectively, the addition of triphenyltin hydride to TADDOL disubstituted acrylates yields only four out of the 16 possible stereoisomers. The observed high stereoselectivity is consistent with the radical tandem cyclohydrostannation mechanism proposed. Only in the case of the hydrostannation of TADDOL diacrylate with trimethyl- and triphenyltin hydrides could the diastereoisomers obtained in higher proportion (5a and 8a) be isolated in pure form. The subsequent reduction (lithium aluminum hydride) of macrolides 5a and 8a afforded the corresponding optically active diols 26 and 27 in high yield. Full 1H, 13C, and 119Sn NMR data are given.
- Gerbino, Dario C.,Koll, Liliana C.,Mandolesi, Sandra D.,Podesta, Julio C.
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p. 660 - 665
(2009/01/30)
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- A highly efficient reduction of group 14 heteroatom-chlorine single bonds by using samarium diiodide-mediated reaction systems
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The reduction of group 14 heteroatom-chlorine single bonds by using samarium diiodide-mediated reduction systems in tetrahydrofuran has been investigated in detail. When the reduction of chlorostannanes and chlorogermanes are conducted by employing excess amounts of samarium diiodide (4 equiv.) at the THF refluxing temperature, the corresponding distannanes and digermanes are obtained in good yields, respectively. By the combination with magnesium metal or samarium metal, a novel samarium diiodide-catalyzed reduction of chlorostannanes and chlorogermanes takes place successfully. In contrast, the reduction of chlorosilanes with SmI2 in THF does not occur at all, because the silylative ring-opening of THF with silyl iodode (formed in situ from chlorosilanes and SmI2) proceeds in preference to the desired reduction of chlorosilanes.
- Kamiya, Ikuyo,Iida, Koichiro,Harato, Nami,Li, Zhi-Fang,Tomisaka, Yuri,Ogawa, Akiya
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p. 437 - 440
(2008/10/09)
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- Aluminumoxyhydride: Improved synthesis and application as a selective reducing agent
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Aluminumoxyhydride (HAlO) has been obtained by the reaction of aluminum hydride with the siloxane (Me2HSi)2O or the stannoxane (Bu3Sn)2O as an amorphous colorless insoluble powder. The highest-purity product resulted from the reaction of H3Al· NMe3 with (Me2HSi)2O. However, HAlO suspensions in tetrahydrofuran (THF) of sufficient quality for synthetic applications can be prepared from commercially available reagents with only minor precautions. A LiAlH4 solution in THF was treated successively with Me 3SiCl and (Me2HSi)2O, followed by heating at 60°C for 20 h. The resulting suspensions are 0.4-0.5 M in active hydride content and selectively reduce aldehydes and ketones to the respective alcohols in the presence of any other common nonprotic functional group.
- Tewari, Brij B.,Shekar, Sukesh,Huang, Longchuan,Gorrell, Carolyn E.,Murphy, Timothy P.,Warren, Kevin,Nesnas, Nasri,Wehmschulte, Rudolf J.
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p. 8807 - 8811
(2008/10/09)
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- Dehydrogenative stannane coupling by platinum complexes
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The complexes Pt(acac)2, (PhMe2P) 2PtMe2, (dppe)PtMe2 (dppe=bis(diphenylphosphino)ethane) , and the (P∩N)PtMe2 complexes [(κ2-P,N)-Ph 2PCH2CH2CH2NMe2]PtMe 2 and [(κ2-P,N)-Ph2PCH2CH 2NMe2]PtMe2 catalyse the formation of distannanes by dehydrogenative coupling of triphenyltin hydride or tri-n-butyltin hydride. While Pt(acac)2 appears to react by a radical mechanism, the bis(stannyl) complexes (PhMe2P) 2Pt(SnR3)2 and (dppe)Pt(SnR3) 2 were observed in the reaction of (PhMe2P) 2PtMe2 and (dppe)PtMe2. At longer reaction periods the complexes (PhMe2P)2Pt(H)SnBu3 and (PhMe2P)2Pt(Ph)SnHPh2, respectively, were formed. There is evidence that the distannanes are formed by a similar mechanism when (P∩N)PtMe2 is employed as the catalyst instead of (R3P)2PtMe2. However, the presence of the P,N-chelating ligand results in the stabilisation of the intermediate (P∩N)Pt(Me)SnR3 and in the formation of redistribution products.
- Thompson, Susan M.,Schubert, Ulrich
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p. 329 - 338
(2008/10/08)
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- Stille couplings catalytic in tin: The "Sn-O" approach
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A one-pot tandem Pd-catalyzed hydrostannylation/Stille coupling protocol for the stereoselective generation of vinyltins and their subsequent union, employing only catalytic amounts of tin, is described. By recycling the organotin halide Stille byproduct back to organotin hydride, a hydrostannylation/cross-coupling sequence can be carried out with catalytic amounts of tin. Such a process is most effective with Me3SnCl serving as the tin source. This protocol allows a 94% reduction of the tin requirement, while maintaining good yields (up to 90%) for a variety of Stille products. Furthermore, since one cycle requires the tin to undergo at least four transformations, each moiety of trialkyltin is experiencing a minimum of 60 reactions over the course of the hydrostannylation/Stille, sequence.
- Gallagher,Terstiege,Maleczka Jr.
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p. 3194 - 3204
(2007/10/03)
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- Wurtz-type reductive coupling reaction of primary alkyl iodides and haloorganotins in cosolvent/H2O(NH4Cl)/Zn media as a route to mixed alkylstannanes and hexaalkyldistannanes
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Mixed tetra-alkylstannanes R3SnR′ (R = Et, n-Pr, n-Bu and R′= Me, Et, n-Pr, n-Bu, n-Pent) and R2SnR′2 (R = n-Bu and R′ = Me, Et, n-Pr, n-Bu) can be easily prepared in a one-pot synthesis via coupling reaction of alkyl iodides R′I with R3SnX (X = Cl, I) and R2SnCl2 compounds in cosolvent-H2O(NH4Cl) medium mediated by zinc dust. Coupling also occurs with (Bu3Sn)2O. It has been verified that reactions are possible only with primary alkyl iodides; with secondary alkyl iodides the coupling reaction fails. When alkyl chlorides and bromides are used ditin compounds are obtained instead of the unsymmetrical tetra-alkylstannanes. This represents a route to hexaalkyldistannanes.
- Marton, Daniele,Tari, Massimo
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- Catalytic dehydrogenative coupling of stannanes by alkoxysilyl heterobimetallic complexes: Influence of the assembling ligand
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The heterobimetallic complexes [(OC)3(R′3Si)Fe(μ-P-Z)Pd(η 3-allyl)] (1, P-Z = Ph2PNHPPh2 (dppa); 2, P-Z = Ph2P(o-C5H4N) (Ph2Ppy); 3, P-Z = Ph2PCH2PPh2 (dppm); R′3 = (OMe)3, Me(OSiMe3)2) are very efficient catalysts for the dehydrogenative coupling of tin hydrides R3SnH (R = Ph, nBu). Besides establishing that siloxy complexes are more active catalysts than their alkoxysilyl counterparts, the present study shows that modifications in the nature of the assembling functional phosphine ligand P-Z result in variations of catalyst efficiency, expressed by the TON (overall turnover number) and TOF (maximum turnover frequency) values and lifetime. The Ph2Ppy-bridged complexes are the most efficient catalysts, and in the case of nBu3SnH, TON and TOF values higher than 1.2 × 106 and 2 × 108, respectively, have been observed. A marked difference in reactivity is also observed between the diphosphine ligands dppa and dppm, with the dppa-bridged complexes being more active than their dppm analogues. The new complex [(OC)3{(Me3SiO)2MeSi}Fe(μ-Ph 2Ppy)Pd(η3-allyl)] (2b) prepared in the course of this work has been structurally characterized by X-ray diffraction.
- Braunstein, Pierre,Durand, Jér?me,Morise, Xavier,Tiripicchio, Antonio,Ugozzoli, Franco
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p. 444 - 450
(2008/10/08)
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- Mechanism of the reaction of tri-n-butylstannyl anion with n-butyl bromide and iodide as studied by the 119Sn CIDNP technique
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The mechanism of the reaction of the tri-n-butylstannyl anion with n-butyl bromide and iodide in THF was studied by the chemically induced dynamic nuclear polarization (CIDNP) technique. Strong 119Sn CIDNP spectra were observed for the first ti
- Wakasa, Masanobu,Kugita, Tsuyoshi
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p. 2941 - 2943
(2008/10/08)
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- The effect of CO on the reaction of (tributyltin)lithium with alkyl and aryl bromides
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The reaction of (tributyltin)lithium with alkyl and aryl bromides in THF was studied in the presence of CO and of p-dinitrobenzene under several reaction conditions. The observed results indicate that electron transfer is involved in the substitution reac
- Nudelman, N. Sbarbati,Carro, Cecilia
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- Reactivity of heterobimetallic alkoxysilyl and siloxy complexes in the catalytic dehydrogenative coupling of tin hydrides
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Heterobimetallic complexes [(OC)3(R3Si)Fe(μ-dppm)Pd(η3-allyl)] 1 (R = OMe, Me, OSiMe3, OSi(H)Me2) and [(OC)3Fe{μ-Si(OR)2(OR)}(μ-dppm)PdCl] 6 (R = Me, SiMe3) are effective catalyst in the dehydrogenative coupling of triorganotin hydrides HSnR′3 (R′ = Ph, nBu). Although the elementary transformations during catalysis appear to take place at palladium, the function of the iron fragment is to provide the palladium center with the appropriate coordination environment through metal-metal bonding and the Si-containing ligand. Indeed, complexes 1 and 6 revealed a higher catalytic activity than mononuclear Pd catalysts. Modifications of the substituents at silicon resulted in considerable variations of the TON (turnover number) and TOF (turnover frequency) values as well as in the lifetime of the catalysts. In the case of siloxy derivatives, TON and TOF values higher than in the case of the alkoxysilyl analogs have been obtained whereas the lifetime of the catalyst is much longer for the latter. Possible mechanisms which rationalize the role of the silicon ligand are discussed. Solvent effects have also been observed. One of the key features of these systems is the retention of the bimetallic nature of the catalyst. TON and TOF higher than 2 × 105 and 3 × 107 h-1, respectively, have been obtained in the case of HSnnBu3. The catalytic activity of 1 toward the dehydropolymerization of tin dihydrides has been tested.
- Braunstein, Pierre,Morise, Xavier
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p. 540 - 550
(2008/10/08)
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- Reaction of Vanadocene with Cyanamide and Bis(tributylstannyl)carbodiimide
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Vanadocene [bis(η5-cyclopentadienyl)vanadium] was reacted with cyanamide to obtain previously unknown bis(η5-cyclopentadienyl)bis(cyanamido)vanadium. When exposed to air, the latter converts to (η5-cyclopentadienyl)bis(cyanamido)vanadium oxide. The reaction of vanadocene or its monochloride with bis(tributylstannyl)carbodiimide produces exclusively, regardless of the reactant ratio, bis[bis(η5-cyclopentadienyl)vanadium]carbodiimide which is readily oxidized in air with intermediate formation of bis(η5-cyclopentadienylvanadiumoxo)carbodiimide.
- Gordetsov,Zimina,Levakova,Kulagina
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p. 764 - 766
(2007/10/03)
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- Synthesis of Benzenesulfonyl Derivatives with N-Metal Bonds
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Reaction of p-NH2C6H4SO2NH2 with (Bu3Sn)2O was used to prepare p-Bu3SnNHC6H4SO2NHSnBu3, whose transmetalation with (η5-C5H5)2V(Cp2V) gave p-CpVNHC6H4SO2NHVCp. When exposed to air, the latter rapidly converted to p-O=VNHC6H4SO2NHVCp and then to the parent sulfonamide. Sulfonamides PhSO2NHMCp were synthesized in a similar way from PhSO2NHSnBu3 and Cp2M or Cp2MCl2 (M = V, Ti, Nb, Mo).
- Gordetsov,Latyaeva,Levakova,Zimina,Cherkasov,Kulagina,Kozina
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p. 780 - 784
(2007/10/03)
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- Heterogeneous palladium-catalyzed regioselective hydrostannation of alkenes
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A heterogeneous palladium catalyst enables the hydrostannation of alkenes with both great efficiency and generality. The method is illustrated for the allylic alcohols shown in Equation (A) (R = Ph (96%), 2- furyl (92%).
- Lautens,Kumanovic,Meyer
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p. 1329 - 1330
(2008/10/09)
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- Reaction of α-(trialkylstannyl)acetylenes with metallic sodium
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α-Trialkylstannylacetylenes react under mild conditions with metallic sodium at the Sn-C(sp) bond to give hexaalkyldistannanes and sodium acetylalkynides in ca. 65 - 85percent yields. - Key words: α-(trialkylstannyl)acetylenes, reaction with sodium; hexaa
- Komarov, N. V.,Andreev, A. A.,Shein, O. G.
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p. 1048 - 1049
(2007/10/02)
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- Electrochemical Formation of Dimeric Organostannyl Compounds
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Organosilyl stannanes were formed by electroreduction of the corresponding organostannyl chlorides or distannanes with silyl chlorides.The Sn-C bond formation was also confirmed in the reduction of a mixture of stannyl and alkyl chlorides.
- Ishiwata, Toyoaki,Nonaka, Tsutomu,Umezawa, Masanobu
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p. 1631 - 1634
(2007/10/02)
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- Regioselective addition of stannylcyanocuprates to acetylenic ethers: A chemical and spectroscopic study
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The reactions of acetylenic ether 1 with higher order cuprates 2a, 2b and 2c were studied chemically and spectroscopically. Conditions were developed to efficiently and regioselectively prepare α- and β-stannylvinyl ethers. 1H and 13C NMR studies of these reactions suggest that in the presence of HMPA, higher order stannylcyanocuprate, (Bu3Sn)2Cu(CN)Li2, 2a, exists in equilibrium with Gilman cuprate, (Bu3Sn)2CuLi.
- Cabezas,Oehlschlager
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p. 432 - 442
(2007/10/02)
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- Method of preparing distannanes
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The present invention relates to a method of preparing hexaalkyl distannanes by converting bis-[trialkyltin]oxide with a stabilized solution of sodium borohydride in alcohol, preferably methanol, in the presence of an inert solvent.
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- Photolysis of 1,3-dimesitylhexamethyltrisilane and 1,2-dimesityltetramethyldisilane
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Irradiation at 254 nm of solutions containing 1,3-dimesitylhexamethyltrisilane, (MesMe2-Si)2SiMe2, leads to the formation of 1-mesityl-1-methylsilene, MesMeSi=CH2, in addition to the anticipated dimethylsilylene, Me2Si:. The coproduct of dimethylsilylene extrusion, 1,2-dimesityltetramethyldisilane, (MesMe2Si)2, is itself photolabile, producing high yields of mesityldimethylsilane, MesMe2SiH, and 1-mesityl-1-methylsilene. Trapping experiments indicate that both molecular elimination and silicon-silicon bond homolysis followed by disproportionation lead to the silene, whose dimerization yields cis- and trans-1,3-dimesityl-1,3-dimethyl-1,3-disilacyclobutanes. Both the cis- and trans-1,3-disilacyclobutanes were structurally characterized by X-ray crystallography. The silene can be trapped by a variety of reagents in high yield.
- Braddock-Wilking, Janet,Chiang, Michael Y.,Gaspar, Peter P.
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p. 197 - 209
(2008/10/08)
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- (Trialkylstannyl)dimethylsilane as a New Precursor of Dimethylsilylene: A Novel Synthesis of 3,4-Disubstituted 1-Silacyclopenta-2,4-dienes
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In the presence of triphenylphosphinepalladium complexes, (trialkylstannyl)dimethylsilane rapidly reacted at room temperature with terminal acetylenes to give 3,4-disubstituted 1-silacyclopenta-2,4-dienes in moderate yield.The formation of 1-silacyclopentadiene derivatives is evidence for the generation of dimethylsilylene species from (trialkylstannyl)dimethylsilane.
- Ikenaga, Kazutoshi,Hiramatsu, Kouji,Nasaka, Norimitsu,Matsumoto, Satoshi
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p. 5045 - 5047
(2007/10/02)
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- N-(η5-Cyclopentadienylvanadium)benzenesulfonamide
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N-(η5-Cyclopentadienylvanadium)benzenesulfonamide has been synthesized for the first time by treating benzenesulfonamide or N-(tributylstannyl)benzenesulfonamide with vanadocene. - Key words: benzenesulfonamide; N-(tributylstannyl)benzenesulfon
- Gordetsov, A. S.,Zimina, S. V.,Moseeva, E. M.,Skobeleva, S. E.,Kulagina, N. V.,Pereshein, V. V.
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p. 2021 - 2023
(2007/10/02)
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- O,O'-Bistributyltin Benzopinacolate (1,1,2,2-Tetraphenylethane-1,2-bisolate) as Thermal Source of Tributylstannyl Radicals
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The previously unknown bistributyltin benzopinacolate was prepared by photolysis of benzophenone in the presence of bistributyltin and used for thermal formation of aryl radicals that undergo subsequent intramolecular addition to an imine bond in an ortho-substituent.
- Tomaszewski, Miroslaw J.,Warkentin, John
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p. 1407 - 1408
(2007/10/02)
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- Organozinnverbindungen XXXIII. Die erste Komplexbildung zwischen Organozinn- und Nitroderivaten: Reactionen der Zinn-Alkyl-Bindung
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Although trimethylstannylbenzene in presence of MeCOCl*AlCl3 undergoes a carbodestannylation to give acetophenone, its 2-NO2, 3-NO2, 4-NO2, and 2,4-(NO2)2 derivatives (1a-d) exhibit a surprising, high activation of the aliphatic C-Sn bond (Me-Sn) which allows a single cleavage to give the corresponding dimethylchlorostannyl nitrobenzenes (2a-d) quantitatively without any aryl-Sn bond cleavage.A strong, hitherto unknown, intramolecular pentacoordination at the tin in 2a and 2d via complexation by the ortho nitro groups, is indicated by the IR, 1H, 13C, and 119Sn NMR spectral data.In contrast, reaction of iodine with 1a-d, or with 2a-d results in exclusive SEar ipso substitution of all stannyl groups.The mechanisms are discussed, preparative procedures and spectroscopic details are described.
- Al-Allaf, Talal A. K.,Kobs, U.,Neumann, W. P.
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- Reactions of organotin hydrides with lithium diisopropylamide and organolithiums. Reactivities of the intermediates and of the lithium hydride produced
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Equimolar lithium diisopropylamide (LDA) and trimethyltin hydride (TMTH) react in tetrahydrofuran (THF) to form diisopropylamine and (trimethylstannyl)lithium, but in diethyl ether or hexanes 2 mol of TMTH is required for complete reaction and the products are diisopropylamine, hexamethylditin, and lithium hydride. When organic halides are present in this reacting system, reduction to alkane or substitution to form the trimethylalkyltin may occur depending on the nature of the halide. These and other observations suggest that (trimethylstannyl)lithium is formed as an intermediate yielding the tetraalkyltin. Studies on the products and stoichiometries of the reductions of alkyl bromides in ether and hexanes suggest that three reducing agents may be involved: TMTH, [Me3Sn(H)N-i-Pr2]-, and [Me3SnSn(H)Me3]-. The latter predominates in ether, and either or both of the others predominate in hexanes. Formation of methylcyclopentane from 1-bromo-5-hexene suggests involvement of a free radical mechanism. When methyllithium is used instead of LDA in the reaction with TMTH, the products are tetramethyltin and lithium hydride. This reaction can also be diverted to reduction by the presence of primary bromides. Aryl bromides react in both systems, but the yields of either substitution or reduction products are low. The lithium hydride formed in these reactions is extremely reactive as a base as shown by a brief study of its reaction with weak carbon acids and amines and as a nucleophile by its reaction with hexamethylditin to form (trimethylstannyl)lithium in THF.
- Reimann, Werner,Kuivila, Henry G.,Farah, Dan,Apoussidis, Theodorus
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p. 557 - 565
(2008/10/08)
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- Synthesis and properties of isocyanate and isothiocyanate d1- and d2-complexes of vanadocene
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The reactions of vanadocene and its halides Cp2VCl and Cp2VCl2 with R3MNCX (M = Sn, Si, X = O, S) and R2M(NCX)2 in various molar ratios have been studied.The reactions proceed either by an exchange of groups, with no change in the oxidation state of vanadium, or by an oxidative addition of pseudohalide ligand: VII -> VIII; VIII -> VIV.Oxidative addition results in the formation of (R3M)2 or gaseous hydrogen (in the reaction with HCl) in the reaction products.We have prepared the first ever monomeric and readily oxidisable d2-complexes of VIII of Cp2VNCX-type and asymmetric d1-complexes of Cp2V(Cl)NCX type, which, although rather stable in air, undergo disproportionation into symmetric d1-complexes on heating.In transmetallation reactions the ligand activity is found to increase in the order Cl A general scheme for the disproportionation reaction of asymmetric complexes of vanadocene is supported by differential thermal analysis data.
- Razuvaev, G. A.,Gordetsov, A. S.,Latyaeva, V. N.,Zimina, S. V.,Skobeleva, S. E.,et al.
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p. 327 - 336
(2007/10/02)
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- PALLADIUM CATALYSIS IN ORGANOTIN CHEMISTRY: ADDITION OF HEXAALKYLDITINS TO ALKYNES
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Tetrakis(triphenylphosphine)palladium(0) catalyses the cis-addition of hexaalkylditins R6Sn2 (R = Me, Et, Bu) to acetylene and 1-alkynes; for R = Bu, however the reaction is not quantitative.With very few exceptions there is no reaction in the case of non
- Mitchell, T.N.,Amamria, A.,Killing, H.,Rutschow, D.
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p. 257 - 266
(2007/10/02)
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- Palladium(0)-mediated Insertion of Isonitriles into the Silicon-Tin Bond
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Insertion of isonitriles into the silicon-tin bond of organosilylstannanes is catalysed by palladium(0) to give organosilyl(N-substituted imino)stannanes.
- Ito, Yoshihiko,Bando, Takashi,Matsuura, Takaharu,Ishikawa, Mitsuo
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p. 980 - 981
(2007/10/02)
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- DIE CHEMIE DER SCHWEREN CARBEN-ANALOGEN R2M, M=Si, Ge, Sn. X. 7-SILA-NORBORNADIENE: REAKTIONEN MIT HALOGENEN UND THERMOLYSE IN GEGENWART VON METALLORGANISCHEN ODER ORGANISCHEN HALOGENIDEN
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The 7-sila-norbornadienes (I-IV) react rapidly with halogens at -20 to +20 deg C to yield Me2SiHal2 (Hal=Cl, Br, I) and the naphthalene or benzene derivatives (V-VIII).Bromine in CCl4 at 0 deg C, however, caused surprising rearrangement in I giving the 2-bromosilylated naphthalene (IX), since an attack at the alkene group seemed to be preferred.Methylation and methoxylation of IX gave respectively X and XI.Careful hydrolysis of IX yielded the disiloxane XII.Insertions of Me2Si into the Si-Hal, Si-H, Si-C, or Sn-C bonds were not observed at 160-200 deg C, whereas insertions into Sn-Cl or Sn-H bonds occurred smoothly via a one-step mechanism.Halogen is abstracted from different C-Hal bonds leading to Me2SiHal2 and sometimes to Me4Si2Hal2.The degradation of the silylene precursors in these cases is always first order and resembles that of spontaneous thermolysis.
- Appler, Hubertus,Neumann, Wilhelm P.
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p. 247 - 260
(2007/10/02)
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- Direct Observation of Stannyl Radicals by Laser-Photolysis of Carbon-Tin and Tin-Tin Bonds
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Photochemical primary processes of carbon-tin and tin-tin bonds were studied at room temperature.The stannyl radicals generated were observed directly by laser-photolysis.
- Mochida, Kunio,Wakasa, Masanobu,Sakaguchi, Yoshio,Hayashi, Hisaharu
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p. 1793 - 1796
(2007/10/02)
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- 1,1-Distannyl 1-alkenes: A new method of formation and some further reactions
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1,1-Distannyl-1-alkenes of the type RR′C=C(SnMe3)2 can be readily prepared from (trimethylstannyl)lithium and geminal dibromoalkenes. An extension of this method to include the preparation of vicinal distannylalkenes is in general not possible. Hydrostannation of the geminal distannylalkenes gives tristannylalkanes; bromodestannylation using N-bromosuccinimide occurs readily, as does halodemethylation at tin using dimethyltin dihalides. Palladium-catalyzed coupling reactions between geminal distannylalkenes and organic halides are possible, but stereoselective monocoupling is probably not realizable. Selected multinuclear NMR data for the compounds prepared are presented.
- Mitchell,Reimann
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p. 1991 - 1997
(2008/10/08)
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