- Platinum ω-Alkenyl Compounds as Chemical Vapor Deposition Precursors. Mechanistic Studies of the Thermolysis of Pt[CH2CMe2CH2CH= CH2]2in Solution and the Origin of Rapid Nucleation
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The compound cis-bis(η1,η2-2,2-dimethylpent-4-en-1-yl)platinum, Pt[CH2CMe2CH2CH= CH2]2 (3), is a recently discovered chemical vapor deposition (CVD) precursor for the deposition of highly smooth platinum thin films without nucleation delays on a variety of substrates. This paper describes detailed mechanistic studies of the pathway by which 3 reacts upon being heated in solution. In various solvents between 90 and 130 °C, 3 decomposes to generate ~1 equiv of 4,4-dimethylpentenes by addition of a hydrogen atom to the pentenyl ligands in 3. The "extra"hydrogen atoms arise by dehydrogenation of other pentenyl ligands; some of these dehydrogenated ligands are released as methyl-substituted methylenecyclobutanes and cyclobutenes. A combination of isotope labeling and kinetic studies suggests that 3 decomposes by C-H activation of both allylic and olefinic C-H bonds to give transient platinum hydride intermediates, followed by reductive elimination steps to form the pentene products, but that the exact mechanism is solvent-dependent. In C6F6, solvent association occurs before C-H bond activation, and the rate-determining step for thermolysis is most likely the formation of a Pt σ complex. In hydrocarbon solvents, the solvent is little involved before C-H bond activation, and the rate-determining step is most likely the formation of a Pt σ complex only for γ-C-H and ?-C-H bond activation, but cleavage or formation of a C-H bond for δ-C-H bond activation. A comparison of the thermolysis reactions under CVD conditions and in solution suggests that the high smoothness of the CVD-grown films is due in part to rapid nucleation (which is a consequence of the availability of low-barrier C= C bond dissociation pathways) and in part to the formation of carbon-containing species that passivate the Pt surface.
- Liu, Sumeng,Zhang, Zhejun,Abelson, John R.,Girolami, Gregory S.
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supporting information
p. 3817 - 3829
(2020/11/13)
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- Palladium-Catalyzed Electrochemical Allylic Alkylation between Alkyl and Allylic Halides in Aqueous Solution
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A new route for the direct cross-coupling of alkyl and allylic halides using electrochemical technique has been developed in aqueous media under air. Catalyzed by Pd(OAc)2, the Zn-mediated allylic alkylations proceed smoothly between a full range of alkyl halides (primary, secondary, and tertiary) and substituted allylic halides. Protection-deprotection of acidic hydrogen in the substrates is avoided.
- Lai, Yin-Long,Huang, Jing-Mei
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supporting information
p. 2022 - 2025
(2017/04/28)
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- Insight into cis-to-trans olefin isomerisation catalysed by group 4 and 6 cyclopentadienyl compounds
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Intramolecular isomerisation of the pendant allyl unit present in the model compound [MoH(eta;5-C5H4SiMe 2CH2CH=CH2)- (CO)3] reported before was investigated by DFT calculations.
- Chahboun, Ghaita,Petrisor, Cristina E.,Gomez-Bengoa, Enrique,Royo, Eva,Cuenca, Tomas
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experimental part
p. 1514 - 1520
(2009/07/10)
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- The solvent effect on the reaction constants of tert-butyl radical addition to 2-substituted allyl chlorides
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The ρ values of free radical SH2′ reactions have been determined in various solvents. The correlation of Hammett ρ with Taft's π* gives a W value of 0.70. The W value is a measure of susceptibility of the reaction constant to change in solvent polarity. However, the W value is 2.64 in the dissociation reactions of substituted benzoic acids. The free radical reactions are less susceptible to the solvent effect than ionic reactions and this could be rationalized in terms of the partial charge formed in the transition state of free radical reaction is less than that of heterolytic reaction. The ρ values in SH2′ reactions might not reflect truly the partial charge separation at transition state, however, it might be a measure of the susceptibility of the reaction to the electronic effect of the substituents.
- Wu, Yuh-Wern,Huang, Hsu-Ting,Huang, Zhau-Jie,Huang, Huang-Ming,Yang, Jyh-Ferng
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p. 4461 - 4466
(2007/10/03)
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- The competitive reactions between electron transfer and radical addition in free radical reactions
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The photolytic reactions of 2-substituted allyl chloride with t-BuHgCl in different solvents were investigated. The reactions proceed the SH2′ reaction mechanism except the substituent is a strong electron-releasing group. The electron transfer process becomes more competitive with the radical addition process when the substituent is a strong electron-releasing group. When the substituent is a strong electron-releasing group such as -CH2SiMe3, the reaction in CH3CN shows pronounced electron transfer process while the reaction in DMSO or THF involves both of the SH2′ and the electron transfer processes. The reaction is solvent dependent. An electron transfer mechanism is discussed.
- Wu, Yuh-Wern,Lu, Cheng-Yi
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p. 1129 - 1134
(2007/10/03)
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- Isomerization of 2-(2-propenoxy)phenyllithium: Tandem anionic cyclization-γ-elimination
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2-(2-Propenoxy)phenyllithium (1), which may be prepared from the corresponding iodide by low-temperature lithium-iodine exchange, rearranges on warming in the presence of TMEDA via 5-exo cyclization to (2,3-dihydrobenzofuranyl)methyllithium (2) followed by γ-elimination to give variable amounts of the lithium salt of 2-(cyclopropyl)phenol (3).
- Bailey, William F.,Punzalan, Eric R.
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p. 5435 - 5436
(2007/10/03)
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- Process for the preparation of 4,4-dimethyl-2-pentene
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1,1,2,3,4,4,6-Heptamethyl-1,2,3,4-tetrahydronaphthalene, a novel naphthalenic compound, is useful as an intermediate for the preparation of 5,6,7,8-tetrahydro-3,5,5,6,7,8,8-heptamethyl-2-naphthalenecarbaldehyde. It is prepared by a process consisting in the addition of an olefin of formula STR1 wherein R1 and R2 represent different substituents and each defines a hydrogen atom or a methyl radical, with p-cymene. 4,4-Dimethyl-2-pentene [compound (III): R1 =CH3 ; R2 =H] is obtained by the co-metathesis reaction of an olefin of formula STR2 wherein R1 and R2 represent identical substituents designating each a hydrogen atom or a methyl radical, with an olefin of formula STR3 wherein R3 and R4, identical or different, designate each a hydrogen atom or a methyl radical in the presence of an appropriate catalyst consisting of Re2 O7 on an inert solid carrier, or of WCl6 /(C2 H5)2 O/Bu4 Sn.
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- Relative Reactivities of Alkyl Chlorides under Friedel-Crafts Conditions
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Competition experiments have been performed to determine the relative reactivities of 23 alkyl chlorides toward allyltrimethylsilane in the presence of catalytic amounts of ZnCl2.The krel scale spans over 11 orders of magnitude from 1-adamantyl chloride (least reactive) to bis(p-methoxyphenyl)methyl chloride (most reactive compound).A fair correlation between the alkylating ability and the SN1 reactivity in solvolysis reactions is found, thus providing a quantitative basis for our long-standing working hypothesis that Lewis acid-catalyzed additions of alkyl halides to CC multiple bonds only yield 1:1 products if the reactants ionize faster than the products.Trityl chlorides do not follow this correlation and are 1E5 times less reactive than predicted from their SN1 reactivities. - Key Words: Alkylation / Allylation / Carbenium ions / Friedel-Crafts reactions / Linear free energy relationships
- Dau-Schmidt, Jan-Peter,Mayr, Herbert
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p. 205 - 212
(2007/10/02)
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- Oxymetallation. Part 24. Preparation of cyclic peroxides by cycloperoxymercuriation of unsaturated hydroperoxides
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Seventeen unsaturated hydroperoxides have been converted by treatment with mercury(II) acetate and/or mercury(II) nitrate into nineteen new mercuriated cyclic peroxides and by subsequent demercuriation with alkaline sodium borohydride, six new mercury-free peroxides have been isolated. The results greatly extend the range of such reactions and provide information about the stereoselectivities and relative ease of several different modes of cycloperoxymercuriation. It is suggested that the reactions with mercury(II) acetate are kinetically controlled whereas those with mercury(II) nitrate show a component of thermodynamic control of product distribution.
- Bloodworth,Curtis,Spencer,Tallant
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p. 2729 - 2750
(2007/10/02)
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- Lithiation and Isomerization of Allylic Amines as a General Route to Enamines and Their Carbonyl Derivatives
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lithium, readily prepared by the lithiation of allyldiphenylamine with n-butyllithium in THF, undergoes alkylation either with organic halides or with carbonyl or azomethine derivatives to yield enamines, which can be converted by protons or other electrophiles into aldehydes or into five-membered heterocycles; lithiation of such allyldiarylamines with other reagents leads principally to isomerisation to enamines (with lithium diisopropylamide) or to carbenoid intermediates (tert-butyllithium and potassium tert-butoxide).
- Eisch, John J.,Shah, Jamshed H.
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p. 2955 - 2957
(2007/10/02)
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- A SIMPLE PROCEDURE FOR THE SYNTHESIS OF THREE-CARBON HOMOLOGATED BORONATE ESTERS AND TERMINAL ALKENES VIA NUCLEOPHILIC DISPLACEMENT IN α-HALOALLYLBORONATE ESTER
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The transfer reactions of α-haloallylboronate ester 1 with representative organolithium and Grignard reagents provide α-alkyl- or α-aryl-substituted allylboronate esters, readily converted into three-carbon homologated boronate esters and terminal alkenes.
- Brown, Herbert C.,Rangaishenvi, Milind V.
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p. 7115 - 7118
(2007/10/02)
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- Allylic and Propargylic Substitution Reactions Involving Radicals Generated from Alkylmercury Halides
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Addition of alkyl radicals to allyl or propargyl derivatives forms adduct radicals which can undergo β-elimination with substituents such as halogen, PhS, PhSO2, Bu3Sn, or HgCl to form the alkyl-substituted propene or allene and an eliminated radical which regenerates the alkyl radical by displacement from an alkylmercurial.With β-oxy substituents, such as O2CR, OP(O)(OEt)2, O3SAr, OPh, OSiMe3, or OH, the adduct radicals can displace the alkyl radical from the alkylmercurial to yield β-substituted alkylmercurials which spontaneously, or in the presence of nucleophiles, undergo an elimination reaction to yield the alkene or allene.Relative reactivities toward tert-butyl radical attack, such as k(allyl chloride)/k(propargyl chloride) = ca. 10, have been determined.A similar relative reactivity is observed in reaction with (t-Bu)2CuLi implicating attack by free tert-butyl radicals.With allyl or propargyl iodide, radical attack leads to iodine atom abstraction.Reaction of propargyl iodide with t-BuHgCl/hν, (t-Bu)2CuLi, or (t-Bu)3ZnLi leads to a mixture of hydrocarbons in which tert-butylallene is present in only trace amounts.Benzene is an important reaction product which seems to be formed via the cyclodimerization of two "propargyl" (C3H3.) radicals.
- Russell, Glen A.,Ngoviwatchai, Preecha,Wu, Yuh Wern
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p. 4921 - 4927
(2007/10/02)
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- CONTRIBUTION A L'ETUDE DES REACTIONS DE COMBINAISON DES RADICAUX ALCOYLE TERTIAIRES EN PHASE SOLIDE
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Disproportionation/combination ratios of self-reacting t-alkyl radicals are estimated in solid phase at low temperature.The low temperature solid state limit was estimated to be 7-25, this value is considerably lower than ratios of the literature (100 to 500) and is compatible with the FISCHER limit in liquid state.In the present work, the ratios are determined by product analysis from the gamma radiolysis of isobutane.
- Gourdin-Serveniere, C.,Fontaine, L. M.,Tilquin, B.
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p. 177 - 188
(2007/10/02)
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- CYCLIZATION OF C7-ALKANES OVER Pt BLACK CATALYST
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C6-and C5-cyclization of heptane isomers (and also, olefin formation as a related process) over Pt-black have been studied in pulse and circulation systems.Hydrogendeficient conditions favour aromatization, via presumably terminal olefins.C5-Cyclization in the presence of more hydrogen is accompanied by internal olefin formation.Relative reactivities of all heptane isomers have been measured; this shows that cyclization is easier between terminal methyl groups.Optimum hydrogen pressures for both types of cyclization have been determined (and compared with hydrogenolysis, too).Earlier mechanism suggestion for aromatization and cyclopentane formation have been confirmed; the distinction between two types of bond shift mechanisms producing aromatics (from substituted pentanes) and saturated isomers, respectively, has recieved additional support facilitating the identification of these two reactions with mechanisms proposed in the literature.
- Zimmer, H.,Paal, Z.,Tetenyi, P.
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p. 513 - 532
(2007/10/02)
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- Hydrogenolysis of Alkanes with Quaternary Carbon Atoms over Pt and Ni Black Catalysts
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Hydrogenolysis of hydrocarbons with quaternary C atoms (neopentane, neohexane, 2,2,3-trimethylbutane, 2,2- and 3,3-dimethylpentanes and 2,2,3,3-tetramethylbutane) has been studied over Pt and Ni black catalysts.The reactivities of different types of C-C bond have been determined.The probability of C-C bond rupture where one of the carbon atoms is quaternary is inversely proportional to the bond dissociation energy.On Pt, two essential types of hydrogenolysis can be distinguished.One reaction is responsible for the breaking of internal C-C bonds attached to the quaternary carbon atom and the other for demethylation.With larger molecules, the former reaction is preferred and the surface intermediate should be 1,4-diadsorbed, while that for the latter reaction is 1,3-diadsorbed.Nickel, as previously suggested, causes terminal C-C rupture, although with branched hydrocarbon reactants internal C-C bond rupture is also possible, presumably via 1,4-adsorption.
- Zimmer, Helga,Tetenyi, Pal,Paal, Zoltan
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p. 3573 - 3586
(2007/10/02)
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- gem-Dimethyl Effect in a Grignard Reagent Cyclization-Cleavage Rearrengament
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(2,2-Dimethyl-4-penten-1-yl)magnesium bromide (1) is in equilibrium with its cyclic isomer, magnesium bromide (2).The equilibrium constant for this cyclization has a value of 2E-3.The gem-dimethyl substitution leads to an increase of a factor of about 22 in the equilibrium constant and also retards the rate of cleavage of 2.The sources of the gem-dimethyl effect in this system are discussed.
- Hill, Alexander E.,Link, Daniel C.,Donndelinger Peter
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p. 1177 - 1182
(2007/10/02)
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- Tantalum and niobium catalysts or catalyst precursors
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Tantalum and niobium catalysts or catalyst precursors of the formula: STR1 wherein R is cyclopentadienyl, which can be substituted with methyl up to five positions, or neopentylidene, R1 is neopentyl or benzyl, n is 0 or 1, R2 is neopentylidene, benzylidene, tetramethylene, or 2,3-dimethyltetramethylene, A is halo or a moiety of the formula YR3 R4 R5 wherein Y is a group 5 element including N, P, As, Sb and Bi and R3, R4, R5 can be the same or different and are C1 -C4 alkyl, aralkyl such as naphthyl, neophyl, tolyl or xylyl, aryl such as benzyl or phenyl or bipyridyl and Z is tantalum or niobium. The compounds selectively dimerize 1-olefins to 1-butenes; m=1 or 2.
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- The Kinetics and Mechanism of Ring Opening of Radicals containing the Cyclobutylcarbinyl System
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The kinetic parameters of β-fission of radicals containing the cyclobutylcarbinyl system have been determined by analysis of the mixtures obtained when suitable chloro-compounds are treated with tributylstannane.Under these conditions ring opening is irreversible and in the rigid bicyclic system (4) is under stereoelectronic control.For ring opening of cyclobutylcarbinyl radical (8) kf = 4.3 x 103 s-1 at 60 deg C, and the best values of the activation parameters appear to be ΔH(excit.) = 12.2 kcal mol-1 and ΔS(excit.) = -7.4 cal mol-1 K-1.Monocyclic systems undergo preferential fission of the more substituted βγ-bond.Methyl substituents at the α-, β-, or δ-positions have little effect but γ-substitution strongly enhances the rate of ring opening.The transition state is reactant-like and has a similar disposition of centres to that (1) for homolytic addition.
- Beckwith, Athelstan L. J.,Moad, Graeme
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p. 1083 - 1092
(2007/10/02)
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