- Synthesis and characterization of cyclopentadienylgallium amide compounds as potential single source precursors to GaN
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The synthesis, spectroscopic characterization, and single crystal X-ray structures of [(η5-C5Me4H)2Ga(μ2-NH2)] (1), [(η5-C5Me5)2Ga(μ2-
- Perrotin,Kennon, Bretni S.,Twamley, Brendan,Miller, Joel S.,Shapiro, Pamela J.
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- Enzyme-like control of carbocation deprotonation regioselectivity in supramolecular catalysis of the nazarov cyclization
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The kinetically controlled, regioselective deprotonation of cyclopentenyl cations is mediated by encapsulation within a metal-ligand assembly. The regiochemistry of the deprotonation step determines which one of two possible products is formed. Moreover, subtle differences in the stereochemistry of the encapsulated cation switch the selectivity of this process (see scheme). Copyright
- Hastings, Courtney J.,Backlund, Mikael P.,Bergman, Robert G.,Raymond, Kenneth N.
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- Reactions of hydrogen sulfide with singly and doubly tucked-in titanocenes
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Hydrogen sulfide reacts with tucked-in titanocene complexes [Ti(III){η5:η1-C5Me4(CH 2)}Cp*] (Cp* = η5-C5Me 5) (2) and [Ti{η4:η3-C 5Me3(CH2)2}Cp*] (3) and their precursors [Cp*2TiMe] (2a) and [Cp*2Ti(η2-Me3SiC≡CSiMe3)] (3a), respectively, to give the corresponding titanocene hydrosulfides [Cp*2Ti(SH)] (4) and [Cp*2Ti(SH)2] (1), respectively. Hydrogen sulfide also cleaves intramolecular σ- or π-Ti-C bonds in ansa-[TiIII(η1:η5: η5-C5Me4SiMe2CHCH 2SiMe2C5Me4)] (5) and ansa-[Ti II(η2:η5:η5-C 5Me4SiMe2CH=CHSiMe2C 5Me4)] (6), affording hydrosulfides ansa- [(η5-CH2Me2SiC5Me 4)2Ti(SH)] (7) and ansa-[(η5-CH 2Me2SiC5Me4)2Ti(SH) 2] (8). The S-H bonds of hydrosulfides 4 and 7 were able to react with the Ti-C bonds in 2 and 5, affording titanocene sulfides [(Cp*2TiIII)2S] (11) and ansa-[{(η5-CH2Me2SiC5Me 4)2TiIII}2S] (12), respectively. Combination of 7 with 2a gave rise to the mixed titanocene sulfide [ansa-{(η5-CH2SiMe2C5Me 4)2Ti}S(TiCp*2)] (13). The titanium(III) d1 electrons in 11-13 form an electronic triplet state well observable by EPR spectra in toluene glass. All the hydrosulfides were decomposed by sunlight. Compound 1 eliminated Cp*H and H2S, while 4 mainly Cp*H. Apparently formed transient [Cp*TiS] species probably gave rise to the serendipitously isolated cluster [{Cp*Ti(S)} 4] (14). Crystal structures of the all complexes were determined by X-ray diffraction analysis.
- Pinkas, Jiri,Cisarova, Ivana,Horacek, Michal,Kubista, Jiri,MacH, Karel
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- Reactivity of Cp*Al towards Silanols: Formation and Hydrolysis of Alumosiloxanes
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Treatment of [Cp*Al]4 (1) (Cp* = pentamethylcyclopentadienyl) with various silanols gave access to the compounds [Al{OSi(OtBu)3}3(DMAP)] (3) (DMAP = 4-dimethylaminopyridine), [HNEt3][Al(OSiPh3)4
- Wittwer, Philipp,Stelzer, Adrian,Braun, Thomas
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- Enzymelike catalysis of the nazarov cyclization by supramolecular encapsulation
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The water-soluble, self-assembled, tetrahedral assembly K 12Ga4L6 (L = 1,5-biscatecholamidenaphthalene) catalyzes the Nazarov cyclization of 1,3-pentadienols with extremely high levels of efficiency. The catalyzed reaction proceeds over a million times faster than the background reaction, an increase comparable to those observed in some enzymatic systems. This catalysis operates under aqueous conditions at mild temperatures and pH, and the reaction is halted by the addition of an appropriate inhibitor. This unprecedented rate enhancement is attributed to both the stabilization of protonated reaction intermediates and the effect of constrictive binding on the bound guest.
- Hastings, Courtney J.,Pluth, Michael D.,Bergman, Robert G.,Raymond, Kenneth N.
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- Ytterbium(III) Complexes Coordinated by Dianionic 1,4-Diazabutadiene Ligands
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A series of new Yb(III) complexes XYb(DAD)2-(L) (X = C5Me5, C5Me4H, N(SiMe3)2, tBuO; DAD = 2,6-R″2C6H3N=C(R′)-C(R′)=NC6H3R″2-2,6, R′ = H, Me, R″ = Me, iPr; L = thf, dme) coordinated by redox-active diazabutadiene ligands in dianionic form were synthesized and characterized. The half-sandwich complexes Cp#Yb(DAD)2-(THF) (Cp# = C5Me5, C5Me4H) were synthesized by the reactions of the ytterbocenes Cp#2Yb(THF)2 with the corresponding DADs in a 1:1 molar ratio. These reactions are accompanied by oxidation of the Yb(II) to Yb(III), cleavage of one Cp#-Yb bond, oxidation of cyclopentadienyl anion, and reduction of the diazabutadiene to dianionic form. It was found that the substituents by the DAD nitrogens (2,6-iPr2C6H3 vs 2,6-Me2C6H3) and imino carbons (H vs Me) do not affect the reaction outcome and afford Cp#Yb(DAD)2-(thf). The amido and alkoxo derivatives XYb(DAD)2-(dme) (X = N(SiMe3)2, tBuO) were obtained by the salt metathesis reactions of the in situ generated species [XYbCl2(thf)n] and Na2(thf)n[2,6-iPr2C6H3NC(Me)C(Me)NC6H3iPr2-2,6]. If the reaction was carried out in the presence of Li ions, it afforded an ate-complex {Li(thf)3}{Yb[2,6-iPr2C6H3NC(Me)C(Me)NC6H3iPr2-2,6]2-[N(SiMe3)2](μ-Cl)}. The X-ray studies of complexes XYbIII(DAD)2-(L) revealed that they feature the 2σ:η2-type of coordination of dianionic DAD ligands. Introduction of Me-substituents by the imino carbons of DADs leads to some elongation of Yb-Cp# bonds compared to the NCHCHN-analogues. The Yb-CNCCN bonds and the dihedral YbNN-NCCN angles were found to be the most sensitive to replacing H by Me. Unlike the formerly reported complex Cp?Yb[2,6-iPr2C6H3NCHCHNC6H3iPr2-2,6]2-(thf), the variable-temperature magnetic measurements (1.8-300 K) of complexes 3-5 and 7-9 did not reveal thermally induced redox isomeric transformations for these compounds. However, for complex (C5Me4H)Yb[2,6-iPr2C6H3NC(Me)C(Me)NC6H3iPr2-2,6](thf) at 9 K, the structural phase transition accompanied by changes of the coordination behavior of the DAD ligand was detected, which might hint for an onset of a temperature-induced redox isomerism. These results clearly indicate high sensitivity of redox isomeric transformations of XYbIII(DAD)2-L to the smallest changes of the structural and electronic properties of the DAD ligands. (Chemical Equation Presented).
- Shestakov, Boris G.,Mahrova, Tatyana V.,Larionova, Joulia,Long, Jêrome,Cherkasov, Anton V.,Fukin, Georgy K.,Lyssenko, Konstantin A.,Scherer, Wolfgang,Hauf, Christoph,Magdesieva, Tatiana V.,Levitskiy, Oleg A.,Trifonov, Alexander A.
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- Pentamethyl cyclopentadiene preparation method
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The invention relates to a pentamethyl cyclopentadiene preparation method which is characterized in that a Grignard reagent is prepared from chloromethane and magnesium in ether solvents under low-temperature conditions, temperature is reduced, tetramethyl cyclopentanone is dropwise added, temperature reaction is performed, and hydrochloric acid is added after reaction to perform dehydration alkene forming reaction. Post-treatment and rectification under vacuum are performed to obtain qualified products. The preparation method has the advantages that raw materials are inexpensive and easy to obtain, yield is high, production cost can be controlled, process steps are short, conditions are mild, and the preparation method is safe, reliable and suitable for industrial production.
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Paragraph 0013-0015
(2019/08/07)
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- Hemilability of the 1,2-Bis(dimethylphosphino)ethane (dmpe) Ligand in Cp?Mo(NO)(κ2-dmpe)
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Reaction of Cp?Mo(NO)Cl2 with 1 equiv of 1,2-bis(dimethylphosphino)ethane (dmpe) in THF at ambient temperature forms [Cp?Mo(NO)(Cl)(κ2-dmpe)]Cl (1), which is isolable as an analytically pure yellow powder in 65% yield. Further addition of 2 equiv of Cp2Co to 1 in CH2Cl2 affords dark red Cp?Mo(NO)(κ2-dmpe) (2), which was isolated in 36% yield by recrystallization from Et2O at -30 °C. Reaction of a benzene solution of 2 with an equimolar amount of elemental sulfur results in the immediate production of dark blue (μ-S)[Cp?Mo(NO)(κ1-dmpeS)]2 (3), which is a rare example of a bimetallic transition-metal complex bridged by only a single sulfur atom and involving Mo=S=Mo bonding. In contrast, reaction of 2 with an excess of sulfur in benzene results in the formation of Cp?Mo(NO)(η2-S2)(κ1-dmpeS) (4). Complex 4 can also be formed by the addition of elemental sulfur to 3, thereby indicating that 3 is a precursor to 4. Cp?Mo(NO)(κ2-dmpe) (2) also undergoes interesting transformations when treated with organic bromides. For instance, reaction of 2 with 5 equiv benzyl bromide in THF produces the bimetallic complex (μ-dmpe)[ Cp?Mo(NO)Br2]2 (5) and bibenzyl after 4 d at 70 °C probably via radical intermediates. In contrast to its reaction with benzyl bromide, complex 2 forms [Mo(NO)Br2(κ2-dmpe)]2 (6), olefin, alkane, and Cp?H when treated with 5 equiv of 1-bromopropane or 1-bromooctane in THF at 70 °C for 72 h. Interestingly, complex 2 does not display any reactivity with bromobenzene or 1-bromoadamantane even after being heated for several days at 70 °C. All new complexes were characterized by conventional spectroscopic and analytical methods, and the solid-state molecular structures of most of them were established by single-crystal X-ray crystallographic analyses.
- Holmes, Aaron S.,Patrick, Brian O.,Levesque, Taleah M.,Legzdins, Peter
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p. 11299 - 11309
(2017/09/25)
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- Reactivity Study of Pyridyl-Substituted 1-Metalla-2,5-diaza-cyclopenta-2,4-dienes of Group 4 Metallocenes
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In this work the reactivity of 1-metalla-2,5-diaza-cyclopenta-2,4-dienes of group 4 metallocenes, especially of the pyridyl-substituted examples, towards small molecules is investigated. The addition of H2, CO2, Ph?C≡N, 2-py?C≡N, 1,3-dicyanobenzene or 2,6-dicyanopyridine results in exchange reactions, which are accompanied by the elimination of a nitrile. For CO2, a coordination to the five-membered cycle occurs in case of Cp*2Zr(N=C(2-py)?C(2-py)=N). A 1,4-diaza-buta-1,3-diene complex is formed by H-transfer in the conversion of the analogous titanocene compound with CH3?C≡N, PhCH2?C≡N or acetone. For CH3?C≡N a coupling product of three acetonitrile molecules is established additionally. In order to split off the metallocene from the coupled nitriles, we examined reactions with HCl, PhPCl2, PhPSCl2and SOCl2. In the last case, the respective thiadiazole oxides and the metallocene dichlorides were obtained. A subsequent reaction produced thiadiazoles.
- Becker, Lisanne,Rei?, Fabian,Altenburger, Kai,Spannenberg, Anke,Arndt, Perdita,Jiao, Haijun,Rosenthal, Uwe
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p. 10826 - 10838
(2016/07/27)
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- Facile C-H, C-F, C-Cl, and C-C Activation by Oxatitanacyclobutene Complexes
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Aryl ketones react readily with oxatitanacyclobutenes bearing pentamethylcyclopentadienyl ligands to form unique titanocene complexes resulting from Cp modification and C-H activation. An intermediate in this reaction is intercepted with various functional groups to form carbonyl insertion, C-F activation, and cyclopropane ring-opening products.
- Nguyen, Trang T.,Bertke, Jeffery A.,Gray, Danielle L.,Hull, Kami L.
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supporting information
p. 4190 - 4193
(2015/09/22)
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- Origins of large rate enhancements in the nazarov cyclization catalyzed by supramolecular encapsulation
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The self-assembled supramolecular host [Ga4L6] 12- (1; L=N,N-bis(2,3-dihydroxybenzoyl)-1,5-diaminonaphthalene) catalyzes the Nazarov cyclization of 1,3-pentadienols with extremely high levels of efficiency. The catalyzed reaction proceeds at a rate over a million times faster than that of the background reaction, an increase comparable to those observed in some enzymatic systems. A detailed study was conducted to elucidate the reaction mechanism of both the catalyzed and uncatalyzed Nazarov cyclization of pentadienols. Kinetic analysis and 18O-exchange experiments implicate a mechanism, in which encapsulation, protonation, and water loss from substrate are reversible, followed by irreversible electrocyclization. Although electrocyclization is rate determining in the uncatalyzed reaction, the barrier for water loss and for electrocyclization are nearly equal in the assembly-catalyzed reaction. Analysis of the energetics of the catalyzed and uncatalyzed reaction revealed that transition-state stabilization contributes significantly to the dramatically enhanced rate of the catalyzed reaction. A self-assembled supramolecular host catalyzes the Nazarov cyclization of 1,3-pentadienols under mild, aqueous conditions. The catalyzed reaction rate is enhanced by a factor of over 106 compared with the background reaction rate, one of the largest reported for supramolecular catalysis. Analysis of the reaction-energy profile revealed that transition-state stabilization contributes significantly to the dramatically enhanced reaction rate (see scheme).
- Hastings, Courtney J.,Bergman, Robert G.,Raymond, Kenneth N.
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supporting information
p. 3966 - 3973
(2014/04/17)
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- Direct observation of cyclic carbenium ions and their role in the catalytic cycle of the methanol-to-olefin reaction over chabazite zeolites
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Carbenium ions in zeolites: Two important carbenium ions have been observed for the first time under working conditions of the methanol-to-olefins (MTO) reaction over chabazite zeolites using 13C NMR spectroscopy. Their crucial roles in the MTO
- Xu, Shutao,Zheng, Anmin,Wei, Yingxu,Chen, Jingrun,Li, Jinzhe,Chu, Yueying,Zhang, Mozhi,Wang, Quanyi,Zhou, You,Wang, Jinbang,Deng, Feng,Liu, Zhongmin
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supporting information
p. 11564 - 11568
(2013/11/06)
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- Reductive elimination: A pathway to low-valent aluminium species
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Compounds Cp*AlH2 (1) and Cp*2AlH (2) reductively eliminate Cp*H in benzene or toluene under reflux conditions to give Al(s) and AlCp*, respectively. The Royal Society of Chemistry 2013.
- Ganesamoorthy, Chelladurai,Loerke, Sinah,Gemel, Christian,Jerabek, Paul,Winter, Manuela,Frenking, Gernot,Fischer, Roland A.
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supporting information
p. 2858 - 2860
(2013/04/24)
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- 4,5-disubstituted N,N′-Di-tert-alkyl imidazolium salts: New synthesis and structural features
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It's getting crowded! The synthesis of a new subfamily of imidazolium cations with exceptionally spatially demanding substitution patterns (see scheme) paved the way to reconcile two antagonising effects: steric hindrance and innately high donating ability/basicity in the peralkylated imidazol-2-ylidene ligands/uncharged bases.
- Grishina, Anastasia A.,Polyakova, Svetlana M.,Kunetskiy, Roman A.,Cisarova, Ivana,Lyapkalo, Ilya M.
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supporting information; experimental part
p. 96 - 100
(2011/03/21)
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- 1,4-HYDROGENATION OF DIENES WITH RU COMPLEXES
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The present invention relates to the use of Ru complexes, having a cyclopentadienyl derivatives and a diene as ligands, together with some acidic additives for improving the selectivity in the 1,4-hydrogenation of conjugated dienes into the corresponding "cis "-alkene as major product, i.e. wherein the two substituents in position 2,3 of said diene are in a cis configuration in the corresponding alkene.
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Page/Page column 13
(2008/12/04)
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- Pentamethylcyclopentadienide in organic synthesis: Nucleophilic addition of lithium pentamethylcyclopentadienide to carbonyl compounds and carbon-carbon bond cleavage of the adducts yielding the parent carbonyl compounds
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Lithium pentamethylcyclopentadienide (C5Me5Li, Cp*Li) reacted with aromatic aldehyde to provide the corresponding carbinol in excellent yield. The carbinol returns to the parent aldehyde and pentamethylcyclopentadiene upon exposure to acid or due to heating. Chlorodimethylaluminum is essential as an additive to attain the nucleophilic addition of Cp*Li to aliphatic aldehyde. The carbinol derived from aliphatic aldehyde returns to the parent aldehyde and pentamethylcyclopentadiene by the action of a catalytic amount of 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ). The reversible addition/elimination of the Cp* group can represent a protection of aldehyde. Mechanistic details of the carbon-carbon bond cleavage are also disclosed.
- Uemura, Minoru,Yagi, Kazunari,Iwasaki, Masayuki,Nomura, Kenichi,Yorimitsu, Hideki,Oshima, Koichiro
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p. 3523 - 3535
(2007/10/03)
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- Trivalent organic lanthanoid complex, catalyst for production of (meth) acrylic polymer, and (meth) acrylic polymer
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This invention provides an easily synthesized trivalent organic lanthanoid complex which can be used as a polymerization catalyst for (meth) acrylic monomers. The trivalent organic lanthanoid complex is represented by the general formula (1): wherein M represents Sc, Y or a lanthanide atom, R1 represents a hydrogen atom, a C1-10 alkyl group or a C1-10 alkyl group containing a silicon atom, R2 groups independently represent a C1-10 alkyl group, and n is 1 or 2.
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- Process for the preparation of cyclopentadienyl metal salt and process for the preparation of derivative of cyclopentadiene using the same
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A cyclopentadienyl metal salt is prepared by reacting a cyclopentadiene and a metal hydride in the presence of an amine compound. Furthermore, a derivative of a cyclopentadiene in which a phenyl group is bonded to its cyclopentadienyl moiety through an element of the 14 group of the Periodic Table is prepared using such a reaction.
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- The reaction of benzene with diethylamine in the presence of an iridium(I)/mercury(II) based system: a model route for the direct amination of aromatic hydrocarbons
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N,N-Diethylaniline is formed under mild conditions either by the direct amination of benzene with diethylamine in the presence of 5-C5Me5)(CO)2> 1 and HgSO4, or by reacting (C6H5)2Hg or C6H5HgCl/Ag2SO4 with diethylamine in the presence of 1.A preliminary investigation about the chemistry underlying these reactions is also reported.Keywords: Iridium; Amination; C-H activation; N-H activation; Mercury; Catalysis
- Diversi, Pietro,Ermini, Luca,Ingrosso, Giovanni,Lucherini, Antonio,Pinzino, Calogero,Sagramora, Laura
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- Heat of Formation and Stabilization Energy of the Pentamethylcyclopentadienyl Radical
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From the thermolysis of 1 in the presence of 1-60 bar oxygen between 70 and 100 deg C the activation energy for its dissociation is found to be 27.9 kcal * mol-1.Combining this result with the enthalpy of formation of 4 and a forcefield value for 1 leads to DHdeg (Me5C5-H) = 74.1 kcal * mol-1 and ΔHfdeg (2) = 16.1 kcal * mol-1, which differs by 5.4 kcal * mol-1 from a value published recently by Walton.The low dissociation enthalpy of 1 is caused only by relieve of 28 kcal * mol-1 of strain.With an intrisic radical stabilization energy (IRSE) of 17.3 kcal * mol-1 for 2 there is no justification for an extra stabilization due to cyclic conjugation. - Key Words: Oxygen trapping / Heat of formation / Radical stabilization energy / Supercritical fluid reactions
- Roth, Wolfgang R.,Hunold, Frank
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p. 1119 - 1122
(2007/10/02)
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- Solution calorimetric, equilibrium, and synthetic studies of oxidative addition/reductive elimination of C5R5H (R = H, Me, indenyl) to/from the complexes M(CO)3(RCN)3/(η5-C5R 5)M(CO)3H (M = Cr, Mo, W)
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Equilibrium data are reported for the reaction CpMo(CO)3H + 3MeCN ? Mo(CO)3(MeCN)3 + CpH. Over the temperature range 43-82°C, ΔH = -11.2 kcal/mol, ΔS = -51.3 cal/(mol°C). Calorimetric data for the enthalpies of displacement of C5R5H by nitriles are reported: Cr, R = Me, -0.7 ± 0.7 kcal/mol, M = W, R = H, -5.6 ± 0.7, R = Me, -5.4 ± 0.7 kcal/mol. The enthalpy of reaction of Na+(indenyl)- with (p-xylene)Mo(CO)3 forming Na+Mo(CO)3(indenyl)- is -17.3 ± 0.2 kcal/mol, approximately 10 kcal/mol less than the corresponding reaction of Na+C5H5-. The heat of reaction of (indenyl) W(CO)3H with EtCN forming W(CO)3(EtCN)3, -20.0 ± 0.8 kcal/mol, is approximately 14 kcal/mol more exothermic than the corresponding reaction of the cyclopentadienyl complex, also in keeping with a reduced M-indenyl ground-state bond energy. Synthetic strategies to the (C5R5)M(CO)3H complexes are summarized.
- Kubas, Gregory J.,Kiss, Gabor,Hoff, Carl D.
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p. 2870 - 2876
(2008/10/08)
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- Hydrazido(1-) and 2,2-dimethylhydrazido(1-) derivatives of permethylscandocene. Preparation and structural characterization of their products from reactions with acetonitrile: (η5-C5Me5)2ScN(H)C(CH 3)NNH2 and (η5-C5Me5)2ScN(H)C(CH 3)NNMe2
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A rare example of an unsubstituted hydrazido(1-) complex, Cp*2ScN(H)NH2 (Cp* = (η5-C5Me5)), prepared by reaction of 1 equiv of anhydrous hydrazine with Cp*2ScCH3, reacts with acetonitrile to form Cp*2ScN(H)C(CH3)NNH2. The crystal structure of Cp*2ScN(H)C(CH3)NNH2 (monoclinic system, space group P21/n (No, 14), with a = 9.506 (3) A?, b = 14.742 (2) A?, c = 15.609 (2) A?, β = 92.45 (2)°, V = 2187.3 (8) A?3, Z = 4, and d = 1.177 g·cm-3) revsals 2 five-membered, nearly planar [ScN(H)C(CH3)NNH2] ring. The results of a labeling study using 15N≡CCH3 are consistent with a mechanism involving insertion of acetonitrile into the Sc-N bond of Cp*2ScNHNH2, followed by tautomerization to form Cp*2ScN(H)C(CH3)NNH2. The closely related compounds Cp*2ScN(H)NMe2 and Cp*2ScN(H)C(CH3)NNMe2 also have been prepared by using an analogous reaction pathway, and the structure of the latter has been determined as well (monoclinic system, space group P21/n (No. 14), with a = 10.953 (2) A?, b = 19.733 (1) A?, c = 11.441 (1) A?, β = 101.30 (1)°, V = 2424.9 (5) A?3, Z = 4, and d = 1.138 g·cm-3), revealing a four-membered, nearly planar [ScN(H)C(CH3)N(NMe2)] ring.
- Shapiro, Pamela J.,Henling, Lawrence M.,Marsh, Richard E.,Bercaw, John E.
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p. 4560 - 4565
(2008/10/08)
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- (Pentamethylcyclopentadienyl)indium(I) and -indium(III) compounds. Syntheses, reactivities, and X-ray diffraction and electron diffraction studies of In(C5Me5)
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The golden yellow compound In(C5Me5) has been prepared in 62% yield from InCl and Li(C5Me5) in diethyl ether and fully characterized according to its physical and solubility properties, its reaction with dilute aqueous HCl, a cryoscopic molecular weight study in cyclohexane, IR and 1H NMR spectroscopic properties, a single-crystal X-ray diffraction study, and a gas-phase electron diffraction study. The other products of this reaction have been identified as In(C5Me5)2Cl, indium metal, and (C5Me5)2 in 5.0, 21, and 2.5% yields, respectively. The identity of the yellow indium(III) product In(C5Me5)2Cl was confirmed by its independent synthesis from InCl3 and Li(C5Me5) in a 1:2 mol ratio and full characterization. The orange-yellow compound In(C5Me5)Cl2 has also been synthesized from InCl3 and Li(C5Me5) in a 1:1 mol ratio in order to distinguish it from In(C5Me5)2Cl. However, the attempted preparation of In(C5Me5)3 from InCl3 and either Li(C5Me5) or Na(C5Me5) was unsuccessful. A noteworthy observation of the chemical properties of the (pentamethylcyclopentadienyl)indium(I) and -indium(III) compounds was their decomposition in benzene solution to form (C5Me5)2 and other products. Additional studies of prepurified In(C5Me5) confirmed decomposition in THF and pyridine but demonstrated its stability in cyclohexane. The compound In(η5-C5Me5) crystallizes in the rhombohedral space group R3 (C3i2; No. 148) with unit cell parameters (hexagonal setting) a = 20.182 (4) A?, c = 13.436 (3) A?, V = 4739 12) A?3, and Z = 18. Single-crystal X-ray diffraction data (Mo Kα, 2θ = 4.5-50.0°) were collected with a Syntex P21 automated four-circle diffractometer; the structure was solved and refinement converged with RF = 3.6%. and RwF = 3.3% for all 1870 symmetry-independent data (none rejected) and RF = 2.5% and RwF = 2.9% for those 1444 reflections with |Fo| > 6σ(|Fo|). The η5-C5Me5 ligand is symmetrically bound to indium with In-C = 2.581 (4)-2.613 (4) A? (average = 2.595 A?) and In?centroid = 2.302 A?. The In(η5-C5Me5) units are arranged about centers of 3 (S6) symmetry, with indium atoms on the interior and η5-C5Me5 units on the exterior of hexameric units in which In-In distances are 3.942 (1)-3.963 (1) A?. The centroid → indium vectors do not point toward the center of the hexaindium cluster as in other main-group clusters. The molecular structure of In(C5Me5) in the gas phase consists of discrete monomeric units with the indium(I) atom being situated 2.288 A? above the ring centroid. Ab initio calculations were carried out on In(C5H5) and In(C5Me5) in an attempt to understand the effects of methyl groups on the bonding between indium(I) and the cyclopentadienyl ring.
- Beachley Jr.,Blom, Richard,Churchill, Melvyn Rowen,Faegri Jr., Knut,Fettinger, James C.,Pazik,Victoriano
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p. 346 - 356
(2008/10/08)
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- Decamethylsilicocene - The First Stable Silicon(II) Compound: Synthesis, Structure, and Bonding
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Reaction of dichlorobis(pentamethylcyclopentadienyl)silane with naphthalene-lithium, -sodium, or -potassium leads to elemental silicon and to decamethylsilicocene, (Me5C5)2Si (4).Compound 4 is formed as the only product in the reduction of dibromobis(pentamethylcyclopentadienyl)silane with anthracene-potassium. 4 is a thermally stable, colorless, air-sensitive ?-complex.Its NMR spectra are typical for a group 14 metallocene, the 29Si-NMR signal appears at very high field strength (δ = -398 ppm).CV and MS data of 4 prove the instability of the (Me5C5)Si+ ion, which easily looses a Me5C5 radical.X-ray crystallographic studies show the presence of two geometrical isomers, 4a and 4b, in the monoclinic unit cell.Isomer 4a is isotypical with decamethylferrocene, isomer 4b possesses the expected bent-metallocene-type structure.Space-filling models indicate the interplane angle in 4b to be of the largest possible value.Due to GED studies, 4 has a bent-metallocene-type structure in the gas phase.The He(I) PE spectrum of 4 is compared with those of the heavier homologues (Me5C5)2Ge (6), (Me5C5)2Sn (7), (Me5C5)2Pb (8).A strong shift to higher energy of the band assigned to the group 14 element lone pair is observed in going from 8, 7, or 6 to 4.Calculations have been carried out for structural models of the parent silicocene, (H5C5)2Si, on the basis of the MNDO procedure and of the HF theory (STO-3G and STO-3G* basis sets).The calculated geometrical parameters and orbital energies are compared with those derived from the GED experiment and from the PE spectrum.The bathochromic shift in the electronic absorption spectra going from 4 to 6-8 is explained on the basis of MNDO calculations for the parent metallocenes.
- Jutzi, Peter,Holtmann, Udo,Kanne, Dieter,Krueger, Carl,Blom, Richard,et al.
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p. 1629 - 1640
(2007/10/02)
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- Organolanthanide and organoactinide oxidative additions exhibiting enhanced reactivity. 5. Stoichiometry, kinetic, and mechanistic studies of (C5Me5)2YbII·OEt2 oxidative-addition reactions and of (C5Me5)2YbIIIR (R = R, X) YbIII ...
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Full title: Organolanthanide and organoactinide oxidative additions exhibiting enhanced reactivity. 5. Stoichiometry, kinetic, and mechanistic studies of (C5Me5)2YbII·OEt2 oxidative-addition reactions and of (C5Me5)2YbIIIR (R = R, X) YbIII-Grignard reactions with alkyl and aryl halides. Evidence for the dominance of inner-sphere mechanisms. (C5Me5)2YbII·OEt 2 undergoes atom-abstraction oxidative addition with alkyl and aryl halides according to the generalized stoichiometry 1.0(C5Me5)2YbII·OEt 2 + (1 + a)RX → (1 - a)(C5Me5)2YbIIIX + (a)(C5Me5)1YbIIIX2 + (a)C5Me5R + 1.0Et2O + 1.0[R-R, R-H(alkanes), R(-H)(olefins)]. A reactive Yb-alkyl intermediate, (C5Me5)2YbIIIR, is formed from R? trapping by diamagnetic (C5Me5)2YbII. This (C5Me5)2YbIIIR intermediate and the initial product (C5Me5)2YbIIIX react further with RX in subsequent YbIII-Grignard reactions that are retarded by added Et2O and, therefore, apparently operate via an inner-sphere pathway. The observed YbIII-Grignard stoichiometries are (C5Me5)2YbIIIR + 2RX → (C5Me5)2YbIIIX2 + C5Me5R + R-R and (C5Me5)2YbIIIX + RX → (C5Me5)1YbIIIX2 + C5Me5R. The absolute rates of reaction of RX with (C5Me5)2YbII·OEt2 are found to be first-order each in (C5Me5)2YbII·OEt-2 and RX, with an added inverse dependence upon Et2O. The Et2O dependence is consistent with a requirement for a site of coordinative unsaturation and an inner-sphere pathway. Comparison of the rates of reactions of (C5Me5)2UIII(Cl)(THF) and (C5Me5)2YbII·OEt2 with RX provides compelling evidence for participation of electron transfer in these net atom-abstraction reactions.
- Finke,Keenan,Watson
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p. 263 - 277
(2008/10/08)
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- On the Reaction of (Pentamethylcyclopentadienyl)lithium with Halomethanes and Formyl Compounds
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In view to the synthesis of pentamethylcyclopentadienyl-substituted methane derivatives ("pentamethylcyclopentadienyl-carbon compounds") reactions of (pentamethylcyclopentadienyl)lithium with halomethans, formates, and corbon dioxide were investigated.While treatment with tri- and tetrahalomethanes leads to benzene derivatives via molecular rearrangement, reactions with formates and carbon dioxide yield pentamethylcyclopentadienyl-substituted methane derivatives.Attempts to prepare disubstituted species show the formation of by-products only.
- Kohl, Franz X.,Jutzi, Peter
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p. 1539 - 1544
(2007/10/02)
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- Silver(I)-Catalyzed Isomerization of Water-Soluble Quadricyclanes
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In aqueous ammonia, silver(I)-catalyzed isomerization of quadricyclanes to norbornadienes was investigated.The catalytic action of silver(I) perchlorate induced rapid and clean isomerization of water-soluble quadricyclanes 1b-g to the corresponding norbornadienes 2b-g even at room temperature.In the isomerization, the silver(I) catalyst might attack 1 from the five-membered ring, which was different from the directions observed in the cobalt(II)-porphyryn- and rhodium(I)-catalyzed reactions.The present reactions proceed via the formation of the cationic species and the successive cleavage of the highly strained cyclopropane ring of 1 to give 2.
- Maruyama, Kazuhiro,Tamiaki, Hitoshi
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p. 3967 - 3970
(2007/10/02)
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- SYNTHESIS AND THERMOCHEMISTRY OF HFMo(CO)3C5Me5; COMPARISON OF CYCLOPENTADIENYL AND PENTAMETHYLCYCLOPENTADIENYL LIGANDS
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Toluenemolybdenum tricarbonyl reacts quantitatively with pentamethylcyclopentadiene in THF at room temperature yielding HMo(CO)3C5Me5.The heat given off in this reaction has been measured by solution calorirmetry and indicates there is little difference i
- Nolan, Steven P.,Hoff, Carl D.,Landrum, John T.
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p. 357 - 362
(2007/10/02)
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- The Photoisomerization of 1,2,3,4,5-Pentamethyl-5-vinyl-1,3-cyclopentadiene
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The title compound 1 is shown to give, both upon direct irradiation at 254 nm and upon acetophenone-sensitized photolysis at 300 nm, the syn-vinyl-pentamethylhousene 5, which spontaneously rearranges in a -sigmatropic process to give the bicycloheptadiene skeleton 2.Based on the photochemical behaviour of selectively deuterated starting material, the suggestion is made that the direct photolysis produces the vinylhousene skeleton by a classic electrocyclization, whereas the sensitized reaction reaches the same target via a di-?-methane rearrangement.The bicycloheptadiene derivative 2 gives pentamethylhomoprismane 3 upon prolonged irradiation at 254 nm.
- Burger, Ulrich,Etienne, Robert
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p. 2057 - 2062
(2007/10/02)
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- AN IMPROVED SYNTHESIS OF 1,2,3,4,5-PENTAMETHYLCYCLOPENTADIENE
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An inexpensive three-step synthesis for large-scale preparation of 1,2,3,4,5-pentamethylcyclopentadiene is reported.Improvement of Burger's route involving 2,3,5,6-tetrahydro-2,3,5,6-tetramethyl-γ-pyrone and 2,3,4,5,-tetramethylcyclopent-2-enone raised the overall yield to about 34percent of the desired compound (originally 8percent).
- Kohl, Franz X.,Jutzi, Peter
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p. 119 - 121
(2007/10/02)
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- INTRODUCTION OF THE PENTAKIS(METHOXYCARBONYL)CYCLOPENTADIENYL LIGAND IN STANNOCENE CHEMISTRY
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Decamethylstannocene reacts with pentakis( methoxycarbonyl)cyclopentadiene with elimination of pentamethylcyclopentadiene, yielding pentakis(methoxycarbonyl)pentamethylstannopcene and decakis(methoxycarbonyl)stannocene.
- Kohl, Franz X.,Schlueter, Ewald,Jutzi, Peter
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p. C37 - C38
(2007/10/02)
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- Nafion-Catalyzed Photoreaction. Photoisomerization of 3-Methylene-1,2,4,5,6,6-hexamethylcyclohexa-1,3-diene
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The heptamethylbenzenonium cation 2 was shown to be produced when a CH2Cl2 solution of 3-methylene-1,2,4,5,6,6-hexamethylcyclohexa-1,3-diene (1) is brought into contact with "anhydrous" Nafion in its acid form.Treatment of the Nafion with methanolic sodium hydroxide regenerates 1.Under the conditions used here, the number of active sites on the Nafion was found to be 0.347 mmol/g.Irradiation of the Nafion with light of wavelength greater than 380 nm caused 2 to be converted mostly to vinylcyclopentadiene 5, with minor amounts of pentamethylcyclopentadiene and hexamethylbenzene also being produced.No photoisomerization of 1 took place when it was irradiated under the same conditions in the absence of Nafion.The quantum efficiency for the conversion of 2 adsorbed onto the Nafion was found to be 0.48 +/- 0.05; the same value as is found for the isomerization of 2 in homogeneous solutions.The product 5 could be displaced from the Nafion by more 1.This permitted the reaction to be carried out in a continuous mode with the Nafion functioning as a photocatalyst for the process.
- Childs, Ronald F.,Mika-Gibala, Alicja
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p. 4204 - 4207
(2007/10/02)
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- Photolysis of the Carbon-Hydrogen Bond in Pentamethylcyclopentadiene. Properties of the Pentamethylcyclopentadienyl Radical
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Irradiation of pentamethylcyclopentadiene (A) in liquid solution with u.v. light results in homolysis of the ring C-H bond to give the pentamethylcyclopentadienyl radical (B) , and atomic hydrogen which abstracts hydrogen from a second molecule of (A) to give molecular hydrogen and a second radical (B).The radicals (B) self-react at a diffusion-controlled rate (2kt 2 x 1E9 l mol-1 s-1 in hexane at 25 degC) by two different routes.The first, which is thermally and photolytically reversible, is the combination to give the dehydrodimer (C), and the second, which is irreversible, is the disproportionation to give the parent cyclopentadiene (A) and the tetramethylfulvene (D).
- Davies, Alwyn G.,Lusztyk, Janusz
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p. 692 - 696
(2007/10/02)
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- Photolysis of heptamethylbenzenonium cation in aqueous acids. Preparation of pentamethylcyclopentadiene
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Irradiation of heptamehylbenzenium ion in a variety of aqueous acids using light of wavelength greater than 350 nm leads to the formation of pentamethylcyclopantediene and acetone.In 50percent HBF4 and 70percent HClO4 this photolysis is very clean and can be used as a convenient preparation of pentamethylcyclopentadiene.A mechanism is proposed for the reaction.
- Childs, Ronald F.,Zeya, Maung,Dain, Robert P.
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