cas 75-76-3, Tetramethylsilane | Articles data

Articles about 75-76-3Total 77 be found

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Structural tracking of the potassium-mediated magnesiation of anisole
Final destination: The potassium-mediated magnesiation of anisole has been monitored by a combination of X-ray crystallographic and NMR spectroscopic studies. Departing from a heteroleptic alkyl-amido base and anisole, the reaction first stops at an ortho
Clegg, William,Conway, Ben,Garcia-Alvarez, Pablo,Kennedy, Alan R.,Mulvey, Robert E.,Russo, Luca,Sassmannshausen, Joerg,Tuttle, Tell
p. 10702 - 10706
(2009)
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Catalytic Difunctionalization of Unactivated Alkenes with Unreactive Hexamethyldisilane through Regeneration of Silylium Ions
A metal-free, intermolecular syn-addition of hexamethyldisilane across simple alkenes is reported. The catalytic cycle is initiated and propagated by the transfer of a methyl group from the disilane to a silylium-ion-like intermediate, corresponding to the (re)generation of the silylium-ion catalyst. The key feature of the reaction sequence is the cleavage of the Si?Si bond in a 1,3-silyl shift from silicon to carbon. A central intermediate of the catalysis was structurally characterized by X-ray diffraction, and the computed reaction mechanism is fully consistent with the experimental findings.
Wu, Qian,Roy, Avijit,Irran, Elisabeth,Qu, Zheng-Wang,Grimme, Stefan,Klare, Hendrik F. T.,Oestreich, Martin
p. 17307 - 17311
(2019)
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Cobalt-catalysed alkene hydrogenation: A metallacycle can explain the hydroxyl activating effect and the diastereoselectivity
Bis(phosphine)cobalt dialkyl complexes have been reported to be highly active in the hydrogenation of tri-substituted alkenes bearing hydroxyl substituents. Alkene substrates containing ether, ester, or ketone substituents show minimal reactivity, indicating an activating effect of the hydroxyl group. The mechanistic details of bis(phosphine)cobalt-catalysed hydrogenation were recently evaluated computationally (X. Ma, M. Lei, J. Org. Chem. 2017, 82, 2703-2712) and a Co(0)-Co(ii) redox mechanism was proposed. However, the activating effect of the hydroxyl substituent and the accompanying high diastereoselectivity were not studied. Here we report a computational study rationalizing the role of the hydroxyl group through a key metallacycle species. The metallacycle is part of a non-redox catalytic pathway proceeding through Co(ii) intermediates throughout. The preference for alcohol over ether substrates and the high diastereoselectivity of terpinen-4-ol hydrogenation are correctly predicted in computations adopting the new pathway, whereas the alternative redox mechanism predicts ethers rather than alcohols to be more reactive substrates. Additional experimental evidence supports the role of the hydroxyl group in the metallacycle mechanism. Our work highlights the importance of employing known substrate preferences and stereoselectivities to test the validity of computationally proposed reaction pathways.
Morello, Glenn R.,Zhong, Hongyu,Chirik, Paul J.,Hopmann, Kathrin H.
p. 4977 - 4982
(2018)
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Polymer and metal oxide supported alkali metal naphthalenides: Application in the generation of lithium and sodium reagents
Highly coloured paramagnetic polymer supported lithium 5,5′ and sodium 6,6′ naphthalenide complexes have been prepared from the reaction of THF solutions of lithium and sodium biphenylide with polystyrene bearing -CH2SiMe2(C10H7) groups. Treating chloropropyl functionalised silica, alumina and titania surfaces with H3Al · NMe3 or H3Ga · NMe3 afford hydroxyl depleted surfaces. Successive treatment with lithium biphenylide, 1-(chlorodimethylsilyl)naphthalene and an alkali biphenylide affords supported alkali naphthalenide complexes which generate in high yield lithium and sodium reagents when treated with a range of organic halides, nitriles and phosphates, as found for 6,6′ and 7,7′.
Van Den Ancker, Tania R.,Raston, Colin L.
p. 283 - 300
(1998)
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Aston,Kennedy,Messerly
p. 2343
(1941)
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Bildung siliciumorganischer Verbindungen. CVII. Bildung und Struktur des trans-trans-trans-Nonamethyl-hexasilaperhydrophenalens
trans-trans-trans-2,2,4,6,6,8,10,10,12-Nonamethyl-2,4,6,8,10,12-hexasilaperhydrophenalene 6 (m.p. 170 deg C) is formed from the substituted cyclic carbosilane 3 at 25 deg C (5 h) in the presence of AlBr3 by elimination of SiMe4.At 35 deg C (5 h) the formation of the all-cis-isomer 6a is observed in addition to 6.On the other hand the thermal transformation of 6 into 6a was not observed below 420 deg C.None of the other possible isomers were detected.Compound 6 reacts with MeLi to give 7 via lithiation of the central C atom.The hydrolysis of 7 leads to a mixture of 6 and 6a in a 2/1 ratio.Compound 6 crystallizes orthorhombically space group P212121 (no.19); a = 2221.3, b = 1651.3, c = 667.3 pm; Z = 4; 2169 hkl; R = 0.053).Owing to the different size of the substituents on both sides of the polycyclic system the molecule is arched and the six-membered rings are flattened.The Si-C bond lengths decrease progressively from the central C atom to the periphery of the molecule(188.5 to 186.2 pm).It is shown that only the curvature of the polycyclic system causes a decrease in the endocyclic bond angles at the Si atoms (to 108.2 deg) and an increase in those at the C atoms (to 118.0 deg) as well as the flattening of the six-membered rings.
Fritz, G.,Volk, H.,Straub, M.,Schnering, H. G. von,Peters, K.,Peters, E.-M.
p. 109 - 118
(1988)
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FORMATION OF ORGANOMETALLIC COMPOUNDS OF CARBENE AND CARBINE TYPES BY THE INTERACTION OF RLi WITH NEODYMIUM AND YTTRIUM CHLORIDES IN VARIOUS MEDIA
It has been established that in the interaction of NdCl3 and YCl3 with RLi, where R=CH2C6H5, CH2C(CH3)2C6H5, CH2Si(CH3)3, unusual organometallic compounds are formed.They are stable in hydrocarbon solutions.The benzyl and neophyl derivatives are carbene type complexes containing one R group at a trivalent metal atom.In all cases the reaction is accompanied by the evolution of RH as the main product and some stilbene and tolan when R=CH2C6H5.The mechanism of this reaction is discussed.
Dolgoplosk, B. A.,Tinyakova, E. I.,Guzman, I. Sh.,Vollerstein, E. L.,Chigir, N. N.,et al.
p. 249 - 255
(1980)
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A General and Selective Synthesis of Methylmonochlorosilanes from Di-, Tri-, and Tetrachlorosilanes
Direct catalytic transformation of chlorosilanes into organosilicon compounds remains challenging due to difficulty in cleaving the strong Si-Cl bond(s). We herein report the palladium-catalyzed cross-coupling reaction of chlorosilanes with organoaluminum reagents. A combination of [Pd(C3H5)Cl]2 and DavePhos ligand catalyzed the selective methylation of various dichlorosilanes 1, trichlorosilanes 5, and tetrachlorosilane 6 to give the corresponding monochlorosilanes.
Naganawa, Yuki,Nakajima, Yumiko,Sakamoto, Kei
supporting information
p. 601 - 606
(2021/01/13)

Nickel-Catalyzed Selective Cross-Coupling of Chlorosilanes with Organoaluminum Reagents
Nickel-catalyzed cross-coupling reactions of chlorosilanes with organoaluminum reagents were developed. An electron-rich Ni(0)/PCy3 complex was found to be an effective catalyst for the desired transformation. The reaction of dichlorosilanes 1 proceeded to give the corresponding monosubstituted products 2. Trichlorosilanes 4 underwent selective double substitution to furnish the corresponding monochlorosilanes 2. Overall, the selective synthesis of a series of alkylmonochlorosilanes 2 from di- and trichlorosilanes was achieved using the present catalytic systems.
Naganawa, Yuki,Guo, Haiqing,Sakamoto, Kei,Nakajima, Yumiko
p. 3756 - 3759
(2019/09/12)

Hydrodechlorination of (CH3)3SiCHCl2 over Pd, Ni, Co and Fe supported on AlF3
Gas phase hydrodechlorination (HDC) process of Me3SiCHCl 2 was studied in a flow reactor at 200 °C using a 2% metal loading (w/w) of four different monometallic catalysts (Pd/AlF 3, Ni/AlF 3,Co/AlF 3 and Fe/AlF 3). The catalysts were prepared by sol-gel method and structurally examined by BET method, FT-IR and XPS techniques. The XPS technique showed that Ni II, Fe III and Co III exist as oxides. The major products in the HDC process of Me 3SiCHCl 2 were identified by GC and GC-MS and found to include Me 3SiCH 2Cl, Me 3SiCl, and Me 4Si. The effect of these catalysts on the quantitative conversion, selectivity and conversion rates are reported. [Figure not available: see fulltext.]
Hina, Rateb,Arafa, Isam,Ennab, Omar
p. 353 - 358
(2017/03/23)

Half-sandwich rare-earth metal tris(alkyl) ate complexes catalyzed phosphaguanylation reaction of phosphines with carbodiimides: An efficient synthesis of phosphaguanidines
The phosphaguanylation reaction of phosphines with carbodiimides catalyzed by half-sandwich yttrium tris(trimethylsilylmethyl) ate complexes is achieved for the first time to efficiently prepare phosphaguanidines. The catalyst system of the yttrium ate complex displays better catalytic activity than those of neutral yttrium complexes.
Ma, Wangyang,Xu, Ling,Zhang, Wen-Xiong,Xi, Zhenfeng
p. 7649 - 7655
(2015/10/12)

Wagner-Meerwein-Type Rearrangements of Germapolysilanes - A Stable Ion Study
(Chemical Equation Presented). The rearrangement of tris(trimethylsilyl)silyltrimethylgermane 1 to give tetrakis(trimethylsilyl)germane 2 was investigated as a typical example for Lewis acid catalyzed Wagner-Meerwein-type rearrangements of polysilanes and polygermasilanes. Direct 29Si NMR spectroscopic evidence is provided for several cationic intermediates during the reaction. The identity of these species was verified by independent synthesis and NMR characterization, and their transformation was followed by NMR spectroscopy.
Albers, Lena,Meshgi, Mohammad Aghazadeh,Baumgartner, Judith,Marschner, Christoph,Müller, Thomas
supporting information
p. 3756 - 3763
(2015/08/19)

PROCESS FOR THE PRODUCTION OF SILANE PRODUCTS FROM CALCIUM SILICIDE
A process for preparing a reaction product including a silane product includes step (i), (ii), and (iii). Step (i) is contacting an organohalide with a calcium silicide at a temperature from 300 °C to 700 °C to form the reaction product including a spent reactant and the silane product. The silane product has formula RmHnSiX(4-m-n), where each R is independently a monovalent organic group, each X is independently a halogen atom; subscript m is 0 to 4; subscript n is 0 to 2; and a quantity (m + n) is 0 to 4. Step (ii) is contacting, at a temperature from 200 °C to 1400 °C, the spent reactant with a silane of formula HaRbSiX(4-a-b), where subscript a is 0 to 4, subscript b is 0 or 1, a quantity (a + b) ≤ 4. The silane of formula HaRbSiX(4-a-b) is distinct from the silane product of formula RmHnSiX(4-m-n). When the quantity (a + b) 2; thereby forming a reactant. Step (iii) is contacting the reactant formed in step (ii) with an additional organohalide at a temperature from 300 °C to 700 °C to form an additional silane product of formula RmHnSiX(4-m-n). Steps (ii) and (iii) are performed separately and consecutively after step (i).
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Paragraph 0052

(2014/11/11)

Synthesis of the first persilylated ammonium ion, [(Me3Si) 3NSi(H)Me2]+, by silylium-catalyzed methyl/hydrogen exchange reactions
This work describes the unexpected synthesis and characterization of the first persilylated ammonium ion, [(Me3Si)3NSi(H)Me 2]+, in the reaction of (Me3Si)3N with [Me3Si-H-SiMe3][B(C6F5) 4]. NMR and Raman studies revealed a transition-metal-free silylium ion catalyzed substituent redistribution process when [Me3Si-H- SiMe3]+ was used as the silylating reagent. These observations were affirmed in the reaction with [Et3Si-H-SiEt 3][B(C6F5)4]. A Lewis acid catalyzed scrambling process always occurs if an excess of silanes is present in the formation of silylium cations while employing the standard Bartlett-Schneider- Condon type reaction. Additionally, the thermodynamics of this process was accessed by DFT computations at the pbe1pbe/aug-cc-pVDZ level, indicating alkyl substituent exchange equilibria at the silane and preference of the formation of [(Me3Si)3NSi(H)Me2]+ over [(Me 3Si)4N]+.
Labbow, Rene,Reiss, Fabian,Schulz, Axel,Villinger, Alexander
supporting information
p. 3223 - 3226
(2014/08/05)

METHOD FOR PREPARING AN ORGANO-FUNCTIONAL SILANE
A process includes reacting an organometallic cuprate and a silicon precursor in the presence of a solvent. The process produces a reaction product including an organo-functional silane.
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Paragraph 0026

(2014/05/24)

Reactions of d0 tungsten alkylidyne complexes with O2 or H2O. Formation of an oxo siloxy complex through unusual silyl migrations
(Me3SiCH2)3(Me3SiC) W←OPMe3 (1), an adduct between (Me3SiCH 2)3WCSiMe3 (2) and OPMe3, reacts with O2 to give OW(OSiMe3)(CH
Morton, Laurel A.,Miao, Maozhong,Callaway, Tabitha M.,Chen, Tianniu,Chen, Shu-Jian,Tuinman, Albert A.,Yu, Xianghua,Lu, Zheng,Xue, Zi-Ling
p. 9555 - 9557
(2013/10/08)

Acceptorless photocatalytic dehydrogenation for alcohol decarbonylation and imine synthesis
It has come to light: Renewed interest in conversions of highly oxygenated materials has motivated studies of the organometallic-catalyzed photocatalytic dehydrogenative decarbonylation of primary alcohols into alkanes, CO, and H2 (see scheme). Methanol, ethanol, benzyl alcohol, and cyclohexanemethanol are readily decarbonylated. The photocatalysts are also active for amine dehydrogenation to give N-alkyl aldimines and H2.
Ho, Hung-An,Manna, Kuntal,Sadow, Aaron D.
supporting information; experimental part
p. 8607 - 8610
(2012/09/11)

(Py)2Co(CH2SiMe3)2 as an easily accessible source of "coR2"
(Py)2CoR2 (R = CH2SiMe3) is easily prepared from (Py)4CoCl2 and RLi. It is fairly stable at room temperature and serves as a convenient source of CoR2 for transfer to other ligands. Unfortunately, (Py)2CoR2 was obtained only as an oil, but the structure of the related complex (Py) 2CoR-2 (R- = CH2CMe2Ph) could be confirmed by a single-crystal X-ray diffraction study. Transfer of the CoR 2 fragment from (Py)2CoR2 or (TMEDA)CoR 2 to diiminepyridine-type ligands (1-6) was studied as a function of ligand steric and electronic properties. Reaction with N-2,6-dimethylphenyl (1) and N-2,4,6-trimethylphenyl (2) ligands produced diamagnetic monoalkyl complexes; the structure of (1)CoR was confirmed by X-ray diffraction. With the less shielding N-phenyl (3) and N-benzyl (4) ligands, 1H NMR indicated formation of diamagnetic CoI alkyl species, but they were not stable enough to allow isolation. Fluorinated ligand 5 appears to be less reactive and-despite its supposedly stronger φ-acceptor character-also does not lead to formation of a stable CoI alkyl complex. With PyBOX ligand 6, high-spin dialkyl complex (6)CoR2 was observed by 1H NMR. Based on these observations and DFT calculations, a mechanism is proposed for formation of diiminepyridine CoI alkyls that involves formation of a high-spin κ2 complex, spin flip to give a low-spin κ3 complex, and irreversible loss of an alkyl radical.
Zhu, Di,Janssen, Femke F. B. J.,Budzelaar, Peter H. M.
experimental part
p. 1897 - 1908
(2010/06/14)

Formation of silicon-carbon bonds by photochemical irradiation of (η5-C5H5)Fe(CO)2SiR3 and (η5-C5H5)Fe(CO)2Me to Obtain R3SiMe
Photochemical irradiation of an equimolar mixture of (η5 -C5H5)Fe(CO)2SiR3, FpSiR 3, and FpMe leads to the efficient formation of the silicon-carbon-coupled product R3SiMe, R3 = Me 3, Me2Ph, MePh2, Ph3, ClMe 2, Cl2Me, Cl3, Me2Ar (Ar = C 6H4-p-X, X = F, OMe, CF3, NMe2). Similar chemistry occurs with related germyl and stannyl complexes at slower rates, Si > Ge Sn. Substitution of an aryl hydrogen to form FpSiMe2C6H4-p-X has little effect on the rate of the reaction, whereas progressive substitution of methyl groups on silicon by Cl slows the process. Also, changing FpMe to FpCH2SiMe3 dramatically slows the reaction as does the use of (η5-C 5Me5)Fe(CO)2 derivatives. A mechanism involving the initial formation of the 16e intermediate (η5-C 5H5)Fe(CO)Me followed by oxidative addition of the Fe-Si bond accounts for the experimental results obtained.
Fortier, Skye,Zhang, Yongqiang,Sharma, Hemant K.,Pannell, Keith H.
body text
p. 1041 - 1044
(2010/04/25)

METHODS AND APPARATUS FOR FORMING GASEOUS ORGANOSILICON COMPOUNDS
The present application is directed to a method for producing, from a solid organosilane compound, a mixture of gaseous organosilicon compounds having a desired molar ratio, the method comprising the step of pyrolysing the solid organosilane while maintaining a predetermined pressure which is selected to provide the desired molar ratio of gaseous organosilicon compounds. Associated apparatus and control mechanisms are also disclosed.
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Page/Page column 35-39

(2009/07/03)

Unusual Decomposition of 1,2-Bis(trimethylsiloxy)benzene in the Presence of Gallium Triiodide
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Voronkov, M. G.,Tsyrendorzhieva, I. P.,Dubinskaya, E. I.
p. 1969 - 1970
(2007/10/03)

Unusual Transformations of Trimethylphenoxysilane in the Reaction with Gallium Oxide
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Voronkov, M. G.,Tsyrendorzhieva, I. P.,Albanov, A. I.,Shergina, N. I.,Klyba, L. V.,Dubinskaya, E. I.
p. 656 - 657
(2007/10/03)

Reaction of Octamethylcyclotetrasiloxane with Aluminum, Gallium, and Silicon Iodides
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Voronkov, M. G.,Tsyrendorzhieva, I. P.,Albanov, A. I.,Shergina, N. I.,Klyba, L. V.,Dubinskaya, E. I.
p. 654 - 655
(2007/10/03)

Phenyl heterocycles as cox-2 inhibitors
The invention encompasses the novel compound of Formula I useful in the treatment of cyclooxygenase-2 mediated diseases. STR1 The invention also encompasses certain pharmaceutical compositions for treatment of cyclooxygenase-2 mediated diseases comprising compounds of Formula I.
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(2008/06/13)

Use of inhibitors of cyclooxygenase in the treatment of neurodegenerative diseases
The present invention provides a method of treating a neurodegenerative disease and in particular Alzheimers disease which comprises administering to a human in need thereof a therapeutically effective amount of a non-steroid COX-II inhibitor. Although a wide range of COX-II inhibitors may be employed but it is preferred to employ compounds of the Formula I: STR1
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(2008/06/13)

Process for preparing allylic silane compounds
A method for preparing an allylic silane compound of the formula AmRnSiCl4-n-mis disclosed, said method comprising reacting (A) a chlorosilane of the formula RnSiCl4-nwith (B) a halogenated allylic compound, said reaction being carried out in an aprotic dipolar organic solvent in the presence of metallic zinc, wherein A represents an allylic group, R is independently selected from the group consisting of a hydrogen atom, saturated hydrocarbon group having 1 to 20 carbon atoms and an unsaturated hydrocarbon group having 1 to 20 carbon atoms , n is an integer having a value of 0 to 3 and m is an integer having a value of 1 to 4.
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(2008/06/13)

1,1,1-Trimethyl-3,3,3-trichlorodisiloxane as a source and a trapping agent for silanones
The pyrolysis of 1,1,1-trimethyl-3,3,3-trichlorodisiloxane (1) was studied and its mechanism involving the formation of dichloro-and dimethylsilanones was proposed. The composition of the condensate from the co-pyrolysis of siloxane 1 and hexamethyldisiloxane indicated that under the pyrolysis conditions the simplest siloxanes can be both the sources and the trapping agents of silanones.
Krasnova,Chernyshev,Sergeev
p. 1238 - 1239
(2007/10/03)

Diaryl bicyclic heterocycles as inhibitors of cyclooxygenase-2
The invention encompasses the novel compound of Formula I as well as a method of treating cyclooxygenase-2 mediated diseases comprising administration to a patient in need of such treatment of a non-toxic therapeutically effective amount of a compound of Formula I. STR1 The invention also encompasses certain pharmaceutical compositions for treatment of cyclooxygenase-2 mediated diseases comprising compounds of Formula I.
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(2008/06/13)

Phenyl heterocycles as cox-2 inhibitors
The invention encompasses the novel compound of Formula I useful in the treatment of cyclooxygenase-2 mediated diseases, STR1 The invention also encompasses certain pharmaceutical compositions for treatment of cyclooxygenase-2 mediated diseases comprising compounds of Formula I.
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(2008/06/13)

Peculiarities in the cleavage by methyllithium of unsymmetrical disilanes
The title reactions did not produce the more stable silyl anions from the disilanes studied, they either occurred by attack at the more electrophilic silicon atom, or led to unexpected products.
Hevesi,Dehon
p. 8031 - 8032
(2007/10/02)

A mild and convenient synthesis of functionalized methyl triflones and vinyl triflones
A general route for the synthesis of methyl triflone derivatives utilizing triflic anhydride is described. Stereoselective synthesis of E-vinyl and dienyl triflones has been accomplished by the Peterson olefination reaction of α-silyl triflone anions.
Mahadevan, Anu,Fuchs
p. 6025 - 6028
(2007/10/02)

UNUSUAL CATALYTIC CONVERSIONS OF PERMETHYLOLIGOSILOXANES. NEW ROUTE TO TETRAMETHYLSILANE AND DIMETHYLSILANONE
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Voronkov, M. G.,Basenko, S. V.,Ustinov, M. V.
p. 273 - 276
(2007/10/02)

NEW PROCEDURE FOR SYNTHESIZING TETRAMETHYLSILANE
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Voronkov, M. G.,Basenko, S. V.,Ustinov, M. V.
p. 1501 - 1502
(2007/10/02)

Reduction of Ruthenium and Iron μ-Methylene Complexes with Hydrosilanes Producing Alkane: a Model System for Methanation via the Fischer-Tropsch Mechanism
Reduction of the Ru and Fe μ-methylene complexes (2: M = Ru, R = H; 3: M = Fe, R = CH2Ph) with hydrosilanes produces alkane (RMe) by way of dinuclear hydrido-methylene and methyl intermediates as confirmed by the reaction of 9 with hydrosilanes; such a reaction sequence can be viewed as a model system for methanation via the Fischer-Tropsch mechanism.
Akita, Munetaka,Oku, Tomoharu,Hua, Ruimao,Moro-oka, Yoshihiko
p. 1670 - 1672
(2007/10/02)

Silicon-Carbon Bond Formation Kinetics: Study of the Reactions of CH3 with SiH3, Si(CH3)3, and SiCl3
The kinetics of three Si-C bond-forming association reactions were investigated at the high-pressure limit: SiH3 + CH3 (1), Si(CH3)3 + CH3 (2), and SiCl3 + CH3 (3).Rate constants were measured using a heatable tubular reactor coupled to a photoionization mass spectrometer.The two radical reactants were produced simultaneously (CH3 always in great excess) using pulsed 193-nm photolysis of suitable precursors diluted in helium, and the radical decays were monitored in time-resolved experiments.The radical decay profiles were fitted to appropriate expressions to obtain the desired rate constants.Reaction 1 was studied between 301 and 526 K yielding the following Arrhenius expression for the association reaction: k1 = (5.6 +/- 2.4) * 10-11 exp((3.0 +/- 1.6) kJ mol-1 / RT). (All rate constants are in the units cm3 molecule-1 s-1.) Reaction 2 was investigated between 306 and 526 K yielding the expression k2 = (5.2 +/- 2.2) * 10-11 exp((2.4 +/- 1.4) kJ mol-1 / RT).Reaction 3 was studied at one temperature, 303 K, where k3 = (1.1 +/- 0.4) * 10-10.Treating these association reactions as cross-combination reactions, the measured rate constants were found to be predicted with reasonable accuracy using the geometric mean rule and the rate constants of the related self-association reactions of the reactant radicals.The mechanisms of these reactions are discussed.
Niiranen, Jukka T.,Gutman, David
p. 9392 - 9396
(2007/10/02)

Generation, characterization, and properties of iron-silylene and iron-silene cationic complexes in the gas phase
Generation, characterization, and properties of iron-silylene (Fe=SiRR′) and iron-silene (Fe(CH2=SiRR′)) cations (R, R′ = H, CH3) are describe in the gas phase by using Fourier transform mass spectrometry (FTMS). Iron-(silylene/silene) cations were formed by reaction of Fe+ with appropriate silanes. Structures of these ions were probed by using both collision-activated dissociation (CAD) and ion/molecule reactions. CAD failed to yield structural information; however, reaction with isotopically labeled ethene provides compelling evidence for formation of iron-silene and iron-silylene species. There is no evidence for the interconversion of iron-silylene and iron-silene species, even upon slow collisional activation or by formation of ethene collision complexes (ca. 40 kcal/mol of excess energy). This indicates that there is a prohibitive barrier for iron mediated interconversion of silene and silylenes. Reactions of iron-silylene and iron-silene species with water and benzene are described. The nature of the bonding is presented and bond dissociation limits are obtained.
Jacobson,Bakbtiar
p. 10830 - 10844
(2007/10/02)

A Study on the Reducing Abilities of Tris(alkylthio)silanes
Tris(methylthio)silane and tris(isopropylthio)silane effectively reduce a variety of organic substrates via free radical mechanisms.These silanes can also be used as hydrosilylating agents for alkenes having electron-donating substituents.The bond dissociation energy of the Si-H bonds have been measured by photoacoustic calorimetry and found to be around 83 kcal mol-1.The absolute rate constants for the reaction of the tert-butoxyl radical with (RS)3SiH have been measured by a laser flash photolysis technique and the optical absorption spectra of the correspondingradicals have been obtained.Multiple scattering Xα calculations showed that the dominant absorption detected in the UV-vis region was due to ?Si-S(e) -> SOMO and SOMO -> ?*Si-S(e) transitions.
Chatgilialoglu, C.,Guerra, M.,Guerrini, A.,Seconi, G.,Clark, K. B.,et al.
p. 2427 - 2433
(2007/10/02)

The Me3Si Substituent Effect on the Reactivity of Silanes. Structural Correlations between Silyl Radicals and Their Parent Silanes
Good linear correlations exist both between the bond dissociation energy of an Si-H bond and the corresponding SiH stretching frequency and between the (29)Si hyperfine splitting of a silicon-centered radical and J((29)Si-H) for the corresponding silane, when the successive substitution at the Si-H function takes place inside a family, i.e., (Me3Si)3-nSi(H)Men, n = 0-3.Explanations for these phenomena are advanced.Such structural correlations allow the characterization of (Me3Si)2Si(H)Me as a radical-based reducing agent with low hydrogen-donating abilities.Rate constants for the reaction of primary alkyl radicals with (Me3Si)2Si(H)Me have been measured over a range of temperatures by using competing unimolecular radical reactions as timing devices.The radical trapping abilities of this silane and other common radical-based reducing agents are compared.
Chatgilialoglu, C.,Guerrini, A.,Lucarini, M.
p. 3405 - 3409
(2007/10/02)

Molecular precursors for indium phosphide and synthesis of small III-V semiconductor clusters in solution
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Douglas, Trevor,Theopold, Klaus H.
p. 594 - 596
(2008/10/08)

Mechanism of CH2.+ Transfer from Distonic Ions X-CH2.+ (X=CH2O, CH2CH2) to ?- and n-Electron Bases in the Gas Phase. A Fourier Transform Ion Cyclotron Resonance (FTICR) Study Supplemented by ab initio MO Calculations
The reactions of acetonitrile, propyne, acetylene, trimethylsilylacetylene, and tetramethylsilane, with distonic ions CH2XCH2.+ are studied in the gas phase using Fourier Transform Ion Cyclotron Resonance (FTICR) mass spectrometry.In line with previous studies, CH2.+ is transferred to the electron lone-pair of the nitrogen atom of CH3CN to generate CH3CN-CH2.+ (4); upon collisional excitation, this ion undergoes competitive losses of H. and CH..While both neutrals originate from the "methylene" unit of 4, detailed studies employing labeledsubstrates and using various types of collision experiments reveal an intriguing dissociation pattern in that the dissociations are preceded by two intramolecular hydrogen migrations giving rise to CH3C(H)=NCH.+ (6) and CH3C=N(H)CH.+ (7).While 6 serves as intermediate en route to loss of H. from the "CH" moiety, 7 is the actual precursor to generate, by loss of CH., protonated acetonitrile, CH3CNH+ (12) (Scheme 5).In addition, 12 is formed by bimolecular proton transfer.In this reaction, translationally excited CX3CN-CY2.+* (X, Y = H, D) transfers X+ to neutral CX3CN to generate CX3CNX+ (Scheme 4).The bimolecular proton transfer as well as the intramolecular isomerizations of 4 to 6 and 7 are subject to very large kinetic isotope effects.In the transfer of CH2.+ to CH3CCH two products are formed .+ (16) and CH2=C=CHCH3.+ (17) presumably via intermediate 18 (Scheme 6)>; the latter is formed by addition of CH2.+ to the less hindered carbon atom of HCCCH3 reflecting the higher stability of the so-formed intermediate compared with addition to C-2.Reactions of 2 and 3 with HCCH do not result in the formation of a detectable CH2.+-transfer product.When using CH2CH2CH2.+ (2) the reaction is prohibited by the endothermicity to generate the initial complex (structurally related to 18).On the other hand, when CH2OCH2.+ (3) is employed, the intermediate of CH2.+ transfer is formed with sufficient energy to split off a hydrogen atom.Preliminary experiments with silicon-containing molecules, like Si(CH3)4 or HCCSi(CH3)3, demonstrate that the favored processes of these neutrals with 2 and 3 are due to charge transfer (in the form of an electron or an anion like CH3- or C2H-) from the silicon-containing molecule to the distonic ions.The experimental results obtained for CH3CN/CH2.+ system are supported by ab initio MO calculations (3-21G/3-21G + ZPVE).
Rusli, Ridwan D.,Schwarz, Helmut
p. 535 - 540
(2007/10/02)

Comparative reactivity of isoelectronic nitrido, methylimido, and oxo complexes of osmium(VI)
The structures, physical properties, and reaction chemistry of isoelectronic alkyl complexes of osmium(VI) are compared. The three, five-coordinate alkyl complexes [NBun4][Os(N)(CH2SiMe3) 4], Os(NMe)(
Marshman, Robert W.,Shapley, Patricia A.
p. 8369 - 8378
(2007/10/02)

Silyl and diphenylsilylene derivatives of (η5-C5Me5)(PMe3)2Ru. Evidence for the base-free silylene complex [(η5-C5Me5)(PMe3) 2Ru=SiPh2]+
The preparation, characterization, and properties of new ruthenium silyl and diphenylsilylene derivatives of Cp*(PMe3)2Ru (Cp* = η5-C5Me5) are described. The silyl complexes Cp*(PMe3)2RuSiR3 (SiR3 = SiEt3 (1), SiPh3 (2), SiPh2Me (3), SiPh2Cl (4)) are obtained directly by reaction of Cp*(PMe3)2RuCH2SiMe3 with the appropriate silane HSiR3 at 80-100 °C. Other conditions lead to loss of 1 equiv of PMe3 to afford the ruthenium(IV) bis(silyl) species Cp*(PMe3)Ru(SiR3)2H (SiR3 = Si(OEt)3 (5), SiPh2Cl (6), SiMe2OEt (7)). The nucleophilic reagents MeMgCl and LiAlH4 displace chloride from 4 to afford 3 and Cp*(PMe3)2RuSiPh2H (8), respectively. The triflate derivative Cp*(PMe3)2RuSiPh2(OTf) (9, OTf = OSO2CF3) is obtained in high yield from reaction of 4 and Me3SiOTf in dichloromethane. Solubility properties and solid-state infrared spectroscopy indicate that 9 possesses a covalent silicon-triflate interaction. Compound 9 exhibits a triplet resonance in the 29Si NMR spectrum at δ 112.39 (2JPSi = 33 Hz). In acetonitrile solution 9 exists mainly as the ionic silylene adduct [Cp*(PMe3)2RuSiPh2(NCMe)]OTf, as determined by 1H NMR spectroscopy, solution infrared spectroscopy, and conductivity measurements. Addition of NaBPh4 to an acetonitrile solution of 9 allows isolation of the silylene adduct [Cp*-(PMe3)2RuSiPh2(NCMe)]BPh4 (10) as a dichloromethane solvate. This procedure also produces significant quantities of [Cp*(PMe3)2Ru(NCMe)]BPh4 (11) as byproduct. Compound 11 was prepared independently by reaction of Cp*(PMe3)2RuCl and AgBPh4 in acetonitrile. Compound 10 exhibits a single broad resonance in its 29Si NMR spectrum at δ 95.75. The thermal stability of 10 in solution and in the solid state is described. 10 reacts with water rapidly to give 11 and the disiloxane Ph2HSiOSiHPh2. It also reacts with LiAlH4 to afford 8 in 37% yield. The acetonitrile of 10 is quite labile and exchanges rapidly with free acetonitrile in solution. A line-shape analysis of variable-temperature 1H NMR spectra of 10 in the presence of 1 equiv of NCMe afforded activation parameters for this exchange process of ΔH? = 14.5 ± 0.3 kcal mol-1 and ΔS? = 14 ± 2 eu. This positive value for the entropy of activation is consistent with a dissociative mechanism and provides evidence for existence of the base-free silylene complex Cp*(PMe3)2Ru=SiPh2+ in solution. Structures of complexes 8, 9, and 10·CH2Cl2 have been determined by single-crystal X-ray diffraction experiments. Crystals of 8 are triclinic, Pl?, with a = 9 362 (1) A?, b = 9.748 (2) A?, c = 16.376 (3) A?, α = 98.18 (2)°, β = 103.71 (2)°, γ = 94.14 (2)°, V = 1428.4 (6) A?3, Z = 2, RF = 2.59%, and RwF = 2.98%. Crystals of 9 are triclinic, Pl?, with a = 10.171 (3) A?, b = 10.802 (3) A?, c = 16.880 (5) A?, α = 86.82 (2)°, β = 88.03 (2)°, γ = 64.00 (1)°, V = 1664.2 (7) A?3, Z = 2, RF = 4.39%, and RwF = 5.61%. Crystals of 10·CH2Cl2 are monoclinic, P21/n, with a = 21.565 (8) A?, b = 10.215 (4) A?, c = 25.59 (1) A?, β = 108.40 (3)°, V = 5349 (3) A?3, Z = 4, RF = 6.32%, and RwF = 6.37%. The Ru-Si distances for these complexes are 2.387 (1) (8), 2.349 (2) (9), and 2.328 (2) A? (10·CH2Cl2). Whereas 8 and 9 exhibit similar staggered conformations with the Cp* and X (Cp*(PMe3)2RuSiPh2X, X = H or OTf) groups in a gauche relationship, 10·CH2Cl2 has a conformation that is skewed toward an eclipsed arrangement of substituents (Cp* centroid-Ru-Si-N dihedral angle = 38.0°). The Si-O distance in 9 is rather long, at 1.853 (5) A?. The Si-N distance in 10·CH2Cl2, 1.932 (8) A?, is consistent with a dative interaction between nitrogen and silicon. Other geometrical parameters for these complexes are compared and discussed.
Straus, Daniel A.,Zhang, Cheng,Quimbita, Grace E.,Grumbine, Steven D.,Heyn, Richard H.,Tilley, T. Don,Rheingold, Arnold L.,Geib, Steven J.
p. 2673 - 2681
(2007/10/02)

5-nitro-2-(3,5-diamino-2,4,6-trinitrophenyl)-1,2,4-triazole, its preparation process and explosive material containing it
The invention relates to 5-nitro-2(3,5-diamino-2,4,6-trinitrophenyl)-1,2,4-triazole of formula: STR1 It is prepared by reacting a 1-halogeno-3,5-diamino-2,4,6-trinitrobenzene with 3-nitro-1,2,4-triazole or one of its alkali metal salts. This triazole derivative can be used as a secondary explosive. It has a lower shock sensitivity than octogen, while still being able to supply a high energy.
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(2008/06/13)

Trimethyllead-Lithium in Tetrahydrofuran: Synthesis of Trimethyl(trimethylplumbyl)silane and of the Trimethylplumbyltrihydridoborate Anion
Solutions of trimethyllead-lithium Li (1), in tetrahydrofuran (THF) (ca. 0.5 M) can be obtained from trimethyllead bromide and an excess of lithium at -78 deg C. 1H, 13C and 207Pb NMR are used for monitoring the formation of the reagent.Extensive decomposition into lead and tetramethyllead is observed at -20 deg C within minutes.The application of this reagent is demonstrated by the synthesis of trimethyl(trimethylplumbyl)silane (2) and its stoichiometric 1:1 reaction with BH3-THF at -78 deg C, leading to lithium trimethylplumbyltrihydridoborate Li (3).The composition of the products in solution follows conclusively from their 1H, 11B, 13C, 29Si, and 207Pb NMR data.The silane 2 decomposes slowly at ambient temperature into Me4Si, Me4Pb and lead.The borate is even less stable, decomposing at temperatures above -30 deg C mainly into lead, Me4Pb, Li and Li. - Keywords: Trimethyllead-Lithium, Trimethyl(trimethylplumbyl)silane, Trimethylplumbyltrihydridoborate Anion, NMR Spectra
Wrackmeyer, Bernd,Horchler, Klaus
p. 1195 - 1198
(2007/10/02)

1,3-Ditungstacyclobutadienes. 4. 1:1 diphenyldiazomethane adducts W2(μ-CSiMe3)2X4?(N 2CPh2). A comparison of the effects of the supporting ligands, X = CH2SiMe3 versus X = O-i-Pr
Hydrocarbon solutions of W2(μ-CSiMe3)2X4(W-W) compounds, where X = CH2SiMe3 and O-i-Pr, have been found to react with diphenyldiazomethane, N2CPh2, at room temperature to give the 1:1 adducts W2(μ-CSiMe3)2X4(N 2CPh2) (1, X = CH2SiMe3; 2, X = O-i-Pr). The dinuclear center of the alkylidyne compound acts as a source of electrons reducing the diazoalkane to a NNCPh2 hydrazonido(2-) ligand. Both compounds have been characterized by 1H, 13C, and IR spectroscopy. The molecular structure of W2(μ-CSiMe3)2(CH2SiMe 3)4(N2CPh2) (1) shows that NNCPh2 is terminally bound to one W atom resulting in a pseudo-trigonal-bipyramidal geometry at that W atom wherein the coordinated NNCPh2 ligand and one of the alkylidyne bridges occupy the axial positions. The other W atom is in a pseudotetrahedral environment. The W-N distance of 1.767 (10) A? together with the WNN angle of 158.2 (8)° suggests partial donation of the nitrogen lone pair to give significant W=N character. Thermolysis of 1 at 120°C in toluene solution results in loss of Si(CH3)4 (1 equiv) and generates, via C-H bond activation, a compound which we formulate, on the basis of 1H and 13C NMR spectroscopic data, as (Me3SiCH2)2W(μ-CSiMe3) 2W-(CH2SiMe3)(NN=C(Ph)-o-C6H 4). At no time was alkylidene formation observed from either thermolysis or photolysis of solutions of 1. On the basis of low-temperature 1H NMR, 13C NMR, and IR spectroscopic data, we formulate that 2 is structurally related to 1. The molecule is fluxional on the 1H NMR time scale due to a pseudorotational process occurring about the trigonal-bipyramidal W atom, ΔG≠rot = 13.4 kcal/mol. Neither thermolysis at 120°C nor photolysis of hydrocarbon solutions of 2 generate alkylidene-containing products, but rather dissociation of N2CPh2 occurs with regeneration of W2(μ-CSiMe3)2(O-i-Pr)4. Crystal data for 1 at -159°C: a = 21.163 (5) A?, b = 22.639 (4) A?, c = 10.403 (1) A?, β = 91.73 (1)°, Z = 4, dcalcd = 1.441 g cm-3, and space group P21/a.
Chisholm, Malcolm H.,Heppert, Joseph A.,Huffman, John C.,Ontiveros, Cynthia D.
p. 976 - 982
(2008/10/08)

Neutral monocyclopentadienyllutetium alky is: In search of steric unsaturation
Addition of a THF solution of NaC5Me5 (1 equiv) to a refluxing THF solution of LuCl3(THF)3 affords after workup [Na(THF·OEt2)]Lu(η5-C5Me 5)Cl3 (1) in ca. 70% yield. Compound 1 reacts cleanly with LiCH(SiMe3)2 in diethyl ether, in the presence of THF (5 equiv) to afford the monoalkyl complex [Li(THF)2]Lu(η5-C5Me 5){CH(SiMe3)2}Cl2 (2) in 69% yield. Addition of tetramethylethylenediamine (TMEDA) to the supernatant liquor after isolation of 2 affords an additional 16% of [Li(TMEDA)]Lu(η5-C5Me5){CH(SiMe 3)2}Cl2 (3). A LiCl-free, mixed alkyl complex, 8, was prepared from reaction of 3 with LiCH2SiMe3 giving initially a mixture of [Li(THF)3]Lu(η5-C5Me5)(CH 2SiMe3){CH(SiMe3)2}Cl (7) and Lu(η5-C5Me5)(CH2SiMe 3){CH(SiMe3)2}(THF) (8). Recrystallization (once) from hexane gave neutral, LiCl-free 8. This is the first reported neutral mixed alkyl organolanthanide complex. The single-crystal X-ray structure determinations of 3 and 7 are reported. In each case the lutetium atom shows a three-legged piano-stool coordination geometry, with the lithium atom in a tetrahedral coordination and linked to the lutetium by one (in 7) or two (in 3) bridging chloride ligands. The lutetium-alkyl bond lengths are 2.367 (6) A? in 3 and 2.394 (16) and 2.344 (18) A? for Lu-CH(SiMe3)2 and 2.353 (17) and 2.314 (18) A? for Lu-CH2SiMe3 for the two distinct molecules of 7, present in the crystal.
Van Der Heijden, Harry,Pasman, Peter,De Boer, Eric J. M.,Schaverien, Colin J.,Orpen, A. Guy
p. 1459 - 1467
(2008/10/08)

Tungsten-carbon, carbon-hydrogen, and carbon-carbon bond activation in the chemistry of 1,2-W2R2(OR′)4(Wu=W) complexes. 2. Metal-carbon bond homolysis and competitive alkane and dihydrogen eliminations in double α-hydrogen activation processes
Thermolysis of bis(alkyne) adducts of formula W2(CH2R)2(MeCCMe)2(O-i-Pr) 4 (1a) (where R = Ph, SiMe3, and t-Bu) in hydrocarbon solutions produces HW2(μ-CR)(μ-C4Me4)(O-i-Pr)4 ((2)H) and (RCH2)W2(μ-CR)(μ-C4Me 4)(O-i-Pr)4 ((2)R) by competitive reaction pathways. The formation of compounds (2)H and (2)R requires coupling of terminal alkyne ligands and double α-hydrogen abstractions of one alkyl ligand. One equivalent of RCH3 or H2 is produced for each mole of (2)H or (2)R formed, respectively. In all cases, (2)H is the major reaction product. In the solid state, a thermal crystal-to-powder decrepitation of (1a)(SiMe3) occurs to produce a 2:1 mixture of (2)H(SiMe3) and (2)R(SiMe3) with t1/2 ≈ 100 days at room temperature. Compounds of formula W2(CH2R)2(R′CCR″) 2(O-i-Pr)4 (where R = t-Bu, R′ = Me, R″ = Et; R = SiMe3 or Ph, R′ = Et, R″ = Me or Et) react thermally to form a mixture of as yet unidentified organometallic products. No analogues of 2 with MC4 rings bearing Et substituents were unequivocally identified. The benzyl derivatives of 1 (where R = Ph) react photochemically at low temperatures (10°C) to form W2(μ-C2R′2)2(O-i-Pr) 4 (3a, R′ = Me; 3c, R′ = Et) and bibenzyl as the major reaction products. Mechanistic studies of the formation of compounds 3 are indicative of metal-carbon bond homolysis. Compounds 2 were characterized by 1H NMR, 13C NMR, and IR spectroscopic studies and elemental analysis. Compounds (2)H(Ph) and (2)R(SiMe3) were structurally characterized by single-crystal X-ray diffraction. The two molecules are virtually isostructural with symmetrical alkylidyne bridges [W-C = 1.96 (2) A? (average)] and single W-W bonds [W-W = 2.77 (2) A? (average)]. The hydride ligand of (2)H(Ph) was not located in the crystallographic study but was assigned the position trans to the η4-C4Me4 ring based on NOE difference NMR experiments. The low-temperature limiting NMR spectra for 2 are consistent with the solid-state structures but at ambient temperatures and above, a fluxional process is observed involving inversion of configuration at one metal center. Mechanistic studies revealed intramolecular first-order reactions for the thermolyses of 1 with the rates of reaction (and rate constants) following the series for the three alkyl ligands kt-Bu > kSiMe3 > kPh and the alkyne ligands substituents (R′ = R″) kMe ? kEt. A small kinetic isotope effect, kH/kD = 1.4, was observed when W2(CD2Ph)2(MeCCMe)2(O-i-Pr) 4 was employed. The activation parameters for (1a)(Ph) and (1a)(SiMe3) are ΔS≠ = -9 eu, ΔH≠ = 21 kcal mol-1 and ΔS≠ = -9 eu, ΔH≠ = 23 kcal mol-1, respectively, indicating that the differences in rates are enthalpic in origin. The data are most consistent with a rate-determining alkyne-coupling step that is followed by the C-H activation processes. Comparisons of these reactions with mononuclear orthometalation and α-hydrogen abstraction reactions are presented. Crystal data for W2(H)(μ-CPh)(μ-C4Me4)(O-i-Pr)4 at -159°C: a = 9.183 (3) A?, b = 15.606 (6) A?, c = 19.977 (9) A?, Z = 4, dcalcd = 1.862 g cm-3, space group P212121; for W2(CH2SiMe3)(μ-CSiMe 3)(μ-C4Me4)(O-i-Pr)4 at -155°C: a = 11.906 (4) A?, b = 15.633 (5) A?, c = 9.584 (3) A?, α = 90.47 (2)°, β = 99.49 (2)°, γ = 91.27 (2)°, dcalcd = 1.738 g cm-3, space group P1.
Chisholm, Malcolm H.,Eichhorn, Bryan W.,Huffman, John C.
p. 67 - 79
(2008/10/08)

Carbon-Carbon Bond-Forming Reactions of Organotransition Metals with α- or γ-Haloorganolithium Reagents
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Negishi, Ei-ichi,Akiyoshi, Kazunari,O'Connor, Brian,Takagi, Kentaro,Wu, Guangzhong
p. 3089 - 3091
(2007/10/02)

Diaminotetrafluoroethoxybenzenes
Tetrafluoroethoxybenzenes, and their acid addition salts, of the general formula: STR1 in which R1 may represent hydrogen or an alkyl having from 1 to 4 carbon atoms and R2, R3 and R4 represent one or more of the same or different substituents selected from hydrogen, an alkyl having 1 to 4 carbon atoms or mono- or dihydroxylalkyls having 1 to 4 carbon atoms, provided that the amino groups are situated relative to one another in an ortho- or meta- position and R1, R2, R3 and R4 do not simultaneously represent hydrogen when the amino groups are arranged in a 2,4- position. The compounds of the invention, along with 2,4-diaminotetrafluoroethoxybenzene, are useful as coupler components in oxidative hair coloring agents. A process for making the compounds, as well as a separate process for making the mono-N-β-hydroxylethyl compounds, is provided.
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(2008/06/13)

THE ACTIVATION OF IMINES TO NUCLEOPHILIC ATTACK BY GRIGNARD REAGENTS
The reaction of trimethylsilyl trifluoromethylmethanesulfonate (trimethylsilyl triflate, TMSOTf) with imines leads to the formation of N-trimethylsilyliminium salts which react efficiently with soft nucleophiles to form secondary amines.
Brook, Michael,Jahangir
p. 893 - 898
(2007/10/02)

Bonding studies on zinc, cadmium, and mercury alkyls and amides, Zn(CH2EMe3)2 (E = C or Si) and M2 (M = Zn, Cd, or Hg). Heats of hydrolysis, standard heats of formation, and Zn-C and M-N (M = Zn, Cd, or Hg) bond energy terms
Calorimetric measurements have been carried out on the heats of hydrolysis of the homoleptic zinc alkyls Zn(CH2EMe3)2 (E = C or Si) and bis(trimethylsilyl)amides M2 (M = Zn, Cd, or Hg) at 25 +/- 0.01 deg C in aqueous hydrochloric (1 M; for the
Guemruekcueoglue, Ismail E.,Jeffery, John,Lappert, Michael F.,Pedley, J. Brian,Rai, Audesh K.
p. 53 - 62
(2007/10/02)

Absolute Rate Constants for Some Intermolecular and Intramolecular Reactions of α-, β-, and γ-Silicon-Substituted Radicals
Rate constants for hydrogen atom abstraction from n-Bu3GeH (kGeH) by Me3SiCH2. (1.), Me3SiCH2CH2. (2.), and Me3SiCH2CH2CH2. (3.) and from n-Bu3SnH (kSnH) by 1. and 3. have been determined at ambient temperatures.The order of decreasing radical reactivity is 1. > n-alkyl > 3. > 2..However, for bromine abstraction from the parent bromides by n-Bu3Sn. and n-Bu3Ge., the order of decreasing reactivity is 1-Br > 2-Br > 3-Br ca. n-alkyl bromide.The Arrhenius equations for reaction of 1. and 3. with n-Bu3SnH were also determined: log (kSnH(1.)/(M-1 s-1)) = (10.2 +/- 0.5) - (3.90 +/- 0.62)/Θ and log (kSnH(3.)/(M-1 s-1)) = (8.4 +/- 0.7) - (2.81 +/- 0.95)/Θ, where Θ = 2.3RT kcal/mol.These kinetic data are discussed in relation to previously measured rate constant ratios, kc5+6/kSnH and kexo5/kendo6, where kc5+6 corresponds to the cyclization of α-, β-, and γ-dimethylsilyl-substituted 5-hexenyl radicals to form 5-membered (kexo5) and 6-membered (kendo6) silacycloalkylmethyl radicals.
Wilt, James W.,Lusztyk, J.,Peeran, Mehoob,Ingold, K. U.
p. 281 - 287
(2007/10/02)

Cu(PMe3)4.
Alkylation of copper(II) acetate with dialkylmagnesium reagents in the presence of tertiary phosphines gives the colorless copper(I) alkyl species. With sterically small phosphines, the complexes are ionic and possess left bracket Cu(PR//3)//4 right bracket cations and left bracket CuR//2 right bracket anions; larger phosphines give electrically neutral CuR(PR//3)//3 coordination complexes. Solution NMR data indicate that reversible phosphine dissociation is a facile process for all of the complexes and that extensive ion pairing occurs in nonpolar solvents. The X-ray crystal structure of the dimethylcuprate complex has been determined.
Dempsey,Girolami
p. 1208 - 1213
(2008/10/08)