Some new organoxy (alkyl) ethynylsilanes

Conclusions Some ethynyl(organoxy)silanes were obtained by the transetherification of CH₃O(CH₃)₂SiC CH with 1,3 dichloroisopropanol, 4-iodophenol, and 3, 5-xylenol, of CH₃O(CH₃)Si(C CH)₂ with ethanol, of CH₃O(CH₃)Si(CH = CH₂) (C CH) with ethanol and propanol, and of CH₃(CH₃O)₂SiC CH with butanol.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 450–451, February, 1977.     

Mechanisms of Heterogeneous Processes in the System SiO2 + CH4: III. Products of >Si

Permenov  D. G.  Radzig  V. A. 《Kinetics and Catalysis》2004,45(2):273-278

DFT study of the mechanism of alkane hydrogenolysis by transition metal hydrides. 1. Interaction of silica-supported zirconium hydrides with methane

Model reactions of silica-supported zirconium hydrides (Si—O—)₃ZrH and (Si—O—)₂ZrH₂ with methane, resulting in cleavage of a C—H bond in the methane molecule and the formation of (Si—O—)₃ZrCH₃ and (Si—O—)₂Zr(H)CH₃ as products were studied using the DFT approach with the PBE density functional. The processes proceed as bimolecular reactions without preliminary formation of agostic complexes. According to calculations, zirconium dihydrides (Si—O—)₂ZrH₂ are more reactive toward the methane C—H bonds than zirconium monohydrides (Si—O—)₃ZrH. The calculated activation energies of the reactions with participation of zirconium dihydrides (Si—O—)₂ZrH₂ are in better agreement with the known experimental data for the Yermakov—Basset catalytic system.     

Ethynylisopropylgermanes and Their Trimethylsilyl Derivatives

The reaction of ethynylmagnesium bromide with chloroisopropylgermanes (i-Pr_{4 - n} GeCl_{/sub> n} , n = 1-3) was used to prepare previously unknown ethynylisopropylgermanes i-Pr_{4 - n} Ge(CCH) _n (n = 1-3). The reaction of Me₃SiCCMgBr with i-PrGeCl₃ afforded i-Pr(Me₃SiCC)_{3 - n} GeCl _n (n = 1, 2). The reaction of the monochloride with BrMdCCH gave i-Pr(HCC)₂GeCCSiMe₃, while with the dichloride, i-Pr(HCC)·Ge(CSiMe₃)₂ formed. The latter compounds were obtained by independent synthesis from i-PrGe(CCH)₃, EtMgBr, and ClSiMe₃. The reaction of (bromomagnesioethynyl)triisopropylgermane with Me₃SiCl gave i-Pr₃GeCSiMe₃.     

Ab initio calculations of potential energy surface for reaction of nucleophilic addition of H− ion to methylacetylene

Within the framework of the Hartree-Fock-Roothaan Method, using double- basis sets 3-21++G and (6-31-H-G//3-21++G), the minimum energy paths (MEPs) have been calculated for reactions of nucleophilic addition of the hydride ion H^– to the methylacetylene molecule: CH₃-CCH+H^–[CH₃-CH=CH]^– (1) CH₃-CCH+H^–[CH₃-C=CH₂]^– (2). It has been established that the activation energy for reaction (2) is 7.02 kJ/mole lower than for reaction (1). An analysis has been made of the character of electron density distribution along the MEP of each reaction. It has been shown that distortion of geometry of the reactants plays an important role in intensifying the interaction of the frontier orbitals. The reasons for nonfulfillment of Markownikoff's rule for these reactions have been determined. The results from the calculations are compared with calculations reported in the literature for the related reaction of nucleophilic addition of the hydride ion H^– to the acetylene molecule: HCCH+H^–[CH₂=CH]^–.Translated from Teoreticheskaya i Éxperimental'naya Khimiya, Vol. 21, No. 3, pp. 303–309, May–June, 1985.     

3-Phenoxy- and 3-phenylthio-1-propynyl substituted derivatives of silicon and germanium

Reactions of bromomagnesiopropargyl phenyl ethers and their isostmctural sulfides BrMgCCCH₂XPh (X = O, S) with MeVinSiCl₂, Me(CH₂Cl)SiCl₂, EtSiHCl₂, and Me₂SiHCl afforded the corresponding 3-phenoxy- and 3-phenylthio-1-propynyl substituted derivatives of silicon (PhXCH₂CC)₂SiRR¹ and PhXCH₂CCSiHMe₂ (X = O, S). Reactions of the above-mentioned Iotsitch reagents with GeCl₄ led to the corresponding germanium derivatives (PhXCH₂CC)₄Ge (X = O, S).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 511–513, March, 1994.     

Photochemistry of Aliphatic Nitroxide Radicals Grafted onto Activated Aerosil Surface

The mechanism of photoinduced transformations of nitroxide radicals SiON(O^·)CH₃ (I) and SiOCH₂N(O^·)CH₃ (II) obtained on the activated aerosil surface was studied. The nitroxides were photolyzed with 436-nm light at 77 K. It was shown that the action of light in the long-wavelength absorption band corresponding to the n–* transition resulted in the dissociation of the O–N or C–N bond in radicals I or II, respectively. The quantum yields of these reactions were found to be 0.6 and 0.002, respectively.     

C-C bond formation at polynuclear metal centers

Studies on C-C bond formation between simple hydrocarbon species such as CH₂, C=CH₂, CH=CH₂, CH₂=CH₂, CH₂=C=CH₂ and CHCH at a diruthenium center suggest that the process is promoted when the dimetal center can readily compensate for the two electrons lost in the formation of the new C-C bond. Thus, whereas -CH₂ and ethene combine only under forcing conditions, the combination of -CH₂ with allene or ethyne, which have additional -electrons available for coordination, occurs readily at room temperature. Likewise, the availability of uncoordinated -electrons in -C=CH₂ allows vinylidene to link rapidly with ethene at room temperature. Alkyne complexes [Ru₂(CO)(-RCCR)(-C₅H₅)₂] (R=CF₃ or Ph) react only under vigorous conditions with additional alkyne to give [Ru₂(CO)(-C₄R₄) (-C₅H₅)₂], but give these same species at room temperature in the presence of acid, shown to be due to the intermediacy of highly reactive 30-electron -vinyl cations. Thermally, alkyne linking proceedsvia three-alkyne species [Ru₂(-C₆R₆)(-C₅H₅)₂] to a four-alkyne complex [Ru₂(-C₈R₈)(-C₅H₅)₂], containing an unprecedented C₈ ligand composed of a C₆ ring with a C₂ tail. Treatment of [Ru₂(CO)(-RCCR)(-C₅H₅)₂] with unsaturated metal fragments gives trimetal complexes such as [Ru₃(CO)₅(₃-CF₃CCCF₃) (-C₅H₅)₂]. The MeCN derivative of this species undergoes unusual linking processes on reaction with additional alkyne to giveinter alia [Ru₃(CO)₃(₃-CCF₃){₃-C₃(CF₃)₃}(-C₅H₅)₂], arising from alkyne cleavage, and [Ru₃(CO)₃{₃-C₄(CF₃)₂(CO₂Me)₂}(-C₅H₅)₂], a closo-pentagonal bipyramidal Ru₃C₄ cluster.     

Mechanisms of Heterogeneous Processes in the System SiO2 + CH4: I. Methane Chemisorption on a Reactive Silica Surface

Experimental and quantum chemical study of reactive silica surface methylation is carried out. The main product of the reaction is the (Si–O)₂Si(H)(CH₃) groups, which are formed via a radical-chain process with the participation of methane molecules and paramagnetic and diamagnetic defects on the oxide surface. Spectral (optical and IR) characteristics of the groups participating in the process (Si–O)₂Si^·–CH₃, (Si–O)₂Si(H)(CH₃), and (Si–O)₂Si(CH₃)(CH₃) are determined. Information on the kinetics of separate steps of the process is obtained including rate constants and the activation energies of steps.     

Diacetylenic Derivatives of Fe2(CO)6(μ-EE′): Spectroscopic Investigations of Fe2(CO)6{μ-EC(H) = C(C≡ CMe)E′} (E = E′, E ≠ E′; E, E′ = S, Se, Te)

The diacetylenic adducts, Fe₂(CO)₆{-EC(H) = C(C CMe)E} (E = E, E E; E, E = S, Se, Te) (1–8) have been obtained from the room temperature stirring of Fe₂(CO)₆(-EE) with HC CC CMe in methanol solvent containing sodium acetate. Compounds 1–8 have been characterized by IR and multinuclear NMR (¹H, ¹³C, ⁷⁷Se, and ^l25Te) spectroscopy. Trends in the chemical shifts of ⁷⁷Se and ¹²⁵Te NMR spectra of Fe₂(CO)₆{-EC(H) = C(C CMe)E} with a variation of EE are discussed.     

Triethynylsilane and some of its Si-substituted derivatives

Conclusions Triethynylsilane and some of its Si-substituted derivatives, corresponding to the general formula (HCC)₃SiX, where X=H, OCH₃, OCOCH₃, OSi(CH₃)₃, OSi(CCH)₃, were synthesized.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2147–2148, September, 1978.     

Reaction of the Hexa-1,3,5-triyne Me3SiC≡CC≡CC≡CSiMe3 with Ru4(CO)13(μ 3-PPh): Parallels with the Chemistry of Alkynes and Diynes

Reaction of Ru₄(CO)₁₃(₃-PPh) (1) with the 1,3,5-hexatriyne Me₃SiCCCCC CSiMe₃ under mild thermal conditions affords initially Ru₄(CO)₁₀(-CO)₂{₄-¹,¹,²-P(Ph)C(CCSiMe₃)C(CCSiMe₃) (2), via the facile formation of a P–C bond in a manner similar to that demonstrated previously with alkynes and diynes. The 62-CVE cluster 2 readily decarbonylates to give crystallographically characterised Ru₄(CO)₁₀(-CO)(₄-PPh){₄-¹,¹,²,²-Me₃SiCCC₂CCSiMe₃} (3). Attempts to further incorporate the pendant alkyne moieties in 3 into the Ru₄ coordination environment were partially successful with Ru₄(CO)₁₀(₄-PPh)(₄-¹,¹,³,³-RC₄R') (4, R/R'=SiMe₃/CCSiMe₃) being formed as a minor product together with the unusual toluene coordinated species Ru₄(CO)₇(⁶-C₆H₅Me)(₄-PPh)(₄-¹,¹,³,³-Me₃SiC₄CCSiMe₄) (5). Cluster 3 reacts with an excess of Me₃SiCCCCCCSiMe₃ to give the open chain cluster Ru₄(CO)₉(₃-PPh){₄-²,²,⁴,⁴,-C₄(CCSiMe₃)(SiMe₃)C₄(CCSiMe₃)₃} (6).     

Synthesis of novel symmetrical and nonsymmetrical 6-membered heterocycles with pendant electron-rich organoiron substituents

The functionalized complexes [(dppe)Cp^*Fe(CC)]₂-(Py) (Py=2,6-C₅H₃N and 3,5-C₅H₃N (dppe=1,2-bis(diphenylphosphino)ethane) were isolated in good yields from reaction of the chloro complex (dppe)Cp^*FeCl with the protected bis-acetylenic heterocyclic precursor. These electron-rich pyridyl ligands constitute interesting examples of organometallic heterocycles bearing redox-active substituents. Attempts to find an alternative route starting from the alkynyl complex [(dppe)Cp^*Fe(CCH)] and the corresponding dibromopyridines using a Sonogashira cross-coupling reaction are also described. By this route, the monofunctionalized products [(dppe)Cp^*Fe(CC)]-2,6-Py-Br and [(dppe)Cp^*Fe(CC)]-3,5-Py-Br could be cleanly isolated. These compounds open the way to the generation of heteroaromatics featuring nonequivalent alkyne substituents such as [(dppe)Cp^*Fe(CC)]-2,6-Py-[(CC)SiMe₃] or [(dppe)Cp^*Fe(CC)]-3,5-Py-[(CC)SiMe₃] by further coupling.In commemoriation of the centenary of Academician A. N. Nesmeyanov.UMR CNRS 6509 Organométalliques et catalyse: Chimie et Electrochimie Moléculaires, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1207–1218, September, 1999.     

α-Acetylene Hydrosilanes as Hydrosilylating Agents for Terminal Arylacetylenes

The hydrosilylation of a number of acetylenes RCCH (R, R' = Ph, CH₂OPh, CH₂SPh) with -ethynylhydrosilanes Me₂SiHCHCR' in the presence of H₂PtCl₆ was investigated. The addition did not occur regioselectively, but was stereospecific and afforded a mixture of - and trans--adducts. The replacement of phenyl substituent by phenoxymethyl both in the molecule of ethynylsilane and the acetylene substrate resulted in growing proportion of the -adduct in the reaction mixture up to 10-60%.     

Mechanisms of Heterogeneous Processes in the System SiO2 + CH4: II. Methylation of >Si=O Groups

The methods of optical and IR spectroscopy and quantum chemistry were used to obtain data on the direction and kinetics of the reaction of a silanone (SiO)₂Si=O with a CH₄ molecule and a methyl radical. Two mechanisms of methylation of silanone groups, molecular and free-radical, are studied. Both processes are accompanied by the formation of (SiO)₂Si(OH)(CH₃) groups. The rate constant of the molecular process is determined and its activation energy is estimated (17 kcal/mol). A methyl radical adds to the silicon atom in a silanone group to form the oxy radical (Si–O)₂Si(O)(CH₃). This radical carries a free-radical process of silanone group methylation. The main channel for the pyrolysis of (Si–O)₂Si(OH)(CH₃) groups is their decomposition with the abstraction of a methane molecule. The activation energy of this process is 70 kcal/mol. Quantum chemical methods were employed to obtain data on possible intermediates in the processes studied and these results are used to interpret spectral and kinetic data.     

Disproportionation of the alkynyl derivatives of alkali metal aluminum hydrides in electron-donor solvents

Conclusions The reaction of disproportionation of mixed hydride alkynyl complexes of aluminum in ether, THF, and hexametapol was studied by²⁷Al NMR, and it was shown that the stability of MAlH(3–n)) (CCR)_n, where M=Li, Na, K, and R=Ph, n-Bu decreases in the order: MAlH(CCR)₃ < MAlH₂(CCR)₂ < MAlH₃(CCR). The tendency of these complexes to disproportionate increases with an increase in the solvation of the cation.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 343–349, February, 1984.We would like to thank A. V. Kisin for recording the²⁷Al NMR spectra.     

Unusual condensation of propargylamine. Generation of the 1,3-di(propargylimino)propane anion coordinated to the cobalt(iii) atom

The reaction of propargylamine with the hexanuclear complex Co^II ₆(₃-OH)₂(OOCCMe₃)₁₀(HOOCCMe₃)₄ or the polymer [Co(OH)_n(OOCCMe₃)_2–n]_x under an argon atmosphere afforded the unstable paramagnetic tetramine complex Co^II(OOCCMe₃)₂(H₂NCH₂CCH)₄ (1). In air, if an excess of propargylamine is present, the latter complex is transformed into the complex Co^III(OOCCMe₃)₂(NH₂CH₂CCH)₂[²-N,N"-(HCCCH₂N=CHCHCH=N—CH₂CCH)] (2) containing a new ligand, viz., the 1,3-di(propargylimino)propane anion, which is a formal analog of the acetylacetonate anion. In contrast to propargylamine, 1,3-diaminopropane reacted with the Co^II trimethylacetate clusters in air to produce the cationic complex [Co^III{1,3-(NH₂)₂(CH₂)₃}₂(OOCCMe₃)₂]⁺OOCCMe₃ ^– (3) without entering into condensation reactions. The structures of the resulting complexes were determined by X-ray diffraction analysis.     

Synthesis of the gold-dirhenium ferrocenylacetylide cluster. The crystal structure of Re2(μ-C≡CFc){Au(PPh3)}(CO)8

The thermal reaction of Re₂(CO)₈(NCMe)₂ with Au(CCFc)PPh₃ afforded the cluster Re₂(-CCFc){Au(PPh₃)}(CO)₈, which was characterized by X-ray diffraction analysis.     

Cyclosilethynes containing exocyclic cyclopentyl and cyclohexyl groups

The reaction of BrMgCCSiMe₂CCSiMe₂CCSiMe₂CCSiMe₂CCMgBr with chloro(cyclopentyl)(methyl)silane in a large excess of THF gave 1-cyclopentyl-1,4,4,7,7,10,10,13,13-nonamethyl-1,4,7,10, 13-pentasilacyclopentadeca-2,5,8,11,14-pentayne. Similarly, 1,10-di(cyclopentyl)- or 1,6-di(cyclopentylmethyl)-1,4,4,7,7,10,13,13,16,16-decamethyl-1,4,7,10,13,16-hexasilacyclooctadeca-2,5,8,11,14,17-hexaynes were synthesized from BrMgCCSiMe₂CCSiMe₂CCMgBr and dichloro(cyclopentyl)methylsilane or dichloro(cyclopentylmethyl)(methyl)silane. Condensation of Me₂Si(CCMgBr)₂ with dichloro(cyclohexyl)-methylsilane afforded 1,7-di(cyclohexyl)-1,4,4,7,10,10-hexamethyl-1,4,7,10-tetrasilacyclododeca-2,5,8,11-tetrayne.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 8, 2004, pp. 1282–1284.Original Russian Text Copyright © 2004 by O. Yarosh, Zhilitskaya, N. Yarosh, Albanov, Klyba, Voronkov.This revised version was published online in April 2005 with a corrected cover date.     

Regioselectivity in the Addition of Nucleophilic Reagents to 1-Alkylthio-2-polyfluoroalkylacetylenes

Calculations for HCCH, HCCCF₃, and H₃CSCCCF₃ were carried out using the MP2(f)/6-31G(d) nonempiric quantum-chemical method. The electronic structure and charge density distribution were examined using natural bond orbitals and the results account for the differences in the direction of nucleophilic attack of the triple bond in HCCCF₃ and H₃CSCCCF₃.