C–C Bond Rupture in the Oxidation of Lower (C2–C6) Alcohols with Hydrogen Peroxide Mediated by Iron-Containing Compounds

C–C bond rupture upon the oxidation of alcohols in the Fe(ClO₄)₃+ H₂O₂system in aqueous acetonitrile at room temperature is found. The relative yield of the products of C–C bond rupture is 20–30% under standard conditions for C₂and C₃alcohols and decreases in the series C₂> C₃> C₄> C₆. The alkyl radical and carboxylic acid are the products of C–C bond rupture in alcohol oxidation. Cyclohexane is a competitive inhibiting agent for C–H bond oxidation in 1-propanol, and it does not affect the yield of the products of C–C bond rupture. When H₂O₂is replaced by tert-BuOOH, the fraction of the products of C–C bond rupture decreases by an order of magnitude. Our data suggest that a non-radical intermediate, likely Fe(III) hydroperoxo complex, is responsible for C–C bond rupture in alcohol under the reaction conditions.     

The Tail Wags the Dog: The Far Periphery of the Coordination Environment Manipulates the Photophysical Properties of Heteroleptic Cu(I) Complexes

In this work we show, using the example of a series of [Cu(Xantphos)(N^N)]⁺ complexes (N^N being substituted 5-phenyl-bipyridine) with different peripheral N^N ligands, that substituents distant from the main action zone can have a significant effect on the physicochemical properties of the system. By using the C≡C bond on the periphery of the coordination environment, three hybrid molecular systems with −Si(CH₃)₃, −Au(PR₃), and −C₂HN₃(CH₂)C₁₀H₇ fragments were produced. The Cu(I) complexes thus obtained demonstrate complicated emission behaviour, which was investigated by spectroscopic, electrochemical, and computational methods in order to understand the mechanism of energy transfer. It was found that the −Si(CH₃)₃ fragment connected to the peripheral C≡C bond changes luminescence to long-lived intra-ligand phosphorescence, in contrast to MLCT phosphorescence or TADF. The obtained results can be used for the design of new materials based on Cu(I) complexes with controlled optoelectronic properties on the molecular level, as well as for the production of hybrid systems.     

Vibrational spectroscopic study of the structure of Ti(III) organometallic compounds

Conclusions A full interpretation was carried out for the vibrational spectra of TiR₃, where R= -CH₂C₆H₅, -CH₂C(CH₃)₂C₆H₅, and-CH₂Si(CH₃)₃. The absorption bands for the Ti-C bonds were delineated. A dimeric structure was established for the compounds studied with a Ti-Ti bond, whose band lies at 230–280 cm^–1. There is an interaction of the titanium atom with the -carbon atom of the ligand for the Ti(III) benzyl and neophyl derivatives.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2736–2739, December, 1987.     

New deoxygenative transformations; reactions of (CO)4Fe[Si(CH3)3]2 with acyclic ethers

The reaction of cis-(CO)₄Fe[Si(CH₃)₃]₂ (I) with CH₃OSi(CH₃)₃ and C₆H₅CH₂-OSi(CH₃)₃ at 80°C affords good yields of [(CH₃)₃Si]₂O and the deoxygenation products RSi(CH₃)₃ (R = CH₃, C₆H₅CH₂). These reactions are proposed to occur via (CO)₄Fe(R)Si(CH₃)₃ intermediates. This is supported by the observed formation of cis-(CO)₄Fe(CH₃)Si(CH₃)₃ (II) during the more rapid reaction of I with (CH₃)₂O; subsequent (CH₃)₄Si elimination occurs. With (C₆H₅CH₂)₂O, I reacts at 80°C to yield C₆H₅CH₂Si(CH₃)₃ and C₆H₅CH₂OSi(CH₃)₃ as primary products. With C₆H₅CH₂OCH₃, I effects regioselective benzyl---oxygen bond cleavage.     

Elucidating the structures of isomeric silylenium ions (SiC3H 9 + , SiC4H 11 + , SiC5H 13 + ) by using specific ion/molecule reactions

Specific ion/molecule reactions are demonstrated that distinguish the structures of the following isomeric organosilylenium ions: Si(CH₃) ₃ ⁺ and SiH(CH₃)(C₂H₅)⁺; Si(CH₃)₂(C₂H₅)⁺ and SiH(C₂H₅) ₂ ⁺ ; and Si(CH₃)₂(i?C₃H₇)⁺, Si(CH₃)₂(n?C₃H₇)⁺, Si(CH₃)(C₂H₅) ₂ ⁺ , and Si(CH₃)₃(π?C₂H₄)⁺. Both methanol and isotopically labeled ethene yield structure-specific reactions with these ions. Methanol reacts with alkylsilylenium ions by competitive elimination of a corresponding alkane or dehydrogenation and yields a methoxysilylenium ion. Isotopically labeled ethene reacts specifically with alkylsilylenium ions containing a two-carbon or larger alkyl substituent by displacement of the corresponding olefin and yields an ethylsilylenium ion. Methanol reactions were found to be efficient for all systems, whereas isotopically labeled ethene reaction efficiencies were quite variable, with dialkylsilylenium ions reacting rapidly and trialkylsilylenium ions reacting much more slowly. Mechanisms for these reactions and differences in the kinetics are discussed.     

Silicium-stickstoff-fluorverbidungen: V. Darstellung neuer silylaminofluorsilane

Compounds of the composition RR′SiFNR″Si(CH₃)₃ (R = H, F, CH₃, C₂H₅, C₃H₇, C₂H₃, C₆H₅, C(CH₃)₃; R = F, CH₃, C₆H₅; R″ = CH₃, C(CH₃)₃, Si(CH₃)₃) are obtained by the reaction of silicontetrafluoride or organo-substituted silicon-fluorides with the lithium salts of alkylsilylamines in a molar ratio of $\text{1}\text{1}$. The disubstituted compounds RSiF(NR′Si(CH₃)₃)₂ (R = H, F, CH₃, C₂H₃, C₆H₅; R′ = CH₃, C(CH₃)₃) result when the reactants are in a $\text{1}\text{2}$ molar-ratio. Likewise the unsymmetrical siliconfluorsilylamines of the formulae F₂Si(NRSi(CH₃)₃) (NR′Si(CH₃)₃) (R = CH₃, R′ = C(CH₃)₃), as well as the trisubstituted compounds FSi(NCH₃Si(CH₃)₃)₃ and FSi(NCH₃Si(CH₃)₃)₂(N(Si(CH₃)₃)₂) were made. By reacting phenyltrifluorsilane with dialkylamines ($\text{1}\text{2}$) C₆H₅SiF₂NR₂(R = CH₃, C₂H₅) was obtained. The IR-, mass-, ¹H and ¹⁹F NMR spectra of the above-mentioned compounds are reported.     

Tin(IV) complexes ofSchiff bases derived from salicylaldehyde and aminoalcohols

11 and 12 molar reactions of tin(IV) chloride with theSchiff bases, HO–C₆H₄CHNROH [where R=–(CH₂)₂–, –CH₂–, –CH(CH₃)–, –(CH₂)₃–, and –CH(C₂H₅)CH₂–] have been studied in different stoichiometric ratios and derivatives of the type SnCl₄(SBH₂) and SnCl₄(SBH₂)₂ (whereSBH₂ represents theSchiff base molecule) have been isolated. These have been characterised by elemental analysis, conductivity measurements and I.R. spectral studies.     

Synthesis and characterization of new heterocyclic Schiff base palladacycles: Ring activation through N-oxide formation

Reaction of the Schiff base ligand derived from 4-pyridinecarboxaldehyde NC₅H₄C(H)N[2′,4′,6′-(CH₃)C₆H₂], (1), with palladium(II) acetate in toluene at 60 °C for 24 h gave [Pd{NC₅H₄C(H)N[2′,4′,6′-(CH₃)C₆H₂]}₂(OCOCH₃)₂], (2), with two ligands coordinated through the pyridine nitrogen. Treatment of the Schiff base ligand derived from 4-pyridinecarboxaldehyde N-oxide, 4-(O)NC₅H₄C(H)N[2′,4′,6′-(CH₃)C₆H₂], (4), with palladium(II) acetate in toluene at 75 °C gave the dinuclear acetato-bridged complex [Pd{4-(O)NC₅H₃C(H)N[2′,4′,6′-(CH₃)C₆H₂]}(OCOCH₃)]₂, (5) with metallation of an aromatic phenyl carbon. Reaction of complex 5 with sodium chloride or lithium bromide gave the dinuclear halogen-bridged complexes [Pd{4-(O)NC₅H₃C(H)N[2′,4′,6′-(CH₃)C₆H₂]}(Cl)]₂, (6) and [Pd{4-(O)NC₅H₃C(H)N[2′,4′,6′-(CH₃)C₆H₂]}(Br)]₂, (7), after the metathesis reaction. Reaction of 6 and 7 with triphenylphosphine gave the mononuclear species [Pd{4-(O)NC₅H₃C(H)N[2′,4′,6′-(CH₃)C₆H₂]}(Cl)(PPh₃)], (8) and [Pd{4-(O)NC₅H₃C(H)N[2′,4′,6′-(CH₃)C₆H₂]}-(Br)(PPh₃)], (9), as air stable solids. Treatment of 6 and 7 with Ph₂P(CH₂)₂PPh₂ (dppe) in a complex/diphosphine 1:2 molar ratio gave the mononuclear complexes [Pd{4-(O)NC₅H₃C(H)N[2′,4′,6′-(CH₃)C₆H₂]}(PPh₂(CH₂)₂PPh₂)][Cl], (10), and [Pd{4-(O)NC₅H₃C(H)N[2′,4′,6′-(CH₃)C₆H₂]}(PPh₂(CH₂)₂PPh₂)][PF₆], (11), with a chelating diphosphine. The molecular structure of complex 9 was determined by X-ray single crystal diffraction analysis.     

Ferrocene Derivatives of Valine and Leucine

Methyl and ethyl esters of valine and leucine were reacted with ferrocenecarbaldehyde to obtain azomethines (C₅H₅)Fe(C₅H₄CH=NCHRCOOR′) whose reactions with sodium borohydride provide ferrocenylmethyl derivatives (C₅H₅)Fe(C₅H₄CH₂NHCHR⋅COOR′) [R=(CH₃)₂CH, (CH₃)₂CHCH₂; R′ = CH₃, C₂H₅]. The latter compounds react with sodium hydroxide to give, after treatment of the reaction mixtures with acetic acid, N-substituted amino acids (C₅H₅)Fe(C₅H₄CH₂NHCHRCOOH).__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 6, 2005, pp. 1046–1048.Original Russian Text Copyright © 2005 by Popova, Yurashevich, Cherevin, Gulevich, Reshetova, Knizhnikov.     

Umsetzungen der Silylphosphine mit LiP(C2H5)2 und LiCH3

Whereas (CH₃)₃Si? P(C₂H₅)₂ does not react with LiP(C₂H₅)₂ (I), there are reactions of SiH-containing silylphosphines with one P(C₂H₅)₂ group as well as of SiH- and Simethylated silylphosphines with (I), yielding phosphorylated products and LiH according to equ. (1) (2). SiH-containing Silylphosphines, being Si? CH₃-free and having more than one P(C₂H₅)₂-group, such as HSi[P(C₂H₅)₂]₃, react with LiP(C₂H₅)₂ by exchange of Li for H, acc. to equ.(3). With (CH₃)₃SiCl, LiSi[P(C₂H₅)₂]₃ yields (CH₃)₃Si? Si[P(C₂H₅)₂]₃ and with SiH₃Br H₃Si? Si[P(C₂H₅)₂]₃. There is a cleavage of the Si? P bond with Li-CH₃ or n? LiC₄H₉. The reaction starts as shown in equ. (4), yielding (CH₃)₃SiH and (CH₃)₃Si? P(C₂H₅)₂ as intermediate products and finally (CH₃)₄Si (equ. 5).     

Reactions of nickelocene with lithium and magnesium alkyls containing β-hydrogen atoms

The reaction of nickelocene with BrMgR, where R=CH₂CH(CH₃)C₆H₅, C₂H₅, (CH₂)₇CH₃ and CH₂CH₂CH₃, have been studied. It was found that the presence of β-hydrogen in R did not cause the total splitting of the carbon–nickel bond but alkylidynetrinickel clusters were formed. It is the first example of the synthesis of alkylidynetrinickel clusters (NiCp)₃CR′ from the organonickel species possessing β-hydrogen. Besides trinickel clusters, the following compounds were always formed in all the studied reactions: (NiCp)₄H₂, (NiCp)₆, CpNi(η³-C₅H₇) and (NiCp)₂(μ-C₅H₆). The structure of (NiCp)₃CCH(CH₃)Ph has been determined by a single-crystal X-ray diffraction study.     

Investigation of conjugation in the Si-O-C-C-N system by nuclear magnetic resonance

The proton-magnetic-resonance spectra were investigated for 19 -aminoethoxysilanes in the R_4-nSi(OCH₂CH₂NR₂)_n and R_3-m(CH₂CH₂OR)_m series, where R=CH₃, C₂H₅, or C₆H₅; R=H, CH₃, C₂H₅, or Si(CH₃)₃; and the values of n and m are 1–4 and 1–3, respectively. In the Si-O-C-C-N system the effect of substituents at the nitrogen or silicon atoms is transmitted either by conjugation in the chain or, when the conjugation is broken, by an induction mechanism.     

Unterschiedliche Cyclisierungsmechanismen von Aminofluorsilanen

Different Mechanisms of the Cyclisation of Aminofluorosilanes The reaction of aminofluorosilanes of the type RR′SiFNHR″ (R = H, F, CH₃, C₂H₃, C₆H₅, C(CH₃)₃; R′ = C(CH₃)₃, NiC₃H₇Si(CH₃)₃, NC(CH₃)₃Si(CH₃)₃, N[Si(CH₃)₃]₂; R″ = iC₃H₇, C(CH₃)₃, C₆H₅) with butyllithium depends on the steric influence of the ligands. With increasing size of the ligands the reaction takes its pathway from the substitution under LiF elimination via dimerisation with additional elimination of butan to the C? H cleavage and cyclisation via a methylen group. A further increase of the size of the substituted groups leads through the intermediate formation of a silicenium-ylid to ring closure reactions. These occure by migration of a methanid ion leading to intermolecular nucleophilic substitution. The isolated acyclic and heterocyclic compounds are described and the mass and ¹H-n.m.r. spectra are reported.     

MNDO/3 study of the relative reactivity of ethylene derivatives upon addition to the benzyl radical

The transition states for the addition of a benzyl radical to substituted ethylenes CH₂=CHX were determined by the MNDO/3 method, where X=H, CF₃, CN, CH₃, C₄H₉, C(CH₃)₃, CO₂CH₃, and Si(CH₃)₃. The activation energies of the forward and back reactions were determined.A. N. Nesmeyanov Institute of Organometallic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 7, pp. 1676–1679, July, 1992.     

Silica-supported cyclopentadienyl-rhodium(I), -cobalt(I), and -titanium(IV) complexes

The silylated cyclopentadiene derivative, (MeO)₃Si(CH₂)₃C₅H₅, synthesised from commerically-available (MeO)₃Si(CH₂)₃Cl, has been used to prepare the complexes [η⁵-(MeO)₃Si(CH₂)₃C₅H₄]Rh(CO)₂, [η⁵-(MeO)₃Si(CH₂)₃C₅H₄]Rh(COD) (COD = cyclo-octa-1,5-diene), and [η⁵-(MeO)₃Si(CH₂)₃C₅H₄]₂TiCl₂. The complex [η⁵-(MeO)₃Si(CH₂)₃C₅H₄]TiCl₃, prepared by reaction of NaC₅H₄(CH₂)₃Si(OMe)₃ with TiCl₄ (1/1 molar ratio) and also by reaction of [η⁵-(MeO)₃Si(CH₂)₃C₅H₄]Ti(OEt)₃ with CH₃COCl, proved to be very unstable. Attempts to synthesise the complex [η⁵-(MeO)₃Si(CH₂)₃C₅H₄](η⁵-C₅H₅)TiCl₂, either by reaction of [η⁵-(MeO)₃Si(CH₂)₃C₅H₄]TiCl₃ with NaC₅H₄ or reaction of (η⁵-C₅H₅)TiCl₃ with NaC₅H₄(CH₂)₃Si(OMe)₃, gave none of the expected product and only (η⁵-C₅H₅)₂TiCl₂ could be isolated from these reactions. The cyclo-octadiene rhodium complex supported on silica has been shown to be an efficient cyclotrimerization catalyst, and the silica-supported titanium complex (SIL-(CH₂)₃C₅H₄)₂TiCl₂ is, after reduction with butyllithium, an efficient and selective catalyst for the hydrogenation of alk-1-enes.     

Beiträge zur Chemie der Alkylverbindungen von Übergangsmetallen. XLIV. Tetrakis(alkoxycarbonylmethyl)titan-Verbindungen

Contributions to the Chemistry of Transition Metal Alkyl Compounds. XLIII. Tetrakis(alkoxycarbonylmethyl)titanium Compounds Organotitanium(IV) compounds of the type (ROCOCH₂)₄Ti (R ? C₂H₅, i-C₃H₇, t-C₄H₉, C₆H₅, C₆H₅CH₂) were obtained by reactions of ROCOCH₂Li derivatives with TiCl₄ at low temperature. The compounds which decompose only above 90°C were characterized by the hydrolysis products, anaerobic reactions with iodine, and the i.r. spectra. The bond conditions are discussed.     

Kinetics and mechanism of acid hydrolysis of peroxyketals

The kinetics of hydrolysis of aliphatic ketone di-tert-butylperoxyketals R¹R²C=O, R¹, R²=CH₃, CH₃; CH₃, C₂H₅; CH₃, n-C₃H₇; CH₃, n-C₆H₁₃; CH₃, i-C₅H₁₀; CH₃, i-C₄H₉; C₂H₅, i-C₃H₇; n-C₄H₉, n-C₄H₉; CH₃, C₆H₅-CH₂, in dioxane in the presence of H₂SO₄ were investigated by IR spectroscopy. It was found that the reaction is reversible and takes place according to the equation R¹R²C· (OOC(CH₃)₃)₂ + H₂O;_H+ R¹R²C=O + 2HOOC(CH₃)₃. The proposed mechanism of hydrolysis includes the fast, quasiequilibrium formation of protonated peroxyketal and subsequent formation of the alkylperoxycarbenium ion. A three-parameter correlation equation is proposed for describing the initial rates of hydrolysis of R¹R²C(oo-t-Bu)₂ peroxyketals.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2501–2506, November, 1990.     

Photochemical reaction between cyclohexyl isocyanide and π-cyclopentadienyldicarbonyltrimethylsilyliron(II)

The photoreaction between C₅H₅Fe(CO)₂Si(CH₃)₃ (I) and cyclohexyl isocyanide leads to the sequential replacement of both carbonyl groups by the isocyanide. Both the racemic monosubstituted product, C₅H₅Fe(CO)(C₆H₁₁NC)Si(CH₃)₃ (II) and the disubstituted product, C₅H₅Fe(C₆H₁₁NC)₂Si(CH₃)₃ (III) have been isolated and characterized. Photoreaction between the disubstituted product III and C₅H₅Fe(CO)₂Si(CH₃)₃ in a sealed tube gives the monosubstituted product, II. Thermal initiation of the above reactions failed. The disubstituted product III is stable under both the thermal and photochemical conditions used; thus, insertion of isocyanide into FeSi bond was observed not to occur.     

EPR study of the rearrangement of (C2H5)3SiCH2CH2ĊCl2 radicals

Conclusions It has been established that the rearrangement of (C₂H₅)₃Si(CH₂)₂Cl₂ radicals into (C₂H₅)₂Si(CH₃CH)(CH₂)₂CCl₂H takes place by an intramolecular mechanism with 1,5-migration of a hydrogen atom. The rate constant for the isomerization has been determined at 20°C and found to be (2.2 ± 0.3)·10³ sec^–1.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2512–2516, November, 1988.     

Preparation of Silicates Using HSi(OC2H5)3 and Their NO x -Adsorption Behavior

The preparation and NO-adsorption/desorption behavior of Li, Ca and Ba silicates were investigated aiming at the application to a NO_x-absorbent. Li silicate was prepared by reaction of HSi(OC₂H₅)₃ with aqueous lithium silicate solution (LSS). Ca and Ba silicates were prepared from gels obtained using CH₃Si(OC₂H₅)₃, Si(OC₂H₅)₄, HSi(OC₂H₅)₃ and alkaline-earth alkoxides. The surface of these silicates indicated the solid basicity of H₀ = 9 and adsorbed the acidic gas of NO. FT-IR spectra of the silicates adsorbing NO showed the absorption peaks in the range of 1300–1600 cm^{– 1} corresponding to ionic and covalent nitrate NO₃^–. The complete desorption of adsorbed NO species occurred above 500°C in the Li silicate, above 500°C in the Ca and Ba silicates prepared using CH₃Si(OC₂H₅)₃, and above 700°C in the Ba and Ca silicates prepared using Si(OC₂H₅)₄. Regarding the Ca and Ba silicates, the difference in siloxane structure is thought to cause the difference in adsorption state and desorption behavior of NO.