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A novel type of photoisomerization of aryldisilanes, which involves 1,3-migration of a β-trimethylsilyl group from silicon to a fluorinated aromatic carbon accompanied by backward 1,3-migration of the fluorine to the α-silicon, was found during irradiation of 2,6-difluorophenyldisilanes.

Novel anionic pentacoordinate silicates, p-and m-phenylenebis[trifluoro(phenyl)silicates] and related mono-silicates were synthesized and their structures were determined by means of X-ray crystallography and NMR spectroscopy. Addition of a fluoride ion to a difluoro(phenyl)silyl group caused the significant decrease of the σP+ value as determined by 13C NMR spectroscopy.

The n(Si)→3p(Si) absorption maxima of silylenes were shifted significantly red by introducing trimethylsilyl and trimethylgermyl substituents. The origin of the substituent effects will be attributed to the σ-electron donating ability of the trimethylmetal groups which lift the energy level of n(Si) orbital significantly.

The formation of adducts of silicenium ions with acetonitrile (N-silylacetonitrilium ions) was elucidated by means of NMR spectroscopy during the hydride abstraction from hydrosilanes by trityl TFPB in CD2Cl2 in the presence of excess acetonitrile. The results indicate that acetonitrile is not a non-nucleophilic solvent suitable for formation of free silicenium ions, but stabilizes the ions by complexation giving tetracoordinate silicon species in solution.

The intermediacy of trialkylsiloxycarbenium ions was demonstrated by NMR spectroscopy during the reduction of ketones with hydrosilanes catalyzed by trityl tetrakis[3,5-bis(trifluoromethyl)phenyl]borate. It is suggested that the non-nucleophilic nature of the counter anion plays an important part in the modification of the reaction courses.

Transition state structures for the reaction of allyltetrafluorosilicate with formaldehyde as well as structures of the silicate and related compounds were located with ab initio MO calculations. The origin of the unique reactivity of pentacoordinate allylsilicates observed experimentally is discussed on this basis.

Aliphatic and aromatic aldimines are crotylated in a regiospecific and diastereo selective manner by the reaction with (E)- and (Z)-crotyltrifluorosilanes in the presence of cesium fluoride to give homoallylamines in high yields.

2,3-Halophenylene-bridged polysilaalkane macrocages 1b and 1c were synthesized as novel molecular gyroscopes. X-ray crystallographic data showed that the structures of the macrocages were deformed ...

The synthesis of [2]rotaxanes without polar functional groups was achieved by protodesilylation of the corresponding phenylene-bridged 1,12-disilacyclodocosanes in 20–30% isolated yields. The molec...

1,3-Digermabicyclo[1.1.0]butane 2 was synthesized as yellow crystals. The molecular structure, 13C NMR and UV–vis spectra, and theoretical calculations have revealed that 2 is a typical long bond i...

Disilacycloalkadienes with bridged halophenylene rings have been successfully synthesized via ring-closing metathesis reactions. Molecular structures of these macrocycles were fully characterized b...

A molecular gyroscope which has a phenylene rotator encased in three long siloxaalkane spokes was synthesized. The phenylene ring is observed by X-ray crystallography at three rotational positions ...

The first anti-tricyclo[3.1.0.02,4]hexasilane 1 was synthesized as pale yellow crystals. Irradiation (λ > 370 nm) of 1 gave its skeletal isomer, tricyclo[2.2.0.02,5]hexasilane 2, in 80% yield. The ...

A novel dinuclear palladium complex with one bridging dialkylsilylene ligand 6 was synthesized by the reaction of isolable dialkylsilylene 7 (R2Si:) with two equiv of bis(tricyclohexyl)phosphinepal...

1,4,9,12-Tetrakis(trimethylsilyl)dibenzodehydro[12]annulene (3) was synthesized by the Eglinton coupling reaction in a good yield. In contrast to parent dibenzodehydro[12]annulene, 3 has extremely ...

Using ring-closing hydrosilylation, trans- and cis-isomers of 2,5-dichrolo-1,4-phenylene-bridged macrocyclic polysila-alkanes were synthesized as molecular tops with a frame and characterized by X-...

Selective bridgehead chlorination of permethylbicyclo[2.2.2]octasilane 1 giving the corresponding 1-chloro- (2a) and 1,4-dichlorobicyclooctanes 3a was achieved using BCl3 in chloroform. 1-Chlorobic...

An absorption and emission spectroscopic study of an inclusion complex of permethyldecasilane (1) with γ-cyclodextrin in water has shown that the silicon main chain of 1 has an all-trans rod-like conformation in the hydrophobic cavities of γ-cyclodextrin at room temperature.

In the presence of Lu3+ and Sc3+ ions, p-pentamethyldisilanylacetophenone shows dual fluorescence, characteristic of a phenylpentamethyldisilane with an electron-accepting substituent on benzene ring, where the wavelengths of the LE (locally excited) and ICT (intramolecular charge transfer) band maxima and their relative intensity are dependent on the metal ions.

1,2-Dilithiotetrakis(trialkylsilyl)disilanes [(R3Si)2SiLi]2 (R3Si = t-BuMe2Si and i-Pr2MeSi) were prepared as stable off-white powder by the reduction of the corresponding tetrakis(trialkylsilyl)disilenes with lithium in THF. The 1,2-dilithiodisilanes reacted with water, iodomethane, and chlorosilanes to give the corresponding disubstituted products in high yields.

The hydrogenation of bistrimethylsilylactylene, bis(trimethylsilyl)-1,3-diynes, and related silylalkynes giving the corresponding saturated compounds were achieved by using diimide prepared in situ from p-toluenesulfonyl hydrazide in diglyme. The present method was applicable to the synthesis of saturated 12- and 18-membered oligosilacycloalkanes.

The nonresonant two-photon absorption spectrum of poly(dihexylsilylene) (1) in 3-methylpentane solution showed an abrupt thermochromism with a similar transition temperature to the one-photon absor...

Catalytic dehydrogenative polymerization of phenylsilanes with electron-withdrawing substituents using dimethylzirconocene as a catalyst afforded the corresponding polysilanes with rather high molecular weights. Significant substituent effects were observed on the electronic spectra of the polymers.

Potasium-18-crown-6 and tetraethylammonium ion salts of pentafluoro-9,10-disila-9,10-dihydroanthracene anion (5a and 5b) have an unsymmetrical transannular 1,4-fluorine bridge in the solid states. In solution, 5a and 5b show a facile intramolecular fluorine exchange.

A persistent silyl radical, tris(t-butyldimethylsilyl)silyl radical, (t-BuMe2Si)3Si· (1), was produced by two new methods in addition to a conventional hydrogen abstraction from the corresponding hydrosilane: one-electron oxidation of (t-BuMe2Si)3SiNa (2) by NO+BF4− and one-electron reduction of (t-BuMe2Si)3SiBr (3) by sodium.

Facile Si-Si bond cleavage reactions of cation radicals of jet-cooled clusters of (p-cyanophenyl)pentamethyldisilane with H2O or CH3OH were found to occur via intracluster nucleophilic attack of a solvent molecule by means of resonance-enhanced two photon ionization mass spectrometry.

Thermal isomerization of hexakis(t-butyldimethylsilyl)tetrasilabicylo[1.1.0]butane (2) to the corresponding tetrasilacyclobutene (1) as well as photochemical isomerization of 1 to 2 was confirmed using substituent-labeling experiments to proceed via 1,2-silyl-migration instead of skeletal isomerization.

A series of oligo(1,1-silole)s, Me3Si[SiC4Me4]n SiMe3 (3: n=3, 4:n=4, 5:n=5) were synthesized and characterized. X-ray diffraction analysis of tersilole 3 revealed that the pentasilane backbone has almost all-trans conformation. The oligo(1,1-silole)s show distinct UV absorptions due to σ-σ*, σ-π*, and π-π* transitions.

Hyperbranched polymethacrylates were synthesized by group transfer self-condensation polymerization of 2-(2-methyl-1-triethylsiloxy-1-propenyloxy)ethyl methacrylate. The hyper-branched structure of...

Non-resonant two-photon (NRTP) excitation of a 1,4-dioxane solution of trans-4-bromostilbene induces selective homolytic carbon-bromine bond fission, in contrast to the corresponding single-photon (SP) excitation, where the cis-trans isomerization in predominant.

Tartrate-ester modified allylsilanes, 2-allyl-1,3,2-dioxasilolane-4,5-dicarboxylic esters, (1), were found to serve as useful reagents for regiospecific and stereoselecive allylation of aldehydes. ...

A new intramolecular fluoride-ion donor-acceptor system, pentafluoro-1,4-disilacyclohexane anion showed an unusually rapid intramolecular intersilicon fluoride-ion exchange synchronized with ring inversion.

Intramolecular fluoride-ion donor-acceptor systems such as [p- and m-(difluorophenylsilyl)phenyl]trifluorophenylsilicates showed a new mode of fluoride-ion exchange reactions in solution, for which a concerted bimolecular exchange mechanism through cyclophane-like transition states was proposed on the basis of a dynamic 13C NMR analysis of rates and activation parameters.

R2SiT2 type of compounds (R = alkyl, aryl, OMe; T = tropolonato) have been found to hold rather exceptionally hexacoordinate dialkyl- and diarylsilicon geometry with two bidentate tropolonato ligands both in the solid state and in solution. A facile intramolecular stereoisomerization of these neutral hexacoordinate silicon compounds was observed by temperature dependent NMR spectroscopy in solution.

Reactions of allyltrifluorosilanes with β-functional-α,β-enones such as o-hydroxy- and o-aminophenyl ketones and 1,3-diketones in the presence of triethylamine yielded the corresponding tertiary homoallyl alcohols in regiospecific and highly diastereoselective manner.

Non-resonant two-photon excitation induced dramatical change in the photoreaction pathways of stilbenes. Typically, irradiation of cis-stilbene with 532 nm laser pulses caused only isomerization to trans-stilbene in hexane at room temperature; the cyclization to dihydrophenanthrene was completely suppressed.

Non-resonant two-photon excitation of 2,2-diphenylhexamethyltrisilane with a 532 nm pulsed laser light induced the two major reactions, silylene extrusion and migration of the β-trimethylsilyl group with a quite different selectivity from that for the single-photon excitation.

ESR spectra of parent and six substituted cyclopentadienyl radicals (R–C5H4·; R=H, D, Me, Et, iso-pr, t-Bu, Me3SiCH2), generated from the corresponding R–C5H4–SnMe3 by an SH2 attack on Sn with the photochemically generated t-butoxy radical, are recorded and discussed.

Trimethylsilylpotassium, prepared in a nonpolar solvent by the reaction of hexamethyldisilane with potassium methoxide in the presence of 18-crown-6, is a useful reagent for efficient homogeneous electron transfer. The first esr spectra of anion radicals of benzophenone and naphthalene in n-hexane as well as those in THF and benzene were recorded.

Reduction of azo compounds with a system of a trialkylchlorosilane and lithium has been found to afford bis(trialkylsilyl)amines in the presence of a transition metal halide as a catalyst in THF. The reaction course was significantly modified by using t-butyldimethylchlorosilane as a trialkylchlorosilane.

Photolysis of several biphenyls bridged by Si–X–Si chains are described where the X’s are O, S, NH, and Fe(CO)4. Dimethylsilathione was successfully generated by this method and the first evidence of reductive elimination from bis(silyl)iron to give disilane was demonstrated.

The cation radical of [PhSiMe2SiMeo3]\overset+· has been found by ESR not to be regarded as a weakly perturbed benzene cation radical like [PhSiMe3]\overset+· but as an Si-Si σ cation radical similar to [Me3SiSiMe3]\overset+·.

4-Dicyanomethylene-1-trimethylsilylsilacyclohexane (2a) and the trisilane analog (2b) showed the intramolecular CT bands in the absorption spectra. In combination with the results of the X-ray structure analysis of 2a, the origin of the σ(Si–Si)-π CT interaction was ascribed to the through-bond orbital interaction.

Photolysis of the title compound afforded silafluorene and dibenzo-1,2-disilacyclohexadiene as primary photoproducts. Two reactive intermediates, tetramethyldisilene and dimethylsilylene, were detected by trapping. The dimethylgermylene, derived from the germanium analog, was first observed by electronic spectra.

Pentacoordinate hydridosiliconates were prepared via the reaction of trichlorosilane with dilithiated hexafluorocumyl alcohol and characterized spectroscopically. The facile reduction of carbonyl compounds with the siliconates is indicative of the highly activated Si–H bond in the anionic hydridosiliconates.

An ESR study of cation radicals of allyltrimethylsilane and derivatives generated by 60Co γ-irradiation in frozen trichlorofluoromethane revealed the large polarization of the SOMO as a consequence of the enhanced σ–π conjugation.

Cation radicals of several alkyl- and silyl-substituted benzenes in frozen trichlorofluoromethane were investigated by ESR. All the substituents were found to act as an electron donor to the benzene cation, preferring the M–H σ bond eclipsing pπ orbitals. The results may afford a good evidence for the conformational consequences of hyperconjugation.

ESR spectra of cation radicals of trialkylsilyl-substituted ethers and sulfides have provided an experimental measure of the mixing between a silicon–carbon σ bonding orbital and a nonbonding orbitals on oxygen and sulfur atoms in the singly occupied molecular orbital.

Tetrakis(trimethylsilyl)butatriene was readily prepared by flash vacuum pyrolysis of hexakis(trimethylsilyl)-2-butyne. The physical and chemical properties of the butatriene are described.

UV, CT, and PE spectra of eight phenyl-substituted silanes and germanes of the type of PhMe2E-E′Me3 (E = Si, Ge; E′ = C, Si, Ge, Sn) are recorded. Extensive σ–π conjugation between σ(E-E′) and π orbitals is demonstrated to determine the unique electronic structures of these compounds.