Search

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 molecular structure of rotaxane 1a showed that the wheel is not at the center of the rod but on a dimethylene group of the dumbbell. By detailed NMR analyses, facile shuttling of the wheel was found to control the geometry of the dumbbells in the rotaxanes. [ABSTRACT FROM AUTHOR]

Hexakis( tert-butyldimethylsilyl)bicyclo[1.1.0]tetrasilane ( 3), which is known to isomerize to the corresponding cyclotetrasilene 4above 0 °C, was synthesized via an alternative synthetic route and isolated at low temperatures as air-sensitive yellow crystals. The short-bond structure of 3was disclosed by X-ray analysis and DFT calculations, and facile ring flipping of 3below 0 °C with the activation parameters of Δ H‡= 6.67 ± 0.18 kcal mol −1and Δ S‡= −22.7 ± 0.8 cal mol −1K −1was observed. [ABSTRACT FROM AUTHOR]

A kinetic study of the thermal irreversible isomerization of an isolable dialkylsilylene into the corresponding cyclic silene revealed that the activation enthalpy (ΔH‡) and entropy (ΔS‡) are 18.49 ± 0.43 kcal mol−1and −20.32 ± 1.35 cal mol−1K−1, respectively. The relatively low ΔH‡and negative ΔS‡values are in accord with the concerted 1,2-silyl migration via a cyclic transition state as previously proposed. The cyclic silene in benzene-d6isomerized photochemically into the corresponding alkenylsilane via 1,3-hydrogen shift. [ABSTRACT FROM AUTHOR]

The reactions of isolable dialkylstannylene 1 with 1-adamantanoyl, 2,2-dimethylpropanoyl, benzoyl, and substituted benzoyl chlorides afford the corresponding acyl(chloro)stannanes in good yields. Similar reactions with more reactive acetyl and propanoyl chlorides do not give the corresponding insertion products but the corresponding dichlorostannane by the overreaction. The benzoyl(chloro)stannane reacts with acetyl chloride to afford the corresponding 1,2-dione and the dichlorostannane quantitatively. Acyl(chloro)stannanes obtained were fully characterized by multinuclear NMR spectroscopy, high-resolution mass spectrometry, and by single-crystal X-ray diffraction studies. [ABSTRACT FROM AUTHOR]

The reactions of isolable dialkylsilylene 1 with aromatic acyl chlorides afforded aroylsilanes 3a–3c exclusively. Aroylsilanes 3a–3c were characterized by 1H-, 13C-, and 29Si-NMR spectroscopy, high-resolution mass spectrometry (HRMS), and single-crystal molecular structure analysis. The reaction mechanisms are discussed in comparison with related reaction of 1 with chloroalkanes and chlorosilanes. [ABSTRACT FROM AUTHOR]

The reaction of isolable dialkylstannylene 1 with an excess amount of CS2 produces an isomeric mixture of 3,3'-distanna-2,2',4,4'-tetrathiabicyclobutylidene 8 and 3,7-distanna-2,4,6,8-tetrathiabicyclo[3.3.0]oct-1(5)-ene 9 with a ratio depending on the reaction conditions. Compounds 8 and 9 are separated by column chromatography and characterized by NMR spectroscopy and X-ray crystallography. Detailed investigation of the reaction has revealed that the initial product is 8, which isomerizes to 9 irreversibly under the catalytic influence of 1 as a Lewis acid. The above view is supported by the theoretical DFT calculations. Treatment of 1 with ArN=C=O [Ar = 2,6-iPr2C6H3] affords the corresponding carbamoyl(hydroxyl)stannane 11 via the hydrolysis of the corresponding silaaziridinone formed by the [1 + 2] cycloaddition reaction of 1 with the N=C double bond of the isocyanate. Stannylene 1 reacts with ArN=C=S, giving a mixture of complex products, while 1 does not react with CO2. [ABSTRACT FROM AUTHOR]