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A cyclic (alkyl)(amino)bromoborane (CAABBr) was synthesized by a reaction of the corresponding hydroborane with bromine in the presence of triethylamine. Reduction of the resulting CAABBr with Li p...

Cyclic (alkyl)(amino)silylene (CAASi) 1 has been found to successfully dehydrogenate 1,4-dihydroaromatic compounds containing various substituents to afford the corresponding aromatic compounds. The observed high substrate generality proves 1 to be a potential 1,4-dehydrogenation reagent for organic compounds. For the reaction with 9,10-dimethyl-9,10-dihydroanthracene, silylene 1 activated not only benzylic C-H bonds but also aromatic C-H bonds to yield a silaacenaphthene derivative, which is an unprecedented reaction of silylenes. The results of the experimental and computational study of the reaction of CAASi 1 with 9,10-dihydroanthracene and 1,4-cyclohexadiene are consistent with the notion that 1,4-dehydrogenation with CAASi 1 proceeds mainly through a stepwise hydrogen-abstraction mechanism.

Direct activation of inert C(sp3 )-H bonds by main group element species is yet a formidable challenge. Herein, the dehydrogenation of cyclohexene and 1,2,3,4-tetrahydronaphthalene through the allylic/benzylic and homoallylic/homobenzylic C-H bond activation by cyclic (alkyl)(amino)silylene 1 in neat conditions is reported to yield the corresponding aromatic compounds. As for the reaction of cyclohexene, allylsilane 3 and 7-silanorbornene 4 were also observed, which could be interpreted as a direct dehydrogenative silylation reaction of monoalkenes at the allylic positions. Experimental and computational studies suggest that the dehydrogenation of cyclohexene at the homoallylic position was accomplished by a combination of silylene 1 and radical intermediates such as hydrosilyl radical INT1 or cyclohexenyl radical H, which are generated in the initial step of the reaction.

Activation of H2 by compounds of main-group elements has received considerable attention. Herein, we report synthesis of novel monoboryl- and monoamino-substituted disilenes and their characterization by a combination of NMR spectroscopy and single-crystal X-ray diffraction analysis. The monoboryldisilene reacts with two molecules of H2 to provide the corresponding trihydridodisilane and hydroborane, whereas the aminodisilene does not react with H2 under the same conditions. The present results together with our previous results indicate that the presence of the boryl-substituent on the Si=Si double bond is essential to activate the H2 molecule. The low lying empty 2p orbital on the boron atom that interacts effectively with the π*(Si=Si) orbital could be responsible for the activation of H2 .

A spiro-type cyclotrisilene was synthesized by the novel Si–Si coupling reaction of a disilenide and a base-adduct of bromosilylene and characterized by a combination of spectroscopic and crystallo...

The push–pull effect has been widely used to effectively tune π-electron systems. Herein, we report the synthesis and properties of 1-amino-2-boryldisilene 1 as the first push–pull disilene. Its spectroscopic and structural features show substantial interactions between the Si═Si double bond and the amino and boryl substituents. The π → π* absorption band of 1 is remarkably red-shifted compared to that of the corresponding alkyl-substituted disilene 2. Treatment of 1 with H2 resulted in the cleavage of two molecules of H2 under concomitant formation of the corresponding trihydridodisilane and hydroborane.

Although many stable disilenes (silicon–silicon doubly-bonded compounds) containing organic π-electron systems have been reported, stable disilenes with heteroaromatic groups remain rare. Herein, we report the synthesis of monodisilenyl-substituted thiophene 1, anthracene 4, acridine 5, and mesitylene 7 and bis(disilenyl)-substituted thiophene 2, 2,2′-bithiophene 3, and anthracene 6via reactions of dialkylmesityldisilenide 8 with the corresponding haloarenes. Disilenes 1–7 show absorption bands with contributions of intramolecular charge transfer (ICT) transitions from π(disilene) to π*(aryl). In the ICT transitions, (bi)thienyl groups as well as anthryl and acrydinyl groups serve as electron acceptors for the SiSi double bonds.

Bicyclo[1.1.0]tetrasila-1(3)-ene 1b was synthesized and isolated as orange crystals. While 1b has a highly distorted SiSi double bond in the bicyclic silicon framework similar to that of the previously reported 1a, 1b has less bulky SiMe3 substituents than SiiPrMe2 substituents that were involved in 1a. Accordingly, the molecular structure and electronic properties of 1b resemble those of 1a, but 1b readily reacts with carbon tetrachloride and methanol. The reaction of 1b with carbon tetrachloride providing a cyclic tetrachlorotetrasilane and an acyclic hexachlorotetrasilane suggests the generation of a 1,3-dichlorobicyclo[1.1.0]tetrasilane and its isomer, a tetrasiladiene, the latter of which was supported by the formation of an acyclic tetrasilane during the reaction of 1b with methanol.

Although the synthesis of several bis(disilenes) has already been reported, the number of reported conjugation modes between the Si═Si double bonds remains limited. Herein, we report the properties of the stable pentasila-1,4-diene 1, which was obtained from the reaction of two equivalents of disilenide 4 with dichlorodimethylsilane. The π(Si═Si)→π*(Si═Si) absorption band of 1 is considerably broadened and red-shifted compared to those of the corresponding monodisilene and hexasila-1,5-diene, but blue-shifted relative to those of typical tetrasila-1,3-dienes. The bathochromic shift and the broadening of the absorption band in 1 should be attributed to the homoconjugation between Si═Si double bonds through the SiMe2 unit.

Although many stable disilenes (silicon-silicon doubly-bonded compounds) containing organic π-electron systems have been reported, stable disilenes with heteroaromatic groups remain rare. Herein, we report the synthesis of monodisilenyl-substituted thiophene 1, anthracene 4, acridine 5, and mesitylene 7 and bis(disilenyl)-substituted thiophene 2, 2,2'-bithiophene 3, and anthracene 6via reactions of dialkylmesityldisilenide 8 with the corresponding haloarenes. Disilenes 1-7 show absorption bands with contributions of intramolecular charge transfer (ICT) transitions from π(disilene) to π*(aryl). In the ICT transitions, (bi)thienyl groups as well as anthryl and acrydinyl groups serve as electron acceptors for the Si[double bond, length as m-dash]Si double bonds.

A platinum(0) complex bearing a cyclic (alkyl)(amino)silylene and a 1,3-divinyl-1,1,3,3-tetramethyldisiloxane (DVTMS) was synthesized and isolated in the form of colorless crystals. The single-crystal X-ray diffraction analysis of this complex in combination with theoretical calculations indicated that the Pt→Si π-back-donation in this complex is weaker than that in the corresponding cyclic-dialkylsilylene-ligated Pt complex. The performance of this complex in the catalytic hydrosilylation of (Me3SiO)2MeSi-H with various terminal alkenes that contain functional groups was comparable to that of the corresponding cyclic dialkylsilylene/DVTMS Pt(0) complex.

Regioselective cycloaddition of dialkylsilylene upon irradiation at 440 nm converts azulene and guaiazulene to bicyclic [4]dendralene and heptafulvene derivatives, respectively. Significant σ–π interactions in the resulting new silacycles were suggested using UV-vis spectra and theoretical calculations.

Regioselective cycloaddition of dialkylsilylene upon irradiation at 440 nm converts azulene and guaiazulene to bicyclic [4]dendralene and heptafulvene derivatives, respectively. Significant σ–π interactions in the resulting new silacycles were suggested using UV-vis spectra and theoretical calculations.

A persistent dialkylsilanone was synthesized by the dehydrobromination of a dialkylbromosilanol with tris(trimethylsilyl)silyl potassium in solution at -80 °C: It was characterized by NMR and IR spectroscopy, and was tested in several reactions. In (29) Si NMR spectrum in [D8 ]toluene, the signal due to the unsaturated silicon nuclei was observed at 128.7 ppm. Reactions of the dialkylsilanone with water and mesitonitrile oxide gave a silanediol and a [2+3] cycloadduct, respectively. The silanone remains intact in [D8 ]toluene below -80 °C for at least two days, while it undergoes unprecedented isomerization to give a siloxysilene by means of 1,3-silyl migration at higher temperatures.