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Although isolable silicon analogs of acetylene have been extensively studied, the silicon analogs of vinylidene, which is a short-lived isomer of acetylene, remain scarce. Herein, we report isolabl...

Development of efficient bond formation reactions remains important in organic and main-group-element chemistry. Herein, we report the metal-free one-pot condensation reaction of 1-iodo-3-trimethyl...

Although the oxidative coupling of disilenides, i.e., the disilicon analogues of vinyl anions, represents a promising route to extend the conjugation between Si═Si double bonds, previously reported synthetic routes to disilenides involve strongly reducing conditions. Herein, we report a novel synthetic route to disilenides from stable disilenes via the selective cleavage of Si(sp2)–Si(sp3) bonds under milder reaction conditions. Using this method, a 1,4-bis(trimethylsilyl)tetrasila-1,3-diene (5) was synthesized from the corresponding silyl-substituted disilene. Moreover, Et3Si-substituted tetrasila-1,3-diene 7 was synthesized via tetrasila-1,3-dien-1-ide 6, which is the first example of a functionalized tetrasila-1,3-diene.

A platinum(0) complex, bearing a 1,3-divinyl-1,1,3,3-tetramethyldisiloxane (DVTMS) and an isolable dialkylsilylene ligand, was successfully synthesized by the reaction between the dialkylsilylene and Karstedt’s catalyst. The downfield-shifted 29Si NMR resonance, the smaller 1JSi,Pt value, and the longer Si–Pt distance in this complex relative to the corresponding parameters in related bis(phosphine)-coordinated silylene-platinum complexes suggest weaker π-back-donation from the Pt center to the silylene, which is, however, still significant when compared to related DVTMS-ligated Pt complexes bearing N-heterocyclic carbenes, N-heterocyclic two-coordinate silylenes, or base-stabilized three-coordinate silylenes. The title complex displays excellent catalytic activity in the hydrosilylation of terminal olefins that contain functional groups such as epoxide and amine moieties.

A stable dialkylphosphinyl radical, 2,2,5,5-tatrakis(trimethylsilyl)-1-phosphacyclopentan-1-yl (RH2P•), showed both irreversible one-electron oxidation and reduction peaks at −0.24 and −2.29 V vs ferrocene/ferrocenium couple. One-electron reduction of RH2P• with KC8 in the presence of 18-crown-6 (18-c-6) or [2.2.2]cryptand (crypt-222) gave the corresponding phosphides [K(18-c-6)]+[RH2P]− and [K(crypt-222)]+[RH2P]−. Whereas [K(18-c-6)]+[RH2P]− exists as a contact ion pair, [K(crypt-222)]+[RH2P]− exists as a solvent-separated ion pair in the solid state. Reaction of RH2P• with AgOTf afforded an unexpected product, a silver(I) phosphaalkene complex.

The reactions of isolable dialkylsilylene 2,2,5,5-tetrakis(trimethylsilyl)-1-silacyclopentane-1,1-diyl with different types of ketones such as adamantanone, acetone, benzophenone, and cyclopropenones proceed smoothly at room temperature to afford the corresponding siloxirane, silyl enol ether, 2-oxa-silacyclopentene, and unusual cyclopropenylsilanes, respectively, without formation of any secondary or side-reaction products. The electronic structure of various types of model carbonyl silaylides was investigated using DFT calculations. The diversity of the reaction modes is explained by invoking the substituent effects on the electronic nature of the initially formed carbonyl silaylides.

Silylenecyclotetrasilane 4 synthesized as marginally stable orange crystals undergoes ring expansion to give cyclopentasilene 5 quantitatively with the activation parameters of ΔH⧧ = 24.8 ± 1.0 kcal mol−1 and ΔS⧧ = +6.5 ± 3.2 cal mol−1 K−1. The activation parameters and DFT calculations support that the isomerization of 4 to 5 proceeds through stepwise double 1,2-silyl migrations.

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

Ethynylsilyllithiums [R1R2(R3CC)SiLi: R1 = R2 = t-BuMe2Si, R3 = Me3Si (5a); R1 = R2 = t-BuMe2Si, R3 = Ph (5b); R1 = R2 = R3 = Me3Si (5c); R1 = t-BuMe2Si, R2 = Ph, R3 = Me3Si (5d); R1 = t-BuMe2Si, ...

Cycloaddition of an isolable dialkylsilylene converted nonemissive 2,3,4,5-tetraphenylcyclopentadienone to an emissive siloxycyclopentadiene, which shows aggregation-enhanced emission behavior with...

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...

X-ray analysis of the first trigermaallene (3) and 1,3-digermasilaallene (4) revealed that the trimetallaallene skeletons are not linear but significantly bent, similarly to the corresponding trisilaallene 2. In contrast to 2, no dynamic disorder was observed for 3 and 4.

Upon irradiation of a stable cyclotrisilene, 1,3,3-tris(tert-butyldimethylsilyl)-2-[tris(tert-butyldimethylsilyl)silyl]cyclotrisilene (5), in toluene with a low-pressure mercury-arc lamp, the isome...

The platinum silyl-substituted η2-disilene complex (Me3P)2Pt[Si(SiMe2(t-Bu))2]2 (4) was synthesized by the reaction of cis-(Me3P)2PtCl2 (5) with 1,2-dilithiotetrakis(tert-butyldimethylsilyl)disilane (6) in THF at −50 °C for 3 h. The X-ray structural analysis revealed that 4 can be regarded as a metalladisilacyclopropane with very weak π-complex character.

Stable disilenes having two different trialkylsilyl substituents [SiASiBSiSiSiASiB ((E)-2 and (Z)-2) and SiA2SiSiSiB2 (3), where SiA = t-BuMe2Si and SiB = i-Pr2MeSi] were prepared and characterized. Disilene (E)-2 was found by X-ray crystallography to have the highest planarity around the SiSi bond among isolated tetrasilyldisilenes. Temperature-dependent 29Si NMR spectra of a mixture of (E)- and (Z)-2 revealed the facile intramolecular isomerization between (E)-2 and (Z)-2 with a free energy of activation less than 15 kcal/mol at 300 K; the value is ca. 10 kcal/mol smaller than those of E,Z-isomerization of other known stable disilenes with aryl or alkyl substituents. The origin of the low barrier for the silyl-substituted disilenes is ascribed to the effective σ−π interaction at the transition state of the isomerization. In addition to the rotational isomerization, the isomerization of 2 to 3 was also observed at higher temperatures.