Stable Push–Pull Disilene: Substantial Donor–Acceptor Interactions through the SiSi Double Bond

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 <b>1</b> 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 <b>1</b> is remarkably red-shifted compared to that of the corresponding alkyl-substituted disilene <b>2</b>. Treatment of <b>1</b> with H₂ resulted in the cleavage of two molecules of H₂ under concomitant formation of the corresponding trihydridodisilane and hydroborane

A Dialkylsilylene-Pt(0) Complex with a DVTMS Ligand for the Catalytic Hydrosilylation of Functional Olefins

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 ¹<i>J</i>_Si,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 <i>N</i>-heterocyclic carbenes, <i>N</i>-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

Pentasila-1,4-diene: Homoconjugation between SiSi Double Bonds via a SiMe₂ Unit

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 <b>1</b>, which was obtained from the reaction of two equivalents of disilenide <b>4</b> with dichlorodimethylsilane. The π­(SiSi)→π*­(SiSi) absorption band of <b>1</b> 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 <b>1</b> should be attributed to the homoconjugation between SiSi double bonds through the SiMe₂ unit

Redox Reactions of a Stable Dialkylphosphinyl Radical

A stable dialkylphosphinyl radical, 2,2,5,5-tatrakis­(trimethylsilyl)-1-phosphacyclopentan-1-yl (R^H₂P^•), showed both irreversible one-electron oxidation and reduction peaks at −0.24 and −2.29 V vs ferrocene/ferrocenium couple. One-electron reduction of R^H₂P^• 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)]⁺[R^H₂P]⁻ and [K­(crypt-222)]⁺[R^H₂P]⁻. Whereas [K­(18-c-6)]⁺[R^H₂P]⁻ exists as a contact ion pair, [K­(crypt-222)]⁺[R^H₂P]⁻ exists as a solvent-separated ion pair in the solid state. Reaction of R^H₂P^• with AgOTf afforded an unexpected product, a silver­(I) phosphaalkene complex

Anthryl-Substituted 3‑Silylene-2-silaaziridine Obtained by Isomerization of Disilacyclopropanimine: An Exocyclic Silene Showing a Distinct Intramolecular Charge Transfer Transition

An anthryl-substituted exocyclic silene, 3-silylene-2-silaaziridine, was synthesized by isomerization of the corresponding disilacyclopropanimine. The UV–vis spectrum of the silene shows a distinct intramolecular charge transfer (ICT) transition from the π orbital of the SiC double bond to the π* orbital of the anthryl moiety. The relatively high-lying π­(SiC) orbital of the 3-silylene-2-silaaziridine moiety and the low-lying π* orbital of the anthryl group would be responsible for the distinct ICT band

Anthryl-Substituted 3‑Silylene-2-silaaziridine Obtained by Isomerization of Disilacyclopropanimine: An Exocyclic Silene Showing a Distinct Intramolecular Charge Transfer Transition

An anthryl-substituted exocyclic silene, 3-silylene-2-silaaziridine, was synthesized by isomerization of the corresponding disilacyclopropanimine. The UV–vis spectrum of the silene shows a distinct intramolecular charge transfer (ICT) transition from the π orbital of the SiC double bond to the π* orbital of the anthryl moiety. The relatively high-lying π­(SiC) orbital of the 3-silylene-2-silaaziridine moiety and the low-lying π* orbital of the anthryl group would be responsible for the distinct ICT band

New Isolable Dialkylsilylene and Its Isolable Dimer That Equilibrate in Solution

The new isolable dialkylsilylene <b>3</b> bearing a bidentate alkyl substituent was synthesized. Recrystallization of silylene <b>3</b> gave yellow crystals of <b>3</b> and orange-red crystals of tetraalkyldisilene <b>4</b>, a dimer of <b>3</b>. In the solid state, <b>3</b> exists as a monomer with a closest distance of 6.745 Å between dicoordinate silicon atoms, while disilene <b>4</b> has a remarkably long SiSi double bond distance of 2.252 Å. An equilibrium between <b>3</b> and <b>4</b> in solution was observed by NMR and UV–vis spectroscopies, and the thermodynamic parameters of the equilibrium were estimated to be Δ<i>H</i> = −36 ± 3 kJ mol^–1 and Δ<i>S</i> = −170 ± 15 J mol^–1 K^–1. Analysis of the percent buried volume, a measure of the steric demand around the divalent silicon, showed that the flexible steric bulkiness of the alkyl substituent of <b>3</b> and <b>4</b> allows the reversible dimerization of silylene <b>3</b> to disilene <b>4</b> and the isolation of both species

New Isolable Dialkylsilylene and Its Isolable Dimer That Equilibrate in Solution

The new isolable dialkylsilylene <b>3</b> bearing a bidentate alkyl substituent was synthesized. Recrystallization of silylene <b>3</b> gave yellow crystals of <b>3</b> and orange-red crystals of tetraalkyldisilene <b>4</b>, a dimer of <b>3</b>. In the solid state, <b>3</b> exists as a monomer with a closest distance of 6.745 Å between dicoordinate silicon atoms, while disilene <b>4</b> has a remarkably long SiSi double bond distance of 2.252 Å. An equilibrium between <b>3</b> and <b>4</b> in solution was observed by NMR and UV–vis spectroscopies, and the thermodynamic parameters of the equilibrium were estimated to be Δ<i>H</i> = −36 ± 3 kJ mol^–1 and Δ<i>S</i> = −170 ± 15 J mol^–1 K^–1. Analysis of the percent buried volume, a measure of the steric demand around the divalent silicon, showed that the flexible steric bulkiness of the alkyl substituent of <b>3</b> and <b>4</b> allows the reversible dimerization of silylene <b>3</b> to disilene <b>4</b> and the isolation of both species

Siloxy-Substituted Cyclopentadiene Showing Aggregation-Enhanced Emission: An Application of Cycloaddition of Isolable Dialkylsilylene

Cycloaddition of an isolable dialkylsilylene converted nonemissive 2,3,4,5-tetraphenylcyclopentadienone to an emissive siloxycyclopentadiene, which shows aggregation-enhanced emission behavior with a light blue fluorescence (λ_em = 474 nm, Φ_F = 0.11) in the solid state rather than in solution

Siloxy-Substituted Cyclopentadiene Showing Aggregation-Enhanced Emission: An Application of Cycloaddition of Isolable Dialkylsilylene

Cycloaddition of an isolable dialkylsilylene converted nonemissive 2,3,4,5-tetraphenylcyclopentadienone to an emissive siloxycyclopentadiene, which shows aggregation-enhanced emission behavior with a light blue fluorescence (λ_em = 474 nm, Φ_F = 0.11) in the solid state rather than in solution