Synthesis, structure and reactivity of a carborane-fused silylene 1-{[PhC(NtBu)2]Si}-1,2-C2B10H11

Synthetic, structural and reactivity studies of a boryl-ethynyl Silylene

The salt metathesis of a boryl-ethynyl lithium salt {[(HCDipN)2]B-CC-Li} with a monochlorosilylene [LSi(:)Cl; L = PhC(NtBu)2] produced an isolable boryl-ethynyl silylene {1; [(HCDipN)2]B-CC-Si(L)}. The Si(II) center in 1 possesses a nonbonding lone pair and forms a covalent bond with the ethynyl group. The characterization of 1 was carried out by multinuclear NMR spectroscopy, single-crystal X-ray structure analysis and DFT calculations. Additionally, a reactivity study of 1 was conducted towards oxygen-containing and aryl C-F substrates.

Diverse Reactions of o-Carborane-Fused Silylenes with C≡E (E = C, P) Triple Bonds

The reactivities of o-carborane-fused silylenes toward molecules with C≡E (E = C, P) bonds are reported. The reactions of bis(silylene) [(LSi:)C]₂B₁₀H₁₀ (1a, L = PhC(NtBu)₂) with arylalkynes afforded bis(silylium) carborane adducts 2 and 3, showing a Si(μ-C₂)Si structure with an open-cage nido-carborane backbone. In contrast, the reaction of 1a with a phosphaalkyne AdC≡P (Ad = 1-adamantyl) smoothly furnished compound 4, comprising fused CPSi rings with a C=Si double bond and Si-Si single bond, and the related formation mechanism was investigated by DFT calculations. Furthermore, when monosilylene [(LSi:)C]CHB₁₀H₁₀ (1b) was employed to react with AdC≡P, compound 5 was isolated. The structure of 5 features a 1,2,3-triphosphetene core. All products were characterized by NMR spectroscopy and/or X-ray crystallography.

Isolation of Silacycles from the Reactions of a Monochlorosilylene LSi(:)Cl (L = PhC(NtBu)2) with Ethynyl Lithium Salts

The reactions of amidinate silylene chloride LSi(:)Cl (L = PhC(NtBu)₂) with TMS- and Ph-ethynyl lithium salts gave rise to silacycles 1 and 4, respectively. The formation of 1 and 4 may undergo cyclo-condensations of transient ethynylsilylene intermidiates and the activation of an amidinate backbone. The distinct structures of 1 and 4 may be derived from the different electronic or steric properties of ethynyl substituents, and their formation mechanisms were investigated by density functional theory (DFT) calculations. Moreover, a sequential reaction of LSi(:)Cl with BH₃·SMe₂ and TMSC≡CLi as well as a reaction of LSi(:)Cl with TMSC≡CLi under O₂ exclusively obtained ethynylsilanes 2 and 3, respectively, which indicated that either blocking a lone pair of a Si(II) atom or oxidizing Si(II) to Si(IV) prevents the further conversion of ethynylsilylenes to silacycle 1. All products were characterized by NMR spectroscopy and X-ray crystallography.

Zinc and Cadmium Complexes of Chelating N-Heterocyclic Silylene and Their Reactivity toward Elemental Chalcogens

The reactions of the pyridine-functionalized silylene L^NSi [L = PhC(NtBu)₂; N = 2-(methylamido)pyridine] with zinc and cadmium halides are described. These resulted in the formation of a series of zinc and cadmium silylene complexes: [L^NSi-ZnX₂] (X = Cl, Br, I) and [{L^NSi-CdI₂}₂], which is the first cadmium silylene compound. Subsequent reaction of these silylene complexes with elemental sulfur and selenium under mild conditions at room temperature afforded under activation of these elements the corresponding silanethione-stabilized zinc [(L^NSi═S)-ZnX₂] (X = Cl, I) and cadmium [(L^NSi═S)-CdI₂] complexes and the silaneselenone-stabilized zinc species [(L^NSi═Se)-ZnCl₂]. A selective insertion of the group 16 elements into the M-Si bond of the silylenes was observed. Because of metal coordination, the Si-chalcogen bond lengths in the silanethiones and silaneselenones are enlarged and thus range between a single and a double bond. All new compounds were fully characterized by single-crystal X-ray diffraction analyses, multinuclear NMR spectroscopy, elemental analyses, and IR spectroscopy.

Reactivity of an N-heterocyclic silylene with a 1,1'-ferrocenediyl backbone towards carbonyl compounds, including carbon suboxide

Reactions of a silylene with a ketene and with carbon suboxide are reported, respectively leading to the first silaallene oxide and to a silylketene, whose reaction with water affords the first structurally characterised stable methyleneketene and constitutes a unique type of single-crystal-to-single-crystal transformation of a molecular solid by a stoichiometric gas-solid chemical reaction.

An Isolable Bis(Silanone-Borane) Adduct

The reaction of bis(silylenyl)-substituted ferrocene 1 with two molar equivalents of BPh3 yields the corresponding bis(silylene-borane) Lewis adduct 2. The latter is capable to activate CO2 to furnish the borane-stabilized bis(silanone) 3 through mono-oxygenation of the dative SiII →B silicon centers under release of CO. Removal of BPh3 from 3 with PMe3 affords the corresponding 1,3,2,4-cyclodisiloxane and the Me3 P-BPh3 adduct. All isolated new compounds were characterized and their molecular structures were determined by single-crystal X-ray diffraction analyses.