Infrared spectroscopic detection of the disilenyl (Si2H3) and d3-disilenyl (Si2D3) radicals in silane and d4-silane matrices

Directed Gas Phase Formation of the Elusive Silylgermylidyne Radical (H3 SiGe, X2 A'')

The previously unknown silylgermylidyne radical (H₃ SiGe; X² A'') was prepared via the bimolecular gas phase reaction of ground state silylidyne radicals (SiH; X² Π) with germane (GeH₄ ; X¹ A₁ ) under single collision conditions in crossed molecular beams experiments. This reaction begins with the formation of a van der Waals complex followed by insertion of silylidyne into a germanium-hydrogen bond forming the germylsilyl radical (H₃ GeSiH₂ ). A hydrogen migration isomerizes this intermediate to the silylgermyl radical (H₂ GeSiH₃ ), which undergoes a hydrogen shift to an exotic, hydrogen-bridged germylidynesilane intermediate (H₃ Si(μ-H)GeH); this species emits molecular hydrogen forming the silylgermylidyne radical (H₃ SiGe). Our study offers a remarkable glance at the complex reaction dynamics and inherent isomerization processes of the silicon-germanium system, which are quite distinct from those of the isovalent hydrocarbon system (ethyl radical; C₂ H₅ ) eventually affording detailed insights into an exotic chemistry and intriguing chemical bonding of silicon-germanium species at the microscopic level exploiting crossed molecular beams.

Formation and IR spectrum of monobridged Si2H4 isolated in solid argon

The infrared (IR) spectrum of monobridged Si₂H₄ (denoted as mbr-Si₂H₄) isolated in solid Ar was recorded, and a set of lines (in the major matrix site) observed at 858.3 cm^-1, 971.5 cm^-1, 999.2 cm^-1, 1572.7 cm^-1, 2017.7 cm^-1, 2150.4 cm^-1, and 2158.4 cm^-1 were characterized. The species was produced by the electron bombardment of an Ar matrix sample containing a small proportion of SiH₄ during matrix deposition. Upon photolysis of the matrix samples using 365 nm and 160 nm light, the content of mbr-Si₂H₄ increased. The band positions, relative intensity ratios, and D-isotopic shift ratios of the observed IR features are generally in good agreement with those predicted by the B3LYP/aug-cc-pVTZ method. In addition, the photochemistry of the observed products was discussed.

Formation of Higher Silanes in Low-Temperature Silane (SiH4) Ices

A novel approach for the synthesis and identification of higher silanes (SinH2n+2, where n ≤ 19) is presented. Thin films of (d4-)silane deposited onto a cold surface were exposed under ultra-high-vacuum conditions to energetic electrons and sampled on line and in situ via infrared and ultraviolet-visible spectroscopy. Gas phase products released by fractional sublimation in the warm-up phase after the irradiation were probed via a reflectron time-of-flight mass spectrometer coupled with a tunable vacuum ultraviolet photon ionization source. The formation mechanisms of (higher) silanes were investigated by irradiating codeposited 1:1 silane (SiH4)/d4-silane (SiD4) ices, suggesting that both radical-radical recombination and radical insertion pathways contribute to the formation of disilane along with higher silanes up to nonadecasilane (Si19H40).