The hydrogen-bridged disilyl cation 6 with an 1,8-naphthalenediyl backbone was synthesized and was characterized by NMR spectroscopy and X-ray crystallography, supported by quantum mechanical computations. The SiHSi linkage is symmetrical, corresponding to a single minimum potential, and the structural parameters are in agreement with the presence of a two electron-three center bond in 6. Treatment of disilyl cation 6 with alkyl fluorides yields the disilylfluoronium ion 10. The SiFSi group in the disilyl fluoronium ion 10 is symmetrical with an average SiF bond length of 175.9(8) and a bent angle beta = 130 degrees . Both cations catalyze the hydrodefluorination reaction of alkyl and benzyl fluorides to give alkanes.

An optomechanical sensor suitable for the study of quantum effects has been developed and characterized. The sensor reads out the vibrations of a microfabricated miniature silicon mechanical oscillator which forms one end mirror of a high finesse Fabry-Pérot cavity. The mechanical quality factor is up to Qϭ300 000 at 300 K and rises up to Qϭ4ϫ10 6 at 4 K. The thermal noise of the oscillator has been measured in the time and frequency domains at room temperature and at 4.5 K. The prospects for observing the standard quantum limit are discussed.

Well-shuffled: An unexpected substituent distribution reaction via alkyldiarylsilylium ions leads to a distribution of substituents. Starting from alkyldiaryl silanes, this reaction provides a facile synthetic approach to sterically highly hindered triarylsilylium ions. These silylium ions can be applied in dihydrogen activation reactions.

The history of silyl cations has all the makings of a drama but with a happy ending. Being considered reactive intermediates impossible to isolate in the condensed phase for decades, their actual characterization in solution and later in solid state did only fuel the discussion about their existence and initially created a lot of controversy. This perception has completely changed today, and silyl cations and their donor-stabilized congeners are now widely accepted compounds with promising use in synthetic chemistry. This review provides a comprehensive summary of the fundamental facts and principles of the chemistry of silyl cations, including reliable ways of their preparation as well as their physical and chemical properties. The striking features of silyl cations are their enormous electrophilicity and as such reactivity as super Lewis acids as well as fluorophilicity. Known applications rely on silyl cations as reactants, stoichiometric reagents, and promoters where the reaction success is based on their steady regeneration over the course of the reaction. Silyl cations can even be discrete catalysts, thereby opening the next chapter of their way into the toolbox of synthetic methodology.

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We report the reconstruction of the quantum state of squeezed vacuum generated by a continuouswave optical parametric amplifier. Homodyne detection and tomographic reconstruction methods were used to obtain the density matrix in the Fock (number state) representation. The photon number distribution exhibits odd-even oscillations, a manifestation of the photon pair production in the secondorder nonlinear medium.

Reaction of 1,4-dipotassio-1,1,4,4-tetrakis(trimethylsilyl)tetramethyltetrasilane with [(Me3Si)2N]2Sn led to the formation of an endocyclic distannene via the dimerization of a transient stannylene. In the presence of strong donor molecules such as PEt3, the stannylene could be trapped as adduct. Reaction of the PEt3 derivative with B(C6F5)3 gave rise to the formation of the stannylene B(C6F5)3 adduct.

The preparation of triethylphosphine adducts of cyclic disilylated or digermylated germylenes was achieved by reaction of 1,4-dipotassio-1,1,4,4-tetrakis(trimethylsilyl)tetramethyltetrasilane with GeBr2·(dioxane) and PEt3. Phosphine abstraction with B(C6F5)3 allowed formation of the base-free germylenes, which undergo 1,2-trimethylsilyl shifts to the germylene atom to form the respective silagermene or digermene, which further dimerize in [2 + 2] cycloadditions to tricyclic compounds. The reasons responsible for the germylenes’ completely different reactivities in comparison to the previously studied analogous stannylenes and plumbylenes were elucidated in a theoretical study.