Die Bindungsverhältnisse in schweren Analoga des Cyanwasserstoffs: der merkwürdige Fall des HPSi

ChemInform Abstract: Cyclic SiS2: A New Perspective on the Walsh Rules.

Cyclic SiS2 is detected in the low-current dc discharge products of a mixture of SiH4 and H2S by Fourier transform microwave spectroscopy.

Germanium Dicarbide: Evidence for a T-Shaped Ground State Structure

The equilibrium structure of germanium dicarbide GeC2 has been an open question since the late 1950s. Although most high-level quantum calculations predict an L-shaped geometry, a T-shaped or even a linear geometry cannot be ruled out because of the very flat potential energy surface. By recording the rotational spectrum of this dicarbide using sensitive microwave and millimeter techniques, we unambiguously establish that GeC2 adopts a vibrationally averaged T-shaped structure in its ground state. From analysis of 14 isotopologues, a precise r0 structure has been derived, yielding a Ge–C bond length of 1.952(1) A and an apex angle of 38.7(2)°.

Cyclic SiS2: a new perspective on the Walsh rules.

Cyclisches SiS2 - die Walsh-Regeln in neuem Licht

Exotic SiO(2)H(2) Isomers: Theory and Experiment Working in Harmony.

Replacing carbon with silicon can result in dramatic and unanticipated changes in isomeric stability, as the well-studied CO2H2 and the essentially unknown SiO2H2 systems illustrate. Guided by coupled-cluster calculations, three SiO2H2 isomers have been detected and spectroscopically characterized in a molecular beam discharge source using rotational spectroscopy. The cis,trans conformer of dihydroxysilylene HOSiOH, the ground-state isomer, and the high-energy, metastable dioxasilirane c-H2SiO2 are abundantly produced in a dilute SiH4/O2 electrical discharge, enabling precise structural determinations of both by a combination of isotopic measurements and calculated vibrational corrections. …

GERMANIUM DICARBIDE: EVIDENCE FOR A T−SHAPED GROUND STATE STRUCTURE

The equilibrium structure of germanium dicarbide GeC2 has been an open question since the late 1950s. Although most high-level quantum calculations predict an L-shaped geometry, a T-shaped or even a linear geometry cannot be ruled out because of the very flat potential energy surface. By recording the rotational spectrum of this dicarbide using sensitive microwave and millimeter techniques, we unambiguously establish that GeC2 adopts a vibrationally averaged T-shaped structure in its ground state. From analysis of 14 isotopologues, a precise r0 structure has been derived, yielding a Ge–C bond length of 1.952(1) A and an apex angle of 38.7(2)°.

Rotational spectrum and equilibrium structure of silanethione, H2SiS

Unsubstituted silanethione, H(2)Si=S, has been characterized experimentally for the first time by means of rotational spectroscopy; the equilibrium structure of this fundamental molecule has been evaluated through a combination of experimental data from a total of ten isotopologues and results of high-level coupled-cluster calculations.

Bonding in the heavy analogue of hydrogen cyanide: the curious case of bridged HPSi.

The bonding of firstand second-row elements differ dramatically. The simplest unsaturated silicon hydrides Si2H2 and Si2H4 exhibit quite unusual geometries [1] compared to the analogous hydrocarbon molecules. For example, the most stable form of Si2H2 is nonplanar with C2v symmetry and two bridging H atoms, in sharp contrast to linear acetylene, HC! CH. Phosphorus and nitrogen share many of the same bonding characteristics, but P prefers single over multiple bonds. For these reasons, it may be difficult to predict the most stable isomeric arrangement, even for a small molecule with a single Por Si atom and especially when it contains both. Silicon–phosphorus bonds are important in materials…

Silicon Oxysulfide, OSiS: Rotational Spectrum, Quantum-Chemical Calculations, and Equilibrium Structure.

Silicon oxysulfide, OSiS, and seven of its minor isotopic species have been characterized for the first time in the gas phase at high spectral resolution by means of Fourier transform microwave spectroscopy. The equilibrium structure of OSiS has been determined from the experimental data using calculated vibration-rotation interaction constants. The structural parameters (rO-Si = 1.5064 A and rSi-S = 1.9133 A) are in very good agreement with values from high-level quantum chemical calculations using coupled-cluster techniques together with sophisticated additivity and extrapolation schemes. The bond distances in OSiS are very short in comparison with those in SiO and SiS. This unexpected fi…

Spectroscopic Detection and Structure of Hydroxidooxidosulfur (HOSO) Radical, An Important Intermediate in the Chemistry of Sulfur-Bearing Compounds

The rotational spectrum of hydroxidooxidosulfur, HOSO, an intermediate of particular interest in the combustion of sulfur-rich fuels, has been determined to high accuracy from gas-phase measurements. Detection of specific isotopic species using isotopically enriched gases suggests that HOSO is formed in our discharge nozzle via the reaction H + SO2 (+M) → HOSO (+M). A precise experimental r0 geometry has also been derived from the isotopic analysis; HOSO has a cis configuration, but the subtle structural question of its planarity remains unresolved. From the derived spectroscopic constants, in situ and remote sensing for this fundamental radical can now be undertaken in a variety of environ…