Full-dimensional variational calculations are reported for the isomerising disilyne molecule, Si2H2. Large-scale calculations using coordinates based on orthogonal satellite vectors permitted the computation of excited vibrational state energies and wavefunctions for all four isomeric forms: dibridged Si(H2)Si, monobridged Si(H)SiH, disilavinylidene H2SiSi, and trans-bent HSiSiH. Energies and wavefunctions have been determined for the lowest 2400 totally symmetric vibrational states; this set includes highly excited states above all three chemically relevant isomerisation barriers--up to about 8300 cm(-1) above the (dibridged) ground state. States strongly localised in the dibridged, monobridged, and disilavinylidene regions of the potential energy surface have been found as well as many partially or fully delocalised states. For the trans-bent form, only partially localised states have been identified. Comparisons are made with similar literature calculations on the isovalent acetylene-vinylidene system HCCH/H2CC.
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The formation of a 1,4-disilabenzene and its isomerization into a disilabenzvalene derivative.
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Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.
A stable 1,4-disilabenzene was generated from the reaction of a stable disilyne with 3-hexyne. Its photochemical isomerization afforded the corresponding disilabenzvalene, which was structurally characterized by a single-crystal X-ray diffraction analysis.
View Article and Find Full Text PDFThe vibrational bound states of isomerising disilyne.
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Chemistry Department, University of Aberdeen, Meston Walk, Aberdeen AB24 3UE, United Kingdom.
Full-dimensional variational calculations are reported for the isomerising disilyne molecule, Si2H2. Large-scale calculations using coordinates based on orthogonal satellite vectors permitted the computation of excited vibrational state energies and wavefunctions for all four isomeric forms: dibridged Si(H2)Si, monobridged Si(H)SiH, disilavinylidene H2SiSi, and trans-bent HSiSiH. Energies and wavefunctions have been determined for the lowest 2400 totally symmetric vibrational states; this set includes highly excited states above all three chemically relevant isomerisation barriers--up to about 8300 cm(-1) above the (dibridged) ground state.
View Article and Find Full Text PDFComputational Studies of Bridging Structures and Isomerism in Substituted Disilynes.
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EaStCHEM School of Chemistry, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9ST, Scotland, United Kingdom.
The substituted disilyne molecules, Si2Li2 and Si2HX, where X = Li, F, and Cl, have been investigated using the high-level CCSD(T) and CCSD(T)-F12 ab initio methods. The calculations have found or confirmed the existence of several isomeric forms and transition states for each molecule. Optimized geometries, relative energies, and harmonic vibration frequencies are reported.
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Phys Chem Chem Phys
May 2012
Chemistry Department, University of Aberdeen, Meston Walk, Aberdeen, AB24 3UE, UK.
Article Synopsis
- A semi-global analytical potential energy surface for the isomerising disilyne molecule Si2H2 has been created, accurately reflecting over 50,000 ab initio energy points using a least-squares fitting approach.
- The surface includes all four known isomeric forms of disilyne and key transition states, successfully reproducing experimental spectroscopic data for the dibridged and monobridged isomers, while making predictions for the other forms.
- Detailed studies on critical points reveal strong agreement between theoretical calculations and experimental findings, indicating significant multireference character at different critical points and enhancing the understanding of the molecule's dynamics.
Unusual reactivity of a disilyne with 4-dimethylaminopyridine: formation of an intramolecularly N-coordinated silylene and its isomerization to a zwitterionic silyl anion.
J Am Chem Soc
May 2011
Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.
Reaction of isolable 1,1,4,4-tetrakis[bis(trimethylsilyl)methyl]-1,4-diisopropyltetrasila-2-yne (1) with an equiv amount of 4-dimethylaminopyridine unexpectedly produced the intramolecularly N-coordinated silylene 2 as the primary product. However, 2 was not thermally stable at room temperature in solution and slowly isomerized to silyl anion 3 with a zwitterionic structure via 1,2-hydrogen migration followed by Si-N bond formation.
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