Video Experimental Relacionado
Updated: Jul 10, 2026
10:37
Spatial Separation of Molecular Conformers and Clusters
Published on: January 9, 2014
Pruebas cristalográficas de un ión sililio libre
Kee-Chan Kim1, Christopher A Reed, Douglas W Elliott
1Department of Chemistry, University of California, Riverside, CA 92521-0403, USA.
Science (New York, N.Y.)
|August 6, 2002
Resumen
Este estudio proporciona evidencia de un catión silílico de tres coordenadas, [(Mes) 3Si]+, estabilizado por un anión carborano. Los voluminosos grupos mesitilo protegen el centro de silicio, permitiendo su aislamiento y caracterización.
Área de la Ciencia:
- Química del organosilicio Química del organosilicio
- Química del carborano Química del carborano
- Química estructural de las estructuras.
Sus antecedentes:
- Las especies de silicio de tres coordenadas suelen ser productos intermedios altamente reactivos.
- La estabilización de los cationes silílicos es crucial para comprender el enlace y la reactividad del silicio.
- Estudios anteriores se han centrado en los cationes silílicos transitorios o aquellos con sustitutos menos voluminosos.
Objetivo del estudio:
- Para sintetizar y caracterizar un cationo silílico estable de tres coordenadas.
- Investigar las propiedades estructurales y electrónicas de un catión silílico estéricamente impedido.
- Confirmar la preservación de la triple coordinación en las diferentes fases.
Principales métodos:
- La difracción de rayos X de un solo cristal de [(Mes) 3Si][H-CB11Me5Br6].C6H6.6.
- Espectroscopia de resonancia magnética nuclear (RMN) de 29Si en estado sólido.
- Comparación con la RMN en estado de solución y los estudios computacionales en fase gaseosa.
Principales resultados:
- La estructura cristalina revela un catión silílico discreto y plano de tres coordenadas, [(Mes) 3Si]+.
- Los voluminosos grupos orto-metilo en los sustituyentes de mesitilo (Mes) protegen efectivamente el centro de silicio.
- El desplazamiento químico de 29Si NMR en estado sólido (226,7 ppm) coincide estrechamente con los valores de la solución y la fase gaseosa, confirmando la estabilidad.
- El anión carborano y las moléculas de solvado de benceno están bien separadas del catión sililo.
Conclusiones:
- Los cationes silílicos estables de tres coordenadas pueden ser aislados y caracterizados.
- La protección estéril por grupos arilo voluminosos es clave para estabilizar estas inusuales especies de silicio.
- El centro de silicio de tres coordenadas permanece intacto en el estado sólido, la solución y la fase gaseosa.
Videos de Conceptos Relacionados
02:54Trends in Lattice Energy: Ion Size and Charge
An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. The lattice energy of a compound is a measure of the strength of this attraction. The lattice energy (ΔHlattice) of an ionic compound is defined as the energy required to separate one mole of the solid into its component gaseous ions. For the ionic solid sodium chloride, the lattice energy is the enthalpy change of the process:
02:39Phase Transitions: Melting and Freezing
Heating a crystalline solid increases the average energy of its atoms, molecules, or ions, and the solid gets hotter. At some point, the added energy becomes large enough to partially overcome the forces holding the molecules or ions of the solid in their fixed positions, and the solid begins the process of transitioning to the liquid state or melting. At this point, the temperature of the solid stops rising, despite the continual input of heat, and it remains constant until all of the solid is...
02:58Crystal Field Theory - Octahedral Complexes
Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
Tetrahedral Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
01:27Lattice Energies of Ionic Crystals
Lattice energy represents the energy released when gaseous cations and anions combine to form an ionic solid, reflecting the strength of electrostatic interactions within the crystal. This process is fundamentally governed by Coulombic attraction between oppositely charged ions, where the potential energy varies inversely with the interionic distance and directly with the product of ionic charges. As ions approach one another, the electrostatic energy becomes increasingly negative, indicating a...
01:26Imperfections in Crystal Structure: Stoichiometric Point Defects
Schottky defects arise when some lattice points in a crystal, such as those in NaCl, remain unoccupied, creating lattice vacancies without disturbing the overall electrical neutrality of the crystal. This defect is common in ionic crystals where the positive and negative ions are similar in size, as seen in sodium chloride and cesium chloride. The presence of Schottky defects enables the crystal to conduct electricity to a small extent through an ionic mechanism. Electric fields cause nearby...