Hispanopedia WikiEl pentametilbismuto (o pentametilbismutorano [ 2 ] ) es un compuesto organometálico que contiene cinco grupos metilo unidos a un átomo de bismuto con fórmula Bi(CH 3 ) 5 . Es un ejemplo de compuesto hipervalente . Su forma molecular es bipirámide trigonal . [ 3 ]
Producción
El pentametilbismuto se produce en un proceso de dos etapas. Primero, el trimetilbismuto reacciona con cloruro de sulfurilo para obtener diclorotrimetilbismuto, que luego reacciona con dos equivalentes de metillitio disueltos en éter. [ 4 ] La solución azul se enfría a −110 °C para precipitar el producto sólido.
- Bi(CH 3 ) 3 + SO 2 Cl 2 → Bi(CH 3 ) 3 Cl 2 + SO 2
- Bi(CH₃ ) ₃Cl₂ + 2LiCH₃ → Bi ( CH₃ ) ₅ + 2LiCl
Propiedades
At -110 °C, Bi(CH3)5 is a blue-violet solid. The methyl groups are arranged in a trigonal bipyramid, and the bond-lengths of methyl with bismuth are all the same. However, the molecule is not rigid, as can be determined from the nuclear magnetic resonance spectrum that shows all methyl groups are equivalent.[4] It is stable as a solid, but in the gas phase, when heated or in solution decomposes to trimethylbismuth.[3][4] The colour is unusual for bismuth or other hypervalent pnictide compounds, which are colourless. Calculations show that the colour is due to HOMO-LUMO transition. The HOMO is ligand based, whereas the LUMO is modified by relativistically stabilised bismuth 6s orbitals.[5]
Reactions
If excess methyllithium is used in production, an orange hexamethylbismuth salt, LiBi(CH3)6, is formed.[6][4]
References
- ↑Urben, Peter (2013). Bretherick's Handbook of Reactive Chemical Hazards. Academic Press. p. 742. ISBN 9780080523408.
- ↑Hellwinkel, Dieter (1883). "Penta- and hexaorganyl derivatives of the main group five elements". Wittig Chemistry. Topics in Current Chemistry. Topics in Current Chemistry. 109: 1–63. doi:10.1007/BFb0018055. ISBN 3-540-11907-8.
{{cite journal}}: ISBN / Date incompatibility (help) - 12Greene, Tim M.; Downs, Anthony J.; Pulham, Colin R.; Haaland, Arne; Verne, Hans Peter; Volden, Hans Vidar; Timofeeva, Tatjana V. (November 1998). "Molecular Structures of Pentamethylarsenic(V) and Trimethyldichloroarsenic(V) by Gas Electron Diffraction and ab Initio Calculations:? Molecular Mechanics Calculations on Pentamethylarsenic(V), Pentaphenylarsenic(V), and Related Compounds". Organometallics. 17 (24): 5287–5293. doi:10.1021/om980520r.
- 1234Wallenhauer, Stephan; Seppelt, Konrad (18 May 1994). "Methylbismuth(V) Compounds". Angewandte Chemie International Edition in English. 33 (9): 976–978. doi:10.1002/anie.199409761.
- ↑ Conradie, Jeanet; Ghosh, Abhik (febrero de 2017). "El color azul violeta del pentametilbismuto: un efecto visible de espín-órbita" . ChemistryOpen . 6 ( 1): 15–17 . doi : 10.1002/open.201600131 . PMC 5288750. PMID 28168144 .
- ↑ Wallenhauer, Stephan; Seppelt, Konrad (enero de 1995). "Compuestos de metilantimonio(V) y bismuto(V): una comparación estructural". Química Inorgánica . 34 (1): 116– 119. doi : 10.1021/ic00105a021 .
Lectura adicional
- compuestos de organobismut
- Moléculas hipervalentes
- Complejos de metilo