Chemistry:Metallabenzene

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Structure of the metallabenzene TpIrC5H5(Cl)[1]

The parent metallacyclobenzene has the formula LnM(CH)5. They can be viewed as derivatives of benzene wherein a CH center has been replaced by a transition metal complex. Most metallabenzenes do not feature the M(CH)5 ring itself, but, instead, some of the H atoms are replaced by other substituents.[2]

Classification

Metallabenzene complexes have been classified into three varieties; in such compounds, the parent acyclic hydrocarbon ligand is viewed as the anion C5H5−. The 6 π electrons in the metallacycle conform to the Hückel (4n+2) theory.[3]

Three classes of stable metallabenzenes.

Preparation and structure

The first reported stable metallabenzene was the osmabenzene Os(C5H4S)CO(PPh3)2.[4][2] Characteristic of other metallaarenes, the Os-C bonds are about 0.6 Å longer than the C-C bonds (in benzene these are 1.39 Å), resulting in a distortion of the hexagonal ring. 1H NMR signals for the ring protons are downfield, consistent with aromatic "ring current." Osmabenzene and its derivatives can be regarded as an Os(II), d6 octahedral complex.

Interactions between these orbitals give rise to a cyclically delocalized pi electronic structure.

Metallabenzenes have also been characterized with metals ruthenium,[5][6][7][8] iridium,[9][10] platinum,[11][12][13] and rhenium.[14]

References

  1. ↑ Ángela Vivancos; Margarita Paneque; Manuel L. Poveda; Eleuterio Álvarez (2013). "Building a Parent Iridabenzene Structure from Acetylene and Dichloromethane on an Iridium Center". Angew. Chem. Int. Ed. 52 (38): 10068–10071. doi:10.1002/anie.201305319. PMID 23934753. 
  2. ↑ 2.0 2.1 Bleeke, J.R. (2001). "Metallabenzenes". Chem. Rev. 101 (5): 1205–27. doi:10.1021/cr990337n. PMID 11710218. 
  3. ↑ Thorn, D.L.; Hoffmann, R. (1979). "Delocalization in Metallocycles". Nouv. J. Chim. 3 (1): 39. 
  4. ↑ Elliott, G.P.; Roper, W.R.; Waters, J.M. (1982). "Metallacyclohexatrienes or 'metallabenzenes.' Synthesis of osmabenzene derivatives and X-ray crystal structure of [Os(CSCHCHCHCH)(CO)(PPh3)2]". J. Chem. Soc., Chem. Commun. (14): 811–813. doi:10.1039/C39820000811. 
  5. ↑ Zhang, H.; Xia, H.; He, G.; Wen, T.; Gong, L.; Jia, G. (2006). "Synthesis and characterization of stable ruthenabenzenes". Angewandte Chemie International Edition in English 45 (18): 2920–2923. doi:10.1002/anie.200600055. PMID 16566052. 
  6. ↑ Zhang, H.; Feng, L.; Gong, L.; Wu, L.; He, G.; Wen, T.; Yang, F.; Xia, H. (2007). "Synthesis and Characterization of Stable Ruthenabenzenes Starting from HC⋮CCH(OH)C⋮CH". Organometallics 26 (10): 2705. doi:10.1021/om070195k. 
  7. ↑ Wu, L.; Feng, L.; Zhang, H.; Liu, Q.; He, X.; Yang, F.; Xia, H. (2008). "Synthesis and characterization of a novel dialdehyde and cyclic anhydride". The Journal of Organic Chemistry 73 (7): 2883–2885. doi:10.1021/jo800052u. PMID 18336045. 
  8. ↑ Clark, G. R.; O'neale, T. R.; Roper, W. R.; Tonei, D. M.; Wright, L. J. (2009). "Stable Cationic and Neutral Ruthenabenzenes". Organometallics 28 (2): 567. doi:10.1021/om800857k. 
  9. ↑ Bleeke, J. R.; Xie, Y. F.; Peng, W. J.; Chiang, M. (1989). "Metallabenzene: synthesis, structure, and spectroscopy of a 1-irida-3,5-dimethylbenzene complex". Journal of the American Chemical Society 111 (11): 4118. doi:10.1021/ja00193a064. 
  10. ↑ Bleeke, J. R.; Xie, Y. F.; Bass, L.; Chiang, M. Y. (1991). "Metallacyclohexadiene and metallabenzene chemistry. 5. Chemical reactivity of metallabenzene". Journal of the American Chemical Society 113 (12): 4703. doi:10.1021/ja00012a061. 
  11. ↑ Jacob, V.; Weakley, T. J. R.; Haley, M. M. (2002). "Metallabenzenes and Valence Isomers. Synthesis and Characterization of a Platinabenzene". Angewandte Chemie International Edition 41 (18): 3470–3473. doi:10.1002/1521-3773(20020916)41:18<3470::AID-ANIE3470>3.0.CO;2-4. PMID 12298068. 
  12. ↑ Landorf, C. W.; Jacob, V.; Weakley, T. J. R.; Haley, M. M. (2004). "Rational Synthesis of Platinabenzenes†". Organometallics 23 (6): 1174. doi:10.1021/om034371a. 
  13. ↑ Jacob, V.; Landorf, C. W.; Zakharov, L. N.; Weakley, T. J. R.; Haley, M. M. (2009). "Platinabenzenes: Synthesis, Properties, and Reactivity Studies of a Rare Class of Metalla-aromatics†". Organometallics 28 (17): 5183. doi:10.1021/om900439z. 
  14. ↑ Poon, K. C.; Liu, L.; Guo, T.; Li, J.; Sung, H. H. Y.; Williams, I. D.; Lin, Z.; Jia, G. (2010). "Synthesis and Characterization of Rhenabenzenes". Angewandte Chemie International Edition 49 (15): 2759–2762. doi:10.1002/anie.200907014. PMID 20229549. 



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