Metallabenzene

Structure of the metallabenzene TpIrC₅H₅(Cl)[1]

The parent metallacyclobenzene has the formula L_nM(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 They can be viewed as derivatives of benzene wherein a CH center has been replaced by a transition metal complex.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]

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), d^6 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. hdl:10261/97363. PMID 23934753.
2. 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. S2CID 45468728.