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Bulky cyclopentadienyl ligands
Topic: Chemistry
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In the area of organometallic chemistry, a bulky cyclopentadienyl ligand is jargon for a ligand of the type C5H5−nR−n where R is a branched alkyl and n = 3 or 4. Representative examples are the tetraisopropyl derivative C5HiPr−4 and the tris(tert-butyl) derivative 1,2,4-C5H2tBu−3. These ligands are so large that their complexes behave differently from the analogues derived from pentamethylcyclopentadienyl, itself a bulky ligand.
General properties of complexes
Because they cannot closely approach the metal, these bulky ligands can stabilize high spin complexes, such as (C5H2tBu3)2Fe2I2. These large ligands stabilize highly unsaturated derivatives such as (C5H2tBu3)2Fe2N2.
Synthesis and reactions
The (tert-butyl)cyclopentadiene is prepared by alkylation of cyclopentadiene with tert-butyl bromide in the presence of sodium hydride and dibenzo-18-crown-6.[1] The intermediate in this synthesis is di-tert-butylcyclopentadiene. This compound is conveniently prepared by alkylation of cyclobutadiene with tert-butyl bromide under phase-transfer conditions.[2][1]
Illustrative of the unusual complexes made possible with these bulky ligands is molecular iron nitrido complex (tBu3C5H2)2Fe2N2.[3] In contrast to (C5Me5)2Ir2Cl4, (tBu3C5H2)IrCl2 is monomeric.[4]
Related bulky ligands
Less bulky ligand are of the type C
5H
3R−
2 where R is a branched alkyl. Examples include the di-tert-butyl and related trimethylsilyl derivatives. One such complex is U(C
5H
3(SiMe
3)
2)
3.[5]
References
- ↑ 1.0 1.1 Reiners, Matthias; Ehrlich, Nico; Walter, Marc D. (2018). "Synthesis of Selected Transition Metal and Main Group Compounds with Synthetic Applications". Inorganic Syntheses. 37. p. 199. doi:10.1002/9781119477822.ch8. ISBN 978-1-119-47782-2.
- ↑ Hyster, Todd K. (2015). "1,3-Di-tert-butylcyclopentadiene". Encyclopedia of Reagents for Organic Synthesis. pp. 1–2. doi:10.1002/047084289X.rn01866. ISBN 9780470842898.
- ↑ Reiners, Matthias; Maekawa, Miyuki; Daniliuc, Constantin G.; Freytag, Matthias; Jones, Peter G.; White, Peter S.; Hohenberger, Johannes; Sutter, Jörg et al. (2017). "Reactivity studies on [Cp′Fe(μ-I)]2: Nitrido-, sulfido- and diselenide iron complexes derived from pseudohalide activation". Chemical Science 8 (5): 4108–4122. doi:10.1039/C7SC00570A. PMID 30155215.
- ↑ Shimogawa, Ryuichi; Takao, Toshiro; Suzuki, Hiroharu (2017). "Half-sandwich Cyclopentadienyl Iridium Dichloride Monomer Cp‡IrCl2 (Cp‡ = 1,2,4-tri-tert-butylcyclopentadienyl)". Chemistry Letters 46 (2): 197–199. doi:10.1246/cl.160937.
- ↑ Eralie, Dylan M. T.; Ducilon, John; Gorden, Anne E. V. (2025). "Uranium Chemistry: Identifying the Next Frontiers". Inorganic Chemistry 64 (2): 767–784. doi:10.1021/acs.inorgchem.4c02173. PMID 39190695.
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