In the area of organometallic chemistry, a bulky cyclopentadienyl ligand is jargon for a ligand of the type C 5H 5−nR− n where R is a branched alkyl and n = 3 or 4. Representative examples are the tetraisopropyl derivative C 5HiPr− 4 and the tris(tert-butyl) derivative 1,2,4-C 5H 2tBu− 3. These ligands are so large that their complexes behave differently from the pentamethylcyclopentadienyl analogues. Because they cannot closely approach the metal, these bulky ligands stabilize high spin complexes, such as (C5H2tBu3)2Fe2I2. These large ligands stabilize highly unsaturated derivatives such as (C5H2tBu3)2Fe2N2.
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]
References
^ a bReiners, Matthias; Ehrlich, Nico; Walter, Marc D. (2018). "Synthesis of 1,3,5-Tri-tert-Butylcyclopenta-1,3-diene and Its Metal Complexes Na{1,2,4-(Me3C)3C5H2} and Mg{η5-1,2,4-(Me3C)3C5H2)2". Inorganic Syntheses. 37: 199. doi:10.1002/9781119477822.ch8.
^Hyster, Todd K. (2015). "1,3-Di-tert-butylcyclopentadiene". Encyclopedia of Reagents for Organic Synthesis: 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; Meyer, Karsten; Maron, Laurent; Walter, Marc D. (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. PMC 6099922. PMID 30155215.