In the area of organometallic chemistry, a bulky cyclopentadienyl ligand is

jargon Jargon is the specialized terminology associated with a particular field or area of activity. Jargon is normally employed in a particular communicative context and may not be well understood outside that context. The context is usually a partic ...

for a ligand of the type where R is a branched

alkyl In organic chemistry, an alkyl group is an alkane missing one hydrogen. The term ''alkyl'' is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of . A cycloalkyl is derived from a cycloal ...

and ''n'' = 3 or 4. Representative examples are the tetra

isopropyl In organic chemistry, propyl is a three-carbon alkyl substituent with chemical formula for the linear form. This substituent form is obtained by removing one hydrogen atom attached to the terminal carbon of propane. A propyl substituent is often ...

derivative and the tris( ''tert''-butyl) derivative . These ligands are so large that their complexes behave differently from the

pentamethylcyclopentadienyl 1,2,3,4,5-Pentamethylcyclopentadiene is a cyclic diene with the formula C5Me5H (Me = CH3). 1,2,3,4,5-Pentamethylcyclopentadiene is the precursor to the ligand ''1,2,3,4,5-pentamethylcyclopentadienyl'', which is often denoted Cp* (C5Me5) and read ...

analogues. Because they cannot closely approach the metal, these bulky ligands stabilize

high spin complex Crystal field theory (CFT) describes the breaking of degeneracies of electron orbital states, usually ''d'' or ''f'' orbitals, due to a static electric field produced by a surrounding charge distribution (anion neighbors). This theory has been used ...

es, such as (C₅H₂^''t''Bu₃)₂Fe₂I₂. These large ligands stabilize highly unsaturated derivatives such as (C₅H₂^''t''Bu₃)₂Fe₂N₂.

Synthesis and reactions

The (''tert''-butyl)cyclopentadiene is prepared by alkylation of

cyclopentadiene Cyclopentadiene is an organic compound with the formula C5H6.LeRoy H. Scharpen and Victor W. Laurie (1965): "Structure of cyclopentadiene". ''The Journal of Chemical Physics'', volume 43, issue 8, pages 2765-2766.