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.