tsüklopentadienüül

Cyclopentadienyl, often abbreviated as Cp, is an organic compound with the chemical formula C5H5. It is a cyclic five-membered ring structure with alternating double and single bonds, giving it aromatic character. This aromaticity makes the cyclopentadienyl anion particularly stable.

The cyclopentadienyl anion, Cp-, is formed by the deprotonation of cyclopentadiene. It is a planar, monovalent anion with six pi electrons, satisfying Hückel's rule for aromaticity. This stability makes Cp- a common ligand in organometallic chemistry.

When bonded to a metal atom, the cyclopentadienyl group typically acts as a ligand, forming stable metal complexes. These complexes are often referred to as metallocenes. A classic example is ferrocene, [Fe(C5H5)2], where an iron atom is sandwiched between two cyclopentadienyl rings.

Cyclopentadienyl ligands can coordinate to metal centers in various ways, most commonly in a h5-η5 fashion, where all five carbon atoms of the ring are bonded to the metal. This mode of bonding is prevalent in metallocenes. Other coordination modes are also possible, though less common.

Organometallic compounds containing cyclopentadienyl ligands have found applications in catalysis, materials science, and as precursors for chemical vapor deposition. Their unique electronic and structural properties make them versatile building blocks in synthetic chemistry. The study of these compounds has significantly advanced the field of organometallic chemistry.