Sandwich compound

In <a href="/facts/Organometallic_chemistry/bhqFz2P0">organometallic chemistry</a>, a sandwich compound is a <a href="/facts/Chemical_compound/37FXqqtv">chemical compound</a> featuring a <a href="/facts/Metal/PT8hNX6R">metal</a> bound by <a href="/facts/Hapticity/7MDtzehL">haptic</a>, <a href="/facts/Covalent_bond/EzMLf3Pz">covalent bonds</a> to two <a href="/facts/Arene_compound/3EXq8Tgf">arene</a> (ring) <a href="/facts/Ligand/6etB3qeW">ligands</a>. The arenes have the formula CnHn, substituted derivatives (for example Cn(CH3)n) and <a href="/facts/Heterocycle/8oYSjJxY">heterocyclic</a> derivatives (for example BCnHn+1). Because the metal is usually situated between the two rings, it is said to be "sandwiched". A special class of sandwich complexes are the <a href="/facts/Metallocenes/AecA5Qrk">metallocenes</a>.
The term sandwich compound was introduced in organometallic nomenclature in 1956 in a report by J. D. Dunitz, L. E. Orgel and R. A. Rich, who confirmed the structure of <a href="/facts/Ferrocene/jKtu9Cp8">ferrocene</a> by <a href="/facts/X-ray_crystallography/WtI0F5DN">X-ray crystallography</a>. The correct structure, in which the molecule features an iron atom sandwiched between two parallel <a href="/facts/Cyclopentadienyl/2cw59tjx">cyclopentadienyl</a> rings, had been proposed several years previously by <a href="/facts/Robert_Burns_Woodward/bAQeInCb">Robert Burns Woodward</a> and, separately, by <a href="/facts/Ernst_Otto_Fischer/v8zCR6Ke">Ernst Otto Fischer</a>. The structure helped explain puzzles about ferrocene's <a href="/facts/Conformational_isomerism/JflrT5Ws">conformers</a>. This result further demonstrated the power of <a href="/facts/X-ray_crystallography/WtI0F5DN">X-ray crystallography</a> and accelerated the growth of <a href="/facts/Organometallic_chemistry/bhqFz2P0">organometallic chemistry</a>.

Sandwich compound open-in-new

Sandwich compound