sandwich compounds
Compounds in which a metal atom is located between the faces of two parallel and planar (or nearly so) ring structures, e.g. bis(\(\eta ^{5}\)-cyclopentadienyl)iron (ferrocene), dibenzenechromium.
See also:
PAC, 1995, 67, 1307. (Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1364 [Terms] [Paper]