Metallocenes are a class of chemical compounds that consist of a metal atom sandwiched between two cyclopentadienyl anions. These compounds typically feature transition metals, such as iron, nickel, or titanium, and are known for their unique sandwich-like structure. This arrangement allows for interesting chemical properties and reactivity. Metallocenes are often used in various applications, including catalysis and materials science. Their stability and ability to form complexes make them valuable in the development of new materials and chemical processes. Additionally, they have been studied for their potential use in medicine and nanotechnology.