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 structure and stability. The cyclopentadienyl rings can donate electrons to the metal, enhancing its reactivity and allowing for various applications in catalysis and materials science. The most well-known example of a metallocene is ferrocene, which contains an iron atom between two cyclopentadienyl rings. Metallocenes have gained attention in fields like organic chemistry and polymer science due to their ability to form stable complexes and their potential use in developing new materials and catalysts.