Bis(benzene)chromium

Bis(benzene)chromium is a chemical compound with the formula Cr(C6H6)2. This organometallic compound is a classic example of a transition metal arene complex. The compound is not of practical importance, but is a fundamental compound in organometallic chemistry, the area of chemistry that studies chemical compounds containing bonds between carbon and a metal.

Structure and Bonding

Bis(benzene)chromium is composed of a chromium atom sandwiched between two benzene rings. The molecular geometry of the compound is known as a "sandwich complex", a term coined by the British chemist Geoffrey Wilkinson, who shared the Nobel Prize in Chemistry for his work on such compounds.

The chromium atom in bis(benzene)chromium is in the +2 oxidation state. Each benzene ring donates three pi electrons to the chromium atom, forming a total of six coordinate covalent bonds. This results in a stable 18-electron complex.

Synthesis

Bis(benzene)chromium was first synthesized in 1953 by the German chemist Ernst Otto Fischer. The synthesis involves the reaction of chromium(III) chloride with benzene in the presence of a Lewis acid such as aluminium chloride.

Properties

Bis(benzene)chromium is a purple solid at room temperature. It is stable in air, but reacts with strong oxidizing agents. The compound is soluble in common organic solvents such as dichloromethane and tetrahydrofuran.

Applications

While bis(benzene)chromium itself has no practical applications, the study of this compound has greatly contributed to the understanding of the bonding and reactivity of organometallic compounds. This knowledge has been applied in the development of catalysts for important industrial processes such as the polymerization of ethylene and the hydroformylation of alkenes.

See also

• Sandwich compound
• Organometallic chemistry
• Ernst Otto Fischer
• Geoffrey Wilkinson