Organometallics

Organometallics are compounds that feature a direct bond between a metal and carbon, including metal–carbon covalent bonds in alkyl, aryl, vinyl, hydrido, alkylidene, and related ligands. The field spans transition metals, main-group elements such as magnesium and lithium in organomagnesium (Grignard) and organolithium reagents, along with specialty compounds containing metal–carbon bonds in metallocenes and related sandwich complexes. Organometallic chemistry bridges inorganic and organic chemistry and underpins many industrial processes and synthetic methodologies.

Common classes include Grignard reagents RMgX and organolithiums RLi, along with stable metallocene examples such as ferrocene Fe(C5H5)2. Transition-metal complexes bearing ligands like CO, cyclopentadienyl, allyl, or alkyl groups act as catalysts for polymerization and cross-coupling (Suzuki, Kumada, Negishi) and olefin metathesis.

Bonding concepts: metal–carbon bonds can be covalent with significant character, and many reactions proceed via two-electron steps or three-center interactions. Common reaction patterns include oxidative addition, migratory insertion, and reductive elimination in catalytic cycles, as well as transmetallation in cross-coupling. The 18-electron rule provides a useful heuristic for stability in many complexes.

Synthesis and handling: many organometallics are air- and moisture-sensitive, requiring inert atmosphere and anhydrous solvents. Characterization relies on X-ray crystallography, NMR spectroscopy, IR and MS.

Impact: organometallics enable polymerization catalysis, carbon–carbon bond formation, and transformations that are difficult by purely organic routes. The field has a long history from Grignard and Ziegler–Natta chemistry to modern C–H activation and metathesis catalysts.