Flyover complex

In organometallic chemistry, a flyover complex features two metals bridged by the fragment OC(RC=CR)₂. Some flyover complexes are symmetrical and some are not.

Structure of an asymmetrical flyover complex (C₅H₅)₂Fe₂[(CCF₃)₄CO]CO. The Fe-Fe bond length is 258.8 picometers.^[1]

Structure of the flyover complex Fe₂(C₄H₄CO)(CO)₆, which has idealized C₂-symmetry.

Common examples are the iron carbonyl derivatives, which are typically air-stable, soluble in nonpolar solvents, and red-orange in color.^[2] These diiron complexes arise by the reaction of alkynes with iron carbonyls. Such reactions are known to generate many products, e.g. complexes of cyclopentadienones and para-quinones.^[3]

Some ferrole complexes react with tertiary phosphines to give the substituted flyover complex Fe₂(CO)₅(PR₃)(C₄R₄CO). They insert alkynes en route to tropones (R₆C₇O).^{[4] [5]}