Flyover complex

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

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]

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]}

References

1. Davidson, John L.; Green, Michael; Stone, F. Gordon A.; Welch, Alan J. (1976). "Insertion Reactions of Hexafluorobut-2-yne, Tetrafluoroethylene, and Hexafluoroacetone with η⁵-Cyclopentadienyl-Iron, -Ruthenium, -Palladium, and -Molybdenum Complexes; Molecular and Crystal Structures of [Fe₂(CO){C₄(CF₃)₄CO}(η⁵-C₅H₅)₂] and [Fe{COCF₂C₅H₅}(η⁵-C₅H₅)]". J. Chem. Soc., Dalton Trans. (20): 2044–2053. doi:10.1039/dt9760002044.
2. Fehlhammer, W.P.; Stolzenberg, H. (1982). "Dinuclear Iron Compounds with Hydrocarbon Ligands". In Geoffrey Wilkinson; F. Gordon A. Stone; Edward W. Abel (eds.). Comprehensive Organometallic Chemistry. pp. 513–613. doi:10.1016/B978-008046518-0.00051-9. ISBN 9780080465180.
3. Piero Pino; Irving Wender, eds. (1968). Organic Syntheses via Metal Carbonyls Volume 1. NY: Wiley Interscience.
4. Giordano, Roberto; Sappa, Enrico; Cauzzi, Daniele; Predieri, Giovanni; Tiripicchio, Antonio (1996). "Reactions of the 'Ferrole' Complex [Fe₂(CO)₆(C₂Et₂)₂] with Group 15 Donor Ligands and with Alkynes. Stepwise Formation and Disengagement of Tropones. Crystal and Molecular Structure of [Fe₂(CO)₅{(CEt)₂CO(CEt)₂CHCPh}]". Journal of Organometallic Chemistry. 511 (1–2): 263–271. doi:10.1016/0022-328X(95)05936-J.
5. Fagan, Paul J. (1995). "Dinuclear Iron Compounds with Hydrocarbon Ligands". Comprehensive Organometallic Chemistry II. pp. 231–258. doi:10.1016/B978-008046519-7.00058-7. ISBN 9780080465197.