PROTONATION OF IRON DIENE TRIS(PHOSPHITE) COMPLEXES

The protonation of (η4-diene)iron (tris(phosphite)) complexes yields (η3-alkenyl)iron (tris(phosphite)) cations. The noble gas (18-electron) configuration of the iron center is attained through a bonding interaction with a hydrogen atom which is also bound to the carbon atom adjacent to the allylic portion of the π-enyl ligand. The hydrogen atom coordination and resultant distortion of the π-enyl group give rise to unusual 1H NMR parameters. In the π-butenyl complexes, rotation of the methyl group bearing the coordinated hydrogen atom can be frozen out on the NMR time scale. In π-cycloalkenyl complexes, an exchange process, involving the endo hydrogen atoms on the two carbon atoms adjacent to the π-enyl group, can be frozen out on the NMR time scale for cyclohexenyl and cycloheptenyl complexes. The process is still rapid at the lowest temperatures investigated for the cyclooctenyl complex. © 1979, American Chemical Society. All rights reserved.