Synthesis and structures of substituted tetramethylcyclopentadienyl dinuclear metal carbonyl compounds

Abstract

Cyclopentadienes (C5Me4R) [R = Allyl (1), n-Butyl (2), Benzyl (3), and PhMe-2 (4)] reacted with Fe(CO)5 in refluxing xylene to give new substituted tetramethylcyclopentadienyl dinuclear iron carbonyl complexes [(η 5-C5Me4R)Fe(CO)(μ-CO)]2 [R = Allyl (5), n-Butyl (6), Benzyl (7), and PhMe-2 (8)], respectively. The four new complexes 5–8 were characterized by elemental analysis, IR, and 1H NMR spectra. The crystal structures of complexes 5–7 were determined using single crystal X-ray diffraction. The crystal structure of complex 5 showed that allyl underwent isomerization to give the corresponding methyl-vinyl. A possible mechanism is discussed. The X-ray crystal structures of complexes 5, 6, and 7 confirm the structure with bridging and terminal CO groups. They show that the steric effects of substituents influence the Fe–Fe bond distances of the complexes.