Molecular structures of the pentaphenylcyclopentadienyl iron complexes [(C5Ph5)Fe(CO)2R] (R = Me, Ph, iPr and Bu)

The PdII-catalysed reaction of [(C5Ph5)Fe(CO)2Br] with Grignard compounds RMgX or butyl lithium gave the iron alkyl/aryl complexes [(C5Ph5)Fe(CO)2R] (R = Me, Ph, iPr and Bu) in 59-73% yield, namely, dicarbonylmethyl(η5-pentaphenylcyclopentadienyl)iron, [Fe(CH3)(C35H25)(CO)2], dicarbonyl(η5-pentaphenylcyclopentadienyl)phenyliron, [Fe(C6H5)(C35H25)(CO)2], dicarbonyl(isopropyl)(η5-pentaphenylcyclopentadienyl)iron, [Fe(C3H7)(C35H25)(CO)2], and butyldicarbonyl(η5-pentaphenylcyclopentadienyl)iron, [Fe(C4H9)(C35H25)(CO)2]. The crystal structure determinations showed the usual `paddle-wheel' orientation of the phenyl rings, with an average canting angle of ca 50°. The bond parameters are mainly dictated by the steric requirements of the alkyl/aryl groups and only the phenyl complex shows electronic effects.