Electrochemistry and UV/visible spectroscopy of phosphino-substituted bis(η5-indenyl)iron(II) complexes

Six phosphino-functionalized diindenyl ferrocenes have been characterized by UV/vis spectroscopy and cyclic voltammetry in dichloromethane. The complexes contain the following ligands: 1-diphenylphosphino- (1), 1-diphenylphosphino-2-methyl- (2), 1-diphenylphosphino-3-methyl- (3), 1-diphenylphosphino-3-trimethylsilyl- (4), 1-diphenylphosphino-2,3-dimethyl- (5), and 1-diphenylphosphino-4,7-dimethyl-indenide (6). The cyclic voltammetry shows an approximately additive relationship between oxidation potential and the type of substituent and its ring position, but with increasing substitution leading to lower than otherwise expected oxidation potentials. The UV/vis spectra show two absorptions with the low energy band moving to lower energy with increasing substitution on the C5 ring.