A Study of Mono- and 1,1‘-Diphosphaferrocenes as Building Blocks for π-Conjugated Systems

Abstract

The synthesis of mono- and 1,1‘-diphosphaferrocenes bearing thienyl or phenyl substituents at the PCα carbon is described. Monophosphaferrocenes can be obtained using a “one-pot” procedure involving the oxidative coupling of phenyl- or thienyl-capped octa-1,7-diynes with zirconocene. This route implies a Cp transfer from a Zr species to the iron centers. These novel compounds have been characterized by X-ray diffraction study, and their optical and electrochemical behaviors have been elucidated. These data revealed that the optical gaps vary with the substitution pattern and the nature of the metallocene (mono vs diphosphaferrocenes), whereas their electrochemistry is mainly controlled by the structure of the metallocene. The lowest gaps are obtained with thienyl-substituted mono- and diphosphaferrocenes. Compared to the corresponding oligomers featuring phosphole units, these phosphaferrocene-based compounds exhibit higher thermal stability and higher HOMO−LUMO separation.