The Lewis acid-catalyzed polycondensation of ferrocene with phenyldi-chlorophosphine is described. Under a variety of conditions, using melt and solution condensation conditions, followed by a mild postoxidation treatment, polymers composed of ferrocenylene units interconnected by phenylphosphoryl groups are obtained. The soluble, but largely infusible, products possess number-average molecular weights up to 3500 (6000 upon subfractionation). Elemental compositions vary with reaction conditions; optimal consistency with the ideal ferrocenylene(phenyl)phosphoryl recurring unit results from use of a moderate ferrocene excess and smallest possible solvent concentrations at temperatures not exceeding 105°. Much as in previously described polyacylations of ferrocene, a minor side reaction is observed which involves rupture of the metal-to-ring bond in ferrocene with subsequent incorporation of cyclopentylene groups into the polymer. This departure, however insignificant, from the purely aromatic poly-phosphine oxide composition results in thermal and oxidative stabilities not markedly superior to those of earlier ferrocenylene-methylene polymers.