The reaction of (h5-C5Me5)(CO)2FeP:PR [R = 2,4,6-(Me3C)3C6H2] with S and Se in THF at 20 Deg afforded the novel complexes (h5-C5Me5)(CO)2FeP(:E):PR with a ligand formally derived from the metaphosphite ion PO2-. Only the S deriv. appeared to be stable at ambient temp., whereas the Se compd. in soln. slowly rearranged to the selenadiphosphiranyl complex I. The structure of the S deriv. was established by a single-crystal x-ray diffraction study.