In the coordination sphere of transition metals, ligand-free P1, P2, cyclo-P3, P4, cyclo-P5and cyclo-P6, can be stabilized in polynuclear clusters, as phosphorus-containing metallatetrahedranes, as compounds with PAchains, and as triple-decker complexes with cyclo-P3, cyclo-P5, and cyclo-P6, sandwiched between metal-complex fragments.