Metal-assisted formation of phosphorus-oxygen heterocyclic complexes

Article abstract of DOI:10.1021/om00001a017

Starting with bis(dialkylamino)phosphine oxides or triphosphoxane [R₂NPO]₃ rings, transition metal complexes containing P₄O₄, P₅O₅, and P₆O₆ heterocycles have been assembled. Specific products isolated were found to depend critically on reaction conditions, the metal, and its ancillary ligands, as well as the phosphorus substituent. While only monometallic products were obtained from divalent precursors of the nickel triad, bimetallic complexes were also produced from the group 6 metal carbonyls. In general, larger rings were obtained at higher temperatures. Only P₃O₃ and P₄O₄ products were formed around molybdenum, while P₅O₅ structures could also be assembled about chromium, nickel, palladium, and platinum centers. One of the iron carbonyl complexes was found to feature an unusual η¹-P[OP(O)]₂P ring, the product of a double POP to PP(=O) rearrangement. In addition, a dichromium P₆O₆ cluster complex featuring the novel hexaphosphoxane ring was synthesized from bis(cis-2,6-dimethylpiperidino)phosphine oxide. Use of isolated monometallic P_nO_n complexes as ligands yielded heterobimetallic products as well as phosphoxane ring transfer reactions. The X-ray crystal structures of five representative complexes containing FeP₄O₄ (14), Cr₂P₄O₄ (19a, 19b), Cr₂P₆O₆ (21), and MoFeP₄O₄ (25) cores, respectively, are reported.