organic compounds
The title compounds, cis- and trans-C7H16O5P2, display chair conformations of the heterocyclic rings, with much larger absolute torsion angles around C—O—C (> 72°) than around P—C—P (< 47°). Ring angles are lower than tetrahedral at phosphorus, but higher at carbon and oxygen, with a maximum of 116.03 (12)° for the P—C—P angle of the cis isomer. Several C—HO contacts, including one as short as HO = 2.27 Å, can be classified as hydrogen bonds.