cis- and trans-1,3-Diethoxy-1,3-diphosphorinane-1,3-dione

The title compounds, cis- and trans-C₈H₁₈O₄P₂, crystallize with one and two independent molecules, respectively, in the asymmetric unit. These are the first structures of 1,3-diphosphorinanes with no further annelation. All three diphosphorinane rings are similar, with chair conformations that are flattened in the region of the P—C—P moiety. The ring angles at phosphorus are all less than, and those at carbon greater than, ideal tetrahedral angles [maximum 116.21 (11)° for P—C—P in the cis isomer]. The acidic methylene groups, lying between the P atoms, are involved in the shortest C—H...O hydrogen bonds (H...O < 2.35 Å).

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