Di-μ-nitrato-bis-(μ-octa-ethyl pyro-phospho-ramide)-bis-[aqua-dinitratocalcium(II)]

The title compound, di-μ-nitrato-κ³ O,O':O;O:O,O'-bis-(μ-octa-ethyl pyro-phos-pho-ramide-κ² O:O')bis-[aqua-bis-(nitrato-κ² O,O')calcium(II)], [Ca₂(NO₃)₄(C₁₆H₄₀N₄O₃P₂)₂(H₂O)₂] was obtained as a side product during the work up of the synthesis of octa-ethyl pyro-phospho-ramide and represents the first structurally characterized complex of this ligand. The compound crystallizes in the monoclinic space group P2₁/n and the asymmetric unit contains one pyro-phospho-ramide mol-ecule and one Ca²⁺ ion coordinated to two nitrate ions and one water mol-ecule. The complex exists as a dimer with a centre of inversion located between two eight-coordinate calcium(II) centres, which are bridged by two nitrate ions and two octa-ethyl pyro-phospho-ramide ligands. Each Ca²⁺ cation is also coordinated to a further nitrate anion, acting as a bidentate ligand, and a water mol-ecule. The complexes stack parallel to the a axis and are held in place by a network of inter-molecular O-H⋯O hydrogen bonds also running parallel to a.