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.