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

Duncan Micallef,Ulrich Baisch

doi:10.1107/s205698902100699x

Abstract

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.

Highlights

(C16H40N4O3P2)2(H2O)2] was obtained as a side product during the work up of the synthesis of octaethyl pyrophosphoramide 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 pyrophosphoramide molecule and one Ca2+ ion coordinated to two nitrate ions and one water molecule
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 octaethyl pyrophosphoramide ligands

Summary

Chemical context

The structures of octaethyl pyrophosphoramide, (O((Et2N)2PO)2), and its complexes have not been determined to date. Given the structural similarity of O((Et2N)2PO) to the more widely studied Schradan ligand, octamethyl pyrophosphoramide, O((Me2N)2PO) (Goehring & Niedenzu, 1956), it might be expected that the complexes of these two ligands would have related structures. Schradan has been reported as a bridging ligand in two dimeric Eu3+ complexes (Chan et al, 2020). We report what we believe to be the first example of a metal-coordinated octaethyl pyrophosphoramide complex, which is dimeric and has the formula [Ca(O((Et2N)2PO)2(NO3)2(H2O)]2

Structural commentary

Synthesis and crystallization