X-ray diffraction study of bisphosphonate metal complexes: Mg, Sr and Ba complexes of (dichloromethylene)bisphosphonic acid P,P′-dibenzoyl anhydride

The first alkaline earth metal complexes of a dibenzoyl derivative of clodronic acid were prepared and characterised by X-ray crystallography, elemental analysis and infrared spectroscopy. The complexes were [Mg{[Cl2C(PO2O(C(O)C6H5))2](H2O)5} · H2O] (1), [Sr2{[Cl2C(PO2O(C(O)C6H5))2]2(H2O)9} · H2O]n (2) and [Ba{Cl2C(PO2O(C(O)C6H5))2}(H2O)2]n (3). The monomeric units of 1 and the polymeric chains of 2 and 3 form 2D layer-like structures through intermolecular hydrogen bonds. The Cl2C(PO2O(C(O)C6H5))22− ligand acts as a bridging and chelating ligand, forming six- and eight-membered chelate rings with metal atoms. In addition, the previously determined polymeric calcium complex of clodronate, [Ca2{Cl2C(PO3)2}(H2O)6 · 4.5H2O]n(4), was synthesised by hydrolysis method from the dibenzoyl derivative of clodronic acid.

Graphical abstractMg, Sr and Ba complexes of (dichloromethylene)bisphosphonic acid P,P′-dibenzoyl anhydride have been prepared and characterised by X-ray crystallography, elemental analysis and infrared spectroscopy. The monomeric units of [Mg{[Cl2C(PO2O(C(O)C6H5))2](H2O)5} · H2O] (1) and the polymeric chains of [Sr2{[Cl2C(PO2O(C(O)C6H5))2]2(H2O)9} · H2O]n (2) and [Ba{Cl2C(PO2O(C(O)C6H5))2} · (H2O)2]n (3) form 2D layer-like structures through intermolecular hydrogen bonds.Figure optionsDownload full-size imageDownload as PowerPoint slide