A structural study of alkaline earth metal complexes of (dichloromethylene)bisphosphonic acid P-morpholinium- and P-pyrrolidinium-P′-methyl esters

Abstract

Three alkaline earth metal complexes, [Mg(CH3PO3CCl2PO2NC4H8O)(H2O)3]n (1), [Ba(CH3PO3CCl2PO2NC4H8O)(H2O)2]n (2) and [Sr2(CH3PO3CCl2PO2NC4H8)2(H2O)3.5]n (3), were prepared and structurally characterized in a study of the complexing properties of amide ester derivatives of (dichloromethylene)bisphosphonic acid, and their crystal structures were determined. All three compounds are coordination polymers. Compounds 1 and 2 consist of 1D chains. In 1, the chains contain two independent octahedral Mg atoms in special positions, connected by L1 ligands, L1 = (Cl2CP2O5MeNC4H8O)2−. In 2, the seven-coordinated Ba2+ cations are connected to polymeric chains by L1 ligands, and the metal atom is coordinated by five O atoms of three different L1 ligands. The coordination polyhedron around the Ba2+ cation is a distorted monocapped trigonal prism. In 3, the two-dimensional framework is built up from one-dimensional chains containing two independent seven-coordinated Sr atoms connected by two crystallographically independent L2 ligands, L2 = (Cl2CP2O5MeNC4H8)2−. The coordination polyhedron around the Sr2+ cations is a distorted monocapped trigonal prism. In 3 the chains are connected into a layered structure through the Sr(1) atoms, while in compounds 1 and 2 a layer-like construction is formed through hydrogen bonds.