Syntheses, X‐ray Diffraction Study and Characterisations of Ni and Zn Complexes of Clodronic Acid and Its Dibenzoyl Derivative

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Four new nickel and zinc bis(phosphonates) were prepared, and their crystal structures were determined by single‐crystal X‐ray diffractometry: [{Na2Ni3(Cl2C(PO2O(C(O)C6H5))2)(H2O)20}{Cl2C(PO2O(C(O)C6H5))2}]n (1), [{Na2Zn3(Cl2C(PO2O(C(O)C6H5))2)(H2O)20}{Cl2C(PO2O(C(O)C6H5))2}]n (2), [Ni2{Cl2C(PO3)2}(H2O)7]·4H2O (3) and [Zn2{Cl2C(PO3)2}(H2O)7]·6H2O (4). In addition, the spectroscopic and thermal properties of the compounds 1–4 were studied by infrared spectroscopy and thermogravimetric analysis. The coordination polymers 1 and 2 form, through intermolecular hydrogen bonds, 2D layer‐like structures, whereas the aqua ligands and lattice water molecules of the monomeric compounds 3 and 4 form hydrogen bonds in three dimensions giving rise to a 3D network. In the isomorphous structures 1 and 2 the octahedral Na and Ni/Zn atoms form μ‐H2O‐bridged stepped metal chains where the Cl2C(PO2O(C(O)C6H5))22– ligands (L1) are monodentately coordinated to the Na and Ni/Zn atoms, and the lattice L1 ligands are located in a trans position with respect to the chain. The isostructural Ni and Zn complexes of clodronic acid, 3 and 4, are formed by a hydrolysis method from the L1 ligand. There, the clodronate ligand acts as a bridging and chelating ligand with the octahedral Ni and Zn atoms. The bulky and hydrophopic benzoyl groups of the L1 ligand in structures 1 and 2 lead to dense packing modes. The clodronic acid ligand of structures 3 and 4, in turn, has a higher coordination flexibility and forms voids, where the water clusters are trapped by hydrogen bonds.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)