Structural study of metal complexes of bisphosphonate amide ester: copper, magnesium, zinc and cadmium complexes of (dichloromethylene)bisphosphonic acid P-piperidinium-P′-methyl ester

Abstract

Four metal complexes of (dichloromethylene)bisphosphonic acid P-piperidinium-P′-methyl ester were prepared and their crystal structures determined by X-ray single-crystal diffraction. The complexes were [{Cu₃(CH₃PO₃CCl₂PO₂NC₅H₁₀)₃(H₂O)₂}(H₂O)₃]₂ (1), [(MgCH₃PO₃CCl₂PO₂NC₅H₁₀)(H₂O)₃]_n (2), [{NaZn_1.5(CH₃PO₃CCl₂PO₂NC₅H₁₀)₂(H₂O)₂}(H₂O)]_n (3) and [{Cd(CH₃PO₃CCl₂PO₂NC₅H₁₀)(H₂O)₃}(H₂O)]_n (4). The methyl ester of the piperidine derivative of Cl₂MBP forms with copper the first wheel-like metal complex of bisphosphonate. The packing of this hexameric compound 1 consists of channels occupied by aqua ligands and lattice water molecules. Compounds 2–4 are polymers consisting of 1-D chains of different composition; in 3, coordinated Na⁺ cations hold the chains together, forming a 2-D layered structure. Compounds 2 and 4 form layers through hydrogen bonds.