New in Situ Condensation Reaction of Amino Diphosphonic Acids: A Series of Bicyclic Phosphonate Derivatives and Three Novel Water Clusters

A new in situ low-temperature, low-pressure hydrothermal condensation reaction of amino diphosphonic acids affords a series of phosphonate derivatives with bicyclic structures. By using such bicyclic phosphonate ligands, three compounds, namely, [Zn 2 (L 1 )(phen) 4 ]·12H 2 O ( 1 ), [Ni(Im) 6 ] 3 (L 2 ) 2 (ImH) 2 ·24H 2 O ( 2 ), and [Cu 2 (L 3 )(phen) 2 (H 2 O) 2 ]·9H 2 O ( 3 ) (phen = 1,10-phenanthroline, Im = imidazole, L 1 H 4, L 2 H 4, and L 3 H 4 represent different bicyclic phosphonate derivatives), have been synthesized and structurally characterized by single-crystal X-ray crystallography. Novel water clusters with different structural motifs, such as T4(3)5(0)A0 water tape in 1, TU water tape in 2, and L5(4)5(5)15(14) water layer in 3, are discussed in detail. The coordination mode of the metal ion and the use of the appropriate second ligand, which would influence the reaction and structures of the final products are also discussed.