catena-Poly[diaquacadmium(II)-μ-(diethyl dichloromethylenebisphosphonato)-κ³O,O′:O′′-tetraaquacadmium(II)-μ-(diethyl dichloromethylenebisphosphonato)-κ³O:O′,O′′]

Abstract

The title compound, [Cd(C5H10Cl2O6P2)(H2O)3]n, is isomorphous with the Zn and Mg complexes of the (Cl2CP2O6Et2)2− ligand. The structure can be described as centrosymmetric octahedral Cd atoms with two symmetrically chelating [Cl2C(PO3Et)2]2− ligands, connected into polymeric chains along the [110] direction by further octahedral Cd atoms.

Structures of Bisphosphonate Metal Complexes: Zinc and Cadmium Complexes of Clodronate and Its Partial Ester Derivatives

“…Previously, some Zn and Cd complexes of methylenebis(phosphonate) MBP, [H 2 C(PO 3 H) 2 ] 2- , and its analogues etidronate, [(CH 3 )(HO)C(PO 3 H) 2 ] 2- , and alendronate, [(NH 3 CH 2 CH 2 CH 2 )(HO)C(PO 3 H) 2 ] 2- , have been reported. − The structures of these metal complexes are either molecular (monomers and dimers) 17,18,21 or polymeric chains, layers, or three-dimensional networks. − ,− The new metal compounds 1 − 4 , and also the Zn and Cd complexes of the (dichloromethylene)bis(phosphonic acid) P , P ‘-diethyl ester, are different from the Zn and Cd complexes of MBP and its derivatives etidronate and alendronate. − The structures of the Zn complexes of clodronate and its ester derivatives are all different, one-dimensional single-chains, and the structure of the Cd complex of clodronate is two-dimensional and double-layered, while the structures of the Cd complexes of the ester derivatives are a one-dimensional chain and a tetramer …”

“…In addition, the binding mechanism of the ligands and coordination spheres of the metals are similar. The bisphosphonate ligands have high affinity to form chelate rings with metal cations; MBP, etidronate, and alendronate as well as clodronate and its ester derivatives all form six-membered chelate rings with Zn 2+ and Cd 2+ cations. − , The only exception is compound 3 , in which the bisphosphonate ligand is coordinated terminally to two different metal cations and is not chelated. Another interesting binding mechanism of clodronate was also found: clodronate coordinated to a metal cation through its chlorine atom, forming a unique Cd−Cl(C) bond in compound 2 .…”

“…Altogether, the structures of the Zn and Cd complexes of clodronate and its ester derivatives, together with the previously published structures, indicate that the dimensionalities of the structures decrease with increasing size of the alkyl substituent.On the other hand, it can be assumed that esterification of clodronate does not totally prevent the formation of the polymeric structures, but it could increase the porosity of the structure by increasing the distance between the structural units. −,− …”

“…Previously, we reported the structures of polymeric Ca and Ba complexes , and a monomeric Sr complex of clodronate, [Cl 2 C(PO 3 H) 2 ] 2- , as well as alkaline earth metal complexes of P , P ‘-diethyl (dichloromethylene)bis(phosphonate), [Cl 2 C(PO 3 Et) 2 ] 2- , and Mg and Ca complexes of P , P ‘-diisopropyl (dichloromethylene)bis(phosphonate), [Cl 2 C(PO 3 Pr i ) 2 ] 2- . The results showed that clodronate and its ester derivatives produce both molecular and polymeric structures with metals, and moreover, the structures of the metal complexes indicate that the dimensionalities of the structures decrease with increasing size of the alkyl substituent. −,− We have also succeeded to prepare Zn and Cd complexes of the diethyl ester derivative of clodronate, and the structures proved to be one-dimensional chains and isomorphous with the Mg complex of the same ligand . Here we report the structures of the Zn and Cd complexes of clodronate [{NaZn(Cl 2 CP 2 O 6 H)(H 2 O) 5 }] n ( 1 ) and [{Cd 2 (Cl 2 CP 2 O 6 )(H 2 O) 4 }·H 2 O] n ( 2 ) and the Zn and Cd complexes of the P , P ‘-diisopropyl (dichloromethylene)bis(phosphonate) [{Zn(Cl 2 CP 2 O 6 Pr i 2 )(H 2 O) 3 }·H 2 O] n ( 3 ) and [{Cd 2 (Cl 2 CP 2 O 6 Pr i 2 ) 2 (MeOH) 2 (H 2 O) 2 }·H 2 O] 2 ( 4 ).…”