Novel Cd(II) coordination polymers with flexible disulfoxide ligands: effects of ligand spacers, terminal groups and counter anions on the complex framework formations.

Five novel Cd(II) coordination polymers with three structurally related flexible disulfoxide ligands, [Cd(L1)32]n (1), [Cd(L2)32(CHCl3)]n (2), [Cd(L2)(NO3)2(H2O)]n (3), [Cd2(L3)2(NO3)4]n (4) and [Cd(L3)32]n (5), where L1= 1,3-bis(phenylsulfinyl)propane, L2= 1,4-bis(phenylsulfinyl)butane and L3= 1,4-bis(ethylsulfinyl)butane, were synthesized and structurally determined by X-ray diffraction. Complex 1 has a 2D layer structure, in which part of the L1 ligands bridge the Cd(II) ions to form double-bridging chains and the other part of ligands link such chains to form a 2D framework. Complexes 2 and 5 are isomorphous, showing unusual 2D (3,6) network structures containing triangular grids. Complex 3 adopts a 2D (4,4) network formed by L2 linking the NO3- bridged (Cd-O-N-O-)n 1D zigzag chains. By contrast, is a 1D chain, in which two Cd(II) centers are bridged by mu2-O of sulfoxide groups to form a dinuclear unit, and L3 ligands link such dinuclear units to form a 1D double-bridging chain. The structural differences among such complexes show that the ligand nature and counter anions have important influences on the complex structures, which may provide a rational method for controlling the framework formation in metal-organic coordination polymers.