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

Abstract

Five novel Cd(II) coordination polymers with three structurally related flexible disulfoxide ligands, {[Cd(L¹)₃](ClO₄)₂}_n (1), {[Cd(L²)₃](ClO₄)₂(CHCl₃)}_n (2), [Cd(L²)(NO₃)₂(H₂O)]_n (3), [Cd₂(L³)₂(NO₃)₄]_n (4) and {[Cd(L³)₃](ClO₄)₂}_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, 4 is a 1D chain, in which two Cd(II) centers are bridged by μ₂-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.