Metal-organodiphosphonate chemistry: Hydrothermal syntheses and structures of Zn(II) and Cd(II) coordination polymers with xylyldiphosphonate ligands

Hydrothermal reactions of zinc(II) acetate dihydrate or cadmium(II) nitrate tetrahydrate with xylyldiphosphonic acid isomers in the presence of an organonitrogen chelating ancillary ligand provided a series of materials of the (M(II)-organonitrogen chelate)/xylyldiphosphonate family. One-dimensional structures were observed for [Zn(H2O)(bpy)(1,2-HO3PC8H8PO3H)] (1), [Zn(bpy)(1,3-HO3PC8H8PO3H)]·H2O (2·H2O), [M(o-phen)(1,3-HO3PC8H8PO3H)] (M = Zn (5·H2O), M = Cd (11), and [Zn(tpyprz)(1,2-HO3PC8H8PO3H)] (7), while the phases [M(bpy)2(1,4-H2O3PC8H8PO3H2)(1,4-HO3PC8H8PO3H)] (M = Zn (3) and Cd(9)) exhibited virtual layered structures constructed from { M ( bpy ) 2 ( 1 , 4 - H 2 O 3 PC 8 H 8 PO 3 H 2 ) } n 2 n + chain hydrogen-bonded to the {HO3PC8H8PO3H}2- charge compensating anions. The two-dimensional structures are represented by [M(o-phen)(1,2-HO3PC8H8PO3H)] (M = Zn (4) and Cd (10)) and [Cd(bpy)(1,3-HO3PC8H8PO3H)] (8). Expansion into three-dimensions occurs only with the spatially extended 1,4-xylyldiphosphonate ligand in [Zn4(o-phen)4(1,4-HO3PC8H8PO3)2(1,4-HO3PC8H8PO3H)]·3H2O (6·3H2O) and [Cd(o-phen)(1,4-HO3PC8H8PO3H)] (12).