Synthesis and characterization of 2D and 3D structures from organic derivatives of polyoxometalate clusters: Role of organic moiety, counterion, and solvent

New organic derivatives of "inverse-Keggin" polyoxometalate (POM) clusters, [Mo₁₂O46(AsR)₄]^4- (R = C₆H₄-4-COOH, C₆H₃-4-OH-3-NO₂, C₆H₄-4-OH), have been synthesized. Structures of the corresponding sodium or iron salts were elucidated by single-crystal X-ray diffraction and shown to be 3D structures connected through hydrogen bonds and/or O - Na - O linkages. Parameters which influence the final solid-state architecture, such as the crystallizing solvent, organic moiety, and counterions, have been examined. The hydrogen-bonding ability of the solvent affects the connectivity of the POM clusters through interactions with the organic group and the inorganic core. The organic groups influence the structure through hydrogen bonds to other organic groups, to neighboring clusters, and/or to solvent molecules. Hydrogen bonding between the organic groups and the solvent appears to inhibit some possible connectivity patterns, such as the hydrogen-bonded dimerization of carboxylic acid groups. Na⁺ ions were found directly bonded to the cluster oxo ligands and provided linkages between clusters. Larger cations, such as transition metals, did not show this interaction, and other bonding methods dominated.