Imidodiphosphates ⊖N[PO(OR)2]2 and Imidodiphosphonates ⊖N[POR2]2 are effective chelating ligands for a variety of metal cations including even Na⊕, for which a lipophilically wrapped hexameric polyion cluster has been structurally characterized. The corresponding hexameric lithium and polyrubidium ion complexes reported here exhibit considerable structural differences: The rather small Li⊕ cations of coordination number five and tetraphenylimidodiphosphate form an isolated hexameric aggregate analogous to the Na⊕ one, whereas the larger Rb⊕ with coordination number seven and (3,4-dimethylphenyl)substituents crystallizes as a chain polymer. Based on the crystal structures, the dominant Coulomb attractions between cations and anions, the spatial requirement of the ligands and the essential phenyl/phenyl interactions in their lipophilic skin are discussed
Mixed crystals of tetrakis(3,4-dimethylphenyl)imidodiphosphate salts with alkalication ratios K⊕/Rb⊕ (1:5) and Rb⊕/Cs⊕ (1:1), (1:3) as well as (3:1) have been grown by suspending finely ground stoichiometric mixtures of alkali carbonates in toluene solutions of the strongly chelating ligand HN(PO(OR)2)2 - The cation ratios were measured by Total Reflexion X-Ray Fluorescence (TXRF) analysis and the single crystal structures of the polymeric K⊕/Rb⊕ as well as the Rb⊕/Cs⊕ imidodiphosphate salts determined by X-ray structure analysis. The selectivity of the various alkali ions for insertion in the crystal lattices of the individual imidodiphosphate salts has been confirmed by concentration-dependent crystallizations and discussed based on the structural analysis of the differing ligand conformations. The unit cell parameter dependence on the alkali cation radii provided information on van der Waals interactions between adjacent phenyl rings of the imidodiphosphate ligands and suggests the selective alkali cation insertion to be partly due to supramolecular repulsion within the lipophilic phenyl skin during the selfaggregation of the polymeric salt chains
Four differently methyl-substituted tetraphenyl imidodiphosphates [(H3C)nC6H5-n]2PO-NH-PO[C6H5-n(C3)n] (n = 1, 2), i. e. the 4-, 3,4-, 3,5-and 2,3-derivatives, have been crystallized and their structures determined to gain information on the spatial requirements as ligands in the corresponding cesium salts. According to the packing coefficients calculated from the structural data, they increase in the sequence 4<3,5<3,4<2,3. The most perturbed structural motif is the hydrogen bonded, eight-membered of each the dimer subunits.