Inorganic Chemistry, Vol.48, No.23, 11079-11084, 2009
Phosphonoacetate as a Ligand for Constructing Layered and Framework Alkali Metal Uranyl Compounds
The hydrothermal reactions of KCl, RbCl, CsOH, and CsCl with phosphonoacetic acid and uranium trioxide at 180 degrees C for three to five days results in the formation of five different crystalline uranyl carboxyphosphonates, K[(UO2)(2)(PO3CH2CO2) center dot (PO3CH2CO2H)(H2O)] center dot H2O, Cs[(UO2)(2)(PO3CH2CO2)(PO3CH2CO2H)(H2O)] center dot H2O, CS[(UO2)(2)(PO3CH2CO2)(PO3CH2- CO2H)(H2O)] center dot H2O, Cs[(UO2)(PO3CH2CO2)], and Cs-3[(UO2)(4)(PO3CH2O2)(2)(PO3CH2CO2H0.5)(2)] center dot nH(2)O, respectively. In all compounds, the UO22+ moieties are bound by phosphonate and carboxylate forming pentagonal bipyramidal environments around the uranium centers. At low pH, some of the carboxylate portions of the phosphonoacetate are protonated. The addition of hydroxide removes these protons, and a different structure is adopted. In contrast to all other uranyl carboxyphosphonates, Cs-3[(UO2)(4)(PO3CH2O2)(2)(PO3CH2CO2H0.5)(2)] center dot nH(2)O adopts a three-dimensional network structure with large channels along the c axis that house the Cs+ cations.