Carbonate Complexes [C(NH2)3]6[An(CO3)5] · nH2O (An = Th, U, Np, and Pu; n = 3 and 4): Synthesis and Structures

摘要

Two series of isostructural double An(IV) and guanidinium carbonates were obtained as single crystals of the formula [C(NH2)3]6[An(CO3)5] ·nH2O (An = Th, U, Np, and Pu; n = 3 (I) and 4 (II)) and examined by X-ray diffraction. For the Pu(IV) complexes, a = 10.490(2) A, b = 33.798(5) A, c = 10.519(2) A, β = 119.414(7)°, space group P2_1/c, Z = 4, R = 0.0369 (I) and a = 16.0895(18) A, b = 13.1458(14) A, c = 16.6951(18) A, β = 108.116(6)°, space group C2/c, Z=4,R = 0.0171 (II). Both series of complexes contain the anions [An(CO3)5]~(6-), in which the An atom is coordinated to five chelating bidenate carbonate ions. The coordination polyhedra of the An atoms are distorted bicapped square antiprisms. Within both the series, the An—O bond lengths decrease monotonically only for the sequence Th—U—Np. The average Np—O and Pu—O bond lengths in both tri- and tetrahydrates are virtually equal. The IR and electronic absorption spectra of the complexes obtained were studied. The absorption bands due to the f—f transitions experience bathochromic shifts in the spectra of the U~(4+) and Pu~(4+) carbonate complexes and hypsochromic shifts in the spectra of the Np~(4+) complexes.