Crystal structures of aquotris(salicylato)samarium(III), and aquotris(salicylato)americium(III)

Two isostructural compounds (C7H5O3)3Sm.H2O and (C7H5O3)3Am.H2O are monoclinic, space group P21/c, and have unit-cell dimensions: a = 13.641 (3) A, b = 6.752 (1) A, c = 24.202 (7) A, β = 113.24 (2)0 and a = 13.69 (2) A, b = 6.762 (2) A, c = 24.14 (1) A, β = 112.89 (5)0, respectively; Z = 4. Heavy-atom methods were used to determine the structure from x-ray diffraction data. Refinement of parameters by least-squares methods was carried out using 3280 observations on the Sm compound and 1401 on the Am. The R/sub F/ values obtained were 0.037 and 0.055 for the two refinements. There are no discrete molecules of the complex in the crystal; instead each metal ion is linked to six different salicylato ions through a variety of modes in which both the carboxylate and phenolic oxygen atoms participate. Cross-linking of metal ions produces endless chains along the b axis and only van der Waals contacts exist between the chains. A total of eight atoms from the salicylato ligands plus one from a water molecule comprise the metal coordination. There is also evidence for some hydrogen bonding among the ligands. The bonding pattern within the salicylato ions is the same for all three independent ligands. It is characterized by equivalence of bond lengths to carboxylate oxygen atoms, by distortion of the benzene ring from hexagonal symmetry, by a short C--C bondto the carboxyl group, and by a short C--O bond to the hydroxyl group. Except for the carboxyl group, which is ionized, the molecular shape is the same as for salicylic acid. Analogous compounds containing La and Nd were shown to have this structure also