Syntheses and Crystal Structures of Diaquatris(m-hydroxybenzoato)lanthanoid(III) m-Hydroxybenzoic Acid Dihydrate (M=La, Ce, Pr, and Nd), and Di-μ-(m-hydroxybenzoato)bis{triaquabis(m-hydroxybenzoato)lanthanoid(III)} Dihydrate (M=Sm, Gd, Dy, Er, and Yb)

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Abstract
Two types of lanthanoid(III) m-hydroxybenzoates, indicated in the title, have been synthesized, and the crystal and molecular structures of four representative complexes, where M=La (1), Nd (2), Sm (3), and Er (4), were determined by the single-crystal X-ray diffraction method. They are all triclinic, space group P\bar1, and the cell constants are as follows: (1) a=12.351(11), b=15.533(10), c=9.250(4) Å, α=109.86(4), β=101.40(6), γ=62.95(6)°; (2) a=12.287(4), b=15.542(7), c=9.194(3) Å, α=109.64(3), β=101.46(3), γ=62.83(3)°; (3) a=10.580(1), b=12.006(5), c=10.105(2) Å, α=111.14(2), β=90.27(1), γ=97.16(2)°; (4) a=10.586(4), b=11.943(6), c=10.027(5) Å, α=111.11(3), β=90.53(4), γ=97.26(4)°. The final R values obtained were (1) 0.039, (2) 0.038, (3) 0.030, and (4) 0.039. The central metal atoms of both types of complexes are octa-coordinated, and each is in a square-antiprism geometry. In 1 and 2, one free acid molecule is present, and the molecule is hydrogen-bonded to the oxygen atoms of the coordinated water molecules through its carboxyl oxygen atoms. 1 and 2 have linear polymeric structure, and each pair of the metal atoms is bridged by a pair of the carboxylate ligands, while 3 and 4 have a dimeric structure, where metal atoms are bridged by two carboxylate ligands.