Reactions of a tetravanadate anion, [V(4)O(12)](4-), with a series of lanthanide(III) salts yield three types of lanthanide complexes of macrocyclic polyoxovanadates: (Et(4)N)(6)[Ln(III)V(9)O(27)] [Ln = Nd (1), Sm (2), Eu (3), Gd (4), Tb (5), Dy (6)], (Et(4)N)(5)[(H(2)O)Ho(III)(V(4)O(12))(2)] (7), and (Et(4)N)(7)[Ln(III)V(10)O(30)] [Ln = Er (8), Tm (9), Yb (10), Lu (11)]. Lanthanide complexes 1-11 are isolated and characterized by IR, elemental analysis, single-crystal X-ray diffraction, and extended X-ray absorption fine structure spectroscopy (EXAFS). Lanthanide complexes 1-6 are composed of a square-antiprism eight-coordinated Ln(III) center with a macrocyclic polyoxovanadate that is constructed from nine VO(4) tetrahedra through vertex sharing. The structure of 7 is composed of a seven-coordinated Ho(III) center, which exhibits a capped trigonal-prism coordination environment by the sandwiching of two cyclic tetravanadates with a capping H(2)O ligand. Lanthanide complexes 8-11 have a six-coordinated Ln(III) center with a 10-membered vanadate ligand. The structural trend to adopt a larger coordination number for a larger lanthanide ion among the three types of structures is accompanied by a change in the vanadate ring sizes. These lanthanide complexes are examined by EXAFS spectroscopies on lanthanide L(III) absorption edges, and the EXAFS oscillations of each of the samples in the solid state and in acetonitrile are identical. The Ln-O and Ln···V bond lengths obtained from fits of the EXAFS data are consistent with the data from the single-crystal X-ray studies, reflecting retention of the structures in acetonitrile.

Keywords: Polyoxometalates / Vanadates / Lanthanides / Inorganic ligandsThree discrete early-lanthanide complexes with cyclic polyoxovanadate ligands, [LaV 10 O 30 ] 7-(1), [CeV 9 O 27 ] 6-(2), and [PrV 9 O 27 ] 6- (3), were synthesized by reaction of [VO 3 ]with early-lanthanide(III) salts. Complexes 1-3 were composed of a Ln III center in square-antiprism coordination mode with coordinated all-inorganic ligands [V n O 3n ] n-(n = 9 or 10), which were constructed from a cyclic linkage of nine or ten VO 4 tetrahedra through vertex sharing. Structural investigation of lanthanum complex 1 revealed a ten-membered ring of VO 4 units in which eight VO 4 units were coordinated to the lanthanum atom through their oxido groups and two VO 4 units [a]

An all-inorganic complex, [Mn 2 {(VO 3 ) 5 } 2 ]6-(1), was synthesized, and the structure determination reveals a dinuclear manganese complex coordinated by two cyclic pentavanadate ligands. The cyclic pentavanadate units sandwich the edge-sharing octahedral dimanganese core through coordination of the oxido group of the pentavanadate. A dinuclear cobalt complex with a cyclic decavanadate, [Co 2 (OH 2 ) 2 -(VO 3 ) 10 ] 6-(2), was also synthesized. The structure analysis reveals a dinuclear cobalt complex with a macrocyclic decavanadate, which is composed of 10 VO 4 units joined by the vertex sharings. The CoO 6 octahedrons are edge-shared, with each cobalt octahedron coordinated to five oxido groups from the decavanadate. The remaining site is occupied by

)] 5-, in both the solid and solution states through extended X-ray absorption fine structure (EXAFS) studies. The existence of the chiral inorganic species in acetonitrile with double-stranded V8 chains was confirmed through EXAFS oscillations.

The title compounds are characterized by single crystal XRD, IR, and EXAFS. The lanthanide polyoxovanadates are extremely hygroscopic. (IIIa)·MeCN, (IIIb)·MeCN, and (IIIe)·MeCN crystallize in the orthorhombic space group P2 1 2 1 2 1 with Z = 8. (IIIf)·4MeCN crystallizes in the monoclinic space group P21/c with Z = 12 and (V)·4MeCN in the monoclinic space group P21/n with Z = 4. (VIIa-d)·2MeCN crystallize in the monoclinic space group P21/n with Z = 2. The compounds (IIIa-f) exhibit a structure with a nine-membered vanadium ring and a square-antiprismatic coordination sphere. (VIIa-d) adopt an octahedral coordination mode with a ten-membered vanadium ring, and the structure of (V) contains a trigonal-prismatic coordination environment by two sandwiching, cyclic tetravanadates with a capping H 2 O ligand. -(NISHIO, M.; INAMI, S.; KATAYAMA, M.; OZUTSUMI, K.; HAYASHI*, Y.; Inorg. Chem. 51 (2012) 2, 784-793, http://dx.