title: A novel series of vanadium-sulfite polyoxometalates: synthesis, structural, and physical studies.
abstract: Reaction of NH4VO3 with sulfur dioxide affords the hexanuclear cluster (NH4)2(Et4N)[(V(IV)O)6(mu4-O)2(mu3-OH)2(mu3-SO3)4(H2O)2]Cl x H2O (1), and the decapentanuclear host-guest compound (Et4N)5{Cl subset [(VO)15(mu3-O)18(mu-O)3]} x 3 H2O (2). Sequential addition of magnesium oxide to an acidic aqueous solution of NH4VO3 (pH approximately 0) followed by (NH4)2SO3 resulted in the formation of either the non-oxo polymeric vanadium(IV) compound trans-(NH4)2[V(IV)(OH)2(mu-SO3)2] (3) or the polymeric oxovanadium(IV) sulfite (NH4)[V(IV)O(SO3)1.5(H2O)] x 2.5 H2O (4) at pH values of 6 and 4, respectively. The decameric vanadium(V) compound {Na4(mu-H2O)8(H2O)6}[Mg(H2O)6][V(V)10(O)8(mu6-O)2(mu3-O)14] x 3 H2O (5) was synthesised by treating an acidic aqueous solution of NH4VO3 with MgO and addition of NaOH to pH approximately 6. All the compounds were characterised by single-crystal X-ray structure analysis. The crystal structure of compound 1 revealed an unprecedented structural motif of a cubane unit [M4(mu4-O)2(mu3-OH)2] connected to two other metal atoms. Compound 3 comprises a rare example of a non-oxo vanadium(IV) species isolated from aqueous solution and in the presence of the reducing agent SO3(2-), while compound 4 represents a rare example of an open-framework species isolated at room temperature (20 degrees C). In addition to the synthesis and crystallographic studies, we report the IR and magnetic properties (for 1, 2 and 3) of these vanadium clusters as well as theoretical studies on compound 3.
authors.affiliation: Department of Chemistry, Section of Inorganic and Analytical Chemistry, University of Ioannina, 45110 Ioannina, Greece.
authors.forename: Haralampos N
authors.initials: HN
authors.lastname: Miras
authors.forename: Raphael G
authors.initials: RG
authors.lastname: Raptis
authors.forename: Nikolia
authors.initials: N
authors.lastname: Lalioti
authors.forename: Michael P
authors.initials: MP
authors.lastname: Sigalas
authors.forename: Peter
authors.initials: P
authors.lastname: Baran
authors.forename: Themistoklis A
authors.initials: TA
authors.lastname: Kabanos
mesh_terms: D000838:Anions / Q000737:chemistry; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008280:Magnetics; D008958:Models, Molecular; D015394:Molecular Structure; D013447:Sulfites / Q000737:chemistry*; D013696:Temperature; D017973:Tungsten Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D017968:Vanadium Compounds / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D000838:Anions; D013447:Sulfites; D017973:Tungsten Compounds; D017968:Vanadium Compounds