Synthese And Property Study Of The Methylation And Protonation B-type Anderson Hexamolybdochromates

The aim of this thesis is to investigate the reaction mechanism: protonation and methylation of the triply bridging oxygen atoms (connect with the centre Cr) and the bridging oxygen atoms (Mo-O-Mo) based on the B-type Anderson hexamolybdochromates by the reaction with transition metal complex, which would unveil the possible reaction mechanism of B-type Anderson hexamolybdochromates functionalized by tris(alkoxo) moieties. This will provides new principle for the further investigation of B-type Anderson hexamolybdochromates functionalized by organic ligands.Four new polyoxometalate compounds have been synthesized by using Na₃[Cr(OH)₆Mo₆O₁₈]·8H₂O precursor on the basis of convenient aqueous solution synthesis methods and structurally characterized by IR, TG and single crystal X-ray diffractions. The thermal stabilities and magnetic properties of these compounds have been studied.The compound 1 is a methylated production which is obtained by the dehydration between a nonacidic proton of B-type Anderson hexamolybdochromates triply bridging oxygen atoms and a hydroxyl group arising from the methanol molecule. By a slight change of the pH and the the amount of methanol, the methylated production fails to occur for compound 2, the anions [Cr(OH)₆Mo₆O₁₈]^3- of compound 2 contain two kinds of bond lengths Cr-O. This phenomenon indicates that the methylated intergradation maybe exist in the reaction processes, intergradation has demethylated when the reaction conditions were changed. Compound 3 is a product of the bridging oxygen atom protonated, 3D extended framework by the hydrogen-bonding interactions among the [CrMo₆(OH)₇O₁₇]^2- polyoxoanions, [Ni(bpy)₂(H₂O)₂]²⁺ cations, anions and Lattice water molecules, the 1D channels present are constructed by the building blocks of hydrogen-bonding. Compound 4 failed to obtain the protonated product by changed the pH.The successful prepared compounds 1 and 2 testified that the dehydration reaction can employ between the methanol and theμ3-O atoms from B-type Anderson hexamolybdochromates. Thus, the realization of B-type Anderson molybdocromate functionalized by organic ligand is not limited to tris-(hydroxymethyl)methane ligands. All the hydroxyl-containing ligands are possible reacting with B-type Anderson molybdocromate to realize the organic functionalization. The synthesis of compound 3 provided confirmation of the reaction mechanism for the B-type Anderson molybdocromate functionalized by organic ligands.