Preparation and Characterization of Series of Triheteropolymolybdate Complexes

Abstract

Three new polymolybdate heteropoly complexes were synthesized in the laboratory having Al³⁺, Co²⁺, Ni²⁺ and Cu²⁺ hetero cations. The synthesis of the three polymolybdate hetero poly complexes were prepared in acid medium at reflux temperature The products were isolated separately, washed in ethanol and dried. The dried residues obtained posses light and dark brown colour. All the three residues of polymolybdate are paramagnetic at room temperature having magnetic moment varying from 3.02 to 3.78 BM. The magnetic moment values of triheteropoly molybdate complexes suggest the six co-ordinated octahedral around Co(II) and Ni(II) environment in the weak field. The IR spectra of all the three residue exhibit strong absorption band of hydrogen bonded H₂O group in the complexes along with metal-oxygen-metal and metal-oxygen, where metal may be Mo, Ni, Co or Al. The DTA and TGA curves of polymolybdate residues show decomposition of product in general two steps. The first step of residue involves measure loss in weight due to loss of water molecules and sodium oxide molecules, while the second step loss of weight due to loss of water of constitution. The analysis of all the product based on IR spectrum thermogravimetric studies, elemental estimation and molecular weight determination by cryoscopy method the molecular formula may be suggested as: Na₄[NiAl₂Mo₁₂O₄₂]·28H₂O, Na₄[CuCoMo₁₂O₄₀]·60H₂O and Na₈[CoAl₂Mo₁₂O₄₄]·94H₂O.