Synthesis and characterisation of tetraphenylarsonium halochromates

Abstract

Tetraphenylarsonium halochromate (halo=fluoro, chloro and bromo) complexes are synthesised and characterised by spectral and thermal studies. The effect of ionic size and electronegativity of halide ions on the infrared spectra, X-ray emission spectra, activation energy of the first decomposition step and thermal stability of the complexes are investigated. The complexes possess tetragonal unit cell with a=b=12.93 Angstrom and c=7.68 Angstrom. These complexes decompose in two exothermic stages. Cleavage of one Ph-As bond to give triphenylarsine and reduction of Cr(VI) to Cr(III) occur simultaneously. First step mass loss corresponds to the loss of two phenyl halide molecules and 3/2 moles of oxygen. The overall kinetics of the first step is described by diffusion controlled reaction mechanism with a function g(alpha)=[1-(1-alpha)(1/2)]. The second step decomposition is due to the further degradation of triphenylarsine. The final product is Cr2O3.