Study of complexing of heteropolyligands [X(OH)6Mo6O18]3- (X=Cr(3), Al(3)) with iron (2) ions by spectrophotometry method

Complexing of heteropolyanions (HPA) [X(OH)6Mo6O18]3-(X=Cr(3), Al(3)) with Fe(2) ions was studied the method of spectrophotometry. Behaviour of [Cr(OH)6Mo6O18]3- in aqueous solutions depending on time, acidity and dilution, was studied. The composition (Fe(2):HPA=1:1) and stability of the complexes depending on solution pH were ascertained. The band of charge transfer Fe(2)3d→Mo(6)4d was isolated. On the basis of d-d transition attribution it is shown that iron (2) is in high-spin octahedric state, while HPA studied are comparable with water molecules is regards the strength of crystal field