| Abstract: The self-association and adduct formation of the transition metal chelates, viz, iron(Ⅲ). cobalt(Ⅲ), copper(Ⅱ), nickel(Ⅱ) of acetylacetone in tetrahydrofurane were investigated with the aid of quantitative size exclusion chromatography. Tris (acetylacetonato) cobalt(Ⅲ) in thesolution exists in the form of a single chelate molecule. Bis(acetylacetonato) copper(Ⅱ) and Tris (acetylacetonato) iron(Ⅲ) react with the solvent to form adducts. Tris (acetylacetonato) iron(Ⅲ) in tetrahydrofurane also self-associated to form a polydisperse aggregate with association number from 2 to 10. Addition ligand exchanging occured in tetrahydrofurane for bis(acetylacetonato) nickel(Ⅱ) hydrate and a small amount of aggregate with association number around 6 is also present. The relative contents of the chelate, adduct and aggregate are evaluated from the chromatographic data. The refractive index increments of the chelates and that of the coordinated metals are determined from the R.I. detecting response constants of the chelates in the elucnt. Both the refractive index increments of the coordinated metals and the lag of the chromatographic retention values of the chelates increase in the order of Ni, Cu, Co, Fe, which is the same as that of the first ionization energies of the transition metals. |
