CORRELATION-ANALYSIS OF ARYLIC STRENGTHENING OF THE EXTRACTION CAPACITY OF BIDENTATE ORGANOPHOSPHORUS EXTRACTANTS

This paper is devoted to the so-called effect of ''anomalous arylic st rengthening'' (AAS) observed upon extraction of a series of elements, mainly actinides and lanthanides, by bidentate neutral organophosphoru s compounds (BNOPC). This ''anomalous'' effect is an increase in the e xtraction capacity of a reagent when alkyl substituents at the phospho rus atom are replaced with more electronegative aryl groups. The influ ence of phenyl substituents at the phosphorus atom on the reactivity o f organophosphorus compounds of various types was considered. Based on the data on electronic effects of substituents, hypotheses were formu lated about the reasons for AAS involving phenyl groups that are biphi lic because they have substituents capable of manifesting both donor a nd acceptor properties depending on several factors such as, e.g., the nature of the reaction center, the character of the attacking reagent , the nature of the solvent, etc. When a strong complex of a metal wit h a phenyl-substituted reagent of BNOPC is formed during extraction, t he phenyl groups become donating, and additional strengthening of the complex appears.