KINETICS OF FORMATION AND DISSOCIATION OF THE TERNARY COMPLEX ION NTANE-2,4-DIONATO)(NITRILOTRIACETATO)CHROMATE(III) IN AQUEOUS-MEDIA

Synthesis of solid [Cr(nta)(H2O)(2)] 1, kinetics and equilibrium of it s reaction with pentane-2,4-dione (Hpd) to form [Cr(nta)(pd)](-) 2 (H( 3)nta is nitrilotriacetic acid), aquation of 2 into 1, and some relate d reactions have been described. Parallel proton-independent and inver se proton-dependent paths lead from 1 to 2. The [H+](-1) path arises f rom metal assisted deprotonation of HE, the enol form of Hpd. Aquation of 2 into 1 involves [Cr(Hnta)Cpd)(H2O](+) 2H (Hnta is tridentate nta ) in addition to 2. The nta complex 1 is considerably more labile and a weaker acid than [Cr(H2O)(6)](3+). (C) 1997 Elsevier Science Ltd.