A NUCLEAR-MAGNETIC-RESONANCE STUDY ON LIGAND-EXCHANGE REACTION IN U(VI) NITRATE COMPLEX WITH TYL(PHENYL)-N,N-DIISOBUTYLCARBAMOYLMETHYLPHOSPHINE OXIDE IN ACETONE CONTAINING OXALIC-ACID

In order to examine the effect of oxalic acid(H(2)ox) on the exchange reaction of tyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide ( o phi cmpo) in U(VI) nitrate complex with o phi cmpo; structural and k inetic studies have been carried out for the solutions prepared by dis solving UO2(NO3)(2)(o phi cmpo); o phi cmpo, and H(2)ox in CD3COCD3 us ing P-31 and C-13 NMR method. The number of coordinated o phi cmpo was determined to be 2 by the area integration of P-31 NMR signals of fre e and coordinated o phi cmpo. From the area integration of C-13 signal s of free H(2)ox and coordinated oxalate(Cox), the number of Cox was e stimated to be 1. Hence, the complex with composition ratio of UO22+ : o phi cmpo:Cox=1:2:1 was supposed to be formed in the present solution system. The exchange rate of o phi cmpo in this complex was found to show a first-order dependence on the free o phi cmpo concentrations an d to decrease with increasing free H(2)ox concentrations. From these r esults, it is proposed that the exchange reaction of o phi cmpo procee ds through tile interchange(I) mechanism and that the retardation effe ct of free H(2)ox is due to the formation of outer-sphere complex.