Thiosemicarbazone Complexes of Uranium(IV)

Abstract

The first homoleptic thiosemicarbazone complexes of uranium were isolated by reacting uranium tetrachloride in a salt metathesis or acid-base reaction with four equivalents of Na(BzTSC) or H(BzTSC) (BzTSC=benzylthiosemicarbazone), carrying a non-methylated (L1), monomethylated (L2) or dimethylated (L3) terminal amino group, in moderate yields. [U(BzTSCNH2)4] (1), [U(BzTSCNH(CH3))4] (2) and [U(BzTSCN(CH3)2)4] (3) show a remarkable stability towards air, with oxidation potentials in THF between +0.43 and +0.53 V and reduction potentials between −2.53 and −2.67 V vs. ferrocene/ferrocenium. The simple methylation of the terminal amino group of the ligand allows for controlled changes in the coordination environments of the complexes. Thermogravimetric analyses indicate that the complexes are stable up to 155 °C.