SYNTHESIS AND CHARACTERIZATION OF THE URANIUM ALKYLTHIOLATE COMPLEX U(SPR-I)2(HBPZ3)2

The synthesis and characterization of the uranium alkylthiolate U(SPri)2(HBPZ3)2, where Pz = pyrazolyl, are reported. This complex was characterized by C, H, N elemental analysis, UV-vis/NIR, IR and H-1 NMR spectroscopies and by single crystal X-ray diffraction analysis. The coordination geometry around the uranium is best described as square antiprismatic, distorted towards dodecahedral. In solution thc complex is fluxional and the H-1 NMR spectrum at 300 K shows the equivalence of the pyrazolyl rings. However, at 2 1 0 K the NMR spectrum indicates the same coordination geometry as found in the solid state. The activation energy for the fluxional process was calculated to be DELTA-G(double dagger)Tc = 46 +/- 3 kJ mol-1.