Dioxouranium(VI) and thorium(IV) complexes with 2(2'-pyridyl)1-methylbenzimidazole and reaction of dioxouranium(VI) complex with mercury(II), cobalt(II) and nickel(II)

The biheterocyclic ligand 2(2'-pyridyl)-1-methylbenzimidazole (MePB) forms complexes of the type UO2(MePB)X(2) (X=Cl, I, NO3, CH3COO, 0.5 SO4), UO2(MePB)(2)(NCS)(2) and Th(MePB)(2)X(4) (X = NO3, NCS, I). Reaction of UO2(MePB)Cl-2 with HgCl2 resulted in the formation of the heterobinuclear complex UO2(MePB)HgCl4, whereas the reaction of UO2(MePB)(2)(NCS)(2) with M(NCS)(2) (M = Co-II or Ni-II) yield paramagnetic, octahedral complexes, M(MePB)(2)(NCS)(2) (M = Co, Ni), with the displacement of UO22+ ion. The electronic spectra and the effective magnetic moments of the complexes (4.77 and 2.79 mu(B), respectively) confirmed their octahedral geometry. The complexes were characterized by combination of elemental analyses, conductivity measurements, thermogravimetric studies and IR, electronic, mass and NMR (H-1 and C-13) spectral studies. The H-1 and C-13 NMR signals of the free ligand undergo a downfield shift on complexation. The EIMS of the ligand and FABMS of the complex reveal the molecular mass of the ligand and its fragmentation pattern.