DIOXOURANIUM(VI) AND THORIUM(IV) COMPLEXES OF A BIDENTATE CHELATING BIHETEROCYCLE, 1,1'-DIMETHYL-2,2'-BIIMIDAZOLE

The biheterocycle, 1,1'-dimethyl 2,2'-biimidazole (DMBIm) forms a numb er of mononuclear complexes of the type [UO2(DMBIm)X2] (X = Cl, NCS, N O3, CH3COO, 0.5 SO4); UO2(DMBIm)2I2 and Th(DMBIm)2X4 (X = I, NCS, NO3) . UO2(H2acacen)Cl2 reacts with DMBIm to form the mixed ligand complex [UO2(H2acacen)(DMBIm)Cl2]. Further, the reaction of UO2(DMBIm)Cl2 with HgCl2 yields the hetero-bimetallic complex [UO2(DMBIm)HgCl4]. Element al analyses, conductivity measurements, thermogravimetric studies and IR, electronic, mass and NMR (H-1 & C-13) spectral studies characteriz ed the complexes. The H-1 NMR of the free ligand has two singlets at d elta 7.27 and 7.03 ppm due to the inequivalence of the protons at C-4( 4') and 5(5'), respectively, and a more intense signal at delta 3.94 p pm for the methyl protons (-CH3). These singlets further split into tw o indicating the ligand to be present in the trans-form. In the comple xes, this inequivalence is also confirmed from the appearance of two s inglets at ca 7.26 and 7.49 ppm and the methyl proton signal appears a s a singlet at 3.95 ppm. The coordination results in a downfield shift of the ring protons. The C-13 NMR signals of the free ligand appear a t 138.05, 127.253, 123.109 and 34.82 ppm representing the C-2(2'), C-4 (4'), C-5(5') and methyl carbons, respectively, which shift slightly d ownfield in complexes. DMBIm is coordinated in the cis-form. The EIMS of DMBIm ligand and FABMS of the complex reveal the molecular mass and the fragmentation pattern.