Electronic structure calculations were performed for uranyl(VI) and the imido analogue complexes with the high-nitrogen ligand bitratrazoleamine, or BTA.  For the uranyl structures, we see little change in the uranyl(VI) cation itself with increasing BTA coordination, though the O=U=O angle is slightly bent when coordinated with only one BTA ligand.  Analysis of the stability of the complexes through calculation of the free energy pathway indicates that coordination with one instead of two BTA ligands is more stable, and that a uranyl(VI) dimer structure is more stable than the monomer.  This is in agreement with the experimental crystal structure for uranyl(VI)-BTA complexes, which indicates that these compounds exist as dimers.  The uranium imido analogue behaves similarly, with slightly bent N=U=N angles when the complex is coordinated with only one BTA ligand.  We also find that the complexes become more stable with decreasing BTA coordination.

Structure and stability of uranyl(VI) and uranium(VI) imido complexes with high-nitrogen ligands

249th National Meeting (2015)

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