First 5f-element complexes with the tetradentate BTBP ligand. Synthesis and crystal structure of uranyl(VI) compounds with CyMe4BTBP

Treatment of [UO2(OTf)(2)] or [UO2I2(thf)(3)] with 1 equiv. of CyMe4BTBP in anhydrous acetonitrile led to the formation of [UO2(CyMe4BTBP)(OTf)(2)] (1) and [UO2(CyMe4BTBP)I-2] (2) which crystallized as the cationic forms [UO2(CyMe4BTBP)(py)][OTf](2) (3) and [UO2I(CyMe4BTBP)][I] (4) in pyridine and acetonitrile, respectively. These compounds are unique examples of structurally characterized actinide complexes with a BTBP molecule; this ligand adopts a planar conformation in the equatorial plane of the {UO2}(2+) ion. In pyridine, 1 is dissociated into [UO2(OTf)(2)(PY)(3)] and free CyMe4BTBP and the thermodynamic parameters (K, Delta H, Delta S) of this equilibrium have been determined by H-1 NMR spectroscopy. The ethoxide derivative [UO2(OEt)(CyMe4BTBP)][OTf] (5) crystallized from a solution of I in a mixture of ethanol and acetone under air, and the dinuclear mu-oxo complex [{UO2(CyMe4BTBP)}(2)(mu-O)][I](2) (6) was obtained from [UO2I(thf)(2.7)] and CyMe4BTBP. The crystal structures of 6 and of the analogous derivatives [{UO2(py)(4)}(2)(mu-O)][I](2)(7) and [{UO2(TPTZ)(py)}(2)(mu-O)][I-3](2)(8) exhibit a flexible [{UO2}-O-{UO2}](2+) moiety.