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

Abstract

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)I2] (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, ΔH, ΔS) of this equilibrium have been determined by 1H NMR spectroscopy. The ethoxide derivative [UO2(OEt)(CyMe4BTBP)][OTf] (5) crystallized from a solution of 1 in a mixture of ethanol and acetone under air, and the dinuclear μ-oxo complex [{UO2(CyMe4BTBP)}2(μ-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(μ-O)][I]2 (7) and [{UO2(TPTZ)(py)}2(μ-O)][I3]2 (8) exhibit a flexible [{UO2}–O–{UO2}]2+ moiety.