Pentaaquadioxouranium(VI) triflate–18-crown-6

Synthesis and Structure of the First Transuranium Crown Ether Inclusion Complex: [NpO2([18]Crown-6)]ClO4

“…[12±19] Well-known examples include [UO 2 (H 2 O) 5 ([18]crown-6) 2 (H 2 O)(CH 3 CN) 2 ][ClO 4 ] 2 (central unit: II) [15] and [UO 2 (H 2 O) 5 ([18]crown-6)][CF 3 SO 3 ] 2 . [17] Crown ether inclusion complexes of a transuranic ion in any oxidation state are unknown.On attempting to employ this well-known ability of crown ether ligands to form second-sphere hydrogen-bonded complexes of trans-dioxometal ions (as in II), we were surprised to observe the complete encapsulation of the NpO 2 ion by the [18]crown-6 ligand. Addition of one equivalent of [18]crown-6 to a stirred solution of NpO 2 2 in 1m HX (X ClO À 4 , CF 3 SO À 3 ) resulted in reduction of Np VI to Np V and formation of large turquoise crystals of [NpO 2 ([18]crown-6)][X] (1[X]) over 12 ± 24 h. The presence of an absorption band at 980 nm (e 395 m À1 cm À1 ), characteristic of the NpO 2 ion, [20] in the NIR spectra of the crystalline solids dissolved in 1m HClO 4 confirms that reduction of Np VI to Np V has occurred.…”

“…[12±19] Well-known examples include [UO 2 (H 2 O) 5 ([18]crown-6) 2 (H 2 O)(CH 3 CN) 2 ][ClO 4 ] 2 (central unit: II) [15] and [UO 2 (H 2 O) 5 ([18]crown-6)][CF 3 SO 3 ] 2 . [17] Crown ether inclusion complexes of a transuranic ion in any oxidation state are unknown.…”

“…[8] Indeed, the majority of actinide crown ether complexes exhibit secondsphere hydrogen bonding between the oxygen atoms of the crown ether and water molecules coordinated to the actinide center. [ [17] Crown ether inclusion complexes of a transuranic ion in any oxidation state are unknown.…”

Dimethylsuphoxide and its roles in the coordination chemistry of the uranyl ion

“…The trifluoromethanesulphonate, [CF 3 SO 3 ] -, 'triflate', anion is generally considered to be a weakly coordinating ligand [16], though one of greater basicity than perchlorate, [ClO 4 ] - [17], so that it was of interest to determine if the DMSO solvate of uranyl triflate would differ significantly in structure from that of uranyl per- [18], as do two of the hydrated perchlorates [13], but consideration of its structure is complicated by the presence of a strongly H-bonding crown ether as part of the lattice array. In other circumstances, coordination of triflate to uranium is certainly well-established [19].…”

“…The crystals initially deposited were in the form of extremely fine needles but, on extended standing (~1 yr) of the mixture, some crystals of a size and morphology useful for structure determination were apparent. Analysis: calcd for C 18 …”