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Controlling Cation‐Cation Interactions in Uranyl Coordination Dimers by Varying the Length of the Dicarboxylate Linker
Author(s) -
Maurice Rémi,
Dau Phuong D.,
Hodée Maxime,
Renault Eric,
Gibson John K.
Publication year - 2020
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.202000840
Subject(s) - uranyl , chemistry , dimer , crystallography , stereochemistry , valence (chemistry) , linker , uranium , ion , materials science , organic chemistry , computer science , metallurgy , operating system
The chemistry of linear uranyl(V/VI) dioxo cations, [O yl –U–O yl ] +/2+ , is dominated by coordination of uranium in the equatorial plane. Effects of this constraint were evaluated by experiment and theory for gas‐phase mixed‐valence U V/VI coordination dimers in which uranyl moieties are linked by alkyl dicarboxylates, [(UO 2 + )(UO 2 2+ )(OOC‐(CH 2 ) n‐ 2 ‐COO 2– ) 2 ] – ( n = 3–12). Faster O 2 ‐addition to dimers with short linkers n = 3 and 4, vs. n ≥ 5, suggests a structural difference. Computed structures with the shortest linkers have bridging dicarboxylates and nearly parallel, non‐interacting uranyls. Longer linkers, n = 5–7, accommodate uranyl orientations with distinct U V –U VI end‐on cation‐cation interactions (CCIs), whereby Lewis base O yl from U V coordinates to the acid U VI , denoted as U V O yl ··· U VI . The dimer structure for n = 8 has a U V –U VI side‐on diamond‐shape CCI, with U V O yl ··· U VI and U VI O yl ··· U V interactions. Addition of O 2 to the n = 4 and 5 dimers yields [(UO 2 2+ ) 2 (OOC‐(CH 2 ) n‐ 2 ‐COO 2– ) 2 (O 2 – )] – , with U V oxidized to U VI and O 2 reduced to O 2 – . Whereas O 2 can associate to and oxidize the exposed U V center for dimers with n = 3 and 4, the more crowded U V site in the CCI structures inhibits O 2 addition. The results demonstrate rational structural control of uranyl‐uranyl bonding and reactivity in small coordination complexes.