Thermally Stable Uranium Dinitrogen Complex with Siloxide Supporting Ligands

• Published in: Organometallics 2013-08, Vol.32 (15), p.4214-4222
• Main Authors: Mansell, Stephen M, Farnaby, Joy H, Germeroth, Anne I, Arnold, Polly L
• Format: Article
• Language: English
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om4003957

A new dinitrogen adduct of a homoleptic uranium tris(siloxide) complex, [U{OSi(Mes)3}3]2(μ-η2:η2-N2), is reported. Synthesis of the 15N-labeled isotopomer and Raman spectroscopy confirm the reductive activation of N2 to a (N2)2– dianion. The 15N NMR shift of the 15N2-labeled isotopomer is also reported. Crystallographic characterization shows a side-on (N2)2– coordinated in either an eclipsed or staggered conformation in different crystals. The U–N2–U complex is stable to vacuum and shows high thermal stability, retaining the formally reduced dinitrogen at 100 °C. The parent three-coordinate uranium(III) [U{OSi(Mes)3}3] could not be isolated in our hands, with N2-free syntheses affording only uranium(IV) compounds. The rational synthesis and full characterization of two such U(IV) byproducts, [U{OSi(Mes)3}{N(SiMe3)2}3] and [U{OSi(Mes)3}4], is also reported.