No abstract

Treatment of [UO(2)(Ar(2)nacnac)Cl](2) with 4 equiv. of Li(C(4)H(5)N(2)) results in the formation of a rare uranyl organometallic complex [Li(MeIm)][UO(μ-O)(Ar(2)nacnac)(μ-C,N-C(4)H(5)N(2))(2)] (2), in moderate yield. Reaction of 2 with 1 equiv. of MCl(2) (M = Fe, Co) yields the bimetallic complexes [MCl(MeIm)][UO(2)(Ar(2)nacnac)(μ-N,C-C(4)H(5)N(2))(2)] (M = Fe, 3; M = Co, 4).

Addition of 2 equiv of AgOTf to [UO(2)(Ar(2)nacnac)Cl](2) (Ar(2)nacnac = {(2,6-Pr(i)(2)C(6)H(3))NC(Me)}(2)CH) in the presence of excess pyridine, followed by addition of Cp(2)Co, generates the uranyl(V) complex UO(2)(Ar(2)nacnac)(py)(2) (2), in moderate yield. Complex 2 has proven to be an excellent precursor for the synthesis of other U(V) complexes. Thus, addition of 2,2'-bipyridine (bipy), 1,10-phenanthroline (phen), TMEDA, or 1-methylimidazole (MeIm) to 2 provides UO(2)(Ar(2)nacnac)(bipy) (3), UO(2)(Ar(2)nacnac)(phen) (4), UO(2)(Ar(2)nacnac)(TMEDA) (5), and UO(2)(Ar(2)nacnac)(MeIm)(2) (6), respectively. Complexes 2-6 have been fully characterized and their structures confirmed by X-ray crystallography. Attempts to form the analogous hexavalent uranyl complexes of bipy, phen, and TMEDA have not been successful. However, reaction of [UO(2)(Ar(2)nacnac)Cl](2) with AgOTf and 2 equiv of MeIm leads to the isolation of [UO(2)(Ar(2)nacnac)(MeIm)(2)][OTf] (7), which has been fully characterized. Attempts to ligate sulfur donor ligands to either the UO(2)(Ar(2)nacnac) or the [UO(2)(Ar(2)nacnac)](+) fragments were unsuccessful.

Ein seltener Tetraalkyluranyl‐„at“‐Komplex 1 wurde zum Vergleich mit einem UVI‐Hexaalkyl 2 hergestellt und charakterisiert. Sowohl 1 als auch 2 zeigen präzedenzlose Hochfrequenz‐13C‐NMR‐Verschiebungen (siehe Bild); für 2 entspricht dies einem Rekord für diamagnetische einkernige Komplexe. Relativistische DFT‐Rechnungen belegen, dass diese extremen Verschiebungen auf Spin‐Bahn‐Effekte infolge einer signifikanten Beteiligung des f‐Orbitals an der U‐C‐Bindung zurückzuführen sind.

A rare uranyl-alkyl "ate" complex … … was prepared for comparison with a homoleptic U VI -hexaalkyl. In their Communication on page 3259 ff., P. Hrobµrik, T. Hayton, et al. demonstrate that both complexes feature unprecedented high-frequency methylene 13 C shifts, consistent with large spinorbit effects. Relativistic calculations show that the cause is significant f-orbital involvement in s-bonding.