β‑Diketiminate Derivatives of Alkali Metals and Uranium

Treatment of [M­(Bn)] (M = K, Cs) with [HC­{C­(But)­NDipp}­{C­(But)­NHDipp}] (LButH; Dipp = 2,6-diisopropylphenyl) afforded [K­(LBut)­(THF)n], 1, and [Cs­(LBut)], 2, which were crystallized from hexane or benzene to afford [K­(LBut)­(THF)3], 1a, and [{Cs­(LBut)}­{Cs­(LBut)­(η3-C6D6)}·C6D6]∞, 2a, respectively. Complexes 1 and 2 were utilized in the preparation of the previously reported [U­(LBut)­Cl3], which was cleanly converted to [U­(LBut)­I3], 3, via reaction with an excess of Me3SiI. Attempts to prepare U­(III) complexes incorporating the LBut ligand proved unsuccessful, but utilizing [HC­{C­(Me)­NDipp}­{C­(Me)­NHDipp}] (LMeH) led to the isolation of [U­(LMe)­I2(THF)2], 4, via the reaction of [K­(LMe)] with [U­(I)3(THF)4]. Complex 4 can be derivatized via reaction with [K­(Cp*)] (Cp* = η5-C5Me5) or [K­{N­(SiMe3)2}] to afford [U­(LMe)­(Cp*)­I], 5, and [U­(LMe)­{N­(SiMe3)2}­I], 6, respectively. The reaction of 4 with two equivalents of [K­{N­(SiMe3)2}] did not afford [U­(LMe)­{N­(SiMe3)2}2] as expected, but instead led to the isolation of the U­(IV) species [U­{HC­[C­(Me)­NDipp]­[C­(CH2)­NDipp]}­{N­(SiMe3)2}2], 7, via deprotonation of the LMe ligand. The reduction of 4 with KC8 in benzene afforded the diuranium inverse sandwich complex [{U­(LMe)­I}2(μ-η6:η6-C6H6)], 8, albeit in low yield. Complexes 1–8 have been characterized by single-crystal X-ray diffraction studies, by multielement NMR spectroscopy, and variously by FTIR spectroscopy, elemental analysis, UV/vis/NIR spectroscopy, and solution-state magnetic studies.