Synthesis and Properties of High-Valent Organouranium Complexes Containing Terminal Organoimido and Oxo Functional Groups. A New Class of Organo-f-Element Complexes

Preparation and Reactions of Base-Free Bis(1,2,4-tri-tert-butylcyclopentadienyl)uranium Methylimide, Cp‘2UNMe, and Related Compounds

“…4,8 Thus, the thermal elimination pathway presumably has a high kinetic barrier that is lowered by increasing the steric bulk on the aromatic ring in these C 5 Me 5 derivatives. In the metallocenes derived from 1,2,4-(Me 3 C) 3 …”

“…8,9 However, the least bulky arylamine, aniline, yields (η 5 -C 5 Me 5 ) 2 U(NHPh) 2 , which is stable to elimination of aniline. 4 The primary alkylamines, EtNH 2 and Me 3 CNH 2 , behave similarly. 8 Thus, formation of decamethylmetalloceneuranium imides depends in a very sensitive way on the steric bulk, and perhaps, on the electronic effects of the substituents on the primary amine.…”

“…[1][2][3][4][5][6][7][8][9][10] When the arylamine has sterically bulky substituents such as i-Pr and t-Bu in the 2,6-positions, 3,4 the (η 5 -C 5 Me 5 ) 2 U=NAr derivatives are generally prepared by reaction of (η 5 -C 5 Me 5 ) 2 UMe 2 with one equiv of a primary arylamine, which presumably forms (η 5 -C 5 Me 5 ) 2 U(Me)(NHAr), which eliminates methane forming the imidometallocene. 3,4 When the substituents are somewhat less bulky, for example 2,6-dimethylaniline, the bis-amide derivative is formed, which thermally eliminates the amine forming (η 5 -C 5 Me 5 ) 2 U(NAr)(thf). 8,9 However, the least bulky arylamine, aniline, yields (η 5 -C 5 Me 5 ) 2 U(NHPh) 2 , which is stable to elimination of aniline.…”

Perturbation of the O–U–O Angle in Uranyl by Coordination to a 12-Membered Macrocycle

“…1,2 In contrast to the ubiquity of the trans-uranyl fragment, the cis-uranyl ion is unknown, and all attempts to synthesize a cis-uranyl complex have been unsuccessful thus far. [3][4][5][6] For example, reaction of Cp* 2 UI(THF) with KC 8 and pyridine-Noxide, in an attempt to generate cis-Cp* 2 UO 2 , resulted in formation of the pentamethylcyclopentadienyl dimer and "uranium oxides" (Scheme 1a). 7 Similarly, reaction of Cp' 2 UCl 2 (Cp' = 1,2,4-C 5 H 2 t Bu 3 ) with pyridine-N-oxide and KC 8 afforded a mixed-valent uranium oxo cluster (Scheme 1b).…”

“…4,9,10 Their higher stability, relative to the unobserved oxo analogue, is probably due to a greater reliance on -bonding within the [U(NR) 2 ] 2+ fragment, which diminishes the importance of the 6p orbital participation in the -bonding framework. 11 Similarly, Arnold and co-workers recently reported the isolation of 4 [ (c) 0.5 + 2 bipy Scheme 1.…”