Insertion, Isomerization, and Cascade Reactivity of the Tethered Silylalkyl Uranium Metallocene (η~5-C_5lMe_4SiMe_2CH_2-KC)_2U

摘要

Investigation of the insertion reactivity of the tethered silylalkyl complex (η~5-C_5Me_4SiMe_2CH_2-KC)_2U (l) has led to a series of new reactions for U~C bonds. Elemental sulfur reacts with 1 by inserting two sulfur atoms into each of the U-C bonds to form the bis(tethered alkyl disulfide) complex (η~5-C_5Me_4SiMe_2CH_2-KC)_2U (2). The bulky substrate N,N'-diisopropylcarbodiimide, ~iPrN==C==F N'Pr, inserts into only one of the U-C bonds of 1 to produce the mixed-tether complex (η~5-C_5Me_4SiMe_2CH_2-KC)_2U[/7S-C_5Me_4SiMe_2CH_2C(~iPrN)_2-k~2N,N'] (3). Carbon monoxide did not exclusively undergo a simple insertion into the U-C bond of 3 but instead formed {μ-[η~5-C_5Me_4SiMe_2CH_2C(=N'Pr)O-K~2O,N]U[OC(C_5Me_4SiMe_2CH_2)CN(~iPr)-k~2O,N]_2 (4) in a cascade of reactions that formally includes U-C bond cleavage, C-N bond cleavage of the amidinate ligand, alkyl or silyl migration, U-O, C-C, and C~N bond formations, and CO insertion. The reaction of 3 with isoelectronic tert-butyl isocyanide led to insertion of the substrate into the U-C bond, but with a rearrangement of the amidinate ligand binding mode from K~2 to K~1 to form [η~5:η~2-C_5Me_4SiMe_2CH_2C(=N~tBu)]U[η~5-C_5Me_4SiMe_2CH_2C(=N~iPr)N(~iPr)-kN] (5). The product of double insertion of ~tBuN=C into the U-C bonds of 1, namely [η~5:η~2-C_5Me_4SiMe_2CH_2C(=N~tBu)]_2U (6), was found to undergo an unusual thermal rearrangement that formally involves C-H bond activation, C-C bond cleavage, and C-C bond coupling to form the first formimidoyl actinide complex, [η~5:η~5:η~3-~tBuNC(CH_2SiMe_2C_5Me_4)(CHSiMe_2C_5Me_4)]U(η~2-HC=N~tBu) (7).