Insertion, Isomerization, and Cascade Reactivity of the Tethered Silylalkyl Uranium Metallocene (η5-C5Me4SiMe2CH2-κC)2U

Investigation of the insertion reactivity of the tethered silylalkyl complex (η5-C5Me4SiMe2CH2-κC)2U (1) 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 (η5:η2-C5Me4SiMe2CH2S2)2U (2). The bulky substrate N,N′-diisopropylcarbodiimide, iPrNCNiPr, inserts into only one of the U−C bonds of 1 to produce the mixed-tether complex (η5-C5Me4SiMe2CH2-κC)U[η5-C5Me4SiMe2CH2C(iPrN)2-κ2N,N′] (3). Carbon monoxide did not exclusively undergo a simple insertion into the U−C bond of 3 but instead formed {μ-[η5-C5Me4SiMe2CH2C(NiPr)O-κ2O,N]U[OC(C5Me4SiMe2CH2)CN(iPr)-κ2O,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 κ2 to κ1 to form [η5:η2-C5Me4SiMe2CH2C(NtBu)]U[η5-C5Me4SiMe2CH2C(NiPr)N(iPr)-κN] (5). The product of double insertion of tBuNC into the U−C bonds of 1, namely [η5:η2-C5Me4SiMe2CH2C(NtBu)]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, [η5:η5:η3-tBuNC(CH2SiMe2C5Me4)(CHSiMe2C5Me4)]U(η2-HCNtBu) (7).