Investigation of the insertion reactivity of the tethered silylalkyl complex (eta(5)-C5Me4SiMe2CH2-kappa C)(2)U (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 (eta(5):eta(2)-C5Me4SiMe2CH2S2)(2)U (2). The bulky substrate N,N`-diisopropylcarbodiimide, (PrN)-Pr-i=C=-/+ (NPr)-Pr-i, inserts into only one of the U-C bonds of 1 to produce the mixed-tether complex (eta(5)-C5Me4SiMe2CH2-kappa C)U[eta(5)-C5Me4SiMe2CH2C((PrN)-Pr-i)(2)-kappa N-2,N`] (3). Carbon monoxide did not exclusively undergo a simple insertion into the U-C bond of 3 but instead formed {mu-[eta(5)-C5Me4SiMe2CH2C(=(NPr)-Pr-i)O-kappa O-2,N]U[OC(C5Me4SiMe2CH2)CN(Pr-i)-kappa O-2,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 kappa(2) to kappa(1) to form [eta(5):eta(2)-C5Me4SiMe2CH2C(=(NBu)-Bu-t)]U[eta(5)-C5Me4SiMe2CH2C(=(NPr )-Pr-i)N(Pr-i)-kappa N] (5). The product of double insertion of (BuN)-Bu-t C into the U-C bonds of 1, namely [eta(5):eta(2)-C5Me4SiMe2CH2C(=N(t)u)](2)U (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 formimidoly actinide complex, [eta(5):eta(5):eta(3)-(BuNC)-Bu-t(CH2SiMe2C5Me4)(CHSiMe2C5Me4)]U(eta(2)-HC=(NBu)-Bu-t) (7).