• C[BOND]H activation;
  • insertion;
  • metallocenes;
  • uranium


The synthesis of mixed tethered alkyl uranium metallocenes has been investigated by examining the reactivity of the bis(tethered alkyl) metallocene [(η5-C5Me4SiMe2CH2C)2U] (1) with substrates that react with only one of the U[BOND]C linkages. The effect of these mixed tether coordination environments on the reactivity of the remaining U[BOND]C bond has been studied by using CO insertion chemistry. One equivalent of azidoadamantane (AdN3) reacts with 1 to yield the mixed tethered alkyl triazenido complex [(η5-C5Me4SiMe2CH2C)U(η5-C5Me4SiMe2-CH2NNN-Ad-κ2N1,3)]. Similarly, a single equivalent of CS2 reacts with 1 to form the mixed tethered alkyl dithiocarboxylate complex [(η5-C5Me4SiMe2CH2C)U(η5-C5Me4SiMe2- CH2C(S)22S,S′)], a reaction that constitutes the first example of CS2 insertion into a U4+[BOND]C bond. Complex 1 reacts with one equivalent of pyridine N-oxide by C[BOND]H bond activation of the pyridine ring to form a mixed tethered alkyl cyclometalated pyridine N-oxide complex [(η5-C5Me4SiMe2CH2C)(η5-C5Me4SiMe3)U(C6H4NO-κ2C,O)]. The remaining (η5-C5Me4SiMe2CH2C)2− ligand in each of these mixed tethered species show reactivity towards CO and tethered enolate ligands form by insertion. Subsequent rearrangement have been identified in [(η5-C5Me4SiMe3)U(C5H4NO-κ2C,O)(η5-C5Me4SiMe2C([DOUBLE BOND]CH2)O-κO)] and [(η5-C5Me4SiMe2CH2NNN-Ad-κ2N1,3)U(η5-C5Me4SiMe2C([DOUBLE BOND]CH2)O-κO)].