Synthesis and insertion chemistry of mixed tether uranium metallocene complexes

The synthesis of mixed tethered alkyl uranium metallocenes has been investigated by examining the reactivity of the bis(tethered alkyl) metallocene [(η⁵-C₅Me₄SiMe₂CH₂-κC)₂U] (1) with substrates that react with only one of the U-C linkages. The effect of these mixed tether coordination environments on the reactivity of the remaining U-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-C₅Me₄SiMe₂CH₂-κC)U(η⁵-C₅Me₄SiMe₂-CH₂NNN-Ad-κ²N^1,3)]. Similarly, a single equivalent of CS₂ reacts with 1 to form the mixed tethered alkyl dithiocarboxylate complex [(η⁵-C₅Me₄SiMe₂CH₂-κC)U(η⁵-C₅Me₄SiMe₂- CH₂C(S)₂-κ²S,S^')], a reaction that constitutes the first example of CS₂ insertion into a U⁴⁺-C bond. Complex 1 reacts with one equivalent of pyridine N-oxide by C-H bond activation of the pyridine ring to form a mixed tethered alkyl cyclometalated pyridine N-oxide complex [(η⁵-C₅Me₄SiMe₂CH₂-κC)(η⁵-C₅Me₄SiMe₃)U(C₆H₄NO-κ² C,O)]. The remaining (η⁵-C₅Me₄SiMe₂CH₂-κC)^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(=CH₂)O- κO)] and [(η⁵-C₅Me₄SiMe₂CH₂NNN-Ad-κ²N^1,3)U(η⁵-C₅Me₄SiMe₂C(=CH₂)O-κO)]. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)