Constrained geometry organoactinides as versatile catalysts for the intramolecular hydroamination/cyclization of primary and secondary amines having diverse tethered C-C unsaturation

A series of "constrained geometry" organoactinide complexes, (CGC)An(NMe)₂ (CGC = Me₂-Si(η⁵-Me ₄C₅)(^tBuN); An = Th, 1; U, 2), has been prepared via efficient in situ, two-step protodeamination routes in good yields and high purity. Both 1 and 2 are quantitatively converted to the neutrally charged, solvent-free dichlorides (1-Cl₂, 2-Cl₂) and slightly more soluble diiodides (1-I₂, 2-I₂) with excess Me₃Si-X (X = Cl, I) in non-coordinating solvents. The new complexes were characterized by NMR spectroscopy, elemental analysis, and (for 1 and 2) single-crystal X-ray diffraction, revealing substantially increased metal coordinative unsaturation vs the corresponding Me₂SiCp″ ₂AnR₂ (Cp″ = η⁵-Me₄C ₅; An = Th, R = CH₂-(SiMe₃), 3; An = U, R = CH₂Ph, 4) and Cp′₂AnR₂ (Cp′ = η⁵-Me₅C₅ ; An = Th, R = CH ₂(SiMe₃), 5; An = U, R = CH₂(SiMe₃), 6) complexes. Complexes 1-6 exhibit broad applicability for the intramolecular hydroamination of diverse C-C unsaturations, including terminal and internal aminoalkenes (primary and secondary amines), aminoalkynes (primary and secondary amines), aminoallenes, and aminodienes. Large turnover frequencies (N _t up to 3000 h^-1) and high regioselectivities (≥95%) are observed throughout, along with moderate to high diastereoselectivities (up to 90% trans ring closures). With several noteworthy exceptions, reactivity trends track relative 5f ionic radii and ancillary ligand coordinative unsaturation. Reactivity patterns and activation parameters are consistent with a reaction pathway proceeding via turnover-limiting C=C/C=C insertion into the An-N σ-bond.