The synthesis and characterization of a series of new diamido-thorium(IV) and diamido-uranium(IV) halide and alkyl complexes supported by three different diamido-ether ligands are reported. Reaction of ThCl4 center dot 2DME with [(RNSiMe2)(2)O]Li-2 ([(NON)-N-R]Li-2) in DME when R = Bu-t gives [(NON)-N-tBu]- ThCl5Li3 center dot DME (1), when R = (Pr2Ph)-Pr-i in diethyl ether [(NON)-N-iPr2Ph]-ThCl3Li center dot DME (3) is prepared. Reaction of UCl4 with [(NON)-N-iPr2Ph]-Li-2 in diethyl ether gives {[(2NON)-N-iPr-N-Ph]UCl2}(2) (4). Reaction of ThCl4 center dot 2DME with Li-2[((Pr2PhNCH2CH2)-Pr-i)(2)O] ([(NCOCN)-N-iPr2Ph]-Li-2) in DME gives [(NCOCN)-N-iPr2Ph]ThCl2 center dot DME (5). The addition of 2 equiv of LiCH2SiMe3 to 1 and 5 resulted in salt- and base-free [(NON)-N-tBu]Th(CH2SiMe3)(2) (7) and [(NCOCN)-N-iPr2Ph]Th(CH2SiMe3)(2) (9), respectively. Complexes 1, 3, 4, 7, and 9, as well as previously reported {(NON)-N-tBu]UCl2}(2) (2), [(NON)-N-tBu]U(CH2SiMe3)(2) (6), [(NCOCN)-N-iPr2Ph]U(CH2SiMe3)(2) (8) were examined as catalysts for the intramolecular hydroamination of a series of aminoalkenes. Complexes 6-9 were shown to facilitate the formation of 2-methyl-4,4-diphenylpyrrolidine from 2,2-diphenyl-1-amino-4-pentene at room temperature. For 9, this reaction occurs in less than 15 min, while for other diallcyls 6-8, the reaction takes less than 2 h. Dihalides 1 and 2 facilitated the same reaction at 60 degrees C in 4 h, while 3 and 4 showed no activity under the same conditions. Dialkyl complexes 7-9 were examined for further reactivity with different substrates. The uranium dialkyl 8 was more active than 7 and 9 for the cyclization of 2,2-diphenyl-1-amino-5-hexene and 2,2-diphenyl-1-amino-6-heptene, as well as more active in the cyclization of N-methyl-2,2-diphenyl-1-amino-4-pentene, a secondary amine. All three dialkyls became less active when the steric bulk of the gem-substituents was decreased from diphenyl to cyclopentyl; reactivity further decreased when the steric bulk of the substituents was decreased further to hydrogen.