A Uranium(IV) Triamide Species with Brønsted Basic Ligand Character: Metal–Ligand Cooperativity in the f Block

Abstract

Deprotonation of the tridentate triamine ligand H3N3Mes ((2,4,6-Me3C6H2N(H)CH2CH2)2NH) with 2 equiv of KCH2Ph followed by treatment with 1 equiv of UCl4 afforded the diamidoamine uranium complex (THF)2UCl2(HN3Mes) (1-THF). This species was further derivatized with either O═PPh3 or KCp* to generate (Ph3PO)UCl2(HN3Mes) (1-OPPh3) or Cp*UCl(HN3Mes) (2-Cl), respectively. Deprotonation of 2-Cl with nBuLi furnished the uranium(IV) triamido compound Cp*U(N3Mes-LiCl(THF)2) (3-LiCl), which is stabilized by the presence of LiCl. 3-LiCl reacts readily with alcohols and thiols, including HOPh, HSPh, and HOtBu, to furnish the respective products Cp*U(OPh)(HN3Mes) (2-OPh), Cp*U(SPh)(HN3Mes) (2-SPh), and Cp*U(OtBu)(HN3Mes) (2-OtBu), which show cooperative addition of the H–E (E = O, S) bond across the U–N bond, serving to regenerate the diamidoamine ligand. Similar cooperative addition was noted for 3-LiCl with benzophenone, furnishing Cp*U(N3Mes-OCPh2) (3-OCPh2), which features new U–O and N–C bonds. The Bronsted basici...