Remodeling of N-Heterocyclic Iminato Ligand Frameworks for the Facile Synthesis of Isoureas from Alcohols and Carbodiimides Promoted by Organoactinide (Th, U) Complexes

Abstract

A new class of actinide complexes [(L)­An­(N­{SiMe3}2)3] (An = Th or U) (Th1–Th3 and U1–U3) supported by highly nucleophilic seven-membered N-heterocyclic iminato ligands were synthesized and fully characterized by single-crystal X-ray diffraction. These complexes were successfully exploited as powerful catalysts for the addition of alcohols to carbodiimides to yield the corresponding desirable isourea products at room temperature with short reaction times and excellent yields. Thorough stoichiometric, thermodynamic, and kinetic studies were carried out, allowing us to propose a plausible mechanism for the catalytic reaction.

MgnBu2 Catalyzed the Hydroalkoxylation of Carbodiimides

“…A gradual increase from 73 % to 92 % in the yield has been observed after 12 h with the increase in p K a values of the phenol derivatives 2‐bromophenol, 4‐bromophenol, phenol, and 2‐methylphenol (Table 2, 3 q – 3 t ). This result is consistent with previous literature [7a] . It is worth mentioning that the more sterically encumbered 2‐bromophenol gave 73 % yield of an isomer mixture (isomer ratio=72 : 28).…”

ZnEt2 as a Precatalyst for the Addition of Alcohols to Carbodiimides

“…Thus, in 2016, Eisen and co-workers reported the first examples of actinide-based catalysts with amide ligands for the hydroalkoxylation of carbodiimides ( A in Figure ). In the following years, subsequent reports by the same group would expand this family of catalysts with iminato-supported actinide and hafnium complexes. In 2018, Cantat and co-workers reported 1,5,7-triazabicyclo[4.4.0]­dec-5-ene and its alkali salts (Li + , Na + , K + ) as examples of transition-metal-free catalysts for the hydroalkoxylation of carbodiimides ( B in Figure ), with excellent results in terms of activity for the K + salt .…”

Against All Odds, Uranium and Thorium Iminato Complexes Enable the Cleavage of C═O Bonds in Isocyanates

“…The design and architecture of N-heterocyclic iminato ligands have been a goal for our group. − These ligands are super basic, and in the extreme limits, they have the propensity to donate up to six electrons in 2σ, 4π fashion toward highly electrophilic metals. Thus, these ligands can stabilize high oxidation states for the construction of actinide metal-based complexes (Figure d) .…”