Imido exchange in bis(imido) uranium(VI) complexes with aryl isocyanates

Addition of 1 and 2 equiv of ArNCO (Ar=Ph, 2,4,6-Me3C6H2) to U(NtBu)(2)(I)(2)(OPPh3)(2) yields the aryl-imido complexes U(NAr)(NtBu)(I)(2)(OPPh3)(2) and U(NAr)(2)(I)(2)(OPPh3)(2), respectively. Unlike analogous transition metal reactions this imido exchange reaction does not proceed through a metal oxo intermediate. Density functional theory calculations and 15N-labeling studies suggest this transformation involves the [2 + 2] cycloaddition of the aryl isocyanate C=N bond across the U=N imido ligand to form an N,N-bound ureato intermediate.