Experimental and Computational Studies on Uranium Diazomethanediide Complexes.

Uranium diazomethanediide complexes can be prepared and their synthesis, structure and reactivity were explored. Reaction of the uranium imido compound [η -1,2,4-(Me Si) C H ] U=N(p-tolyl)(dmap) (1) or [η -1,3-(Me C) C H ] U=N(p-tolyl)(dmap) (4) with Me SiCHN cleanly yields the first isocyanoimido metal complexes [η -1,2,4-(Me Si) C H ] U(=NNC)(μ-CNN=)U(dmap)[η -1,2,4-(Me Si) C H ] (2) and {[η -1,3-(Me C) C H ] U[μ-(=NNC)]} (5), respectively. Both compounds exhibit remarkable thermal stability and were fully characterized. According to density functional theory (DFT) studies the bonding between the Cp U and [NNC] moieties is strongly polarized with a significant 5 f orbital contribution, which is also reflected in the reactivity of these complexes. For example, complex 5 acts as a nucleophile toward alkylsilyl halides and engages in a [2+2] cycloaddition with CS , but no reaction occurs in the presence of internal alkynes.