Experimental and Computational Studies on Uranium Diazomethanediide Complexes.

Abstract

Uranium diazomethanediide complexes can be prepared and their synthesis, structure and reactivity were explored. Reaction of the uranium imido compound [η5 -1,2,4-(Me3 Si)3 C5 H2 ]2 U=N(p-tolyl)(dmap) (1) or [η5 -1,3-(Me3 C)2 C5 H3 ]2 U=N(p-tolyl)(dmap) (4) with Me3 SiCHN2 cleanly yields the first isocyanoimido metal complexes [η5 -1,2,4-(Me3 Si)3 C5 H2 ]2 U(=NNC)(μ-CNN=)U(dmap)[η5 -1,2,4-(Me3 Si)3 C5 H2 ]2 (2) and {[η5 -1,3-(Me3 C)2 C5 H3 ]2 U[μ-(=NNC)]}6 (5), respectively. Both compounds exhibit remarkable thermal stability and were fully characterized. According to density functional theory (DFT) studies the bonding between the Cp2 U2+ and [NNC]2- 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 CS2 , but no reaction occurs in the presence of internal alkynes.