Activation of CO Using a 1,2-Disilylene: Facile Synthesis of an Abnormal N-Heterocyclic Silylene

Reaction of the 1,2-disilylene, {ArC(NDip)(2)}Si](2) 1 (Dip = 2,6-diisopropylphenyl, Ar =4-C6H4But), with CO proceeds via insertion of CO into one Si-N bond, and Si-Si bond cleavage, to cleanly give the bis(silylene), {ArC(NDip)(2)}Si(:)O<(CSi(:)(NDip)(2)C)over bar> Ar 2, tinder ambient conditions. The reaction can be partially reversed when solutions of 2 are subjected to UV irradiation. The five-membered heterocyclic fragment of 2 represents the first silicon analogue of an "abnormal" N-heterocyclic carbene (aNHC), a view which is substantiated by a computational analysis of the compound. Reaction of 2 with [Mo(CO)(6)] under UV light affords the chelate complex, [Mo(CO)(4)(kappa(2)-Si,Si-2)] 3, while reaction with [Fe(CO)(5)] gives the unusual silyleneyl bridged complex, [(Fe-2(CO)(6))(mu-Si[(NDip)(2)CAr]}(2)] 4. The same coordination complexes can be accessed by reaction of 1 with [Mo(CO)(6)] or [Fe(CO)(5)] under UV light. As is the case for aNHCs, d-block metal complexes of bis(silylene) 2 could prove useful as bespoke catalysts for organic transformations.