Dimetalloylene (M-E-M) Complexes of Heavier Main Group Elements Ge, Sn, Pb, Bi via Cleavage of E-X Bonds (X = N(SiMe3)2, OtBu) with an Iridium Hydride.

Reactions of the Ir(V) hydride [MeBDIDipp]IrH4 {BDI = (Dipp)NC(Me)CH(Me)CN(Dipp); Dipp = 2,6-iPr2C6H3} with E[N(SiMe3)2]2 (E = Sn, Pb) afforded the unusual dimeric dimetallotetrylenes ([MeBDIDipp]IrH)2(μ2-E)2 in good yields. Moreover, ([MeBDIDipp]IrH)2(μ2-Ge)2 was formed in situ from thermal decomposition of [MeBDIDipp]Ir(H)2Ge[N(SiMe3)2]2. These reactions are accompanied by liberation of HN(SiMe3)2 and H2 by the apparent cleavage of an E-N(SiMe3)2 bond by Ir-H. In a reversal of this process, ([MeBDIDipp]IrH)2(μ2-E)2 reacted with excess H2 to regenerate [MeBDIDipp]IrH4. Variations of the concentrations of reactants led to formation of the trimeric ([MeBDIDipp]IrH2)3(μ2-E)3. The further scope of this synthetic route was investigated with group 15 amides, and ([MeBDIDipp]IrH)2(μ2-Bi)2 was prepared via the reaction of [MeBDIDipp]IrH4 with Bi(NMe2)3 or Bi(O t Bu)3, to afford the first example of a 'naked' two-coordinate Bi atom bound exclusively to transition metals. A viable mechanism that accounts for formation of the products is proposed. Computational investigations of the Ir2E2 (E = Ge, Sn, Pb) compounds characterized them as open-shell singlets with confined nonbonding lone-pairs at the E centers. In contrast, Ir2Bi2 is characterized as having a closed-shell singlet ground state.