A Comparative Study on Dinuclear and Multinuclear Ni(II), Pd(II), and Pt(II) Complexes of a Thiolato-Functionalized, Benzannulated N‑Heterocyclic Carbene Ligand

Dimeric thiolato-bridged Ni­(II) and Pt­(II) NHC complexes 2 and 4 have been synthesized from ligand precursor A through a combined and in situ deprotonation/hydrolysis protocol of a thioester-functionalized benzimidazolium salt in the presence of the respective metal salts. Reactivity studies of 2 and 4, and their previously reported Pd­(II) analogue 1a toward either Me3OBF4, NaOH, or Na2S·9H2O revealed clear differences. Complex 2 decomposed when treated with Me3OBF4. On the other hand, its reaction with aqueous NaOH solution in the presence of NaBF4 yielded trinuclear [Ni3S3O] complex 6, which possesses an interesting [Ni3S3] triangle with a capping μ3-oxido ligand. Pt­(II) analogue 4 was converted to the tetranuclear [Pt4S4] macrocycle 5 when treated with Me3OBF4, in analogy to the result from 1a, while no defined products could be isolated when 4 was treated with either NaOH or Na2S·9H2O. Pd­(II) analogue 1a reacted with Na2S·9H2O to give the tripalladium [Pd3S3S] complex 7 bearing a capping μ3-sulfido ligand.