A naphthalene-based heterobimetallic triazolylidene IrIII/PdII complex: regioselective to regiospecific C–H activation, tandem catalysis and a copper-free Sonogashira reaction

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Abstract
Heterobimetallic complexes featuring mesoionic carbene (MIC) donor ligands are gaining enormous popularity in tandem catalysis owing to the combined action of two different metal centers during catalysis. A rare version of the heterobimetallic PdII/IrIII complex possessing a cyclometalated mesoionic carbene (MIC) ligand is presented along with the analogous homodinuclear PdII complex. A sterically controlled regiospecific cyclometalation towards the formation of a six-membered ring complex over a five-membered ring complex has been performed using a naphthalene-based bis-MIC ligand platform. The interplay between regioselective vs. regiospecific C–H bond activation for the synthesis of cyclometalated IrIII complexes has also been demonstrated using the corresponding naphthyl-derived mono-imidazolylidene ligand. Both homodinuclear PdII and heterobimetallic PdII/IrIII complexes have been characterized using standard spectroscopic techniques including 1H, 13C{1H}, 2D correlation NMR spectroscopy and ESI mass spectrometry. The structure of the cyclometalated heterobimetallic complex has been established by single crystal XRD. The heterobimetallic complex has been employed as a pre-catalyst in the tandem Suzuki–Miyaura/transfer hydrogenation reaction and the homobimetallic PdII complex has been successfully employed as a catalyst in both the Sonogashira coupling and α-arylation of 1-methyl-2-oxindole.
Funding Information
  • Anusandhan National Research Foundation (ECR/2018/002233)
  • University Grants Commission (F.30-363/2017(BSR))

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