Dedicated to Professor F. Ekkehardt Hahn on the occasion of his 65th birthday Heterobimetallic complexes bearing NHC donor ligands are gaining immense popularity in organometallic chemistry and tandem catalysis. It is known that the NHC reacts with Pd II in the presence of pyridine to yield PEPPSI type complexes and the NHC ligands having ortho-CÀ H proton easily orthometalate to Ir III or Rh III centers. Combining these two methodologies in a stepwise fashion, we present here a series of heterobimetallic Ir III À Pd II and Rh III À Pd II complexes from a dicarbene donor ligand featuring cyclometalated Ir III or Rh III and mixed NHC^Py/PPh 3 coordinated Pd II centers. All the heterobimetallic complexes have been structurally characterized by X-ray crystallographic analysis. The heterobimetallic complexes featuring mixed NHC^PPh 3 coordinated Pd II centers show better activity in tandem Suzuki-Miyaura/transfer hydrogenation reactions compared to both, the heterobimetallic complexes possessing PEPPSI type Pd II centers, and the equimolar mixture of their mononuclear Pd II and Rh III or Ir III counterparts. The heterobimetallic complex featuring cyclometalated Ir III and mixed NHC^PPh 3 coordinated Pd II center shows excellent selectivity for 4-biphenylmethanol (isolated yield: 92 %) in tandem catalysis.

A heterobimetallic IrIII/PdII complex from a dicarbene donor ligand featuring cyclometalated IrIII and PEPPSI type PdII is presented along with a homodinuclear PEPPSI type PdII complex starting from the same bis‐imidazolium salt. All the PdII complexes are active precatalyst in both α‐arylation and Suzuki–Miyaura coupling reactions. The heterobimetallic IrIII/PdII complex shows much higher yields in tandem C–C coupling/transfer hydrogenation reactions compared to the equimolar mixture of their mononuclear PdII and IrIII counterparts.

Mononuclear Pd II complexes bearing mixed MIC/Py/PPh 3 donor set ligands are presented starting from a bis-triazolium salt featuring 4,4'-substitution pattern of central biphenyl ring. The mononuclear PEPPSI (pyridine enhanced precatalyst preparation, stabilization and initiation) type complexes bearing triazolylidene donor ligand have been synthesized via an unusual C sp2 -C sp2 decoupling reaction. The complexes have been characterized by 1 H, 13 C{ 1 H} NMR spectroscopy and mass spectrometry. Two of the complexes have also been structurally characterized by single crystal XRD. All the complexes appeared as active precatalysts in α-arylation of amide and Suzuki-Miyaura coupling reactions. Catalytic outcomes clearly indicate the superior activities of the Pd II complexes with mixed MIC/ PPh 3 donor set ligands compared to the corresponding PEPPSI type complexes in α-arylation of oxindole.

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Bimetallic palladium(II) complexes containing classical NHC donor ligands are becoming increasingly popular owing to their various catalytic applications. However, examples of the aforementioned complexes with mixed NHC/PPh3 ligands are still rare. Bimetallic palladium(II) complexes possessing these mixed ligands are described starting from a C2‐symmetric bis‐imidazolium salt containing 4,4′‐substituted central biphenyl ring. All the palladium(II) complexes have been tested as precatalysts in α‐arylation of oxindole and Suzuki–Miyaura coupling reactions. The complex composed of mixed NHC/PPh3 donor ligands shows superior catalytic activity compared with the corresponding PEPPSI type complexes when applied in α‐arylation of oxindole. The dinuclear complexes display better activity compared with the mononuclear complexes. The preliminary electrochemical measurements show the facile oxidation of PdII in the presence of combined NHC/PPh3 ligands compared with a combination of NHC/Py ligands.