Synthesis, Characterization and Single-Crystal X-ray Analysis, biological targeting of Nickel(II) and Palladium(II) Complexes of Tetradentate Amidate NHC Ligands-Selective Formation of aNHC or nNHC Complexes

Abstract A set of nickel (II) and palladium (II) compounds of both tetradentate and bidentate amidate standard N-heterocyclic carbene (NHC) ligands have been synthesized and characterized. These compounds show the coordination of both amidate nitrogen atoms and N-heterocyclic carbene (NHC) groups to the metal center, yielding neutral molecules. A mixture of cis- and trans-isomeric geometries of Pd(II) compounds of bidentate ligands was formed, while a set of intrinsic isomers—shapes of Pd(II) tetradentate derivative ligands—were acquired, with these isomers displaying a combination of “normal-N-heterocyclic carbene” (nNHC) or “abnormal-N-heterocyclic carbene” (aNHC) NHC modalities of coordination. Redesign of the ligand systems resulted in the selective formation of only one isomeric form of Ni(II) and Pd(II) tetra-dentate amidate N-heterocyclic carbene ligands for each synthetic reaction, with these complexes displaying either bis-(abnormal-N-heterocyclic carbene) or bis-(normal-N-heterocyclic carbene) coordination to the metal center.