| Summary: | 碩士 === 國立彰化師範大學 === 化學系 === 101 === The preparation of a series of ligand precursors featuring imidazo[1,2-a]pyridine and amido functional groups is reported. The reactions between the new ligand precursors, pyridine, and palladium acetate in DMF afforded monodentate Pd(II) abnormal carbene complexes. An isomeric Pd(II) normal carbene complex with a formally identical steric environment to that of the abnormal carbene counterpart was also prepared. The isomeric pairs were characterized by X-ray structural studies. Under a different complexation condition of employing PdCl¬2 as metal precursor, a CC-type palladacycle formed by the C–H activation at the ortho-N-phenyl and methylene carbons was obtained. The use of a similar ligand precursor with a NH instead of NMe group produced a palladalactam complex. In contrast to the previous work in the literature, due to the rigidity of the fused heterocyclic ring, the palladalactam complex did not undergo intramolecular proton transfer via the coordinated N atom. Overall, we demonstrated that proper modification of the structures of ligand precursors and complexation conditions allowed us to obtain a full range of intriguing Pd(II) complexes including abnormal and normal carbene complexes, palladalactam, and CC-type palladacycles via A–H bond (A = N, C) activations.
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