Pd(II), Pd(III) and Pd(IV) Cyclometallated Compounds with 2-Arylpyridines and Their Derivatives or Analogues: 44 Years (1980–2023) of NMR and Single Crystal X-ray Studies

Abstract

In this paper, a review on Pd(II), Pd(III), and Pd(IV) cyclometallated compounds with 2-arylpyridines (2-phenylpyridine, 2-benzylpyridine, 2-benzoylpyridine, 2-phenoxypyridine, 2-phenylsulfanylpyridine, 2-anilinopyridine, 2-(naphth-1-yl)pyridine, 2-(naphth-2-yl)pyridine, and their derivatives) and their analogues (2-phenylquinoline and 7,8-benzoquinoline) with 174 references is presented. A total of 672 species, containing κ2-N(1),C(6′)*-palladium (Pd(II), Pd(III), Pd(IV)) or analogous moiety (i.e., chelated by nitrogen of the pyridine-like ring and the deprotonated ortho-carbon of the phenyl-like ring) and thus possessing a character intermediate between metal complexes and organometallics, studied in the years 1980–2023 by NMR spectroscopy and/or single crystal X-ray diffraction (202 X-ray structures, for 186 species), are described. The biological or catalytic activity and luminescence properties of these species, as well as their possible applications as advanced materials were studied and are also quoted.