Pincer Type Ferrocenyl Cyclopalladated Complexes Involving Bi-Negative Terdentate Ligand System and Their Catalytic Evaluation

Abstract

Palladium-catalyzed cross coupling reactions are well-known and extremely helpful processes for synthesizing a variety of diverse organic compounds for commercial and laboratory applications, including agrochemicals and pharmaceutical derivatives. One of the successful strategies for achieving an efficient catalytic result is the use of pincer ligands to produce welldefined metal–ligand coordination. A novel class of compounds known as cyclopalladated molecular complexes, which are also pincer type compounds, have opened up new possibilities for palladium-catalyzed coupling processes. The tridentate, planar geometry surrounding the palladium centre makes unsymmetrical pincer type cyclopalladated compounds even more intriguing. Over the past years, cyclopalladation involving aromatic groups based on organic matter has been extensively researched, and these compounds have demonstrated a range of fascinating biological and catalytic activities. As a part of our interest to explore the influence of different functionalization on the ferrocenyl scaffold, we came across pincer type architecture which revealed that strategic use of the ferrocenyl moieties led to the design of pincer type palladacyclic molecules that are surprisingly active for aryl chloride based C-C cross coupling reactions. The report involves synthetic approach for less known halide free ferrocenyl cyclopalladated pincer complexes involving range of bi-negative tridentate ligand with {C (Fc), N, Y (Ar)} donor atoms (Y = S, O; Ar=NH2, Ph, Ph-OH, 3-C5H4N, 4-C5H4N) and their behavior in cross coupling reaction involving aryl chloride with low catalyst loading and facile reaction condition. Further, we have explored the synthesis of a novel pincer type Pd-complex with unsymmetrical functionalized ferrocenyl scaffold and investigate their behaviour in cross-coupling reactions such as Suzuki–Miyaura, Sonogashira etc. while maintaining low catalyst loading and facile reaction conditions.