Delineating the Role of Substituents on the Coordination Behavior of Aroylhydrazone Ligands in Pd^II Complexes and their Influence on Suzuki–Miyaura Coupling in Aqueous Media

Abstract

Reactions of piperonal aroylhydrazone ligands (HL1–HL4) with [PdCl2(PPh3)2] in CH3OH and CHCl3 afforded four new Pd(II) complexes (1–4) featuring diverse coordination behaviors. These complexes 1–4 were fully characterized by elemental analyses, UV/Visible, FT‐IR and 1H/13C NMR spectra. The variant coordination modes of piperonal aroylhydrazone ligands with Pd(II) ion in these complexes were unambiguously confirmed by single‐crystal XRD study. Though the ligands HL1–HL4 are of similar nature, one of them (HL4) possessing an electron withdrawing nitro group as substitution in the peripheral part of the hydrazone displayed an uncommon ligation towards the palladium ion. An experimentally observed molecular architects were in turn rationalized by density functional theory (DFT) calculations as well as natural bonding analysis (NBO). All these Pd(II) complexes were evaluated for their catalytic potential towards Suzuki–Miyaura cross‐coupling reaction of sterically congested arylboronic acids with (hetero)arylhalides under an open‐flask conditions in aqueous media with low catalyst loading. Advantageously, the selected catalyst was active up to five cycles without significant loss in activity.

Excited-State Intramolecular Proton- and Inter-Polymer Charge-Transfer of Semiconducting Redox Polymers for Fe(III), Cd(II), and Hg(II) Sensing

“…of −C­(O – )­N + , respectively, confirmed the imidol and charged canonical forms of FSP s (Figure S3a–e and Table S8). In FSP s, AMMPSA was confirmed from −SO 3 H str . within 1040–1043 cm –1 (Figure S3a–e and Table S8).…”

One‐pot synthesis of 1,3‐disubstituted imidazo[1,5‐a]pyridines via acceptorless dehydrogenative coupling of primary alcohols promoted by binuclear ruthenium(II) N^O‐chelating complexes

“…The coupling reaction has been ineffective without the catalyst or base (Table 1, Entries 20-21). In addition, increasing the reaction temperature from 110 to 130 C resulted in a marginal change in product yield (Table 1, ntries [18][19].…”

“…[17] It is worth noting that hydrazone-based Ru complexes have garnered significant interest and studied over a number of cross-coupling reactions due to fact that the spectator hydrazone ligand stabilizes the metal oxidation state. [18,19] Hence, we have selected ruthenium complexes comprising hydrazone as catalysts to construct medicinally important imidazo[1,5-a]pyridine derivatives.…”