S. M. Shakil Hussain

Effective palladium(II)-bis(oxazoline) catalysts: synthesis, crystal structure, and catalytic coupling reactions

New bis(oxazoline) ligands and their palladium complexes were synthesized and characterized. X-ray crystal structures of the two new complexes showed distorted square planar geometry with the palladium ion bonded to nitrogens of two bidentate heterocycles in addition to two bromides and two acetate ions for Pd-BOX-1 and Pd-BOX-2, respectively. The complexes adopt a chair structure with a rigid curvature inducing an inherent chirality. The complexes were effective catalysts for Suzuki–Miyaura, Mizoroki–Heck, and copper-free Sonogashira coupling reactions in aqueous dimethylformamide and under aerobic conditions. The reaction conditions were optimized for best solvent, base, and temperature. The substrate scope of the new catalytic system was evaluated for coupling reactions of a variety of aryl halides with aryl boronic acids, alkenes, and alkynes.

Synthesis, crystal structures and catalytic activities of new palladium(II)–bis(oxazoline) complexes

Abstract Palladium–bis(oxazoline) complexes (Pd-BOX-A and Pd-BOX-B) were synthesized and characterized by 1H, 13C NMR, IR and elemental analysis. The molecular structures of the complexes were confirmed by single-crystal X-ray analysis. In both cases, the palladium center is coordinated by the nitrogen atoms of the two oxazoline rings and two chloride ligands in a distorted square planar geometry. Despite the fact that the bis(oxazoline) ligand is achiral, the asymmetrical substitution on the phenyl spacer and the rigid backbone of the complex Pd-BOX-A induce inherent chirality and the compound crystallizes as a racemic mixture. Both complexes were found to be highly effective catalysts for Suzuki–Miyaura, Mizoroki–Heck and Sonogashira cross-coupling reactions. They also show excellent catalytic activities toward carbonylative coupling reactions.

New Pd(II) Binuclear Complexes as Effective Catalysts in Oxidative-Heck Reaction Using Arylboronic Acid Derivatives

A series of new binuclear Pd(II) complexes based on chelating diimines and bridging diphosphine or diimine ligands have been synthesized and characterized successfully. The formula of the new complexes are [Pd2(mbyp)2(DPA)2](PF6)4 (1), [Pd2(mbyp)2(DPE)2] (PF6)4 (2), [Pd2(mbyp)2(4,4-byp)2] (PF6)4 (3), [Pd2(mbyp)2(t-pye)2] (PF6)4 (4) [mbyp = 4,4′-dimethyl-2,2′-bipyridine, DPA = 1,2-bis(diphenylphosphino)acetylene, DPE = 1,2-bis(diphenylphosphino)ethylene, 4,4-byp = 4,4′-bipyridine, and t-ype = trans 1,2-bis(4-pyridyl)ethylene)]. The catalytic activities of the new complexes have been investigated in the coupling of arylboronic acid derivatives to various olefins. Results obtained showed interesting catalytic activities and chemoselectivities for the new complexes in the coupling reactions to produce the conjugate addition and heck coupling products under free base or oxidant conditions.