New seven membered palladacycles: C–Br bond activation of 2-bromo-pyridine derivative by Pd(II)

Abstract

C-Br bond activation followed by a C-C coupling reaction of the 2-bromo-pyridyl unit of [1-phenyl-2-(6-bromopyridin-2-yl)-benzoimidazole] was performed by Pd(CH(2)CMe(2)-o-C(6)H(4))(η(4)-COD). Two new seven membered palladacycles were obtained. A combined experimental and theoretical DFT study elucidates the mechanism for this reaction.

Water-soluble SNS cationic palladium(II) complexes and their Suzuki–Miyaura cross-coupling reactions in aqueous medium

“…4 ). The Pd–Br distance is calculated to be 2.60 Å and is consistent with similar Pd–Br bond lengths found in the literature for single crystal X-ray structures [ 47 – 48 ]. This oxidative addition step involves a low activation energy barrier of −43.9 kcal/mol.…”

“…The reaction then proceeds via transition state TS2 , leading to the cleavage of the C(sp 2 )–Br bond and the formation of a new Pd–C(sp 2 ) bond, to form a cis intermediate of energy −93.0 kcal/mol. The new Pd–C(sp 2 ) bond distance of 2.00 Å falls within the reported Pd–C(sp 2 ) bond distances [ 47 – 48 ]. Since the bromo ligand is larger in atomic radius than the chloro ligands the more stable form of the oxidative addition product is the trans form.…”

Carbon Dioxide-Mediated C(sp3)–H Arylation of Amine Substrates

“…To simulate the reaction conditions, PdCl 2 and amine were mixed in 1% AcOH in DMSO- d 6 , followed by bubbling CO 2 through the solution for 12 h. This gave a complex spectrum containing a carbamate signal as well as new resonances between 121 and 124 ppm in the 13 C NMR spectrum from different CO 2 species. We believe that this supports an on-cycle role for CO 2 as a transient DG acting through a rare seven-membered palladacycle, though further studies are needed.…”

A novel coordination mode of κ1-N-Br-pyridylbenz-(imida, oxa or othia)-zole to Pt(ii): synthesis, characterization, electrochemical and structural analysis

“…A few years ago, we reported the synthesis of seven-membered palladacycles through selective C-Br bond activation of a Br-pyridine-benzimidazole derivative and concomitant C-C coupling bond, where no-innocent cyclooctadiene ligand (COD) plays an essential role (Chart 1b). 19 Also, a ve-membered palladacycles synthesis can be achieved when the COD is displaced by a phosphine ligand (Chart 1c). In 2018, we reported a direct synthesis on rollover palladacycles was achieved via C-H bond activation reaction in remote position on Br-pyridyl-benzothiazole (L PB2 ) by PdCl 2 , where the dimethylformamide plays an important role on the reaction pathway.…”