Improved Oxidative C-C Bond Formation Reactivity of High-Valent Pd Complexes Supported by a Pseudo-Tridentate Ligand

Hydroxopalladium(IV) complexes prepared using oxygen or hydrogen peroxide as oxidants

The cycloneophylpalladium(II) complexes [Pd(CH2CMe2C6H4)(κ2-N,N'-L)], 1 or 2, with L = RO(CH2)3N(CH2-2-C5H4N)2, with R = H or Me, respectively, react with either dioxygen or hydrogen peroxide in the presence of NH4[PF6] to give rare examples of the corresponding hydroxopalladium(IV) complexes [Pd(OH)(CH2CMe2C6H4)(κ3-N,N',N''-L)][PF6], 3 or 4. The complexes 3 and 4 are stable at room temperature and have been structurally characterized. On heating a solution of 3 or 4 in moist dimethylsulphoxide, selective reductive elimination with C(sp2)-O bond formation is observed, followed by hydrolysis, to give the corresponding pincer complex [Pd(OH)(κ3-N,N',N''-L)][PF6] and 2-t-butylphenol as major products. A more complex reaction occurs in chloroform solution. The mechanisms of reaction are discussed, supported by DFT calculations.

DFT Studies on the Mechanisms of Carboamination/Diamination of Unactivated Alkenes Mediated by Pd(IV) Intermediates

Density functional theory (DFT) calculations have been employed to investigate the mechanism of carboamination and diamination of unactivated alkenes mediated by Pd(IV) intermediates. Both reactions share a common Pd(IV) intermediate, serving as the starting point for either the carboamination or the diamination pathway. The formation of this Pd(IV) intermediate encompasses a transition state that substantially impacts the turnover frequency (TOF) of catalytic cycles, with an apparent activation free-energy barrier of 26.1 kcal mol-1. Carboamination of unactivated alkenes proceeds through the coordination of a toluene molecule, C-H activation, inner reductive elimination, and the separation of the carboamination product from this intermediate, while diamination of unactivated alkenes involves the formation of the ion nucleophile, SN2 attack, and the separation of the diamination product. A comparison of the free-energy profiles for carboamination and diamination of unactivated alkenes can elucidate the origin of the chemoselectivity, and Bader's atoms in molecules (AIM) wave function analyses have been performed to analyze the contributions of the outer C-N bonding in the diamination process.

Recent progresses in the chemistry of 12-membered pyridine-containing tetraazamacrocycles: From synthesis to catalysis

This article provides an overview (non-comprehensive) on recent developments regarding pyridine-containing 12-membered tetraazamacrocycles with pyclen or Py2N2 backbones and their metal complexes from 2017 to the present. Firstly, the synthesis...