This communication describes a new and highly practical Pd(II)-catalyzed method for the regio- and chemoselective oxidative functionalization of arenes and alkanes. Carbon-hydrogen bonds of substrates that contain a variety of directing groups (e.g., pyridine, azobenzene, pyrazole, and imine derivatives) are selectively transformed into esters, ethers, and aryl-halides under mild conditions. The scope of this reaction in terms of substrate, directing group, and oxidant is described, and a preliminary catalytic cycle is proposed.
A novel strategy for the immobilization of cytochrome c on the surface of chemically modified electrodes is demonstrated and used to investigate the protein's electron-transfer kinetics. Mixed monolayer films of alkanethiols and omega-terminated alkanethiols (terminated with pyridine, imidazole, or nitrile groups that are able to ligate with the heme) are used to adsorb cytochrome c to the surface of gold electrodes. The use of mixed films, as opposed to pure films, allows the concentration of adsorbed cytochrome to remain dilute and ensures a higher degree of homogeneity in their environment. The adsorbed protein is studied using electrochemical methods and scanning tunneling microscopy.
This communication describes the synthesis of a family of unusually stable palladium(IV) complexes containing two chelating 2-phenylpyridine ligands and two benzoates. These complexes undergo clean C-O bond-forming reductive elimination upon heating, and the mechanism of this catalytically relevant process has been studied in detail. Solvent effects, crossover experiments, Eyring plots (which show DeltaS of -1.4 +/- 1.9 and 4.2 +/- 1.4 in CDCl3 and DMSO, respectively), and Hammett analysis (which shows rho = -1.36 +/- 0.04 upon substitution of the para-benzoate substituent) all suggest that reductive elimination does not proceed via initial dissociation of a benzoate ligand. Instead, an unusual mechanism involving pre-equilibrium dissociation of the N-arm of the phenylpyridine ligand is proposed.
This paper describes the synthesis of a series of Pd(IV) complexes of general structure (N~C)(2)Pd(IV)(O(2)CR)(2) (N~C = a rigid cyclometalated ligand; O(2)CR = carboxylate) by reaction of (N~C)(2)Pd(II) with PhI(O(2)CR)(2). The majority of these complexes undergo clean C-O bond-forming reductive elimination, and the mechanism of this process has been investigated. A variety of experiments, including Hammett plots, Eyring analysis, crossover studies, and investigations of the influence of solvent and additives, suggest that C-O bond-forming reductive elimination proceeds via initial carboxylate dissociation followed by C-O coupling from a 5-coordinate cationic Pd(IV) intermediate. The mechanism of competing C-C bond-forming reductive elimination from these complexes has also been investigated and is proposed to involve direct reductive elimination from the octahedral Pd(IV) centers.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.