Search

The design of homogeneous catalysts based on Ir and other late transition metal complexes using O-donor ligands like acetylacetonate (aca), tropolone, aryloxides, catechols, hydroxyaetophenone to stabilize the complexes to the reaction conditions needed for generating functionalized products is discussed. The outcome of the studies helps to utilize, design new, more effective, thermally protic-and oxidant-stable O-donor catalysts for hydrocarbon conversion.

Two organometallic systems([Ir(Mu-acac-O)(acac-C(super 3)](sub 2) and (Tp)Ru(CO)(Ph)-(NCCH3) is discovered that catalyze hydroarylation of unactivated olefins. Hybridization is dependent on the amount of back-bonding to the olefin, these relationships translate into correlations between the amount of back-bonding and activation energy/thermodynamics.

Acetic acid is an important petrochemical that is currently produced from methane (or coal) in a three-step process based on carbonylation of methanol. We report a direct, selective, oxidative condensation of two methane molecules to acetic acid at 180°C in liquid sulfuric acid. Carbon-13 isotopic labeling studies show that both carbons of acetic acid originate from methane. The reaction is catalyzed by palladium, and the results are consistent with the reaction occurring by tandem catalysis, involving methane C-H activation to generate Pd-C[H.sub.3] species, followed by efficient oxidative carbonylation with methanol, generated in situ from methane, to produce acetic acid., Natural gas, which is composed primarily of methane, is one of the most abundant, low-cost, carbon-based feed stocks available. In spite of this, we are dependent on dwindling petroleum reserves [...]

This review summarizes the deliberations of a workshop colloquium on the 'opportunities for catalysis research in carbon management'. Research progress within the context of greenhouse gas/carbon issues in the areas of hydrogen generation and utilization, carbon dioxide activation, catalysis research to further our search for new and more efficient catalytic processes.

Platinum catalysts are reported for the direct, low-temperature, oxidative conversion of methane to a methanol derivative at greater than 70 percent one-pass yield based on methane. The catalysts are platinum complexes derived from the bidiazine ligand family that are stable, active, and selective for the oxidation of a carbon-hydrogen bond of methane to produce methyl esters. Mechanistic studies show that platinum(II) is the most active oxidation state of platinum for reaction with methane, and are consistent with reaction proceeding through carbon-hydrogen bond activation of methane to generate a platinum-methyl intermediate that is oxidized to generate the methyl ester product., More efficient methods for the oxidation of low-value, light alkane feedstocks, such as natural gas, to the corresponding alcohols or other useful liquid products would accelerate the use of natural [...]

A homogeneous system for the selective, catalytic oxidation of methane to methanol via methyl bisulfate is reported. The net reaction catalyzed by mercuric ions, Hg(II), is the oxidation of methane [...]

The ability of (IPI)Ru(II)[(OH).sub.n][([H.sub.2]O).sub.m] where IPI is the NNN-pincer ligand, 2,6-diimidizoylpyridine to catalyze H/D exchange between hydrocarbons and strongly basic solvents at higher rates than in the case of the solvent alone is described. The evidence indicated that the reaction proceeding by base modulated nucleophilic CH activation could be increased by solvent basicity.

The Catalytica catalyst is successful because the methanol is protected as methyl bisulfate, which is less reactive than methanol toward the catalyst. The analysis has shown a limiting performance for systems that is operated by this type of protection that is well above the Catalytica system.

Several studies are conducted to analyze the localized molecular orbital energy decomposition of the various C-H activation transition states (TSs). The results prove that these discussed metal centers exhibit an electrophilic, ambiphilic and nucleophilic charge transfer in the bond activation.

Se[O.sub.2] has catalyzed the facile oxy-functionalization of [(CO).sub.5]Re(I)-[Me.sup.5-] with I[O.sub.4.sup.-] to generate methanol. Density functional theory calculations have shown that catalysis has involved methyl group transfer from Re to the electrophilic Se center followed by oxidation and subsequent reductive functionalization of the resulting C[H.sub.3]Se(VI) species.

The density functional theory (DFT) is used for studying the mechanisms for the interactions between methylrhenium trioxide (MTO) and [H.sub.2][O.sub.2]/NaOH in THF. The studies have shown that methanol is formed through Baeyer-Villiger type mechanism and another oxygen insertion transition state with a low relative barrier is isolated.

The combined experimental and theoretical evidence is presented for a facile Re-R to Re-OR bond conversion with non-peroxo YOs that proceeds through a low-energy, Baeyer-Villiger (BV)-type, electrophilic O-atom insertion. The results might point to a facile pathway for heteroatom functionalization of M-R intermediates of more electron-rich metals via a BV-type pathway with electrophilic, heteroatom-atom donors, such as YO.

The mechanism of hydroarylation of olefins by a homogeneous Ph-Ir(acac)2(L) catalyst is elucidated by first principles quantum mechanical methods (DFT), with particular emphasis on activation of the catalyst is discussed. Electron-withdrawing substituents on the acac ligands are good modifications for catalysts with higher activity.

A study was conducted to show that O-donor ligands could facilitate the C-H activation reaction as well as selective functionalization of the M-R intermediate for a picolinate platinum system. The results indicate that a well-defined, late metal, N,O-ligated complex, which is competent for arene C-H activation, exhibits thermal and protic stability and is an efficient catalyst for H/D exchange.

The air, protic, and thermally stable O-donor alkoxo complexes, (acac-O,O)2Ir(OMe)(L), 2-L, L=Py and CH3OH, react in stoichiometric CH activation reactions with benzene to generate the corresponding phenyl complex with co-generation of methanol in high yield. This is the first example of such an intermolecular CH activation reaction with a metal-alkoxo complex.

The well-defined, late-metal, O-ligated complexes are demonstrated, which are competent for alkane C-H activation. The O-ligated complexes exhibit high thermal and protic stability, and are efficient catalysts for H/D exchange reactions with alkanes.

Research is presented into anti-Markovnikov arylation catalyzed by a binuclear iridium complex.