Activation of methane by homogeneous catalysts in weakly acidic solvents.

摘要

This dissertation describes the latest development in engaging simple hydrocarbons in reaction by CH activation. From initially fuming oleum condition and catalysis like halogens, the trend goes to gold catalyst in 96% sulfuric acid, and later to variety platinum complexes in weak organic acids. The story concentrates on discovery of basic physical phenomenons to enhance reactivity versus specific synthetic applications.; Chapter One introduces the C-H activation and functionalization of alkanes via the electrophilic mechanism, and discusses the role of non-coordinating solvents and the related problem of inhibition of electophilic catalysts by products such as methanol and water. The simplest iodine and mercury in sulfuric acid catalysts described.; Chapter Two shows another simple catalytic system reported to date for converting methane to a methyl product below 200°C. Gold dissolved in 2% oleum catalyzes the selective, high yield oxidation of methane to methyl bisulfate using selenic acid as stoichiometric oxidant.; Chapter Three discusses in details the mechanism of the most efficient and selective low-temperature catalytic system for the conversion of methane to methanol, comprised of a solution of the complex Pt(bpym)Cl2 (bpym=eta2-{lcub}2,2'-bipyrimidyl{rcub}) in concentrated sulfuric acid, investigated in direct reactions as well as in microscopic reverse reactions of model intermediates.; Chapter Four describe the discovery of highly effective 6-membered transition state for activation benzene in weak acids such as trifluoroacetic acid and other organic acids by Pt(bpym)TFA2.; Chapter Five describes the discovery of new fast CH activation of benzene via conceptually proposed resting state destabilization phenomenon and experimentally supported by Pt(pic)TFA2 (pic-picolinate).; Chapter Six describes the discovery of CH4 CH activation at conditions unprecedented before. Conceptual model for transition state stabilization is discussed and experimentally supported by Pt(nap)TFA2 (nap - 2-(2-Pyridinyl)-1,8-naphthyridine).; Chapter Seven summarizes the above results and makes attempts to show future directions in CH activation.