Transition Metal Mediated Hydrolysis of C–S Bonds: An Overview of a New Reaction Strategy

Abstract

Desulfurization of organosulfur substrates is highly important due to its relation with the industrial hydrodesulfurization (HDS) process of fossil fuels, which helps to eliminate the sulfur-containing impurities such as thiols, sulfide, thiophenes, etc. from crude oil for the production of easily processed and more cleanly combusted fuel with very low sulfur content. While the HDS process involves a hydrogenolysis reaction under a high pressure of hydrogen gas at high temperature, the hydrolysis of C−S bonds of organosulfur substrates at ambient conditions may very well be considered as a potential alternative for model desulfurization reactions. However, unlike the availability of an appreciable number of reports on base, acid, and metal ion mediated hydrolysis of thioesters in the literature, reports on the hydrolysis of more difficult substrates such as thiolates, sulfides, and other organosulfur substrates remained unavailable until 2017. The very recent discovery of a transition metal mediated hydrolysis reaction of C−S bonds at ambient conditions, however, has rapidly filled in this gap within the past few years. Development of this new stoichiometric reaction allowed the desulfurization of a large number of organosulfur substrates, including aliphatic and aromatic thiols, thiocarboxylic acids, sulfides, disulfides, thiophenes, and dibenzothiophene, at ambient conditions and was subsequently converted to a catalytic process for the hydrolysis of thiols. A brief overview of this new reaction strategy, a proposed reaction mechanism, a critical analysis of the efficiency, and future prospects are presented.

Nonheme binuclear transition metal complexes with hydrosulfide and polychalcogenides

“…Subsequently, this Co( ii ) mediated hydrolytic C–S bond cleavage of a series of thiolates at room temperature was investigated in detail using Fe( ii ), Co( ii ), Ni( ii ) and Zn( ii ) in the presence of various binucleating ligands. 9 Based on the results of this detailed investigation, which included control experiments, isotope labeling study (H 2 18 O), and identification and isolation of crucial intermediates, a working mechanism for this first-row transition metal mediated hydrolysis of thiolates was proposed (Scheme 5). Selected features of this new reaction method are the following:…”

“…A detailed discussion on the development of this new reaction method, related mechanistic investigations and further development of a catalytic process for the conversion of thiolates to alcohols/phenols has appeared recently. 9…”

“…It may be noted that the stepwise development of the new synthetic method for the preparation of nonheme binuclear transition metal–hydrosulfido complexes, isolation of the related intermediates, and the proposed working mechanism for the reaction have recently been reviewed by us in detail 9 and thus these aspects have only been mentioned very briefly in the present article. The present feature article discusses the synthetic procedures, solution stability, structural properties, and reactivity of nonheme transition metal–hydrosulfido/–polychalcogenido complexes recently developed by us in the backdrop of various types of transition metal complexes containing sulfur/selenium-derived anions (HE − , E n 2− ; E = S, Se) available in the literature.…”

Chromium–Thiolate Complex Undergoing C–S Bond Cleavage

“…HDS is a crucial industrial catalytic process aimed at producing cleaner hydrocarbon products by eliminating organosulfur impurities from oil such as H 2 S. This process relies on a Mo-sulfide catalyst containing cobalt and operates under high pressure (160–600 psi of H 2 ) and high temperature (300–450 °C). − Developing a desulfurization pathway with reduced energy consumption becomes urgent in order to foster a sustainable industrial paradigm shift. In this context, exploring transition metal ions and their reactivity toward sulfur-based organic substrates emerges as an attractive research avenue to pursue …”