Chemistry
Proton-Initiated Cobalt-Catalyzed Hydrogenation of Alkenes
Document Type
Oral Presentation
Location
Indianapolis, IN
Subject Area
Chemistry
Start Date
13-4-2018 9:15 AM
End Date
13-4-2018 10:15 AM
Sponsor
Donald Linn (Indiana University-Purdue University Fort Wayne)
Description
The hydrogen-rich cobalt dimer was found to be an effective catalyst for the hydrogenation of alkenes. Here we report a bimetallic system that boasts efficiencies comparable to the most active platinum metal-based based homogeneous catalysts. The catalyst performs more than 5000 turnover numbers in alkene at moderate pressure (4 bar) and room temperature with no evidence of deactivation.
Unexpectedly these reactions in tetrahydrofuran (THF) were initially found to be independent of the initial cobalt complex concentration. Subsequently, it was surmised that the residual moisture content in the THF (4-40 ppm), depending on the drying agent, was responsible for this observation. Titration of the [Co2H9]5- resulted in the quantitative evolution of hydrogen. Consequently, titration of the cobalt dimer with precisely one equivalent of phenol in THF solution was required to provide the maximum turnover frequency in catalytic alkene hydrogenation. This is attributed to a rapid reaction between a proton from phenol and the basic dimer to produce the active catalyst species, [CoH3]2-. NMR spectroscopic measurements and ab initio computations by collaborators give further evidence pointing to intermediates that contain one or more alkene units which react with H2 readily in solution to produce alkane and regenerate the putative [CoH3]2- species.
Proton-Initiated Cobalt-Catalyzed Hydrogenation of Alkenes
Indianapolis, IN
The hydrogen-rich cobalt dimer was found to be an effective catalyst for the hydrogenation of alkenes. Here we report a bimetallic system that boasts efficiencies comparable to the most active platinum metal-based based homogeneous catalysts. The catalyst performs more than 5000 turnover numbers in alkene at moderate pressure (4 bar) and room temperature with no evidence of deactivation.
Unexpectedly these reactions in tetrahydrofuran (THF) were initially found to be independent of the initial cobalt complex concentration. Subsequently, it was surmised that the residual moisture content in the THF (4-40 ppm), depending on the drying agent, was responsible for this observation. Titration of the [Co2H9]5- resulted in the quantitative evolution of hydrogen. Consequently, titration of the cobalt dimer with precisely one equivalent of phenol in THF solution was required to provide the maximum turnover frequency in catalytic alkene hydrogenation. This is attributed to a rapid reaction between a proton from phenol and the basic dimer to produce the active catalyst species, [CoH3]2-. NMR spectroscopic measurements and ab initio computations by collaborators give further evidence pointing to intermediates that contain one or more alkene units which react with H2 readily in solution to produce alkane and regenerate the putative [CoH3]2- species.