Decomposition of Formic Acid Catalyzed by a Phosphine‐Free Ruthenium Complex in a Task‐Specific Ionic Liquid

Abstract

The dehydrogenation of formic acid is effectively catalyzed by the Ru complex [{RuCl2(p‐cymene)}2] dissolved in the ionic liquid (IL) 1‐(2‐(diethylamino)ethyl)‐3‐methylimidazolium chloride at 80 °C without additional bases. This catalytic system gives TOF values of up to 1540 h−1. Preliminary kinetic insights show formal reaction orders of 0.70(±0.15), 0.78(±0.03) and 2.00(±0.17) for the Ru catalyst, IL 1, and formic acid, respectively. The apparent activation energy of this process is estimated to be (69.1±7.6) kJ mol−1. In addition, dimeric Ru hydride ionic species involved in the reaction, such as [{Ru(p‐cymene)}2{(H)μ‐(H)‐μ‐(HCO2)}]+ and [{Ru(p‐cymene)}2{(H)μ‐(Cl)μ‐(HCO2)}]+, are identified by mass spectrometry. The presence of water in large amounts inhibits higher conversions. Finally, a remarkable catalytic activity is observed during recycles, indicating this system’s potential for hydrogen gas production.

Selective and mild hydrogen production using water and formaldehyde

“…Therefore, one alternative is chemical hydrogen storage in molecular materials in which the dihydrogen is stored in the form of hydridic and protic hydrogen. Examples are metal hydrides [4][5][6] , ammonia borane derivatives 2,3,7 , formic acid 2,[8][9][10][11][12][13][14][15][16][17] and methanol [18][19][20][21] . Ammonia borane derivatives have a good weight efficiency (r19.4 wt% H 2 ) 2,3,7 , but the solid spentfuels are hardly recyclable.…”

Hydrogen storage in amine boranes: Ionic liquid supported thermal dehydrogenation of ethylene diamine bisborane

“…To confirm the purity of the released hydrogen we investigated the evolved gas via mass spectrometry of representative samples, which has been applied before [4]. In case of the tested [OAc] À ILs CO 2 and in all experiments diborane (B 2 H 6 ) and ammonia (NH 3 ) are possible co-products.…”

Application of Ionic Liquids in Hydrogen Storage Systems

“…(Boddien et al, 2011;Enthaler et al, 2010;Johnson et al, 2010;Scholten et al, 2010;Tedsree et al, 2011;Yasaka et al, 2010;Zhao et al, 2011) Figure 5. Reversible splitting of formic acid.…”

“…Structure of amino-functionalized IL 1. Scholten et al, 2010) While the Dupont group reported only about the application of the chloride IL 1, the Shigroup used various anions, i.e. BF4 -, OTf -, NTf2 -and HCOO -.…”

“…The application of ammonia borane and its derivatives for hydrogen storage is matter of research in the last decade as well as a compound as simple as formic acid, which is in this sense the hydrogenationproduct of carbon dioxide. (Fellay et al, 2008;Loges et al, 2008;Scholten et al, 2010;Stephens et al, 2007) The application of ammonia borane itself is more efficient than elemental hydrogen, but nevertheless accompanied by some problems as well. Since there is a worldwide infrastructure suitable for the deployment of liquid fuels, a solid fuel bears certain disadvantages competing with a liquid fuel.…”