Project

Hydrogen, Activation, ; Homogeneous catalysis, Hydrogenation, ; Metal-free Hydrogenation, ; Transition metal catalyst; Ionic Hydrogenation; Transfer Hydrogenation

Lead
Lay summary
LeadIn a binational Swiss-German cooperation this project addresses fundamental aspects of hydrogen chemistry and developments emphasizing the timely aspects of “metal-free” and “ionic hydrogenation” catalyses proceeding with heterolytic splitting of the H-H bond.Hydrogen chemistry has recently gained importance in conjunction with its potential role as a “clean” energy carrier and its connection to chemical hydrogen storage. A conceptually new, basic research approach to hydrogen chemistry was chosen to solve the remaining chemical enigma of hydrogen transformations. For decades hydrogen research focused mainly on developments of Wilkinson transition metal catalyses with the characteristics of a homolytic splitting of H2. Major drawbacks of this chemistry were the use of noble metal catalysts and the preference for reactions with unpolar unsaturated molecules. These drawbacks are thought to be overcome by utilization of recently emerged aspects of hydrogenations splitting H2 by heterolysis, which are cumulatively denoted as “ionic hydrogenations” and are transition metal or main group element “metal-free” catalyzed. Polar transfer hydrogenations, operating on the basis of a simultaneously occurring double H transfers, are also studied in this project.A comprehensive fundamental approach to hydrogen chemistry is sought consisting of developments for “ionic hydrogenations” and polar transfer hydrogenations, preferably in catalytic form with emphasis on “metal-free” catalysis or very efficient noble metal catalysis. A broad search for new hydrogen related catalyses builds the chemical platform for this Swiss-German cooperation.In conjunction with the vision of dihydrogen as a “clean” future energy carrier and the involvement of dihydrogen reactivity in chemical hydrogen storage materials, this bi-national collaborative project attains considerable socialrelevance. The project would like to contribute to an ultimate profound understanding of dihydrogen chemistry exploring the missing facets of polar and “metal-free” hydrogen and hydrogen related catalyses. Respective new insights are thought to lay the grounds for future chemical developments in hydrogen technology.

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Last update: 21.02.2013

Number	Title	Start	Funding scheme

A binational Swiss-German cooperation project on dihydrogen (H2) chemistry has been set up.Dihydrogen chemistry has recently gained major importance in conjunction with the advent of hydrogen technology and its potential application as a future energy carrier. The development of hydrogen technology requires the use of sophisticated hydrogen chemistry. However, various aspects of hydrogen chemistry related to technology remained to be addressed such as a comprehensive fundamental picture of hydrogen reactivity and developments to circumvent as much as possible noble metal chemistry.A conceptually new, basic research approach to hydrogen chemistry has been chosen to solve the remaining chemical problems of chemical transformations, which comprise processes involving hydrogenations /dehydrogenations and transfer hydrogenations occurring as 1,2-additions/1,2-eliminations or type II dyotropic rearrangements. Under ambient conditions proper hydrogen reactivity requires support from mediating reaction centres, which normally turn out to be catalytic reaction centres showing repetitive turnovers of the molecules. For decades related research focussed on developments of Wilkinson type transition metal catalyses with the characteristics of oxidative addition of H2 to the transition metal centres steps occurring with its formal homolytic splitting. Major drawbacks of this chemistry are however the quite limiting conditions of a “must” to use noble metal catalysts and the strong preference of Wilkinson type catalysts for reactions with mostly relatively unpolar or less polar unsaturated molecules. These drawbacks are envisaged to be overcome by further developments and utilizations of recently emerged aspects of hydrogenation/dehydrogenation and transfer hydrogenation catalysts splitting the H2 molecule formally in a heterolytic fashion. Hydrogenations using heterolytic splitting of H2 are cumulatively denoted as “ionic hydrogenations” and are to the main part also transition metal catalyzed. Only very recently a new type of heterolytic H2 splitting was discovered with main group element compounds and respective “ionic hydrogenation” chemistry was also found to exist. It is denoted as “metal-free”. Transfer hydrogenations are also related to “ionic hydrogenations“ operating on the basis of simultaneously occurring double H transfers, but do not involve hydrogen directly. The catalytic potential of these transfer hydrogenations has yet not fully been exploited. In summary this means that comprehensive chemical developments for “ionic hydrogenations” and transfer hydrogenations are lacking and were therefore taken as targets of this project. A broad search for new hydrogenation catalyses builds the chemical platform for cooperation within this project.Taking advantage of synergistic effects and mutual stimulations the Swiss-German cooperation consists of up with five organometallic chemistry groups, one physical chemistry group and one theoretical group, which set out to study the above listed fundamental aspects of hydrogenation chemistry together with their possible utilizations in form of efficient catalyses. Two groups (Erker, Pfaltz) of the team will get fully involved in the exploration and exploitation of a “metal-free” H2 chemistry using main group elements or organic heteropolar hydrogen splitting systems; two other groups will get partly involved in “metal-free” hydrogen chemistry (Berke, Rieger). Three groups participate in the team in a related “metal-containing” H2 chemistry utilizing transition metal centres (Berke, Grützmacher, Rieger). One group will attempt to trace new intermediates of hydrogen chemistry by sophisticated spectroscopies low-temperature matrices (Sander). Another group will lay the foundation for exact electronic views of the molecules and chemical transformations appearing in this project by application of accurate theoretical calculations (Grimme).Coherent research strategies and unifying views of hydrogen chemistry are the basis for proper concepts within this project. Comprehensiveness in the coverage is combined with academic depth in the explorations of the various chemical aspects. Besides these fundamental chemical aspects, a high degree of sophistication is sought to be invested in the application of sophisticated analytical tools.