Toward the synthesis of earth alkaline hydrazinidoborane

International audienceRecently, hydrazine borane (N2H4BH3) has beenconsidered for solid-state chemical hydrogen storage.Remarkably, it presents four protic hydrogen (Hδ+) intandem with three hydridic hydrogen (Hδ-). Therefore, ithas high gravimetric (15.4 wt%) and volumetric (146g.L-1) hydrogen-storage capacities. In the field, thechallenge has been to dehydrogenate hydrazine boraneto a large extent under mild conditions (i.e. < 85 °C andatmospheric pressure) while avoiding the formation ofhazardous by-product(s), which is essential for mobileand on-board application. However, it failed:temperatures higher than 1000c are required andunwanted gaseous/solid by-products form. To destabilize hydrazine borane, a chemical strategyhas been adopted. It implies mixing hydrazine boranewith lithium hydride [1], which leads to the formationof a derivative, namely lithium hydrazinidoboraneLiN2H3BH3 (hydrogen content 11.6 wt%). Our groupvery recently showed that this compound has twophases [2]: a low temperature one, transforming to ahigh-temperature one at around 90°C. In parallel,another hydrazinidoborane has been prepared bymechano-synthesis. It is sodium hydrazinidoboraneNaN2H3BH3 (hydrogen content of 8.85 wt%) [3]. Then,attempt for elaborating the potassium analog has beenunsuccessful because of the extremely high reactivity ofthe precursors (KH + N2H4BH3). As a next step, wehave envisaged synthesizing earth-alkaline (Mg, Ca)hydrazinidoboranes by mechano-synthesis, using CaH2and MgH2 as precursors. The EPDIC 2014 will be thusa great opportunity to present our last achievements on synthesis and characterization of these last derivativesof hydrazine borane. [1] H. Wu, W. Zhou, F. E. Pinkerton, T. J. Udovic, T. Yildirim, J. J.Rush, Energy Environ. Sci. 2012, 5, 7531.[2] R. Moury, U. B. Demirci, Y. Filinchuk, T. Ichikawa, K. Goshome,P. Miele, chem Matter, submitted[3] R. Moury, U. B. Demirci, T. Ichikawa, Y. Filinchuk, R. Chiriac, A.van der Lee, P. Miele, ChemSusChem, 2013, 6, 667