Synthesis, Crystal Structures, and Hydrogen-Storage Properties of Eu(AlH4)2 and Sr(AlH4)2 and of Their Decomposition Intermediates, EuAlH5 and SrAlH5

Complex Eu(AlH(4))(2) and Sr(AlH(4))(2) hydrides have been prepared by a mechanochemical metathesis reaction from NaAlH(4) and europium or strontium chlorides. The crystal structures were solved from powder X-ray diffraction data in combination with solid-state (27)Al NMR spectroscopy. The thermolysis pathway was analyzed in detail, allowing identification of new intermediate EuAlH(5)/SrAlH(5) compounds. Rehydrogenation experiments indicate that the second decomposition step is reversible.