TETRAHYDROFURAN-SOLUBLE MAGNESIUM DIHYDRIDE BY CATALYTIC-HYDROGENATION OF MAGNESIUM

Upon hydrogenation of magnesium in THF using homogeneous magnesium-anthracene transition-metal halide catalysts in the presence of small amounts of MgCl2 and solubilizing agents L, a dissolved form of magnesium hydride (MgH2') is produced. The preferred L's are quinuclidine (QC) or organomagnesium compounds; however, organoaluminium and -boron compounds can also be used. The fraction n of magnesium hydride produced in the dissolved form and the stability of the MgH2' solutions are investigated as a function of the kind and the amount of solubilizing agents and catalysts. The optimized method for the preparation of MgH2' is described. The magnesium hydride dissolved in THF is characterized by IR spectroscopy. In order to elucidate the role of the solubilizing agents, THF-soluble MgCl2-containing stoichiometric MgH2 . QC model complexes are also prepared and characterized by IR spectra. Advantages and disadvantages of using MgH2' for synthetic purposes instead of catalytically prepared suspensions of magnesium hydride (MgH2*) are discussed.