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 MgCl 2 and solubilizing agents L, a dissolved form of magnesium hydride (MgH' 2 ) 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 MgH' 2 solutions are investigated as a function of the kind and the amount of solubilizing agents and catalysts. The optimized method for the preparation of MgH' 2 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 MgCl 2 ‐containing stoichiometric MgH 2 · QC model complexes are also prepared and characterized by IR spectra. Advantages and disadvantages of using MgH' 2 for synthetic purposes instead of catalytically prepared suspensions of magnesium hydride (MgH 2 ) are discussed.