Tetrahydrofuran‐Soluble Magnesium Dihydride by Catalytic Hydrogenation of Magnesium^*)

Abstract

Magnesium hydride -quinuclidine complexes Upon hydrogenation of magnesium in THF using homogeneous magnesium-anthracene transition-metal halide catalysts in the presence of small amounts of MgCll and solubilizing agents L, a dissolved form of magnesium hydride (MgHi) is produced. The preferred L's are quinuclidine (QC) or organomagnesium compounds; however, organoaluminium and -boron compounds can also be used. The

Solid-State Hydriding Mechanism in the LiBH4 + MgH2 System

“…It is noted that the FTIR analysis also supports the formation of crystalline MgH 2 during the hydrogenation process. As shown in Figure , the characteristic absorbance of crystalline MgH 2 ranging from 1300−900 cm −1 (due to the Mg−H stretching mode) appears after hydrogenation, supporting the conclusion of forming crystalline MgH 2 during hydrogenation derived from the NMR (Figure ) and XRD analyses (Figure ). The formation of crystalline MgH 2 in the hydriding process is likely due to the high isothermal holding temperature (265 °C), whereas the formation of amorphous MgH 2 during ball milling is attributed to continuous deformation and fracturing that prevents the formation of appreciable sizes of MgH 2 crystals.…”

Hydrides of the Main-Group Metals: New Variations on an Old Theme

“…Nevertheless, basic mediasand particularly ethers such as thf and Et 2 Osare the rule for synthetic operations with the main-group metal hydrides at ambient temperatures. These are certainly the normal conditions for working with alane, AlH 3 , 154 and its derivatives, 154,155 magnesium hydrides, 15,156 zinc hydrides, 15,157 and, most recently, the indium hydride HInCl 2 which is reported to be quite stable in thf solution at ambient temperatures. 158 On the other hand, as the metal becomes increasingly electron-rich, controlled protonation in an acidic medium may be realized.…”

“…Direct synthesis from the elements is readily achieved for the binary hydrides of the group 1 and heavier group 2 metals; in appropriate (high pressure) circumstances access can also be gained in this way to BeH 2 ,185a MgH 2 , ,, and AlH 3 , i.e., the only other hydrides which are thermodynamically stable with respect to the elements under anything approaching standard conditions. Elemental hydrogen under pressure is a primary reagent too in the synthesis of certain ternary hydrides, e.g., MMgH 4 (M = Sr 164a or Ba 164b ), Ba 6 Mg 7 H 26 , K 2 ZnH 4 , K 3 [ZnH 4 ]H, and SrND …”

Gas phase models of hydride transfer from divalent alkaline earth metals to CO2 and CH2O

“…Since this process is reversible, magnesium hydrides are promising lightweight hydrogen storage materials. 2,3 Mechanically or chemically activated MgH 2 has also been suggested as a potential anode material for use in Li-ion batteries due to their good hydride transfer properties. 4,5 While MgH 2 itself is poorly soluble in organic solvents, derivatives of the type HMgX (X = NR 2 , OR, halide, Cp, N-heterocyclic carbenes)-in analogy with the closely related Grignard reagent-often exist in the form of dimers or higher oligomers in such solvents.…”

“…4,5 While MgH 2 itself is poorly soluble in organic solvents, derivatives of the type HMgX (X = NR 2 , OR, halide, Cp, N-heterocyclic carbenes)-in analogy with the closely related Grignard reagent-often exist in the form of dimers or higher oligomers in such solvents. 6 These derivatives are effective and selective reducing agents, in particular towards the carbonyl group, 2,[7][8][9] but also towards the CO 2 molecule. [10][11][12] A b-diketiminato magnesium hydride has even been demonstrated to reductively couple two CO molecules, giving an ene-diolate complex as product.…”