Synthesis and Characterization of Magnesium-Hydride Complexes with Alkylene-Bridged Bis(β-diketiminate) Ligands

Three magnesium-hydride complexes (3a–c) supported by alkylene-bridged bis(β-diketiminate) ligands have been synthesized by reacting the respective dinuclear magnesium bis(trimethylsilyl)amide complexes 1a–c with phenylsilane; 3a can alternatively be accessed by the same reaction but starting from the dinuclear magnesium n-butyl complex 2a. Single-crystal X-ray diffraction revealed a dimeric structure in the solid state, with inter- and intramolecular μ2-hydrides bridging the magnesium centers. The properties of the tetranuclear complexes are strongly impacted by the alkylene bridge. While 3b turned out to be virtually insoluble in common solvents, solutions of 3a and 3c are readily obtained, and NMR spectroscopic data indicate that the dimers persist in solution. 3a readily reacts with phenylacetylene, affording the tetranuclear magnesium complex 4a with bridging phenylacetylide groups.