Discrete Magnesium Hydride Aggregates: A Cationic Mg13H18 Cluster Stabilized by NNNN-Type Macrocycles.

Large magnesium hydride aggregates [Mg₁₃(Me₃TACD)₆(μ₂-H₁₂)(μ₃-H₆)][A]₂ ((Me₃TACD)H=1,4,7-trimethyl-1,4,7,10-tetraazacyclododecane; A=AlEt₄, Al nBu₄, B{3,5-(CF₃)₂C₆H₃}₄) were synthesized stepwise from alkyl complexes [Mg₂(Me₃TACD)R₃] (R=Et, nBu) and phenylsilane in the presence of additional Mg^II ions. The central magnesium atom is octahedrally coordinated by six hydrides as in solid α-MgH₂ of the rutile type. Further coordination to six magnesium atoms leads to a substructure of seven edge-sharing octahedra as found in the hexagonal layer of brucite (Mg(OH)₂). Upon protonolysis in the presence of 1,2-dimethoxyethane (DME), this cluster was degraded into a tetranuclear dication [Mg₂(Me₃TACD)(μ-H)₂(DME)]₂[A]₂. [ABSTRACT FROM AUTHOR]