Discrete Magnesium Hydride Aggregates: A Cationic Mg 13 H 18 Cluster Stabilized by NNNN‐Type Macrocycles

Large magnesium hydride aggregates [Mg 13 (Me 3 TACD) 6 (μ 2 ‐H 12 )(μ 3 ‐H 6 )][A] 2 ((Me 3 TACD)H=1,4,7‐trimethyl‐1,4,7,10‐tetraazacyclododecane; A=AlEt 4 , Al n Bu 4 , B{3,5‐(CF 3 ) 2 C 6 H 3 } 4 ) were synthesized stepwise from alkyl complexes [Mg 2 (Me 3 TACD)R 3 ] (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‐MgH 2 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 [Mg 2 (Me 3 TACD)(μ‐H) 2 (DME)] 2 [A] 2 .