Holger Elsen

Simple Access to the Heaviest Alkaline Earth Metal Hydride: A Strongly Reducing Hydrocarbon‐Soluble Barium Hydride Cluster

Reaction of Ba[N(SiMe3 )2 ]2 with PhSiH3 in toluene gave simple access to the unique Ba hydride cluster Ba7 H7 [N(SiMe3 )2 ]7 that can be described as a square pyramid spanned by five Ba2+ ions with two flanking BaH[N(SiMe3 )2 ] units. This heptanuclear cluster is well soluble in aromatic solvents, and the hydride 1 H NMR signals and coupling pattern suggests that the structure is stable in solution. At 95 °C, no coalescence of hydride signals is observed but the cluster slowly decomposes to undefined barium hydride species. The complex Ba7 H7 [N(SiMe3 )2 ]7 is a very strong reducing agent that already at room temperature reacts with Me3 SiCH=CH2 , norbornadiene, and ethylene. The highly reactive alkyl barium intermediates cannot be observed and deprotonate the (Me3 Si)2 N- ion, as confirmed by the crystal structure of Ba14 H12 [N(SiMe3 )2 ]12 [(Me3 Si)(Me2 SiCH2 )N]4 .

Self-Assembly of Magnesium Hydride Clusters Driven by Chameleon-Type Ligands

While magnesium hydride complexes are generally stabilized by hard, bulky N-donor ligands, softer ligands with a broad variety of coordination modes are shown to efficiently adapt themselves to the large variety of Mg2+ centers in a growing magnesium hydride cluster. A P,N-chelating ligand is introduced that displays coordination modes between that of enamide, aza-allyl, and phosphinomethanide. Slight changes in the ligand bite angle have dramatic consequences for the structure type. The hitherto largest neutral magnesium hydride clusters are isolated either in a nonanuclear sheet-structure (brucite-type) or a dodecanuclear ring structure.