Crystal Structure of Na₂Mg₂NiH₆ Revisited

The crystal structure of Na2Mg2NiH6 as published by Kadir and Noréus (Inorg. Chem. 2007, 46, 2220−2223) is revised. While the reported space group symmetry and cell parameters are correct, the Mg and hydride positions need to be interchanged. Consequently, the tetrahedral [NiH4]4− complexes are stabilized by both Na+ and Mg2+ ions and not by Na+ ions only, as was stated by the authors. The metal−hydrogen bond distances of the revised structure model differ by up to 0.6 Å from those reported and are more in line with those usually observed in these sorts of hydrides. An overview of the known cation configurations around solid-state [NiH4]4- complexes is given.