Synthesis and characterization of ternary alkaline-earth transition-metal hydrides containing octahedral [Ru(II)H6]4− and [Os(II)H6]4− complexes

Mg2RuH6, Ba2RuH6, Ca2OsH6, Sr2OsH6, and Ba2OsH6 with the K2PtCl6-type structure have been synthesized. Solid state IR spectroscopy applied to these and other, already known, ternary hydrides from the iron triad shows MH stretching frequencies in the 1500–1850 cm−1 energy range, which are correlated with the size of the cube of counterions surrounding the complexes. Lower frequencies are found with larger counterions. The ν(MH) value increases on going from iron to osmium, indicating that H− ions are well capable of stabilizing divalent osmium, which so far has been found exclusively with good electron-accepting ligands.