Stabilization by hydrogen. Synthetic and structural studies of the Zintl phase Ba5Ga6H2

Synthesis of the phase formerly reported as Ba5Ga6 succeeds only in the presence of hydrogen. The heavy atom structure of Ba5Ga6H2 has been redetermined by single-crystal X-ray diffraction (trigonal P3cl, Z = 2, a = 7.7698(2) Angstrom, c = 14.3902(7) Angstrom), and the hydrogen positions have been elucidated by time-of-flight neutron powder diffraction, The unit cell contains isolated slightly distorted octahedra Ga-6(8-) with barium cations over all edges. Hydride is bound in two types of barium tetrahedra [d(Ba-H) = 2.61-2.62 Angstrom]. The stoichiometry is appropriate for a Zintl phase: (Ba2+)(5)Ga-6(8-)(H-)2.