Europium palladium hydrides.

The first fully structurally characterized ternary europium palladium hydrides (deuterides) are reported. The most Eu rich compound is Eu(2)PdD(4). Its beta-K(2)SO(4) type structure (space group Pnma, a = 749.47(1) pm, b = 543.34(1) pm, c = 947.91(1) pm, Z = 4) contains tetrahedral 18-electron [PdD(4)](4)(-) complex anions and divalent Eu cations. The compound is presumably nonmetallic and shows paramagnetic behavior (mu(eff) = 8.0(2) mu(B)) with ferromagnetic ordering at T(C) = 15.1(4) K. A metallic compound at intermediate Eu content is EuPdD(3). It crystallizes with the cubic perovskite structure (space group Pm3m, a = 380.01(2) pm, Z = 1) in which palladium is octahedrally surrounded by fully occupied deuterium sites. Metallic hydrides at low Eu content form by reversible hydrogen absorption of intermetallic EuPd(2) (Fd3m, a = 775.91(1) pm, Z = 8). Depending on the experimental conditions at least three phases with distinctly different hydrogen contents x exist: EuPd(2)H(x) ( approximately )(0.1) (a = 777.02(2) pm, Z = 8, T = 298 K, p(H(2)) = 590 kPa), EuPd(2)H(x) ( approximately )(1.5) (a = 794.47(5) pm, Z = 8, T = 298 K, p(H(2)) = 590 kPa), and EuPd(2)H(x) ( approximately )(2.1) (a = 802.1(1) pm, Z = 8, T = 350 K, p(H(2)) = 610 kPa). All crystallize with cubic Laves phase derivative structures and have presumably disordered hydrogen distributions.