Europium palladium hydrides

The first fully structurally characterized ternary europium palladium hydri des (deuterides) sire reported. The most Eu rich compound is Eu2PdD4. Its b eta -K2SO4 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 [PdD4](4-) complex anions and divalent Eu cations. The compound is presumably nonmetal lic and shows paramagnetic behavior (mu (eff) = 8.0(2) mu (B)) with ferroma gnetic ordering at T-C = 15.1(4) K. A metallic compound at intermediate Eu content is EuPdD3. It crystallizes with the cubic perovskite structure (spa ce group Pm (3) over barm, a = 380.01(2) pm, Z = 1) in which palladium is o ctahedrally surrounded by fully occupied deuterium sites, Metallic hydrides at low Eu content form by reversible hydrogen absorption of intermetallic EuPd2 (Fd (3) over barm, a = 775.91(1) pm, Z = 8). Depending on the experim ental conditions at least three phases with distinctly different hydrogen c ontents x exist: EuPd2Hx approximate to0.1 (a = 777.02(2) pm, Z = 8, T = 29 8 K, p(H-2) = 590 kPa), EuPd2Hx approximate to1.5 (a = 794.47(5) pm, Z = 8, T = 298 K, p(H-2) = 590 kPa), and EuPd2Hx approximate to2.1 (a = 802.1(1) pm, Z = 8, T = 350 K, P(H-2) = 610 kPa). All crystallize with cubic Laves p hase derivative structures and have presumably disordered hydrogen distribu tions.