Trigonal Ba7Cu3H17 containing tetrahedral [Cu(I)H-4](3-) anions

Ba7Cu3H17 and its deuteride were prepared by hydrogenation (deuteration) of barium-copper alloys at room temperature under a pressure of up to 10 bar, followed by annealing at 370 degrees C at a pressure of up to 160 bar. X-ray and neutron powder diffraction at room temperature indicate trigonal symmetry (space group P31c, Z = 2), cell parameters a = 11.7766(6), c = 7.4616(4) Angstrom (hydride) and a = 11.7633(1), c = 7.4495(1) Angstrom (deuteride). The structure contains tetrahedral 18-electron [CuD4](3-) complex anions with Cu-D bond lengths in the range 1.64(2)-1.78(2) Angstrom, and three symmetry independent tetrahedrally coordinated D- anions with Ba-D bond lengths in the range 2.59(3)-2.92(3) Angstrom.