Abstract
The four compounds A(3)MO(4)H (A = Rb, Cs; M = Mo, W) are introduced as the first members of the new material class of the transition oxometalate hydrides. The compounds are accessible via a thermal synthesis route with carefully controlled conditions. Their crystal structures were solved by neutron diffraction of the deuterated analogues. Rb(3)MoO(4)D, Cs(3)MoO(4)D and Cs(3)WO(4)D crystallize in the antiperovskite-like K(3)SO(4)F-structure type, while Rb(3)WO(4)D adopts a different orthorhombic structure. (2)H MAS NMR, Raman spectroscopy and elemental analysis prove the abundance of hydride ions next to oxometalate ions and experimental findings are supported by quantum chemical calculations. The tetragonal phases are direct and wide band gap semiconductors arising from hydride states, whereas Rb(3)WO(4)H shows a unique, peculiar valence band structure dominated by hydride states.