Li 9Nd 2[PS 4] 5: A new lithium lanthanoid(III) thiophosphate(V)

Abstract

The new ortho-thiophosphate Li 9Nd 2[PS 4] 5 crystallizes monoclinically in the space group C2/ c (no. 15) with a = 1502.64(6), b = 989.31(4), c = 2083.37(9) pm, β = 95.913(4)° ( Z = 4) at room temperature. It can be obtained by the reaction of stoichiometric mixtures of the elements (neodymium, sulfur, red phosphorus) with lithium sulfide (Li 2S) in torch-sealed, evacuated silica ampoules at 950 °C within 8 days. The crystal structure contains only a single crystallographically independent Nd 3+ cation which is eight-fold coordinated by sulfur atoms arranged as bicapped trigonal prism ( d(Nd–S) = 290–295 pm). Together with the three crystallographically different [PS 4] 3− anions the Nd 3+ cations build up a layer of the composition 2 ∞ { ( Nd [ P S 4 ] 3 ) 9 − } which spreads parallel to (0 0 1). Thereby four isolated [PS 4] 3− tetrahedra ( d(P–S) = 202–206 pm, ∢(S–P–S) = 105–115°) are all edge-attached to the Nd 3+ cations. The five crystallographically distinct Li + cations reside inside and between these layers and are coordinated by four, five or six sulfur atoms. Two different sets of Li + cations at a time occupy channels along [0 1 0] and [0 0 1], respectively, providing possible lithium conductivity.