Abstract
Black crystals of Np(PS4), Np(P2S6)2, K11Np7(PS4)13,
and Rb11Np7(PS4)13 have been synthesized by the reactions of Np,
P2S5, and S at 1173 and 973 K; Np, K2S, P, and S at 773 K; and Np,
Rb2S3, P, and S at 823 K, respectively. The structures of these
compounds have been characterized by single-crystal X-ray diffraction
methods. Np(PS4) adopts a three-dimensional structure with Np
atoms coordinated to eight S atoms from four bidentate PS4
3 ligands
in a distorted square antiprismatic arrangement. Np(PS4) is isostructural
to Ln(PS4) (Ln = LaNd, Sm, GdEr). The structure of
Np(P2S6)2 is constructed from three interpenetrating diamondtype
frameworks with Np atoms coordinated to eight S atoms from
four bidentate P2S6
2 ligands in a distorted square antiprismatic
geometry. The centrosymmetric P2S6
2 anion comprises two PS2
groups connected by two bridging S centers. Np(P2S6)2 is isostructural to U(P2S6)2. A11Np7(PS4)13 (A = K, Rb) adopts a threedimensional
channel structure built from interlocking [Np7(PS4)13]11-screw helices with A cations residing in the channels. The
structure of A11Np7(PS4)13 includes four crystallographically independent Np atoms. Three are connected to eight S atoms in
bicapped trigonal prisms. The other Np atom is connected to nine S atoms in a tricapped trigonal prism. A11Np7(PS4)13 is
isostructural to A11U7(PS4)13. From NpS bond distances and charge-balance, we infer that Np is trivalent in Np(PS4) and
tetravalent in Np(P2S6)2 and A11Np7(PS4)13.Np exhibits a behavior intermediate betweenUand Pu in its thiophosphate chemistry.