Synthesis and structural characterization of quaternary thorium selenophosphates: A(2)ThP(3)Se(9) (A = K, Rb) and Cs4Th2P5Se17

Single crystals of A(2)ThP(3)Se(9) (A = K (I), Rb (II)) and Cs(4)Th(2)PsSe( 17) (III) form from the reaction of Th and P in a molten A(2)Se(3)/Se (A K, Rb, Cs) flux at 750 degrees C for 100 h. Compound II crystallizes in the t riclinic space group P (1) over bar (No. 2) with unit cell parameters a = 1 0.4582(5) Angstrom, b = 16.5384(8) Angstrom, c = 10.2245(5) Angstrom, alpha = 107.637(1); beta = 91.652(1); gamma = 90.343(1)degrees, and Z = 2. Compo und II crystallizes in the triclinic space group P (1) over bar (No. 2) wit h the unit cell parameters a = 10.5369(5) Angstrom, b = 16.6914(8) Angstrom , 10.2864(5) Angstrom, alpha = 107.614(1)degrees, beta = 92.059(1)degrees, gamma = 90.409(1)degrees and Z = 2. These structures consist of infinite ch ains of corner-sharing [Th2Se14] units linked by (P2Se6)(4-) anions in two directions to form a ribbonlike structure along the [100] direction. Compou nds I and II are isostructural with the previously reported K2UP3Se9. Compo und III crystallizes in the monoclinic space group P2(1)/c (No. 14) with un it cell parameters a = 10.238(1) Angstrom, b = 32.182(2) Angstrom, c = 10.7 49(2) Angstrom; beta = 95.832(1)degrees and Z = 4. Cs4Th2P5Se17 consists of infinite chains of corner-sharing, polyhedral [Th2Se13] units that are als o linked by (P2Se6)(4-) anions in the [100] and [010] directions to form a layered structure. The structure of LII features an (Se-2)(2-) anion that i s bound eta(2) to Th(2) and eta(1) to Th(1). This anion influences the coor dination sphere of the 9-coordinate Th(2) atom such that it is best describ ed as bicapped trigonal prismatic where the eta(2)-bound anion occupies one coordination site. The composition of III may be formulated as Cs4Th2(P2Se 6)(5/2)(Se-2) due to the presence of the (Se-2)(2-) unit. Raman spectra for these compounds and their interpretation are reported.