Syntheses and Crystal Structures of a New Niobium Polysulfide K6Nb4S22 and two New Dimorphic Tantalum Polysulfides K6Ta4S22

Abstract

The new compounds K 6 Nb 4 S 22 and K 6 Ta 4 S 22 (I) have been synthesised by the reaction of NbS 2 or Ta metal in a K 2 S 3 flux. Using TaS 2 as educt a second modification of K 6 Ta 4 S 22 (II) is obtained. K 6 Nb 4 S 22 and K 6 Ta 4 S 22 (form I) crystallise in the monoclinic space group C2/c with a ϭ 35.634 (2) Å , b ϭ 7.8448 (4) Å , c ϭ 12.1505 (5) Å , β ϭ 100.853 (5)°, V ϭ 3335.8 (3) Å 3 , and Z ϭ 4 for K 6 Nb 4 S 22 and a ϭ 35.563 (7) Å , b ϭ 7.836 (2) Å , c ϭ 12.139 (2) Å , β ϭ 100.56 (3)°, V ϭ 3325.5 (2) Å 3 , and Z ϭ 4 for K 6 Ta 4 S 22 (I). The second modification K 6 Ta 4 S 22 (form II) crystallises in the monoclinic space group P2 1 /c with a ϭ 7.5835 (6) Å , b ϭ 8.7115 (5) Å , c ϭ 24.421 (2) Å , β ϭ 98.733 (9)°, V ϭ 1594.6 (2) Å 3 , and Z ϭ 2. The structures consist of [M 4 S 22 ] 6Ϫ anions composed of two M 2 S 11 sub-units which are linked into M 4 S 22 units via terminal sulfur ligands. The anions are well separated by the

Synthesis, crystal structure and properties of K2Ta2S10: A novel ternary tantalum polysulfide with TaS8 polyhedra forming infinite anionic chains

“…The Ta-S distances range from 2.463(1) to 2.639(1) Å with an average /Ta-SS of 2.527(1) Å for Ta(1) and from 2.455(1) to 2.654(1) Å (average /Ta-SS: 2.526(1) Å ) for Ta(2) ( Table 3). These distances are in good agreement with the values reported for other potassium tantalum sulfides [13,14,16] and the sum of ionic radii of Ta and S as well [27].…”

“…Depending on the reaction conditions and size of the cations, structures with discrete molecular anions [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] or chains [21][22][23][24] are formed. In the case of tantalum, examples include discrete tetrahedral TaQ 4 units like in A 3 TaQ 4 (A ¼ K, Rb, Cs, Q ¼ S, Se) [6][7][8], Ta 2 S 11 groups like in A 4 Ta 2 S 11 (A ¼ K, Rb, Cs) [13][14][15], complex Ta 4 S 22 units like in A 6 Ta 4 S 22 (A ¼ K, Rb, Cs) [16,18,19], and Ta 4 S 25 like in Rb 6 Ta 4 S 25 units [20]. The Ta 2 S 11 unit is composed of two face sharing TaS 7 pentagonal bipyramids and is a building block which may be interconnected through S 2 2À and S 5 2À polyanions yielding the Ta 4 S 22 and Ta 4 S 25 unit.…”

Rb6Nb4S24.4O0.6

“…The Nb-Nb distance amounts to 3.574 (2) Å which is too long for any metal-to-metal interaction [radius: 0.69 Å for Nb 5+ (CN7)] (Shannon, 1976). All values agree well with those reported for Rb 6 Ta 4 S 25 (Stoll et al, 2000) and A 6 Nb 4 S 22 (A = K, Rb, Cs; Bensch & Dürichen, 1996b;Stoll et al, 2002). The three crystallographically independent rubidium cations are in an irregular sulfur environment.…”

In situ studies of a platform for metastable inorganic crystal growth and materials discovery

“…The flux can be nonreactive or reactive; in the latter case the flux itself becomes incorporated into the product (7,8). This wellestablished approach has demonstrated the prolific discovery of novel inorganic materials grown out of low-melting fluxes, from oxides and other chalcogenides (9)(10)(11)(12), to pnictides (13,14), to intermetallics (15), many of which cannot be attained by direct combinations of the elements. Despite the variety of metastable phases formed in these reactions, the classical approach is to predetermine a given set of reaction conditions (e.g., time, temperature, and heating and cooling rates) and wait for completion to isolate and identify the formed compounds.…”