Li₉Yb₂[PS₄]₅ and Li₆Yb₃[PS₄]₅: two lithium-containing ytterbium(III) thiophosphates(V) revisited

Abstract

The lithium ytterbium ortho-thiophosphates Li9Yb2[PS4]5 and Li6Yb3[PS4]5 were prepared through the reaction of stoichiometric amounts of ytterbium metal, elemental sulfur, red phosphorus and lithium hemisulfide at elevated temperatures in sealed silica tubes. The compounds occur as dark red single crystals which crystallize monoclinically in space group C2/c with the lattice parameters a = 1487.98(9), b = 978.63(6), c = 2046.75(12) pm and β = 96.142(3)° for Li9Yb2[PS4]5 (Z = 4) and a = 2814.83(16), b = 997.34(6), c = 3338.52(19) pm and β = 113.685(3)° for Li6Yb3[PS4]5 (Z = 12). Li9Yb2[PS4]5 can be assigned to the structure type of Li9Nd2[PS4]5, whereas the structure of Li6Yb3[PS4]5 the structure is similar to that of the prototypic Li6Gd3[PS4]5. Both structures feature discrete [PS4]3– tetrahedra (d(P–S) = 202–207 pm) and strands of [YbS8]13− polyhedra (d(Yb–S) = 271–319 pm) propagating along [010]. When attributed to the general formula (Li3[PS4]) x (Yb[PS4]) y , ideas of the dimensionality of both structures can be derived. Whilst the lithium-richer Li9Yb2[PS4]5 (x/y = 1.5) develops planes with the composition ∞ 2 { [ Y b [ P S 4 ] 3 ] 6 − } ${}_{\infty }^{2}\left\{{\left[\mathrm{Y}\mathrm{b}{\left[\mathrm{P}{\mathrm{S}}_{4}\right]}_{3}\right]}^{6-}\right\}$ , Li6Yb3[PS4]5 (x/y = 0.667) exhibits a rather complex three-dimensional network of ytterbium-centered polyhedra connected via [PS4]3– tetrahedra with lithium cations in the framework structure ∞ 3 { [ Y b 3 [ P S 4 ] 5 ] 6 − } ${}_{\infty }^{3}\left\{{\left[\mathrm{Y}{\mathrm{b}}_{\mathrm{3}}{\left[\mathrm{P}{\mathrm{S}}_{4}\right]}_{5}\right]}^{6-}\right\}$ . These Li+ cations are hard to locate in both compounds, but reside in four- to sixfold sulfur coordination (d(Li–S) = 235–304 pm). Some Li+ positions are underoccupied and some Li+ cations share sites with Yb3+ cations in Li6Yb3[PS4]5, and even in Li9Yb2[PS4]5 their high displacement values suggest Li+ cation mobility. According to the empirical formulae, three Li+ cations have to be replaced with one Yb3+ cation to reach the lithium-poorer compound and structure (Li6Yb3[PS4]5) starting from the lithium-richer one (Li9Yb2[PS4]5).

Li3La[PS4]2: The First Lithium Lanthanum Ortho‐Thiophosphate

“…Coordination numbers ranging from four to six are quite common for lithium towards sulfur atoms of compounds with thiophosphate anions, regardless of their composition (Li 3 [PS 4 ], [22] Li 4 [P 2 S 6 ] [23] or Li 7 [PS 4 ][P 2 S 7 ] [24] ). In other lithiumcontaining lanthanoid(III) ortho-thiophosphates(V) with the empirical formulae Li 9 Ln 2 [PS 4 ] 5 and Li 6 Ln 3 [PS 4 ] 5 , four-to sixfold coordination spheres can be found as well, [17,18,19,21] e. g. with distances of d(LiÀ S) = 242-293 pm in Li 9 Nd 2 [PS 4 ] 5 [17] or Li 6 Yb 3 [PS 4 ] 5 . [21] The eight crystallographically different sulfur atoms show coordination numbers of three (S1, S7 and S8), four (S2, S3, S4 and S6) and five (S5) towards either lithium, lanthanum or phosphorus ( 4).…”

“…In other lithiumcontaining lanthanoid(III) ortho-thiophosphates(V) with the empirical formulae Li 9 Ln 2 [PS 4 ] 5 and Li 6 Ln 3 [PS 4 ] 5 , four-to sixfold coordination spheres can be found as well, [17,18,19,21] e. g. with distances of d(LiÀ S) = 242-293 pm in Li 9 Nd 2 [PS 4 ] 5 [17] or Li 6 Yb 3 [PS 4 ] 5 . [21] The eight crystallographically different sulfur atoms show coordination numbers of three (S1, S7 and S8), four (S2, S3, S4 and S6) and five (S5) towards either lithium, lanthanum or phosphorus ( 4). The lanthanum-sulfur polyhedra are further corner-sharing (S8) to connect the strings to two-dimensional layers.…”

“…Further studies on the incorporation of the lighter alkali metals (A = Li and Na) into the lanthanoid(III)-thiophosphate(V) matrix failed in the case of sodium, for the complex anion always becomes [P 2 S 6 ] 4À as hexathiodiphosphate(IV) instead of the ortho-thiophosphate(V), e. g. in NaLa[P 2 S 6 ], [14] NaSm[P 2 S 6 ] [15] and NaTb[P 2 S 6 ]. [16] In 2006 and 2007, the first lithium-containing compounds Li 9 Nd 2 [PS 4 ] 5 [17] and Li 6 Gd 3 [PS 4 ] 5 [18] have been published and meanwhile, besides Li 9 Yb 2 [PS 4 ] 5 [19][20][21] and Li 6 Yb 3 [PS 4 ] 5 , [19][20][21] several other Li 9 Ln 2 [PS 4 ] 5 (Ln = Pr, Sm, Dy, Ho, Er and Lu) [19,20] and Li 6 Ln 3 [PS 4 ] 5 (Ln = Gd, Dy, Ho and Lu) [19,18] phases are known, again with complex [PS 4 ] 3À anions in their crystal structures.…”

Two Hitherto Unknown Lithium Holmium(III) Ortho‐Thiophosphates(V): Li9Ho2[PS4]5 and Li15Ho7[PS4]12

“…[6,7,9] Li 3 [PS 4 ] [10,11,12] and Na 3 [PS 4 ] [13] or even the europium(II)-containing LiEu[PS 4 ] [14] are also examples of thiophosphate-based alkali-metal cation conductors. Moreover, the lithium-containing rare-earth metal(III) ortho-thiophosphates(V) with the compositions Li 3 RE[PS 4 ] 2 (RE = La), [15] Li 9 RE 2 [PS 4 ] 5 (RE = Pr, Nd, [16] Sm, Gd, Er, Yb [17] ) [18] and Li 6 RE 3 [PS 4 ] 5 (RE = Y, Gd, Dy, Yb, [17] Lu) [19] can be treated as mixtures of Li 3 [PS 4 ] and RE[PS 4 ] [20] according to (Li 3 [PS 4 ]) x (RE[PS 4 ]) y with a ratio of integer numerators and denominators for the fraction x/y. [4] In the composition Li 3 RE[PS 4 ] 2 , so far only scarcely known, e. g. for RE = La, [15] but also predicted for RE = Y, [21] the x/y-ratio of Li 3 [PS 4 ] to RE[PS 4 ] equals 1.0, whereas for the Li 9 RE 2 [PS 4 ] 5 representatives the x/y-ratio becomes 1.5.…”

“…[4] In the composition Li 3 RE[PS 4 ] 2 , so far only scarcely known, e. g. for RE = La, [15] but also predicted for RE = Y, [21] the x/y-ratio of Li 3 [PS 4 ] to RE[PS 4 ] equals 1.0, whereas for the Li 9 RE 2 [PS 4 ] 5 representatives the x/y-ratio becomes 1.5. With the formula Li 9 RE 2 [PS 4 ] 5 they already occur with RE = Pr, Nd, [16] Sm, Gd, [22] Er and Yb [17] in the Li 9 Nd 2 [PS 4 ] 5 -type structure, [16] while the tentative composition Li 6 RE 3 [PS 4 ] 5 , with a x/y-ratio of 0.667, is realized with RE = Y, Gd, Dy, Yb and Lu in the Li 6 Gd 3 [PS 4 ] 5 -type structure. [19] The title compound Li 15 Ho 7 [PS 4 ] 12 has a similar Li 3 [PS 4 ]-to-RE [PS 4 ] ratio of x/y = 0.714.…”