Die Reihe der nicht-zentrosymmetrischen tetragonalen Lanthanoid(III)-Oxidoantimonat(III)-Chloride LnSb₂O₄Cl (Ln = Gd–Lu)

Abstract

All representatives of the isotypic series LnSb2O4Cl (Ln = Gd–Lu) could be obtained as single crystals, which crystallize just like the prototypic YSb2O4Cl in the non-centrosymmetric tetragonal space group P4212. The steady decrease in lattice parameters from a = 781.08(4) pm and c = 881.47(6) pm for GdSb2O4Cl to a = 764.66(4) pm and c = 877.53(7) pm for LuSb2O4Cl reflect the consequences of the lanthanide contraction, as expected. The Ln 3+ cations reside in the surrounding of eight oxygen atoms arranged as square hemiprisms [LnO8]13−, which are linked by four of their coplanar edges to form layers according to 2 ∞ { [ L n O 8 / 2 e ] 5 − } $\begin{array}{l}2\hfill \\ \infty \hfill \end{array}\left\{{\left[Ln{\text{O}}_{8/2}^{e}\right]}^{5-}\right\}$ parallel to the (001) plane. The Sb3+ cations form ψ1-tetrahedral [SbO3]3– anions together with three oxygen atoms. Two of these anions are connected with additional Sb3+ cations, but the third one shows no extra connectivity. Four ψ1-tetrahedral [SbO3]3– units build an eight-membered ring 0 ∞ { [ Sb 4 O 8 ] 4 − } $\begin{array}{l}0\hfill \\ \infty \hfill \end{array}\left\{{\left[{\text{Sb}}_{4}{\text{O}}_{8}\right]}^{4-}\right\}$ . These isolated rings are arranged parallel to the (001) plane. Between the oxygen-connected triple layers of Ln 3+ and Sb3+ cations with the composition 2 ∞ { [ L n Sb 2 O 4 ] + } $\begin{array}{l}2\hfill \\ \infty \hfill \end{array}\left\{{\left[Ln{\text{Sb}}_{2}{\text{O}}_{4}\right]}^{+}\right\}$ there are single layers of Cl− anions, not connected strongly to any of the trications. Due to the presence of isolated cyclic [Sb4O8]4– anions, these lanthanoid(III) oxidoantimonate(III) chlorides LnSb2O4Cl (Z = 4) can also be described with the molecular formula Ln 2[Sb4O8]Cl2 (Ln = Gd–Lu) for Z = 2.

The True Nature of SmSb2O4Cl: Syntheses and Crystal Structures of Sm2[Sb4O8]Cl2 and Eu2[Sb4O8]Cl2

“…The bridging oxygen atoms exhibit distances from 205 to 209 pm (Table 3) to the Sb 3 + cations, whereas the terminal ones show much shorter values (194-195 pm, Table 3). These distances represent quite typical antimony(III)-oxygen distances, when compared with those in senarmontite [21] [b] 764.59(4) 877.48(6) 1.148 77.25 [11] [a] space group: P4/ncc (no. 130); [b] space group: P42 1 2 (no.…”

“…Thus, these are not really closely connected to another layer, because two layers of Sb 3 + cations flank the layers of Ln 3 + cations via the oxygen atoms according to 2 ∞ {[Sb(LnO e 8=2 )Sb] + }. The Cl À anion layers serve to compensate the charge the [Sb(LnO 4 )Sb] + layers, so without these, no stability for the whole crystal structure would be expected and this fact has again resemblance to the rest of the LnSb 2 O 4 Cl series with Ln = Gd-Lu [11] and YSb 2 O 4 Cl, [10] all crystallizing in the non-centrosymmetric space group P42 1 2 (Table 4). The distances of the Sb 3 + cations to the nearest, but not directly bonded, terminal oxygen atoms (O1') of adjacent rings (dotted green connections in Figure 3 3), they clearly show that Sb 3 + strives for a fourfold coordination, as it is already known for the LnBi 2 O 4 X representatives (Ln = La-Lu, X = Cl-I) [2][3][4] and Sm 1 + x Sb 2À x O 4 X (X = Cl and Br), [5] which might be due to the fact that there is a high-temperature phase present at the reaction temperatures, most likely crystallizing analogously to the P4/mmm-type LnBi 2 O 4 X representatives (Figure 6, top), if necessary stabilized by some Ln 3 + surplus.…”

“…From this point of view, SmSb 2 O 4 Cl and EuSb 2 O 4 Cl resemble a lot the architecture of the following members of the LnSb 2 O 4 Cl series with Ln = Gd-Lu. [11] Even the ψ 4 towards the lighter lanthanoids. The [Sb 4 O 8 ] 4À rings at the heights z/c � 1 / 8 (rotation anti-clockwise) and z/c � 3 / 8 (rotation clockwise), respectively, called layer 1 in the following, can be transferred by inversion symmetry into those at the heights z/c � 7 / 8 (rotation anti-clockwise) and z/c � 5 / 8 (rotation clockwise), respectively, dubbed as layer 2 (Figure 5).…”

“…As in the case of the LnSb 2 O 4 Br representatives and YSb 2 O 4 Br, Sb 3 + again forms ψ 1 -tetrahedra [SbO 3 ] 3À with oxygen atoms in the analogous chloride representatives LnSb 2 O 4 Cl (Ln = Gd-Lu) [11] and YSb 2 O 4 Cl, [10] but here four of these units form a closed eight-membered ring 0 3) via corner-linkage. In this structure, too, there are secondary contacts between all terminal oxygen atoms and the adjacent unbonded Sb 3 + cations.…”

“…×) 349.8(4) Sm[a] 787.13(4) 1765.24(12) 2.243 (2 × 1.121) 82.33 Eu[a] 783.56(4) 1764.06(12) 2.251 (2 × 1.126) 81.54 Gd[b] 781.08(4) 881.47(6) 1.129 80.97[11] Tb[b] 778.53(4) 880.92(6) 1.132 80.39 [11] Dy[b] 776.17(4) 880.…”