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Potassium scandium niobate hydroxide, K3(Sc0.875Nb0.125)Nb2O9H1.75, is a new scandium niobate with a unique cage structure. The structure contains two non-equivalent K+ sites (3m and \overline{6}m2 site symmetry), one disordered Sc3+/Nb5+ site (\overline{3}m site symmetry), one Nb5+ site (3m site symmetry), two O2- sites (m and mm2 site symmetry) and one H+ site (m site symmetry). Both scandium and niobium have octa­hedral environments, which combine to form cages around potassium. One K atom lies in a cube-like cage built of seven octa­hedra, while the other K atom is encapsulated by an eight-membered trigonal face-bicapped prism. The cages form sheets that extend along the ab plane.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270109009421/lg3008sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270109009421/lg3008Isup2.hkl
Contains datablock I

Comment top

Refractory oxides such as Sc2O3, Y2O3, ZrO2, HfO2 and Ta2O5 have been a source of much interest over the years owing to their many practical uses, including applications as high-temperature liners, abrasives and laser hosts. In the process of developing these materials, there were preliminary explorations of refractory mixed metal oxides. Because of the difficulty of making high quality samples of the extremely refractory compounds, and particularly as single crystals, investigation of these metal oxides has been somewhat neglected.

One relatively unexplored system is that of the scandium niobates, which have generally been limited to powders created by conventional solid state methods (Rooksby & White, 1963, 1964). Only in one case was single-crystal growth of ScNbO4 (Ross & Grün, 1990) by chemical vapor deposition reported; however, the crystal size was very small, which prevented complete structural characterization of the material. Hydrothermal solutions have demonstrated the ability to produce single crystals of several classical refractory oxides (Kuznetsov & Sidorenko, 1968). Therefore, a hydrothermal synthesis study of the scandium niobates was undertaken. Using high temperatures, pressures and extremely basic solutions, the title compound was prepared.

The title structure consists of Sc0.875Nb0.125O6 and NbO3(OH)3 octahedral building blocks (Fig. 1). The Sc0.875Nb0.125O6 units are corner sharing via atom O1 with the niobium octahedra. An NbO3(OH)3 octahedron occupies the (110) plane and is face sharing with another niobium octahedron. At 1.867 (3) Å, the three Nb—O1 bonds are much shorter than the 2.189 (5) Å Nb—O2 bonds, distorting the octahedra. This has also been observed in other face-sharing niobium systems (Tyutyunnik et al., 2002; Tarakina et al., 2003). As a result of metal–metal repulsion, the Nb atoms are shifted away from each other. The distortion is compounded by the corner-shared O1 atom bound to the lower valent Sc3+ ion creating the short Nb—O1 bond. This results in an O1—Nb—O1iii bond angle of 100.45 (1)° in contrast to 74.2 (2)° for the O2—Nb—O2iii angle [symmetry code: (iii) -x + y, -x + 1, z]. Contrary to the face-sharing niobates, the Sc0.875Nb0.125O6 octahedra exhibit no distortion. The combined scandium and distorted niobium environments form a framework that extends along the c axis.

A broad IR stretch located at 3313 cm-1 indicates the presence of a hydroxy group. In order to locate the hydrogen site, bond valence sums were calculated. This revealed atom O2 [1.366 valence units (v.u.)] as significantly underbonded compared with atom O1 (2.056 v.u.). Therefore, a site located 0.86 Å from atom O2 was designated H1. This has a bifuricated hydrogen bond to atoms O2i and O2ii [symmetry codes: (i) -x + y, -x + 2, z; (ii) -y + 2, x - y + 2, z] with distances of 2.491 (7) and 2.486 (7) Å, respectively. The H atom was kept fixed with Uiso = 0.10 Å2 and a partial occupancy to provide an electrically neutral formula. Including the hydrogen environment, a recalculation of the bond valence sum for atom O2 provided an acceptable value of 1.975 v.u. Both hydrogen bonds are considered weak (Brown, 1976) because the bond valence attributed to the acceptor O atoms is less than 0.20 valence units. Furthermore, the O2i···O2ii distance is 3.1981 (13) Å. This is much longer than a distance less than or equal to 2.73 Å, which is a requirement of a strong hydrogen bond.

The potassium environments are both 12-coordinate. They have a sixfold coordination of O atoms, which is parallel to the ab plane, with a threefold coordination above and below the plane in the c direction. The coordination environment is created by two different cage enclosures around atoms K1 and K2, seen in Figs. 2 and 3, respectively. The K1 cage is formed by three scandium and four niobium corner-sharing octahedra. They combine to form a cube-like enclosure with one vertex missing. Atom K1 is centrally located in the cage along the (110) plane. The eighth vertex required to complete the cube is occupied by the bifuricated hydrogen bond. The hydrogen bond also contributes to the K2 cage, but is less pronounced in this case. An eight-membered cage composed of two scandium and six niobium octahedra is oriented to construct a trigonal face-bicapped prism with K2 located along the (100) plane. Scandium octahedra form the face-capping pyramid, while the trigonal prism is built of face-sharing niobium octahedra. A similar permethylpolysilane Si8Me14 cage structure has been reported (West & Carberry, 1975). The most notable difference is the tetrahedral coordination of the silicon versus the octahedral scandium and niobium environments. The polysilane cage enclosure is small compared with the large internal volume (5.8 × 5.8 × 7.3 Å) of the scandium/niobium cage structure. This internal volume created by the octahedral environments provides space for the hydrogen-bond network to interact along the ab plane.

The long-range structure (Fig. 4) has alternating sheets of the K1 and K2 cage structures extending along the ab plane. As the K1 sheets propagate in the c direction, they angle themselves as if a mirror plane extends through the middle of the K2 sandwiched sheet. The K2 -6m2 site symmetry causes a 60o rotation from one K2 sheet to the next.

Related literature top

For related literature, see: Brown (1976); Kuznetsov & Sidorenko (1968); Rooksby & White (1963, 1964); Ross & Grün (1990); Tarakina et al. (2003); Tyutyunnik et al. (2002); West & Carberry (1975).

Experimental top

K3(Sc0.875Nb0.125)Nb2O9H1.75 was prepared by hydrothermal synthesis. Powders of Sc2O3 and Nb2O5 in a 2:1 molar ratio were sealed in a silver ampoule with a solution of 20M KOH. The ampoule was placed in a 27 ml Inconel autoclave, heated to 848 K and counter-pressured to 17 000 psi (1 p.s.i. = 6.89 kPa). These conditions were held for 10 d, and after this time the ampoule was opened and the contents washed with deionized water. Single crystals of KNbO3 were the major constituent, and K3(Sc0.875Nb0.125)Nb2O9H1.75 colorless tapering hexagonal rod crystals suitable for single-crystal X-ray diffraction were the minor product. FT–IR: 3313 cm-1 (broad, s OH).

Computing details top

Data collection: CrystalClear (Molecular Structure Corporation & Rigaku, 2006); cell refinement: CrystalClear (Molecular Structure Corporation & Rigaku, 2006); data reduction: CrystalClear (Molecular Structure Corporation & Rigaku, 2006); program(s) used to solve structure: SHELXTL (Version 6.10; Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Version 6.10; Sheldrick, 2008); molecular graphics: Diamond (Brandenburg, 1999); software used to prepare material for publication: SHELXTL (Version 6.10; Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. A view of the full coordination environments of scandium, niobium and potassium drawn with 50% probability displacement ellipsoids. [Symmetry codes: (i) -x + y, -x + 2, z; (ii) -y + 2, x - y + 2, z; (iii) -x + y, -x + 1, z; (iv) -y + 1, x - y + 1, z; (v) -y + 2, x - y + 1, z; (vi) -x + y + 1, -x + 2, z; (vii) -x + 2, -x + y + 1, -z + 1; (viii) y, x, -z + 1; (ix) x - y + 1, -y + 2, -z + 1; (x) -y + 1, x - y + 2, z; (xi) x - 1, y, z; (xii) -x + y - 1, -x + 1, z; (xiii) -x + y + 1, y, -z + 1/2; (xiv) -y + 2, -x + 2, -z + 1/2; (xv) x, x - y + 1, -z + 1/2; (xvi) -x + y + 1, y + 1, -z + 1/2; (xvii) x, x - y + 2, -z + 1/2; (xviii) -y + 1, -x + 2, -z + 1/2; (xix) -x + y, y, -z + 1/2; (xx) x - y + 1, x + 1, z - 1/2; (xxi) -x + 1, -y + 2, z - 1/2; (xxii) y, -x + y + 1, z - 1/2.]
[Figure 2] Fig. 2. A view of the K1 cage built by scandium and niobium octahedra.
[Figure 3] Fig. 3. A view of the K2 cage projected slightly off the ac plane. The bold lines are not bonds, but are included to aid viewing of the trigonal face-bicapped prism cage.
[Figure 4] Fig. 4. An extended view of the long-range cage structure projected slightly off the ac plane. The lighter polyhedra represent the K1 cage, while the darker units correspond to the K2 cage.
Potassium scandium niobate hydroxide top
Crystal data top
K3(Sc0.875Nb0.125)Nb2O9H1.75Dx = 3.846 Mg m3
Mr = 499.84Mo Kα radiation, λ = 0.71073 Å
Hexagonal, P63/mmcCell parameters from 2200 reflections
Hall symbol: -P 6c 2cθ = 2.8–25.3°
a = 5.8416 (15) ŵ = 4.92 mm1
c = 14.604 (5) ÅT = 298 K
V = 431.6 (2) Å3Tapering Hexagonal Rod, colorless
Z = 20.30 × 0.27 × 0.25 mm
F(000) = 473
Data collection top
Rigaku AFC-8S Mercury CCD
diffractometer
178 independent reflections
Radiation source: sealed tube170 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.028
Detector resolution: 14.6306 pixels mm-1θmax = 25.3°, θmin = 2.8°
ω scansh = 77
Absorption correction: multi-scan
(Jacobson, 1998)
k = 77
Tmin = 0.256, Tmax = 0.298l = 1716
3318 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.028Hydrogen site location: difference Fourier map
wR(F2) = 0.081H-atom parameters not refined
S = 1.02 w = 1/[σ2(Fo2) + (0.053P)2 + 2.9407P]
where P = (Fo2 + 2Fc2)/3
178 reflections(Δ/σ)max = 0.006
21 parametersΔρmax = 1.04 e Å3
0 restraintsΔρmin = 0.78 e Å3
Crystal data top
K3(Sc0.875Nb0.125)Nb2O9H1.75Z = 2
Mr = 499.84Mo Kα radiation
Hexagonal, P63/mmcµ = 4.92 mm1
a = 5.8416 (15) ÅT = 298 K
c = 14.604 (5) Å0.30 × 0.27 × 0.25 mm
V = 431.6 (2) Å3
Data collection top
Rigaku AFC-8S Mercury CCD
diffractometer
178 independent reflections
Absorption correction: multi-scan
(Jacobson, 1998)
170 reflections with I > 2σ(I)
Tmin = 0.256, Tmax = 0.298Rint = 0.028
3318 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0280 restraints
wR(F2) = 0.081H-atom parameters not refined
S = 1.02Δρmax = 1.04 e Å3
178 reflectionsΔρmin = 0.78 e Å3
21 parameters
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
Nb20.33330.66670.35759 (5)0.0064 (4)
O20.4839 (7)0.9679 (13)0.25000.0258 (15)
H10.57001.13880.25000.100*0.58
K10.66671.33330.41124 (18)0.0187 (7)
O10.6608 (7)0.8304 (3)0.4165 (2)0.0133 (9)
Sc11.00001.00000.50000.0097 (6)0.88
Nb11.00001.00000.50000.0097 (6)0.13
K21.00001.00000.25000.0388 (11)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Nb20.0060 (5)0.0060 (5)0.0072 (6)0.0030 (2)0.0000.000
O20.026 (2)0.050 (4)0.009 (3)0.025 (2)0.0000.000
K10.0125 (8)0.0125 (8)0.0311 (15)0.0063 (4)0.0000.000
O10.0121 (19)0.0141 (15)0.0131 (18)0.0061 (9)0.0034 (14)0.0017 (7)
Sc10.0091 (7)0.0091 (7)0.0110 (11)0.0045 (4)0.0000.000
Nb10.0091 (7)0.0091 (7)0.0110 (11)0.0045 (4)0.0000.000
K20.0496 (17)0.0496 (17)0.0174 (18)0.0248 (8)0.0000.000
Geometric parameters (Å, º) top
Nb2—O1i1.867 (3)K1—O1xiii3.012 (4)
Nb2—O11.867 (3)K1—O1iv3.012 (4)
Nb2—O1ii1.867 (3)O1—Sc12.105 (3)
Nb2—O2i2.189 (5)O1—K1vi2.9220 (8)
Nb2—O22.189 (5)O1—K22.976 (4)
Nb2—O2ii2.189 (5)O1—K1iv3.012 (4)
Nb2—Nb2iii3.1423 (19)Sc1—O1xiv2.105 (3)
Nb2—K1iv3.376 (3)Sc1—O1xv2.105 (3)
Nb2—K13.4625 (11)Sc1—O1ix2.105 (3)
Nb2—K1v3.4625 (11)Sc1—O1xii2.105 (3)
Nb2—K1vi3.4625 (11)Sc1—O1xvi2.105 (3)
Nb2—K2vii3.7207 (9)Sc1—K1xiv3.6132 (13)
O2—Nb2iii2.189 (5)Sc1—K1vi3.6132 (13)
O2—K22.9253 (8)Sc1—K1xvii3.6132 (13)
O2—K2vii2.9253 (8)Sc1—K1iv3.6132 (13)
O2—K12.994 (5)Sc1—K1xviii3.6132 (13)
O2—K1iii2.994 (5)K2—O2ix2.9253 (8)
K1—O12.9220 (8)K2—O2ii2.9253 (8)
K1—O1viii2.9220 (8)K2—O2xviii2.9253 (8)
K1—O1ix2.9220 (8)K2—O2xv2.9253 (8)
K1—O1x2.9220 (8)K2—O2viii2.9253 (8)
K1—O1i2.9220 (8)K2—O1iii2.976 (4)
K1—O1xi2.9220 (8)K2—O1ix2.976 (4)
K1—O2viii2.994 (5)K2—O1xix2.976 (4)
K1—O2x2.994 (5)K2—O1xv2.976 (4)
K1—O1xii3.012 (4)K2—O1xx2.976 (4)
O1i—Nb2—O1100.45 (14)Nb2—O1—Sc1172.0 (2)
O1i—Nb2—O1ii100.45 (14)Nb2—O1—K189.82 (7)
O1—Nb2—O1ii100.45 (14)Sc1—O1—K190.40 (8)
O1i—Nb2—O2i91.26 (12)Nb2—O1—K1vi89.82 (7)
O1—Nb2—O2i161.57 (17)Sc1—O1—K1vi90.40 (8)
O1ii—Nb2—O2i91.26 (13)K1—O1—K1vi176.77 (19)
O1i—Nb2—O291.26 (12)Nb2—O1—K297.77 (14)
O1—Nb2—O291.26 (13)Sc1—O1—K290.18 (12)
O1ii—Nb2—O2161.57 (17)K1—O1—K288.43 (9)
O2i—Nb2—O274.2 (2)K1vi—O1—K288.43 (9)
O1i—Nb2—O2ii161.57 (17)Nb2—O1—K1iv84.08 (13)
O1—Nb2—O2ii91.26 (12)Sc1—O1—K1iv87.97 (12)
O1ii—Nb2—O2ii91.26 (12)K1—O1—K1iv91.58 (9)
O2i—Nb2—O2ii74.2 (2)K1vi—O1—K1iv91.58 (9)
O2—Nb2—O2ii74.2 (2)K2—O1—K1iv178.15 (13)
O1i—Nb2—Nb2iii117.45 (11)O1—Sc1—O1xiv180.000 (1)
O1—Nb2—Nb2iii117.45 (12)O1—Sc1—O1xv89.81 (14)
O1ii—Nb2—Nb2iii117.45 (12)O1xiv—Sc1—O1xv90.19 (14)
O2i—Nb2—Nb2iii44.12 (13)O1—Sc1—O1ix89.81 (14)
O2—Nb2—Nb2iii44.12 (13)O1xiv—Sc1—O1ix90.19 (14)
O2ii—Nb2—Nb2iii44.12 (13)O1xv—Sc1—O1ix89.81 (14)
O1i—Nb2—K1iv62.55 (11)O1—Sc1—O1xii90.19 (14)
O1—Nb2—K1iv62.55 (12)O1xiv—Sc1—O1xii89.81 (14)
O1ii—Nb2—K1iv62.55 (12)O1xv—Sc1—O1xii180.0
O2i—Nb2—K1iv135.88 (13)O1ix—Sc1—O1xii90.19 (14)
O2—Nb2—K1iv135.88 (13)O1—Sc1—O1xvi90.19 (14)
O2ii—Nb2—K1iv135.88 (13)O1xiv—Sc1—O1xvi89.81 (14)
Nb2iii—Nb2—K1iv180.0O1xv—Sc1—O1xvi90.19 (14)
O1i—Nb2—K157.55 (2)O1ix—Sc1—O1xvi180.0
O1—Nb2—K157.55 (2)O1xii—Sc1—O1xvi89.81 (14)
O1ii—Nb2—K1139.47 (12)O1—Sc1—K153.967 (19)
O2i—Nb2—K1120.10 (4)O1xiv—Sc1—K1126.03 (2)
O2—Nb2—K158.95 (14)O1xv—Sc1—K1123.58 (10)
O2ii—Nb2—K1120.10 (4)O1ix—Sc1—K153.967 (19)
Nb2iii—Nb2—K1103.08 (5)O1xii—Sc1—K156.42 (10)
K1iv—Nb2—K176.92 (5)O1xvi—Sc1—K1126.03 (2)
O1i—Nb2—K1v57.55 (2)O1—Sc1—K1xiv126.03 (2)
O1—Nb2—K1v139.47 (12)O1xiv—Sc1—K1xiv53.967 (19)
O1ii—Nb2—K1v57.55 (2)O1xv—Sc1—K1xiv56.42 (10)
O2i—Nb2—K1v58.95 (14)O1ix—Sc1—K1xiv126.03 (2)
O2—Nb2—K1v120.10 (4)O1xii—Sc1—K1xiv123.58 (10)
O2ii—Nb2—K1v120.10 (4)O1xvi—Sc1—K1xiv53.967 (19)
Nb2iii—Nb2—K1v103.08 (5)K1—Sc1—K1xiv180.00 (8)
K1iv—Nb2—K1v76.92 (5)O1—Sc1—K1vi53.97 (2)
K1—Nb2—K1v115.04 (3)O1xiv—Sc1—K1vi126.033 (19)
O1i—Nb2—K1vi139.47 (12)O1xv—Sc1—K1vi53.97 (2)
O1—Nb2—K1vi57.55 (2)O1ix—Sc1—K1vi123.58 (10)
O1ii—Nb2—K1vi57.55 (2)O1xii—Sc1—K1vi126.03 (2)
O2i—Nb2—K1vi120.10 (4)O1xvi—Sc1—K1vi56.42 (10)
O2—Nb2—K1vi120.10 (4)K1—Sc1—K1vi107.88 (4)
O2ii—Nb2—K1vi58.95 (13)K1xiv—Sc1—K1vi72.12 (4)
Nb2iii—Nb2—K1vi103.08 (5)O1—Sc1—K1xvii126.033 (19)
K1iv—Nb2—K1vi76.92 (5)O1xiv—Sc1—K1xvii53.97 (2)
K1—Nb2—K1vi115.04 (3)O1xv—Sc1—K1xvii126.03 (2)
K1v—Nb2—K1vi115.04 (3)O1ix—Sc1—K1xvii56.42 (10)
O1i—Nb2—K2vii52.42 (11)O1xii—Sc1—K1xvii53.97 (2)
O1—Nb2—K2vii126.64 (2)O1xvi—Sc1—K1xvii123.58 (10)
O1ii—Nb2—K2vii126.64 (2)K1—Sc1—K1xvii72.12 (4)
O2i—Nb2—K2vii51.781 (10)K1xiv—Sc1—K1xvii107.88 (4)
O2—Nb2—K2vii51.781 (10)K1vi—Sc1—K1xvii180.0
O2ii—Nb2—K2vii109.15 (13)O1—Sc1—K1iv56.42 (10)
Nb2iii—Nb2—K2vii65.021 (15)O1xiv—Sc1—K1iv123.58 (10)
K1iv—Nb2—K2vii114.979 (15)O1xv—Sc1—K1iv126.03 (2)
K1—Nb2—K2vii69.76 (2)O1ix—Sc1—K1iv126.03 (2)
K1v—Nb2—K2vii69.76 (2)O1xii—Sc1—K1iv53.97 (2)
K1vi—Nb2—K2vii168.10 (5)O1xvi—Sc1—K1iv53.97 (2)
Nb2iii—O2—Nb291.8 (3)K1—Sc1—K1iv72.12 (4)
Nb2iii—O2—K292.22 (9)K1xiv—Sc1—K1iv107.88 (4)
Nb2—O2—K292.22 (9)K1vi—Sc1—K1iv72.12 (4)
Nb2iii—O2—K2vii92.22 (9)K1xvii—Sc1—K1iv107.88 (4)
Nb2—O2—K2vii92.22 (9)O1—Sc1—K1xviii123.58 (10)
K2—O2—K2vii173.6 (3)O1xiv—Sc1—K1xviii56.42 (10)
Nb2iii—O2—K1174.0 (2)O1xv—Sc1—K1xviii53.97 (2)
Nb2—O2—K182.26 (5)O1ix—Sc1—K1xviii53.97 (2)
K2—O2—K188.03 (9)O1xii—Sc1—K1xviii126.03 (2)
K2vii—O2—K188.03 (9)O1xvi—Sc1—K1xviii126.03 (2)
Nb2iii—O2—K1iii82.26 (5)K1—Sc1—K1xviii107.88 (4)
Nb2—O2—K1iii174.0 (2)K1xiv—Sc1—K1xviii72.12 (4)
K2—O2—K1iii88.03 (9)K1vi—Sc1—K1xviii107.88 (4)
K2vii—O2—K1iii88.03 (9)K1xvii—Sc1—K1xviii72.12 (4)
K1—O2—K1iii103.7 (2)K1iv—Sc1—K1xviii180.0
O1—K1—O1viii119.932 (9)O2ix—K2—O2ii173.6 (3)
O1—K1—O1ix61.15 (13)O2ix—K2—O2xviii66.4 (3)
O1viii—K1—O1ix58.81 (13)O2ii—K2—O2xviii120.000 (1)
O1—K1—O1x119.931 (10)O2ix—K2—O2120.0
O1viii—K1—O1x119.931 (9)O2ii—K2—O253.6 (3)
O1ix—K1—O1x176.77 (19)O2xviii—K2—O2173.6 (3)
O1—K1—O1i58.81 (13)O2ix—K2—O2xv120.000 (2)
O1viii—K1—O1i176.77 (18)O2ii—K2—O2xv66.4 (3)
O1ix—K1—O1i119.931 (9)O2xviii—K2—O2xv53.6 (3)
O1x—K1—O1i61.15 (14)O2—K2—O2xv120.000 (2)
O1—K1—O1xi176.77 (18)O2ix—K2—O2viii53.6 (3)
O1viii—K1—O1xi61.15 (13)O2ii—K2—O2viii120.000 (1)
O1ix—K1—O1xi119.931 (10)O2xviii—K2—O2viii120.0
O1x—K1—O1xi58.81 (13)O2—K2—O2viii66.4 (3)
O1i—K1—O1xi119.931 (9)O2xv—K2—O2viii173.6 (3)
O1—K1—O258.86 (11)O2ix—K2—O1iii118.86 (7)
O1viii—K1—O2123.51 (14)O2ii—K2—O1iii59.03 (7)
O1ix—K1—O291.55 (9)O2xviii—K2—O1iii118.86 (7)
O1x—K1—O291.55 (9)O2—K2—O1iii59.03 (7)
O1i—K1—O258.86 (11)O2xv—K2—O1iii91.84 (8)
O1xi—K1—O2123.51 (13)O2viii—K2—O1iii91.84 (8)
O1—K1—O2viii91.55 (9)O2ix—K2—O1ix59.03 (7)
O1viii—K1—O2viii58.86 (12)O2ii—K2—O1ix118.86 (7)
O1ix—K1—O2viii58.86 (11)O2xviii—K2—O1ix91.84 (8)
O1x—K1—O2viii123.51 (13)O2—K2—O1ix91.84 (8)
O1i—K1—O2viii123.51 (14)O2xv—K2—O1ix118.86 (7)
O1xi—K1—O2viii91.55 (9)O2viii—K2—O1ix59.03 (7)
O2—K1—O2viii64.66 (17)O1iii—K2—O1ix146.49 (6)
O1—K1—O2x123.51 (14)O2ix—K2—O1xix91.84 (8)
O1viii—K1—O2x91.55 (9)O2ii—K2—O1xix91.84 (8)
O1ix—K1—O2x123.51 (14)O2xviii—K2—O1xix59.03 (7)
O1x—K1—O2x58.86 (11)O2—K2—O1xix118.86 (7)
O1i—K1—O2x91.55 (9)O2xv—K2—O1xix59.03 (7)
O1xi—K1—O2x58.86 (11)O2viii—K2—O1xix118.86 (7)
O2—K1—O2x64.66 (17)O1iii—K2—O1xix59.92 (11)
O2viii—K1—O2x64.66 (17)O1ix—K2—O1xix146.49 (6)
O1—K1—O1xii60.31 (12)O2ix—K2—O1xv91.84 (8)
O1viii—K1—O1xii88.42 (9)O2ii—K2—O1xv91.84 (8)
O1ix—K1—O1xii60.31 (12)O2xviii—K2—O1xv59.03 (7)
O1x—K1—O1xii117.19 (9)O2—K2—O1xv118.86 (7)
O1i—K1—O1xii88.42 (9)O2xv—K2—O1xv59.03 (7)
O1xi—K1—O1xii117.19 (9)O2viii—K2—O1xv118.86 (7)
O2—K1—O1xii119.15 (10)O1iii—K2—O1xv146.49 (6)
O2viii—K1—O1xii119.15 (10)O1ix—K2—O1xv59.92 (11)
O2x—K1—O1xii175.23 (13)O1xix—K2—O1xv109.57 (13)
O1—K1—O1xiii117.19 (9)O2ix—K2—O1xx59.03 (7)
O1viii—K1—O1xiii60.31 (12)O2ii—K2—O1xx118.86 (7)
O1ix—K1—O1xiii88.42 (9)O2xviii—K2—O1xx91.84 (8)
O1x—K1—O1xiii88.42 (9)O2—K2—O1xx91.84 (8)
O1i—K1—O1xiii117.19 (9)O2xv—K2—O1xx118.86 (7)
O1xi—K1—O1xiii60.31 (12)O2viii—K2—O1xx59.03 (7)
O2—K1—O1xiii175.23 (13)O1iii—K2—O1xx59.92 (11)
O2viii—K1—O1xiii119.15 (10)O1ix—K2—O1xx109.57 (13)
O2x—K1—O1xiii119.15 (10)O1xix—K2—O1xx59.92 (11)
O1xii—K1—O1xiii56.89 (11)O1xv—K2—O1xx146.49 (6)
O1—K1—O1iv88.42 (9)O2ix—K2—O1118.86 (7)
O1viii—K1—O1iv117.19 (9)O2ii—K2—O159.03 (7)
O1ix—K1—O1iv117.19 (9)O2xviii—K2—O1118.86 (7)
O1x—K1—O1iv60.31 (12)O2—K2—O159.03 (7)
O1i—K1—O1iv60.31 (12)O2xv—K2—O191.84 (8)
O1xi—K1—O1iv88.42 (9)O2viii—K2—O191.84 (8)
O2—K1—O1iv119.15 (10)O1iii—K2—O1109.57 (13)
O2viii—K1—O1iv175.23 (13)O1ix—K2—O159.92 (11)
O2x—K1—O1iv119.15 (10)O1xix—K2—O1146.49 (6)
O1xii—K1—O1iv56.89 (11)O1xv—K2—O159.92 (11)
O1xiii—K1—O1iv56.89 (11)O1xx—K2—O1146.49 (6)
Symmetry codes: (i) y+1, xy+1, z; (ii) x+y, x+1, z; (iii) x, y, z+1/2; (iv) x+1, y+2, z+1; (v) x1, y1, z; (vi) x, y1, z; (vii) x1, y, z; (viii) y+2, xy+2, z; (ix) x+y+1, x+2, z; (x) x+y, x+2, z; (xi) x, y+1, z; (xii) y, x+y+1, z+1; (xiii) xy+1, x+1, z+1; (xiv) x+2, y+2, z+1; (xv) y+2, xy+1, z; (xvi) xy+1, x, z+1; (xvii) x+2, y+3, z+1; (xviii) x+1, y, z; (xix) y+2, xy+1, z+1/2; (xx) x+y+1, x+2, z+1/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O2—H1···O2x0.862.493.1981 (13)140
O2—H1···O2viii0.862.493.1981 (13)140
Symmetry codes: (viii) y+2, xy+2, z; (x) x+y, x+2, z.

Experimental details

Crystal data
Chemical formulaK3(Sc0.875Nb0.125)Nb2O9H1.75
Mr499.84
Crystal system, space groupHexagonal, P63/mmc
Temperature (K)298
a, c (Å)5.8416 (15), 14.604 (5)
V3)431.6 (2)
Z2
Radiation typeMo Kα
µ (mm1)4.92
Crystal size (mm)0.30 × 0.27 × 0.25
Data collection
DiffractometerRigaku AFC-8S Mercury CCD
diffractometer
Absorption correctionMulti-scan
(Jacobson, 1998)
Tmin, Tmax0.256, 0.298
No. of measured, independent and
observed [I > 2σ(I)] reflections
3318, 178, 170
Rint0.028
(sin θ/λ)max1)0.602
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.028, 0.081, 1.02
No. of reflections178
No. of parameters21
H-atom treatmentH-atom parameters not refined
Δρmax, Δρmin (e Å3)1.04, 0.78

Computer programs: CrystalClear (Molecular Structure Corporation & Rigaku, 2006), SHELXTL (Version 6.10; Sheldrick, 2008), Diamond (Brandenburg, 1999).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O2—H1···O2i0.862.493.1981 (13)140
O2—H1···O2ii0.862.493.1981 (13)140
Symmetry codes: (i) x+y, x+2, z; (ii) y+2, xy+2, z.
 

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