The crystal structure of potassium cerium(III) bis(sulfate) monohydrate, KCe(SO4)2·H2O, is built up from irregular independent SO4 tetrahedra, CeO9 polyhedra in the form of distorted tricapped trigonal prisms and K+ ions. Hydrogen bonding between the free water molecule and sulfate groups supplement the ionic bonds characteristic of the rest of the structure.
Supporting information
Crystals of the title compound were synthesized at room temperature by mixing aqueous solutions of Ce(SO4)2·4H2O and KSCN. The solutions were mixed until the yellow color was no longer detected. The colorless solution was allowed to evaporate at room temperature, and within a few days, colorless crystals of KCe(SO4)2·H2O had formed. The compound was characterized by elemental chemical analysis and thermogravimetric studies to determine the formula, which was later confirmed by refinement of the crystal structure.
All H atoms were located from difference Fourier maps and were refined isotropically.
Data collection: program (reference)?; cell refinement: program (reference)?; data reduction: Jana2000 (Petricek & Dusek, 2000); program(s) used to solve structure: SIR97 (Altomare et al., 1999; program(s) used to refine structure: Jana2000; molecular graphics: Diamond (Brandenburg & Berndt, 1999); software used to prepare material for publication: Jana2000.
potassium cerium bis(sulfate) monohydrate
top
Crystal data top
KCe(SO4)2·H2O | F(000) = 732 |
Mr = 389.3 | Dx = 3.258 (2) Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71069 Å |
Hall symbol: -P 2ybc | Cell parameters from 3322 reflections |
a = 10.1163 (2) Å | θ = 2.0–27.0° |
b = 8.588 (4) Å | µ = 6.81 mm−1 |
c = 10.3823 (6) Å | T = 293 K |
β = 118.39 (3)° | Needle, colorless |
V = 793.5 (4) Å3 | 0.1 × 0.05 × 0.03 mm |
Z = 4 | |
Data collection top
Oxford Instruments point-detector diffractometer | 1267 reflections with I > 3σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.034 |
Graphite monochromator | θmax = 27.0°, θmin = 2.3° |
θ/2θ scans | h = −12→11 |
Absorption correction: gaussian (Jana2000; Petricek and Dusek, 2000) | k = −10→10 |
Tmin = 0.483, Tmax = 0.595 | l = 0→13 |
3334 measured reflections | Standard reflections: no; every no reflections |
1729 independent reflections | intensity decay: none |
Refinement top
Refinement on F2 | Weighting scheme based on measured s.u.'s w = 1/(σ2(I) + 0.0004I2) |
R[F2 > 2σ(F2)] = 0.020 | (Δ/σ)max = 0.015 |
wR(F2) = 0.055 | Δρmax = 1.40 e Å−3 |
S = 1.18 | Δρmin = −1.71 e Å−3 |
1729 reflections | Extinction correction: B-C type 1 Lorentzian isotropic (Becker & Coppens, 1974) |
127 parameters | Extinction coefficient: 0.064491 |
All H-atom parameters refined | |
Crystal data top
KCe(SO4)2·H2O | V = 793.5 (4) Å3 |
Mr = 389.3 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 10.1163 (2) Å | µ = 6.81 mm−1 |
b = 8.588 (4) Å | T = 293 K |
c = 10.3823 (6) Å | 0.1 × 0.05 × 0.03 mm |
β = 118.39 (3)° | |
Data collection top
Oxford Instruments point-detector diffractometer | 1267 reflections with I > 3σ(I) |
Absorption correction: gaussian (Jana2000; Petricek and Dusek, 2000) | Rint = 0.034 |
Tmin = 0.483, Tmax = 0.595 | Standard reflections: no; every no reflections |
3334 measured reflections | intensity decay: none |
1729 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.020 | 127 parameters |
wR(F2) = 0.055 | All H-atom parameters refined |
S = 1.18 | Δρmax = 1.40 e Å−3 |
1729 reflections | Δρmin = −1.71 e Å−3 |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
Ce1 | 0.23611 (3) | 0.33680 (3) | 0.46527 (3) | 0.01018 (9) | |
K1 | 0.28298 (12) | 0.68638 (14) | 0.80556 (13) | 0.0281 (4) | |
S1 | −0.01646 (12) | 0.68645 (12) | 0.38915 (11) | 0.0118 (4) | |
S2 | 0.45502 (11) | 0.13151 (12) | 0.82423 (12) | 0.0120 (4) | |
O1 | 0.1973 (4) | 0.0388 (4) | 0.4717 (4) | 0.0232 (15) | |
O2 | −0.1656 (3) | 0.6124 (4) | 0.3303 (4) | 0.0230 (13) | |
O3 | 0.4561 (4) | 0.2443 (4) | 0.9319 (3) | 0.0189 (13) | |
O4 | 0.3277 (3) | 0.0253 (4) | 0.7909 (3) | 0.0185 (13) | |
O5 | 0.5985 (4) | 0.0474 (4) | 0.8861 (4) | 0.0228 (14) | |
O6 | 0.4348 (4) | 0.2103 (4) | 0.6909 (3) | 0.0185 (13) | |
O7 | −0.0276 (3) | 0.8195 (4) | 0.2941 (3) | 0.0200 (13) | |
O8 | 0.0242 (4) | 0.7395 (4) | 0.5379 (3) | 0.0210 (14) | |
O9 | 0.0952 (3) | 0.5791 (4) | 0.3888 (4) | 0.0207 (14) | |
H1 | 0.214 (7) | 0.015 (8) | 0.555 (8) | 0.05 (2)* | |
H2 | 0.107 (9) | −0.024 (9) | 0.415 (8) | 0.07 (2)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Ce1 | 0.00844 (12) | 0.01115 (12) | 0.01038 (12) | 0.00021 (10) | 0.00400 (8) | 0.00070 (11) |
K1 | 0.0221 (5) | 0.0349 (6) | 0.0263 (6) | −0.0039 (5) | 0.0107 (5) | −0.0019 (5) |
S1 | 0.0106 (5) | 0.0130 (5) | 0.0120 (5) | 0.0025 (4) | 0.0055 (4) | 0.0016 (4) |
S2 | 0.0102 (5) | 0.0157 (5) | 0.0101 (5) | 0.0031 (4) | 0.0049 (4) | 0.0035 (4) |
O1 | 0.025 (2) | 0.0197 (17) | 0.024 (2) | −0.0042 (14) | 0.0106 (17) | −0.0019 (15) |
O2 | 0.0123 (16) | 0.0293 (18) | 0.0262 (19) | −0.0085 (13) | 0.0083 (14) | −0.0108 (15) |
O3 | 0.0196 (17) | 0.0235 (17) | 0.0153 (17) | −0.0016 (13) | 0.0098 (14) | −0.0036 (13) |
O4 | 0.0178 (16) | 0.0193 (16) | 0.0197 (18) | −0.0027 (13) | 0.0099 (14) | −0.0008 (13) |
O5 | 0.0187 (17) | 0.0296 (18) | 0.0221 (19) | 0.0097 (14) | 0.0113 (15) | 0.0094 (14) |
O6 | 0.0193 (16) | 0.0242 (17) | 0.0153 (16) | 0.0045 (13) | 0.0110 (14) | 0.0067 (13) |
O7 | 0.0212 (16) | 0.0208 (16) | 0.0175 (16) | 0.0045 (14) | 0.0088 (14) | 0.0068 (14) |
O8 | 0.0244 (18) | 0.0251 (17) | 0.0124 (17) | −0.0009 (14) | 0.0078 (15) | −0.0033 (13) |
O9 | 0.0160 (16) | 0.0201 (17) | 0.027 (2) | 0.0065 (13) | 0.0105 (15) | 0.0025 (14) |
Geometric parameters (Å, º) top
Ce1—O1 | 2.595 (4) | S1—O2 | 1.475 (3) |
Ce1—O2i | 2.578 (5) | S1—O7 | 1.479 (4) |
Ce1—O3ii | 2.508 (4) | S1—O8 | 1.469 (3) |
Ce1—O4ii | 2.671 (4) | S1—O9 | 1.459 (4) |
Ce1—O5iii | 2.449 (3) | S1—H2vii | 2.74 (8) |
Ce1—O6 | 2.496 (3) | S2—O3 | 1.475 (4) |
Ce1—O7iv | 2.514 (2) | S2—O4 | 1.479 (3) |
Ce1—O8i | 2.699 (4) | S2—O5 | 1.468 (4) |
Ce1—O9 | 2.432 (3) | S2—O6 | 1.465 (4) |
Ce1—H1 | 2.96 (7) | S2—H1 | 2.88 (6) |
K1—O1v | 2.981 (5) | O1—O4 | 2.929 (5) |
K1—O2i | 2.897 (3) | O1—O6 | 2.815 (4) |
K1—O3vi | 2.812 (3) | O1—O7viii | 2.852 (4) |
K1—O4vii | 2.960 (4) | O1—O8i | 2.906 (6) |
K1—O6iii | 2.845 (4) | O1—H1 | 0.82 (8) |
K1—O8 | 2.805 (3) | O1—H2 | 0.98 (7) |
K1—H2v | 2.89 (10) | | |
| | | |
O1—Ce1—O2i | 92.36 (13) | O6—Ce1—O7iv | 150.53 (11) |
O1—Ce1—O3ii | 83.38 (13) | O6—Ce1—O8i | 104.56 (12) |
O1—Ce1—O4ii | 124.07 (13) | O6—Ce1—O9 | 139.83 (12) |
O1—Ce1—O5iii | 141.14 (10) | O6—Ce1—H1 | 56.3 (11) |
O1—Ce1—O6 | 67.09 (10) | O7iv—Ce1—O8i | 69.86 (10) |
O1—Ce1—O7iv | 84.79 (10) | O7iv—Ce1—O9 | 68.77 (11) |
O1—Ce1—O8i | 66.55 (12) | O7iv—Ce1—H1 | 97.6 (12) |
O1—Ce1—O9 | 141.24 (11) | O8i—Ce1—O9 | 77.68 (11) |
O2i—Ce1—O3ii | 140.52 (8) | O8i—Ce1—H1 | 63.7 (15) |
O2i—Ce1—O4ii | 143.52 (11) | O9—Ce1—H1 | 141.4 (15) |
O2i—Ce1—O5iii | 74.32 (13) | O2—S1—O7 | 108.58 (17) |
O2i—Ce1—O6 | 73.47 (12) | O2—S1—O8 | 106.8 (2) |
O2i—Ce1—O7iv | 118.18 (10) | O2—S1—O9 | 111.56 (19) |
O2i—Ce1—O8i | 53.18 (9) | O2—S1—H2vii | 139.5 (16) |
O2i—Ce1—O9 | 77.01 (13) | O7—S1—O8 | 110.84 (19) |
O3ii—Ce1—O4ii | 54.05 (10) | O7—S1—O9 | 107.5 (2) |
O3ii—Ce1—O5iii | 84.66 (13) | O7—S1—H2vii | 41.4 (15) |
O3ii—Ce1—O6 | 68.74 (12) | O8—S1—O9 | 111.6 (2) |
O3ii—Ce1—O7iv | 100.56 (10) | O8—S1—H2vii | 74.2 (18) |
O3ii—Ce1—O8i | 148.83 (11) | O9—S1—H2vii | 105 (2) |
O3ii—Ce1—O9 | 127.83 (13) | O3—S2—O4 | 105.9 (2) |
O4ii—Ce1—O5iii | 75.31 (13) | O3—S2—O5 | 110.0 (2) |
O4ii—Ce1—O6 | 116.43 (11) | O3—S2—O6 | 111.1 (2) |
O4ii—Ce1—O7iv | 71.64 (10) | O3—S2—H1 | 131.5 (16) |
O4ii—Ce1—O8i | 138.62 (8) | O4—S2—O5 | 111.7 (2) |
O4ii—Ce1—O9 | 74.80 (13) | O4—S2—O6 | 110.44 (18) |
O4ii—Ce1—H1 | 136.9 (18) | O4—S2—H1 | 46.9 (18) |
O5iii—Ce1—O6 | 74.10 (11) | O5—S2—O6 | 107.8 (3) |
O5iii—Ce1—O7iv | 133.83 (11) | H1—O1—H2 | 99 (7) |
O5iii—Ce1—O8i | 123.88 (14) | O1—H1—O4 | 156 (6) |
O5iii—Ce1—O9 | 72.10 (10) | O1—H2—O7viii | 163 (9) |
O5iii—Ce1—H1 | 128.5 (12) | | |
Symmetry codes: (i) −x, −y+1, −z+1; (ii) x, −y+1/2, z−1/2; (iii) −x+1, y+1/2, −z+3/2; (iv) −x, y−1/2, −z+1/2; (v) x, −y+1/2, z+1/2; (vi) −x+1, −y+1, −z+2; (vii) x, y+1, z; (viii) x, y−1, z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O4 | 0.82 (8) | 2.16 (7) | 2.929 (5) | 156 (6) |
O1—H2···O7viii | 0.98 (7) | 1.90 (7) | 2.852 (4) | 163 (9) |
Symmetry code: (viii) x, y−1, z. |
Experimental details
Crystal data |
Chemical formula | KCe(SO4)2·H2O |
Mr | 389.3 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 293 |
a, b, c (Å) | 10.1163 (2), 8.588 (4), 10.3823 (6) |
β (°) | 118.39 (3) |
V (Å3) | 793.5 (4) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 6.81 |
Crystal size (mm) | 0.1 × 0.05 × 0.03 |
|
Data collection |
Diffractometer | Oxford Instruments point-detector diffractometer |
Absorption correction | Gaussian (Jana2000; Petricek and Dusek, 2000) |
Tmin, Tmax | 0.483, 0.595 |
No. of measured, independent and observed [I > 3σ(I)] reflections | 3334, 1729, 1267 |
Rint | 0.034 |
(sin θ/λ)max (Å−1) | 0.639 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.020, 0.055, 1.18 |
No. of reflections | 1729 |
No. of parameters | 127 |
No. of restraints | ? |
H-atom treatment | All H-atom parameters refined |
Δρmax, Δρmin (e Å−3) | 1.40, −1.71 |
Selected bond lengths (Å) topCe1—O1 | 2.595 (4) | K1—O8 | 2.805 (3) |
Ce1—O2i | 2.578 (5) | S1—O2 | 1.475 (3) |
Ce1—O3ii | 2.508 (4) | S1—O7 | 1.479 (4) |
Ce1—O4ii | 2.671 (4) | S1—O8 | 1.469 (3) |
Ce1—O5iii | 2.449 (3) | S1—O9 | 1.459 (4) |
Ce1—O6 | 2.496 (3) | S2—O3 | 1.475 (4) |
Ce1—O7iv | 2.514 (2) | S2—O4 | 1.479 (3) |
Ce1—O8i | 2.699 (4) | S2—O5 | 1.468 (4) |
Ce1—O9 | 2.432 (3) | S2—O6 | 1.465 (4) |
K1—O1v | 2.981 (5) | O1—O4 | 2.929 (5) |
K1—O2i | 2.897 (3) | O1—O7viii | 2.852 (4) |
K1—O3vi | 2.812 (3) | O1—H1 | 0.82 (8) |
K1—O4vii | 2.960 (4) | O1—H2 | 0.98 (7) |
K1—O6iii | 2.845 (4) | | |
Symmetry codes: (i) −x, −y+1, −z+1; (ii) x, −y+1/2, z−1/2; (iii) −x+1, y+1/2, −z+3/2; (iv) −x, y−1/2, −z+1/2; (v) x, −y+1/2, z+1/2; (vi) −x+1, −y+1, −z+2; (vii) x, y+1, z; (viii) x, y−1, z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O4 | 0.82 (8) | 2.16 (7) | 2.929 (5) | 156 (6) |
O1—H2···O7viii | 0.98 (7) | 1.90 (7) | 2.852 (4) | 163 (9) |
Symmetry code: (viii) x, y−1, z. |
Recently, there has been a great deal of interest in rare earth complexes because of their important physical properties, including magnetism and luminescence (Wegh et al., 2000). Luminescence studies of Ce-doped compounds have demonstrated the fact that trivalent cerium ions give good performance when compared with all other rare earth ions (Nair et al., 2000). Ce gives a different thermostimulated luminescence peak structure probably related to the Ce3+–Ce2+ redox mechanism. In previous studies (Guillou et al., 1993; Audebrand et al., 1998), it was shown that those trivalent Ce compounds could be obtained from a solution of hydrated CeIV sulfate or oxide in nitric acid. An alternative synthesis of a new compound under safer conditions (approximately neutral pH) was encountered while investigating the system Ce(SO4)2·H2O–KSCN–H2O. The high oxidation power of the CeIV ion towards the SCN− group leads to the formation of the new compound, shown here to be potassium cerium(III) bis(sulfate) monohydrate, KCe(SO4)2·H2O.
The structure of the title compound comprises CeO9 polyhedra and SO4 tetrahedra, which are linked by common edges and vertices forming a semi-infinite three-dimensional network. K+ ions occur in structural channels along [010] (Fig. 1).
The coordination environments of the rare earth ions consist of nine O atoms in a configuration best described as an irregular tricapped trigonal prism (Fig. 2a). The nine O atoms are associated with one water molecule and six sulfate groups, two of which share common edges with the CeO9 polyhedra. Each sulfate group bridges three Ce polyhedra (Fig. 3). The Ce—O bond lengths, ranging from 2.432 (3) to 2.697 (4) Å (Table 1), are similar in length to the analogous distances found in NaCe(SO4)2·H2O (Blackburn & Gerkin, 1995) and RbCe(SO4)2·H2O (Robinson & Jasly, 1998). The mean Ce—O distance (2.549 Å) is also in good agreement with the value (2.53 Å) calculated by the bond-valence method (Brown, 1981) for CeIII bonded to nine O atoms.
The ninefold configuration of CeIII in KCe(SO4)2·H2O is typical of the majority of monohydrated alkali metal rare earth sulfate complexes and of rare earth ions in general. For early members of this particular rare earth series, the anionic part of the structure around the rare earth ions is relatively stable, with a coordination number of nine for Ce, Pr, La and Nd (Blackburn & Gerkin, 1994, 1995; Iskhakova et al., 1985, 1988). For later members of this sulfate series, such as Gd (Sarukhanyan et al., 1984), the coordination number decreases to eight, presumably in association with the lanthanide contraction. The rare earth configuration also varies slightly for hydrated alkali metal rare earth chloride complexes involving organic cations on the anionic structure (Mackenstedt & Urland, 1994). The change of the coordination number from nine in the heptahydrates to eight in the hexahydrates of the rare earth chlorides is also relevant (Kepert et al., 1994). Furthermore, the coordination number decreases from nine (in the case of La) (Reuter & Frenzen, 1994) to eight (in the case of Ce—Tb) (Reuter et al., 1994) for the trihydrates of these chlorides.
The two crystallographically inequivalent S atoms are each surrounded by four O atoms, establishing sulfate anions that are without symmetry contraints and which consequently form slightly irregular tetrahedra. The S1- and S2-centred sulfate tetrahedra stack in planes normal to [100], which alternate with respect to each other (Fig. 4). Both S1 and S2 form two shorter, one medium and one longer S—O bond, which range from 1.460 (4) to 1.480 (4) Å and from 1.465 (4) to 1.480 (4) Å in length, respectively, for the S1 and S2 tetrahedra. The O—S—O bond angles are consistent with slightly distorted tetrahedra, ranging from 106.8 (3) to 111.6 (2)° and 105.9 (3) to 111.6 (2)°, respectively, for S1 and S2 tetrahedra (Table 1). Furthermore, the smallest O—S—O angle for both the S1 and the S2 tetrahedron corresponds to the shared O—O edges with the CeO9 polyhedra.
The K+ cations are surrounded by six O atoms, including one water O atom (Fig. 2b). These atoms form an irregular KO6 triangular prism polyhedron; in fact, the K—O distances range from 2.807 (3) to 2.980 (6) Å (Table 1). In the analogous compound LiCe(SO4)2·H2O (Iskhakova et al., 1987), the monovalent cation, with coordination number four, forms LiO4 tetrahedra. The reduction in radii between K+ and Li+ ions is associated with a structural phase change from the compact three-dimensional framework of the present KCe(SO4)2·H2O structure to the layered structure of LiCe(SO4)2·H2O
In contrast to other structural analogues, the water molecule of KCe(SO4)2·H2O appears to be well ordered, being characterized by an O atom whose displacement parameters are consistent with those of other well ordered atoms in the structure. For the NaCe(SO4)2·H2O, NaLa(SO4)2·H2O (Blackburn & Gerkin, 1994, 1995) and AgCe(SO4)2·H2O (Audebrand et al., 1998) [rather than 1997?] analogues, the water O atom was better modelled as disordered equally over two sites.
According to the classical geometry of hydrogen bonds, water molecules are linked to sulfate anions by O—H···O hydrogen bonds (Table 2). Each sulfate tetrahedron establishes one hydrogen bond with a water molecule via the O atom coresponding to the longer S—O bonds, namely atoms O4 and O7, respectively, for the S2 and S1 tetrahedra. O—H···O hydrogen bonds act in the same way as the ionic contacts to provide connectivity between the cerium polyhedra and the sulfate anions, thereby improving the stability of the structure.