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The framework of K2Zn(H2P2O7)2·2H2O contains acid diphos­phate–metallate layers linked by K...O interactions and weak hydrogen bonds. Zn2+ cations are coordinated octahedrally by O atoms from two bidentate [H2P2O7]2− anions and two water mol­ecules.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536803005440/mg6021sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536803005440/mg6021Isup2.hkl
Contains datablock I

Key indicators

  • Single-crystal X-ray study
  • T = 292 K
  • Mean [sigma](P-O) = 0.004 Å
  • R factor = 0.056
  • wR factor = 0.093
  • Data-to-parameter ratio = 18.9

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


Yellow Alert Alert Level C:
REFLT_03 From the CIF: _diffrn_reflns_theta_max 31.58 From the CIF: _reflns_number_total 2154 TEST2: Reflns within _diffrn_reflns_theta_max Count of symmetry unique reflns 2376 Completeness (_total/calc) 90.66% Alert C: < 95% complete
0 Alert Level A = Potentially serious problem
0 Alert Level B = Potential problem
1 Alert Level C = Please check

Comment top

To our knowledge, no mixed dihydrogendiphosphates of the form (A,T)x(H2P2O7)y.zH2O (A = alkaline earth and T = transition metal) have been reported. Some simple alkali metal dihydrogendiphosphates are known: Na2H2P2O7·6H2O (Collin & Willis, 1971), K2H2P2O7 (Larbot et al., 1983), K2H2P2O7.1/2H2O (Dumas et al., 1973), K3H(H2P2O7)2 (Dumas, 1978), K3Na(H2P2O7)2 (Dumas et al., 1980), Rb2H2P2O7·0.5H2O (Averbuch-Pouchart & Durif, 1993a) and Cs2H2P2O7 (Averbuch-Pouchart & Durif, 1993b). Acidic metal diphosphates have been implicated in some enzyme-catalyzed reaction processes (Haromy et al., 1984) and are used as inhibitors in the formation and dissolution of apatite crystals in vitro (Mathew et al., 1993). We recently reported the structures of two hydrogendiphosphates, KM(HP2O7)·2H2O (M = Mn, Zn) (Assaaoudi et al., 2002). We report here the structure of the dihydrogendiphosphate K2Zn(H2P2O7)2·2H2O.

The structure of K2Zn(H2P2O7)2·2H2O can be described in terms of layers parallel to (001) (Fig. 1). Each layer is built up of [KO8], [ZnO6] and [H2P2O7] polyhedra (Fig. 2) sharing corners and edges. The [ZnO6] polyhedra share four corners with two neighbouring [H2P2O7] anions to form the unit [Zn(H2P2O7)2·2H2O], I. The [KO8] polyhedra share one edge to form the unit [K2O14], II. Edge-sharing of units I and II results in a layer parallel to (001). Neighbouring layers are connected by K···O interactions and weak hydrogen bonds.

Each of the two unique phosphorus atoms is coordinated by four O atoms, one of which belongs to a hydroxyl group, in a slightly distorted tetrahedral geometry. The two tetrahedra share a corner (O1) to form the [H2P2O7]2- anion in a roughly eclipsed conformation. The average P—O distance of 1.533 Å is similar to that found in K2H2P2O7 (1.537 Å) and K3H(H2P2O7)2 (1.543 Å). The P—O—P angle of 128.85 (6)° is close to that in Ca2P2O7 (130.0°; Calvo, 1968) and K4P2O7·3H2O (130.3°; Robertson & Calvo 1967). The Zn2+ ions are coordinated in a nearly regular octahedral geometry by two bidentate [H2P2O7]2- anions and two water molecules. The average Zn—O distance of 2.084 Å is close to that in β-Zn2P2O7 (2.121 Å; Calvo, 1965). The [ZnO6] polyhedra are isolated, with the shortest Zn···Zn distance being over 6 Å. The K atoms are eightfold coordinated, with K—O distances ranging from 2.757 (3) to 3.339 (4) Å. The average K—O distance of 2.959 Å is slightly longer than those found in K4P2O7·3H2O (2.812 Å; Dumas & Galigne, 1974) and K2H2P2O7 (2.908 Å; Larbot et al., 1983).

Experimental top

Stoichiometric amounts of ZnCl2 were dissolved in a K4P2O7 solution in distilled water. After it was stirred for 1 d and allowed to stand for two to three weeks, large prismatic colourless crystals were deposited. The crystals were filtered off and washed with a water–ethanol (20:80) solution.

Computing details top

Data collection: SMART (Bruker, 1999); cell refinement: SAINT (Bruker, 1999); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia,1997) and ATOMS (Dowty,1999); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. Projection along the b axis of K2Zn(H2P2O7)2·2H2O. Polyhedra: yellow [H2P2O7], green [ZnO6]; circles: large pink K, small grey H.
[Figure 2] Fig. 2. Coordination polyhedra of [KO8], [ZnO6] and [H2P2O7]. Displacement ellipsoids are at the 50% probability level.
dipotassium zinc bis(dihydrogendiphosphate) dihydrate top
Crystal data top
K2Zn(H2P2O7)2·2H2OZ = 1
Mr = 531.51F(000) = 264
Triclinic, P1Dx = 2.479 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 6.827 (3) ÅCell parameters from 1307 reflections
b = 7.333 (3) Åθ = 2.8–29.8°
c = 7.570 (3) ŵ = 2.84 mm1
α = 80.753 (8)°T = 292 K
β = 72.547 (8)°Prism, colourless
γ = 83.442 (8)°0.33 × 0.12 × 0.04 mm
V = 356.0 (2) Å3
Data collection top
Bruker SMART APEX CCD area-detector
diffractometer
2154 independent reflections
Radiation source: fine-focus sealed tube1244 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.081
ω scansθmax = 31.6°, θmin = 2.8°
Absorption correction: multi-scan
(XPREP; Sheldrick, 1997)
h = 99
Tmin = 0.670, Tmax = 0.893k = 1010
4313 measured reflectionsl = 1010
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)] = 0.056Hydrogen site location: difference Fourier map
wR(F2) = 0.093H-atom parameters constrained
S = 0.86 w = 1/[σ2(Fo2) + (0.001P)2]
where P = (Fo2 + 2Fc2)/3
2154 reflections(Δ/σ)max < 0.001
114 parametersΔρmax = 1.28 e Å3
4 restraintsΔρmin = 0.98 e Å3
Crystal data top
K2Zn(H2P2O7)2·2H2Oγ = 83.442 (8)°
Mr = 531.51V = 356.0 (2) Å3
Triclinic, P1Z = 1
a = 6.827 (3) ÅMo Kα radiation
b = 7.333 (3) ŵ = 2.84 mm1
c = 7.570 (3) ÅT = 292 K
α = 80.753 (8)°0.33 × 0.12 × 0.04 mm
β = 72.547 (8)°
Data collection top
Bruker SMART APEX CCD area-detector
diffractometer
2154 independent reflections
Absorption correction: multi-scan
(XPREP; Sheldrick, 1997)
1244 reflections with I > 2σ(I)
Tmin = 0.670, Tmax = 0.893Rint = 0.081
4313 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0564 restraints
wR(F2) = 0.093H-atom parameters constrained
S = 0.86Δρmax = 1.28 e Å3
2154 reflectionsΔρmin = 0.98 e Å3
114 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*/Ueq
K10.89203 (18)0.26588 (17)0.70406 (16)0.0330 (3)
Zn10.50000.50000.50000.0172 (2)
O1W0.5496 (5)0.7084 (5)0.2659 (4)0.0249 (8)
H1W0.61160.66200.17120.06 (2)*
H2W0.59710.79500.27870.10 (3)*
P10.32331 (18)0.27285 (18)0.24797 (16)0.0165 (3)
P20.75109 (18)0.18972 (18)0.24168 (16)0.0157 (3)
O10.5623 (4)0.2317 (5)0.1528 (4)0.0222 (8)
O20.2936 (5)0.3926 (4)0.3967 (4)0.0189 (7)
O30.2376 (4)0.3499 (5)0.0907 (4)0.0216 (8)
O40.2362 (5)0.0815 (5)0.3359 (5)0.0246 (8)
H40.24920.05490.44140.10 (3)*
O50.7418 (5)0.3276 (5)0.3708 (4)0.0223 (8)
O60.9303 (5)0.2144 (5)0.0615 (4)0.0220 (8)
H61.01680.27380.07750.07 (2)*
O70.7467 (5)0.0092 (5)0.3307 (4)0.0257 (8)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
K10.0422 (7)0.0272 (7)0.0347 (7)0.0050 (6)0.0193 (6)0.0088 (6)
Zn10.0218 (4)0.0135 (4)0.0199 (4)0.0022 (3)0.0085 (3)0.0069 (3)
O1W0.034 (2)0.019 (2)0.022 (2)0.0068 (17)0.0057 (16)0.0045 (16)
P10.0189 (6)0.0152 (7)0.0182 (6)0.0025 (5)0.0077 (5)0.0053 (5)
P20.0181 (6)0.0147 (7)0.0163 (6)0.0024 (5)0.0055 (5)0.0059 (5)
O10.0193 (18)0.031 (2)0.0200 (18)0.0003 (15)0.0082 (14)0.0106 (15)
O20.0205 (17)0.0159 (18)0.0261 (18)0.0012 (14)0.0096 (14)0.0135 (14)
O30.0223 (18)0.025 (2)0.0206 (17)0.0045 (15)0.0114 (15)0.0016 (15)
O40.039 (2)0.0161 (19)0.0243 (19)0.0084 (16)0.0157 (16)0.0006 (15)
O50.0259 (18)0.0209 (19)0.0261 (18)0.0024 (15)0.0102 (15)0.0144 (15)
O60.0221 (18)0.028 (2)0.0192 (18)0.0107 (16)0.0051 (14)0.0083 (15)
O70.036 (2)0.020 (2)0.0218 (18)0.0059 (16)0.0102 (16)0.0004 (15)
Geometric parameters (Å, º) top
K1—O6i2.757 (3)Zn1—O22.080 (3)
K1—O2ii2.775 (3)Zn1—O1Wii2.116 (3)
K1—O4iii2.874 (4)Zn1—O1W2.116 (3)
K1—O7iv2.899 (4)P1—O31.485 (3)
K1—O1Wii2.941 (4)P1—O21.490 (3)
K1—O52.949 (3)P1—O41.556 (3)
K1—O2v3.139 (3)P1—O11.589 (3)
K1—O3ii3.339 (4)P2—O71.505 (3)
Zn1—O5ii2.057 (3)P2—O51.499 (3)
Zn1—O52.057 (3)P2—O61.536 (3)
Zn1—O2ii2.080 (3)P2—O11.603 (3)
O6i—K1—O2ii114.43 (10)O2ii—Zn1—O1W91.69 (14)
O6i—K1—O4iii104.22 (10)O2—Zn1—O1W88.31 (14)
O2ii—K1—O4iii123.60 (10)O1Wii—Zn1—O1W180.000 (1)
O6i—K1—O7iv78.02 (10)Zn1—O1W—K1ii89.76 (11)
O2ii—K1—O7iv150.48 (10)Zn1—O1W—H1W109.5
O4iii—K1—O7iv74.48 (10)K1ii—O1W—H1W107.7
O6i—K1—O1Wii107.72 (10)Zn1—O1W—H2W114.1
O2ii—K1—O1Wii61.43 (10)K1ii—O1W—H2W118.4
O4iii—K1—O1Wii68.78 (10)H1W—O1W—H2W114.7
O7iv—K1—O1Wii143.13 (11)O3—P1—O2116.54 (19)
O6i—K1—O5165.84 (10)O3—P1—O4109.15 (19)
O2ii—K1—O559.76 (9)O2—P1—O4109.95 (19)
O4iii—K1—O572.66 (10)O3—P1—O1104.89 (17)
O7iv—K1—O5113.51 (10)O2—P1—O1109.67 (18)
O1Wii—K1—O558.15 (9)O4—P1—O1106.05 (19)
O6i—K1—O2v113.36 (9)O5—P2—O7114.9 (2)
O2ii—K1—O2v86.82 (9)O5—P2—O6112.91 (19)
O4iii—K1—O2v114.10 (10)O7—P2—O6110.9 (2)
O7iv—K1—O2v63.75 (9)O5—P2—O1110.48 (18)
O1Wii—K1—O2v135.87 (9)O7—P2—O1107.20 (19)
O5—K1—O2v80.01 (9)O6—P2—O199.19 (17)
O6i—K1—O3ii67.22 (9)P1—O1—P2130.8 (2)
O2ii—K1—O3ii47.81 (8)P1—O2—Zn1132.41 (19)
O4iii—K1—O3ii146.43 (9)P1—O2—K1ii109.43 (16)
O7iv—K1—O3ii130.45 (9)Zn1—O2—K1ii95.19 (12)
O1Wii—K1—O3ii82.69 (10)P1—O2—K1vi104.84 (15)
O5—K1—O3ii107.43 (9)Zn1—O2—K1vi113.98 (12)
O2v—K1—O3ii98.56 (8)K1ii—O2—K1vi93.18 (9)
O5ii—Zn1—O5180.0P1—O3—K1ii86.07 (14)
O5ii—Zn1—O2ii92.71 (12)P1—O4—K1iii150.3 (2)
O5—Zn1—O2ii87.29 (12)P1—O4—H4109.5
O5ii—Zn1—O287.29 (12)K1iii—O4—H498.9
O5—Zn1—O292.71 (12)P2—O5—Zn1130.27 (19)
O2ii—Zn1—O2180.000 (1)P2—O5—K1126.92 (18)
O5ii—Zn1—O1Wii93.39 (13)Zn1—O5—K190.68 (11)
O5—Zn1—O1Wii86.61 (13)P2—O6—K1vii125.17 (18)
O2ii—Zn1—O1Wii88.31 (14)P2—O6—H6109.5
O2—Zn1—O1Wii91.69 (14)K1vii—O6—H6115.6
O5ii—Zn1—O1W86.61 (13)P2—O7—K1iv124.14 (17)
O5—Zn1—O1W93.39 (13)
O5ii—Zn1—O1W—K1ii47.92 (12)O1—P1—O4—K1iii75.1 (4)
O5—Zn1—O1W—K1ii132.08 (12)O7—P2—O5—Zn1102.3 (3)
O2ii—Zn1—O1W—K1ii140.53 (11)O6—P2—O5—Zn1129.1 (2)
O2—Zn1—O1W—K1ii39.47 (11)O1—P2—O5—Zn119.1 (3)
O3—P1—O1—P2165.1 (3)O7—P2—O5—K128.7 (3)
O2—P1—O1—P239.2 (3)O6—P2—O5—K199.9 (2)
O4—P1—O1—P279.5 (3)O1—P2—O5—K1150.06 (17)
O5—P2—O1—P147.7 (4)O2ii—Zn1—O5—P2176.4 (3)
O7—P2—O1—P178.2 (3)O2—Zn1—O5—P23.6 (3)
O6—P2—O1—P1166.5 (3)O1Wii—Zn1—O5—P295.1 (3)
O3—P1—O2—Zn1121.3 (2)O1W—Zn1—O5—P284.9 (3)
O4—P1—O2—Zn1113.8 (3)O2ii—Zn1—O5—K140.72 (11)
O1—P1—O2—Zn12.4 (3)O2—Zn1—O5—K1139.28 (11)
O3—P1—O2—K1ii4.4 (2)O1Wii—Zn1—O5—K147.74 (12)
O4—P1—O2—K1ii129.28 (17)O1W—Zn1—O5—K1132.26 (12)
O1—P1—O2—K1ii114.48 (17)O6i—K1—O5—P2110.0 (4)
O3—P1—O2—K1vi94.44 (18)O2ii—K1—O5—P2179.3 (2)
O4—P1—O2—K1vi30.4 (2)O4iii—K1—O5—P230.7 (2)
O1—P1—O2—K1vi146.65 (15)O7iv—K1—O5—P233.1 (2)
O5ii—Zn1—O2—P1166.5 (3)O1Wii—K1—O5—P2106.1 (2)
O5—Zn1—O2—P113.5 (3)O2v—K1—O5—P288.6 (2)
O1Wii—Zn1—O2—P1100.2 (3)O3ii—K1—O5—P2175.49 (19)
O1W—Zn1—O2—P179.8 (3)O6i—K1—O5—Zn134.8 (5)
O5ii—Zn1—O2—K1ii44.12 (12)O2ii—K1—O5—Zn134.43 (10)
O5—Zn1—O2—K1ii135.88 (12)O4iii—K1—O5—Zn1114.12 (12)
O1Wii—Zn1—O2—K1ii137.43 (12)O7iv—K1—O5—Zn1177.92 (10)
O1W—Zn1—O2—K1ii42.57 (12)O1Wii—K1—O5—Zn138.73 (11)
O5ii—Zn1—O2—K1vi51.70 (14)O2v—K1—O5—Zn1126.58 (12)
O5—Zn1—O2—K1vi128.30 (14)O3ii—K1—O5—Zn130.66 (12)
O1Wii—Zn1—O2—K1vi41.62 (15)O5—P2—O6—K1vii124.4 (2)
O1W—Zn1—O2—K1vi138.38 (15)O7—P2—O6—K1vii105.1 (2)
O2—P1—O3—K1ii3.49 (18)O1—P2—O6—K1vii7.4 (2)
O4—P1—O3—K1ii128.74 (15)O5—P2—O7—K1iv100.6 (2)
O1—P1—O3—K1ii117.98 (15)O6—P2—O7—K1iv28.9 (3)
O3—P1—O4—K1iii37.4 (4)O1—P2—O7—K1iv136.19 (18)
O2—P1—O4—K1iii166.4 (3)
Symmetry codes: (i) x, y, z+1; (ii) x+1, y+1, z+1; (iii) x+1, y, z+1; (iv) x+2, y, z+1; (v) x+1, y, z; (vi) x1, y, z; (vii) x, y, z1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O4—H4···O7iii0.821.712.529 (5)175
O6—H6···O3v0.821.702.503 (5)165
O1W—H1W···O3viii0.821.952.731 (5)158
O1W—H2W···O7ix0.782.002.775 (5)171
Symmetry codes: (iii) x+1, y, z+1; (v) x+1, y, z; (viii) x+1, y+1, z; (ix) x, y+1, z.

Experimental details

Crystal data
Chemical formulaK2Zn(H2P2O7)2·2H2O
Mr531.51
Crystal system, space groupTriclinic, P1
Temperature (K)292
a, b, c (Å)6.827 (3), 7.333 (3), 7.570 (3)
α, β, γ (°)80.753 (8), 72.547 (8), 83.442 (8)
V3)356.0 (2)
Z1
Radiation typeMo Kα
µ (mm1)2.84
Crystal size (mm)0.33 × 0.12 × 0.04
Data collection
DiffractometerBruker SMART APEX CCD area-detector
diffractometer
Absorption correctionMulti-scan
(XPREP; Sheldrick, 1997)
Tmin, Tmax0.670, 0.893
No. of measured, independent and
observed [I > 2σ(I)] reflections
4313, 2154, 1244
Rint0.081
(sin θ/λ)max1)0.737
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.056, 0.093, 0.86
No. of reflections2154
No. of parameters114
No. of restraints4
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)1.28, 0.98

Computer programs: SMART (Bruker, 1999), SAINT (Bruker, 1999), SAINT, SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), ORTEP-3 (Farrugia,1997) and ATOMS (Dowty,1999), SHELXL97.

Selected bond lengths (Å) top
K1—O6i2.757 (3)Zn1—O22.080 (3)
K1—O2ii2.775 (3)Zn1—O1Wii2.116 (3)
K1—O4iii2.874 (4)Zn1—O1W2.116 (3)
K1—O7iv2.899 (4)P1—O31.485 (3)
K1—O1Wii2.941 (4)P1—O21.490 (3)
K1—O52.949 (3)P1—O41.556 (3)
K1—O2v3.139 (3)P1—O11.589 (3)
K1—O3ii3.339 (4)P2—O71.505 (3)
Zn1—O5ii2.057 (3)P2—O51.499 (3)
Zn1—O52.057 (3)P2—O61.536 (3)
Zn1—O2ii2.080 (3)P2—O11.603 (3)
Symmetry codes: (i) x, y, z+1; (ii) x+1, y+1, z+1; (iii) x+1, y, z+1; (iv) x+2, y, z+1; (v) x+1, y, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O4—H4···O7iii0.821.712.529 (5)175
O6—H6···O3v0.821.702.503 (5)165
O1W—H1W···O3vi0.821.952.731 (5)158
O1W—H2W···O7vii0.782.002.775 (5)171
Symmetry codes: (iii) x+1, y, z+1; (v) x+1, y, z; (vi) x+1, y+1, z; (vii) x, y+1, z.
 

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