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Pb2(Hg3O4)(CrO4) consists of [CrO4]2- tetra­hedra, linear O-Hg-O dumbbells and divalent Pb atoms in [3+5]-coordination. The HgO2 dumbbells are condensed into [Hg3O4]2- units and can be regarded as a section of the HgO structure. The [Hg3O4]2- complex anions are connected by inter­stitial Pb2+ ions, while the [CrO4]2- tetra­hedra are isolated.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270105012552/ta1488sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270105012552/ta1488Isup2.hkl
Contains datablock I

Comment top

Pb2(Hg3O4)(CrO4) consists of three different structural building units, viz. [CrO4]2− tetrahedra, [Hg3O4]2− anionic strips and, connecting the latter, Pb2+ ions. The [CrO4]2− ion is only slightly distorted; all Cr—O distances are identical within the 1σ limit, and the angles are close to the tetrahedral value.

All crystallographically independent Hg atoms are linearly coordinated by O atoms, and the Hg—O distances decrease remarkably from the central [2.094 (9) and 2.097 (9) Å] to the terminal bonds [2.006 (10) and 2.0154 (10) Å??]. The Hg—O—Hg angles of 111.2 (4)° and 114.7 (4)° result in a zigzag shape of the [Hg3O4]2− anion. The dihedral angle between the two terminal O—Hg—O dumbbells is ca 0.9°, so all atoms are approximately coplanar. These characteristic [Hg3O4]2− units represent a section of the HgO structure and are linked by Pb2+ ions, forming a three-dimensional framework (Figs. 1 and 2).

The two Pb atoms exhibit a stereochemically active lone pair; each atom has three close O-atom contacts on one side [Pb1: 2.246 (10)–2.512 (11), Pb2: 2.309 (10)–2.380 (9) Å], and five considerably more remote neighbours on the other [Pb1: 2.868 (15)–3.610 (10), Pb2: 2.761 (12)–3.228 (11) Å; Table 1 and Fig. 3). Considered as pyramidal PbO3 units, the polyhedra containing Pb2 form dimers via common O8—O8iii [symmetry code: (iii) 2 − x, −y, 2 − z] edges, while those containing Pb1 are arranged as infinite chains along [001], linked via common vertices. The close contacts are formed exclusively with O atoms of the [Hg3O4]2− group, each coordinating to three heavy metal cations (O5 and O8: 1 Hg + 2 Pb; O6 and O7: 2 Hg + 1 Pb).

Atoms O1–O4, belonging to the [CrO4]2− tetrahedra, find their closest Hg and Pb neighbours at distances of 2.57 (O1—Hg2) and 2.76 Å (O4—Pb2), respectively, i.e. atoms O1–O4 reside in the second coordination sphere of Hg and Pb atoms, only.

The title compound is closely related to Pb2(HgO2)(CrO4) (Klein et al., 2002), which was found under similar synthetic conditions. The crystal structure also consists of isolated [CrO4]2− tetrahedra, [HgO2]2 dumbbells, and Pb2+ ions in a (3 + 5) O-atom coordination with closest contacts to O atoms which are not bonded to chromium. Both compounds described here belong to the series of Pb2(HgnOn + 1)(CrO4) compositions and differ in the chain length of the HgnOn + 1 fragment. Another formal member of this family with n = 0, the naturally occurring phoenicochroit, Pb2OCrO4 (Williams et al., 1970), was also observed in our experiments.

Inspecting oxochromates(VI) containing divalent Pb and/or Hg, such as PbCrO4 (Quareni & de Pieri, 1965), HgCrO4 (Stalhandske, 1978), Hg3CrO6 (Hansen et al., 1995) and the compounds mentioned above, general structural trends become obvious. With increasing amounts of the heavy metal cations, the [CrO4]2− tetrahedra tend to separate firstly from Hg-containing entities, and subsequently the number of short Pb—OCrO3 contacts is reduced. As a second structural constant besides the [CrO4]2− tetrahedra, Hg appears in linear coordination in all compounds mentioned here, and structural motifs strongly reminiscent of the HgO structure are formed, i.e. [HgO2]2 dumbbells in Pb2(HgO2)(CrO4), [Hg3O4]2− zigzag chains in the title compound and two-dimensional networks in Hg3CrO6. Pb2+ ions, mostly occurring in a (3 + x) O-atom coordination (x around 5), exhibit the highest flexibility in its coordination sphere among the present cations, and separates and shortens the [HgO]n chains and fragments.

Experimental top

Single crystals of Pb2(Hg3O4)(CrO4) were obtained at elevated oxygen pressures using steel autoclaves. In a typical experiment, HgO, PbO and CrO3 were used as starting materials, and distilled water (2 ml) was added to accelerate the reaction. The ground mixture, placed in gold crucibles, was annealed for 120 h at 753 K and 12 MPa oxygen pressure in stainless steel autoclaves (Linke & Jansen, 1997).

Computing details top

Data collection: X-AREA (Stoe & Cie, 1996); cell refinement: X-AREA; data reduction: X-RED (Stoe & Cie, 1996); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 2001); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. A perspective view of Pb2Hg3O4(CrO4) along [001]. Drawn are Pb atoms, [Hg3O4]2− units and [CrO4]2− tetrahedra.
[Figure 2] Fig. 2. The surrounding of the [Hg3O4]2− unit with six-coordinate PbO3 pyramids and a [CrO4]2− tetrahedron. Displacement ellipsoids are shown at the 50% probability level. [Symmetry codes: (i) 1 + x, y, z; (ii) 1 + x, 1/2 − y, 1/2 + z; (iii) 2 − x, −y, 2 − z; (iv) −1 + x, y, z; (v) 1 − x, −y, 2 − z; (vi) x, 1/2 − y, 1/2 + z; (vii) x, 1/2 − y, −1/2 + z; (viii) −1 + x, 1/2 − y, −1/2 + z.]
[Figure 3] Fig. 3. The (3 + 5)-coordination of the two Pb2+ ions; dashed bonds are longer than 2.52 Å. Displacement ellipsoids are shown at the 50% probability level. [Symmetry codes: (i) 1 + x, y, z; (ii) 1 + x, 1/2 − y, 1/2 + z; (iii) 2 − x, −y, 2 − z; (vi) x, 1/2 − y, 1/2 + z; (vii) x, 1/2 − y, −1/2 + z; (ix) 1 − x, −y, 1 − z; (x) 2 − x, −y, 1 − z; (xi) −1 + x, 1/2 − y, 1/2 + z.]
Dilead trimercury chromate(VI) top
Crystal data top
Pb2(Hg3O4)(CrO4)F(000) = 1968
Mr = 1196.15Dx = 8.417 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 17644 reflections
a = 6.5408 (9) Åθ = 0.0–44.2°
b = 21.947 (3) ŵ = 85.28 mm1
c = 6.9672 (10) ÅT = 293 K
β = 109.304 (11)°Block, red
V = 943.9 (2) Å30.2 × 0.2 × 0.2 mm
Z = 4
Data collection top
Stoe IPDS-II
diffractometer
2292 independent reflections
Radiation source: fine-focus sealed tube2016 reflections with I > 2σ(I)
Plane graphite monochromatorRint = 0.138
Detector resolution: 6.67 pixels mm-1θmax = 28.0°, θmin = 1.9°
ϕ or ω? scansh = 88
Absorption correction: integration
X-SHAPE (Stoe & Cie, 1996)
k = 2828
Tmin = 0.003, Tmax = 0.023l = 99
16447 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)] = 0.045 w = 1/[σ2(Fo2) + (0.079P)2]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.119(Δ/σ)max < 0.001
S = 1.01Δρmax = 3.79 e Å3
2292 reflectionsΔρmin = 4.97 e Å3
128 parametersExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraintsExtinction coefficient: 0.00073 (10)
Crystal data top
Pb2(Hg3O4)(CrO4)V = 943.9 (2) Å3
Mr = 1196.15Z = 4
Monoclinic, P21/cMo Kα radiation
a = 6.5408 (9) ŵ = 85.28 mm1
b = 21.947 (3) ÅT = 293 K
c = 6.9672 (10) Å0.2 × 0.2 × 0.2 mm
β = 109.304 (11)°
Data collection top
Stoe IPDS-II
diffractometer
2292 independent reflections
Absorption correction: integration
X-SHAPE (Stoe & Cie, 1996)
2016 reflections with I > 2σ(I)
Tmin = 0.003, Tmax = 0.023Rint = 0.138
16447 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.045128 parameters
wR(F2) = 0.1190 restraints
S = 1.01Δρmax = 3.79 e Å3
2292 reflectionsΔρmin = 4.97 e Å3
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
Pb10.15994 (9)0.29963 (2)0.92668 (8)0.03118 (18)
Pb20.97308 (9)0.02318 (2)0.73910 (8)0.03034 (17)
Hg10.36147 (8)0.21950 (2)0.90351 (8)0.03032 (17)
Hg20.06588 (9)0.13842 (2)0.86609 (8)0.03149 (18)
Hg30.50352 (8)0.05650 (2)0.82352 (8)0.03087 (18)
Cr0.5853 (4)0.11184 (9)0.3614 (3)0.0282 (4)
O10.326 (2)0.1067 (5)0.218 (2)0.045 (3)
O20.736 (2)0.1421 (6)0.236 (2)0.050 (3)
O30.596 (2)0.1553 (6)0.562 (2)0.053 (3)
O40.674 (2)0.0419 (5)0.4350 (19)0.043 (3)
O50.6871 (16)0.2253 (4)0.7989 (17)0.032 (2)
O60.0348 (15)0.2153 (4)0.9888 (17)0.031 (2)
O70.1767 (16)0.0660 (4)0.7303 (17)0.030 (2)
O80.8240 (16)0.0415 (5)0.9186 (17)0.035 (2)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Pb10.0313 (3)0.0221 (3)0.0425 (3)0.00053 (17)0.0153 (2)0.00009 (18)
Pb20.0319 (3)0.0233 (2)0.0370 (3)0.00023 (18)0.0130 (2)0.00055 (18)
Hg10.0270 (3)0.0248 (3)0.0405 (3)0.00091 (17)0.0128 (2)0.00137 (18)
Hg20.0329 (3)0.0212 (3)0.0424 (3)0.00183 (19)0.0153 (2)0.00009 (18)
Hg30.0287 (3)0.0249 (3)0.0403 (3)0.00141 (18)0.0131 (2)0.00062 (19)
Cr0.0285 (10)0.0220 (9)0.0358 (10)0.0017 (7)0.0127 (8)0.0006 (8)
O10.036 (6)0.039 (6)0.054 (7)0.000 (5)0.006 (5)0.004 (5)
O20.048 (7)0.050 (7)0.057 (7)0.004 (5)0.024 (6)0.016 (6)
O30.062 (8)0.043 (6)0.051 (6)0.006 (6)0.015 (6)0.023 (6)
O40.049 (7)0.023 (5)0.052 (6)0.002 (4)0.011 (5)0.006 (4)
O50.025 (4)0.027 (4)0.043 (5)0.002 (4)0.012 (4)0.000 (4)
O60.022 (4)0.019 (4)0.053 (6)0.002 (3)0.014 (4)0.010 (4)
O70.025 (4)0.018 (4)0.053 (6)0.000 (3)0.018 (4)0.007 (4)
O80.017 (4)0.039 (5)0.050 (5)0.007 (4)0.011 (4)0.002 (4)
Geometric parameters (Å, º) top
Cr—O11.661 (12)Pb1—O7v3.610 (10)
Cr—O21.656 (13)Pb1—Crv3.544 (2)
Cr—O31.675 (12)Pb1—Hg2v3.5840 (9)
Cr—O41.661 (11)Pb1—Hg23.5920 (8)
Hg1—O52.015 (10)Pb2—O82.309 (10)
Hg1—O62.022 (9)Pb2—O8vii2.349 (11)
Hg1—Hg23.3956 (8)Pb2—O7ii2.380 (9)
Hg2—O62.094 (9)Pb2—O42.761 (12)
Hg2—O72.097 (9)Pb2—O1viii2.771 (13)
Hg2—O1i2.576 (12)Pb2—O4ix2.972 (14)
Hg2—O5ii2.639 (10)Pb2—O2ix3.202 (13)
Hg2—Hg33.4749 (8)Pb2—O7viii3.228 (11)
Hg2—Pb1iii3.5840 (9)Pb2—Pb2ix3.6105 (11)
Hg3—O72.029 (10)Pb2—Hg2ii3.6572 (8)
Hg3—O82.006 (10)Pb2—Pb2vii3.6783 (11)
Pb1—O5ii2.246 (10)Pb2—Crix3.736 (2)
Pb1—O62.367 (10)O1—Hg2x2.576 (12)
Pb1—O5iv2.512 (11)O5—Pb1xi2.246 (10)
Pb1—O3v2.868 (15)O5—Pb1xii2.512 (11)
Pb1—O6iii2.910 (11)O5—Hg2xi2.639 (10)
Pb1—O1v2.928 (13)O7—Pb2xi2.380 (9)
Pb1—O2vi2.943 (14)O8—Pb2vii2.349 (11)
O1—Cr—O2112.0 (7)O8—Hg3—Hg2149.0 (3)
O1—Cr—O3107.1 (7)O7—Hg3—Hg233.2 (3)
O1—Cr—O4107.7 (6)O5ii—Pb1—O680.9 (3)
O2—Cr—O3110.1 (8)O5ii—Pb1—O5iv100.0 (3)
O2—Cr—O4109.1 (7)O6—Pb1—O5iv72.3 (3)
O3—Cr—O4110.7 (7)O5ii—Pb1—Hg2v147.0 (3)
O5—Hg1—O6176.0 (5)O6—Pb1—Hg2v83.4 (2)
O5—Hg1—Hg2143.5 (3)O5iv—Pb1—Hg2v47.4 (2)
O6—Hg1—Hg235.1 (2)O5ii—Pb1—Hg247.1 (3)
O6—Hg2—O7175.6 (4)O6—Pb1—Hg233.8 (2)
O6—Hg2—O1i91.6 (4)O5iv—Pb1—Hg284.3 (2)
O7—Hg2—O1i90.3 (4)Hg2v—Pb1—Hg2113.76 (2)
O6—Hg2—O5ii77.5 (4)O8—Pb2—O8vii75.7 (4)
O7—Hg2—O5ii98.3 (3)O8—Pb2—O7ii81.3 (4)
O1i—Hg2—O5ii96.5 (3)O8vii—Pb2—O7ii91.9 (4)
O6—Hg2—Hg133.7 (3)O8—Pb2—Pb2ix120.9 (3)
O7—Hg2—Hg1148.0 (3)O8vii—Pb2—Pb2ix142.2 (3)
O1i—Hg2—Hg1111.8 (3)O7ii—Pb2—Pb2ix61.2 (3)
O5ii—Hg2—Hg1101.7 (2)O8—Pb2—Pb2vii38.2 (3)
O6—Hg2—Hg3146.2 (3)O8vii—Pb2—Pb2vii37.5 (2)
O7—Hg2—Hg332.0 (3)O7ii—Pb2—Pb2vii85.8 (3)
O1i—Hg2—Hg368.7 (3)Pb2ix—Pb2—Pb2vii145.83 (3)
O5ii—Hg2—Hg377.8 (2)Cr—O1—Hg2x141.0 (7)
Hg1—Hg2—Hg3179.37 (2)Hg1—O5—Pb1xi117.3 (5)
O6—Hg2—Pb1iii102.1 (3)Hg1—O5—Pb1xii111.8 (5)
O7—Hg2—Pb1iii73.7 (3)Pb1xi—O5—Pb1xii119.3 (4)
O1i—Hg2—Pb1iii132.0 (3)Hg1—O5—Hg2xi121.8 (4)
O5ii—Hg2—Pb1iii44.5 (2)Pb1xi—O5—Hg2xi94.3 (4)
Hg1—Hg2—Pb1iii104.174 (19)Pb1xii—O5—Hg2xi88.1 (3)
Hg3—Hg2—Pb1iii75.197 (18)Hg1—O6—Hg2111.2 (4)
O6—Hg2—Pb139.0 (3)Hg1—O6—Pb1119.4 (4)
O7—Hg2—Pb1136.7 (3)Hg2—O6—Pb1107.1 (4)
O1i—Hg2—Pb196.9 (3)Hg2—O7—Hg3114.7 (4)
O5ii—Hg2—Pb138.6 (2)Hg3—O7—Pb2xi116.5 (4)
Hg1—Hg2—Pb165.677 (16)Hg2—O7—Pb2xi109.4 (4)
Hg3—Hg2—Pb1113.936 (19)Hg3—O8—Pb2120.3 (5)
Pb1iii—Hg2—Pb169.856 (14)Hg3—O8—Pb2vii122.8 (5)
O7—Hg3—O8176.4 (4)Pb2—O8—Pb2vii104.3 (4)
Symmetry codes: (i) x, y, z+1; (ii) x+1, y, z; (iii) x, y+1/2, z1/2; (iv) x+1, y+1/2, z+1/2; (v) x, y+1/2, z+1/2; (vi) x1, y+1/2, z+1/2; (vii) x+2, y, z+2; (viii) x+1, y, z+1; (ix) x+2, y, z+1; (x) x, y, z1; (xi) x1, y, z; (xii) x1, y+1/2, z1/2.

Experimental details

Crystal data
Chemical formulaPb2(Hg3O4)(CrO4)
Mr1196.15
Crystal system, space groupMonoclinic, P21/c
Temperature (K)293
a, b, c (Å)6.5408 (9), 21.947 (3), 6.9672 (10)
β (°) 109.304 (11)
V3)943.9 (2)
Z4
Radiation typeMo Kα
µ (mm1)85.28
Crystal size (mm)0.2 × 0.2 × 0.2
Data collection
DiffractometerStoe IPDS-II
diffractometer
Absorption correctionIntegration
X-SHAPE (Stoe & Cie, 1996)
Tmin, Tmax0.003, 0.023
No. of measured, independent and
observed [I > 2σ(I)] reflections
16447, 2292, 2016
Rint0.138
(sin θ/λ)max1)0.661
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.045, 0.119, 1.01
No. of reflections2292
No. of parameters128
Δρmax, Δρmin (e Å3)3.79, 4.97

Computer programs: X-AREA (Stoe & Cie, 1996), X-AREA, X-RED (Stoe & Cie, 1996), SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), DIAMOND (Brandenburg, 2001), SHELXL97.

Selected geometric parameters (Å, º) top
Cr—O11.661 (12)Pb1—O3iii2.868 (15)
Cr—O21.656 (13)Pb1—O6iv2.910 (11)
Cr—O31.675 (12)Pb1—O1iii2.928 (13)
Cr—O41.661 (11)Pb1—O2v2.943 (14)
Hg1—O52.015 (10)Pb1—O7iii3.610 (10)
Hg1—O62.022 (9)Pb2—O82.309 (10)
Hg2—O62.094 (9)Pb2—O8vi2.349 (11)
Hg2—O72.097 (9)Pb2—O7i2.380 (9)
Hg3—O72.029 (10)Pb2—O42.761 (12)
Hg3—O82.006 (10)Pb2—O1vii2.771 (13)
Pb1—O5i2.246 (10)Pb2—O4viii2.972 (14)
Pb1—O62.367 (10)Pb2—O2viii3.202 (13)
Pb1—O5ii2.512 (11)Pb2—O7vii3.228 (11)
O1—Cr—O2112.0 (7)O5i—Pb1—O680.9 (3)
O1—Cr—O3107.1 (7)O5i—Pb1—O5ii100.0 (3)
O1—Cr—O4107.7 (6)O6—Pb1—O5ii72.3 (3)
O2—Cr—O3110.1 (8)O8—Pb2—O8vi75.7 (4)
O2—Cr—O4109.1 (7)O8—Pb2—O7i81.3 (4)
O3—Cr—O4110.7 (7)O8vi—Pb2—O7i91.9 (4)
O5—Hg1—O6176.0 (5)Hg1—O6—Hg2111.2 (4)
O6—Hg2—O7175.6 (4)Hg2—O7—Hg3114.7 (4)
O7—Hg3—O8176.4 (4)
Symmetry codes: (i) x+1, y, z; (ii) x+1, y+1/2, z+1/2; (iii) x, y+1/2, z+1/2; (iv) x, y+1/2, z1/2; (v) x1, y+1/2, z+1/2; (vi) x+2, y, z+2; (vii) x+1, y, z+1; (viii) x+2, y, z+1.
 

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