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Single crystals of synthetic (PbCO3)2·BaF2, bis­[lead(II) carbonate] barium difluoride, have been grown under hydro­thermal conditions. The compound crystallizes in the ordered hydro­cerussite [(PbCO3)2·Pb(OH)2] structure and can be derived from a close packing of the metal atoms with a stacking sequence of [c(h)2]3 along the c axis. O and F atoms are situated approximately in the tetrahedral voids, resulting in the formation of a slightly distorted [BaF6O6] icosahedron and a [1+6+3]-coordinate Pb atom, with one short bond to F, six bonds to O and three longer bonds to additional O atoms. The carbonate group deviates only slightly from the geometry of an equilateral triangle.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270102013884/iz1024sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270102013884/iz1024Isup2.hkl
Contains datablock I

Comment top

In the course of experiments on the synthesis of compounds containing a matlockite-type [4 + 4+1] coordination of halogen atoms around the divalent metal, which are promising candidates for optical hole-burning or are suitable as host lattices for doping with rare earth ions to synthesize new luminescent materials, the phases Ba2Pb4F10Br2 - xIx (x = 0–2) were prepared hydrothermally and characterized by single-crystal structure analysis (Weil & Kubel, 2000). Experiments to substitute Cl for Br or I, intended to prepare a new Ba2Pb4F10Cl2 phase, failed, and crystals of composition (PbCO3)2·BaF2 were formed instead. Structure analysis of this phase revealed a metrical relationship (rhombohedral, unit cell with a 5.2 Å and c 23.4 Å in hexagonal setting) and a formula similar to the basic lead carbonate, (PbCO3)2·Pb(OH)2, also known as the mineral hydrocerussite. In its synthetic form, this compound is named `white lead', a pigment with one of the highest opacities reported, and which has been used since ancient times (Soukup, 1999) and is still employed as a nacreous pigment (Morita, 1985; Franz et al., 1992).

The structure of (PbCO3)2·BaF2 can be derived from a close packing of the metal atoms, with a stacking sequence of [c(h)2]3 along the c axis, according to the Jagodzinski notation (Jagodzinski, 1949; Verma & Krishna, 1966). In this sequence, two adjacent layers of Pb atoms, forming the h layers, are separated by a layer of Ba atoms, which represent the c layer (Fig. 1). This arrangement leads to a distorted [6 + 6] icosahedral coordination around the Ba atom, with six shorter bonds to the F atoms and six longer bonds to the corners of the carbonate groups (Fig. 2a). The Pb atom shows a [1 + 6+3] coordination, with one very short (Pb—F) bond to the vertex of the coordination polyhedron, six chelate-type bonds to the edges of three intra-layer CO3 groups and three longer bonds to the corners of CO3 groups of the adjacent layer (Fig. 2 b). The F atoms are approximately situated in the tetrahedral voids of the close-packed arrangement, whereas the O and C atoms are considerably dislocated from the tetrahedral and octahedral voids, respectively. The F atom is surrounded by three Ba atoms and one Pb atom, forming a compressed tetrahedron with a mean angle of 108.6° (Fig. 2c). The O atom shows coordination number 4, with bonds to two Pb atoms, one Ba atom and one C atom. The corresponding coordination polyhedron is a considerably distorted tetrahedron, with a mean angle of 110.6° (Fig. 2 d).

Recently, the structure of (PbCO3)2·Pb(OH)2 was solved from single-crystal X-ray data (Pluth & Steele, 2001), as well as from synchrotron X-ray powder data (Martinetto et al., 2002). The main atomic arrangement is similar to that of (PbCO3)2·BaF2, but in the hydrocerussite structure, one Pb layer is disordered, which corresponds to the Ba layer in the structure of the title compound. The Pb atom is then split around the 3a site and located on the 18 h sites with occupation factors of 1/6. The different crystal chemical behaviour of (PbCO3)2·BaF2 and (PbCO3)2·Pb(OH)2 might be explained by both the lone-pair effect of the PbII atoms and the hydrogen bonding of the OH groups in comparison with the BaII and F atoms, respectively.

Additional crystals of composition (PbCO3)2·MF2 (M is Ca, Sr or Pb) were prepared under similar hydrothermal conditions. They occur as transparent hexagonal plates with lattice constants of a, b 5.20 Å and a stacking disorder along the c axis. Although this reveals a structural analogy between these compounds and (PbCO3)2·BaF2 or (PbCO3)2·Pb(OH)2, the corresponding powder diagrams did not indicate a close relationship.

Experimental top

According to the formula of the desired product, Ba2Pb4F10Cl2, stoichiometric mixtures of KF, KCl, Ba(Ac)2 (Ac is acetate?) and Pb(NO3)2 (all Merck, p·A.) were placed in a Teflon-lined steel autoclave. After filling the reaction chamber with dilute acetic acid (filling degree ca 70%) and a reaction time of 20 d at 523 K, colourless single crystals with hexagonal shape and a maximum diameter of about 0.5 mm had formed. Under these conditions, the acetic acid was oxidized by excess nitric acid [provided by Pb(NO3)2]. Besides the title compound as the main phase, needle-shaped crystals of Pb7F12Cl2 (Aurivillius, 1976) were also observed. Single-phase (PbCO3)2·BaF2 was prepared under similar conditions in demineralized water (523 K for 12 d) from PbCO3 and BaF2 (Riedel de Haën, pure) in the molar ratio 2:1 with addition of small portions of NH4Ac (Merck, p·A.). PbCO3 was obtained by precipitation of a Pb(NO3)2 solution with excess (NH4)2(CO3)2 (Merck, p·A.). IR spectroscopic measurements did not indicate any incorporation of water or OH- into the structure of (PbCO3)2·BaF2.

Refinement top

The crystal shape was optimized by minimizing the internal R value of selected reflections [I>20σ(I)] using the program HABITUS (Herrendorf, 1993–97). The habit so derived was used for the numerical absorption correction.

Computing details top

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ATOMS (Dowty, 1998); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. The crystal structure of (PbCO3)2·BaF2 in projection along [100], with the layer-stacking sequence of [c(h)2]3 along [001].
[Figure 2] Fig. 2. Coordination polyhedra, with anisotropic displacement ellipsoids drawn at the 70% probability level, for (a) [BaO6F6], (b) [PbFO9], (c) [FBa3Pb] and (d) [OPb2BaC].
bis[lead(II) carbonate] barium difluoride top
Crystal data top
(PbCO3)2BaF2Dx = 6.462 Mg m3
Mr = 709.74Mo Kα radiation, λ = 0.71073 Å
Trigonal, R3mCell parameters from 2163 reflections
a = 5.1865 (4) Åθ = 2.6–29.0°
c = 23.4881 (8) ŵ = 51.41 mm1
V = 547.18 (6) Å3T = 293 K
Z = 3Plate, colourless
F(000) = 8940.22 × 0.13 × 0.05 mm
Data collection top
Siemens SMART CCD area-detector
diffractometer
237 independent reflections
Radiation source: fine-focus sealed tube236 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.069
ω scansθmax = 29.8°, θmin = 2.6°
Absorption correction: numerical
(HABITUS; Herrendorf, 1993-97)
h = 77
Tmin = 0.013, Tmax = 0.138k = 77
2535 measured reflectionsl = 3232
Refinement top
Refinement on F20 restraints
Least-squares matrix: full w = 1/[σ2(Fo2) + (0.0071P)2 + 10.9202P]
where P = (Fo2 + 2Fc2)/3
R[F2 > 2σ(F2)] = 0.020(Δ/σ)max < 0.001
wR(F2) = 0.044Δρmax = 2.38 e Å3
S = 1.34Δρmin = 1.32 e Å3
237 reflectionsExtinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
19 parametersExtinction coefficient: 0.0061 (3)
Crystal data top
(PbCO3)2BaF2Z = 3
Mr = 709.74Mo Kα radiation
Trigonal, R3mµ = 51.41 mm1
a = 5.1865 (4) ÅT = 293 K
c = 23.4881 (8) Å0.22 × 0.13 × 0.05 mm
V = 547.18 (6) Å3
Data collection top
Siemens SMART CCD area-detector
diffractometer
237 independent reflections
Absorption correction: numerical
(HABITUS; Herrendorf, 1993-97)
236 reflections with I > 2σ(I)
Tmin = 0.013, Tmax = 0.138Rint = 0.069
2535 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0200 restraints
wR(F2) = 0.044 w = 1/[σ2(Fo2) + (0.0071P)2 + 10.9202P]
where P = (Fo2 + 2Fc2)/3
S = 1.34Δρmax = 2.38 e Å3
237 reflectionsΔρmin = 1.32 e Å3
19 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
Ba0.00000.00000.00000.0166 (3)
Pb0.00000.00000.215633 (15)0.0106 (2)
F0.00000.00000.3101 (3)0.0258 (19)
O0.1435 (5)0.2871 (10)0.5694 (2)0.0135 (9)
C0.00000.00000.5705 (5)0.013 (2)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Ba0.0210 (4)0.0210 (4)0.0078 (4)0.01049 (18)0.0000.000
Pb0.0115 (2)0.0115 (2)0.0089 (3)0.00573 (12)0.0000.000
F0.036 (3)0.036 (3)0.005 (3)0.0181 (15)0.0000.000
O0.0102 (15)0.006 (2)0.023 (2)0.0032 (10)0.0007 (9)0.0013 (17)
C0.018 (4)0.018 (4)0.003 (4)0.0089 (19)0.0000.000
Geometric parameters (Å, º) top
Ba—Oi2.850 (5)F—Oxxii3.110 (8)
Ba—Oii2.850 (5)F—Ovii3.129 (5)
Ba—Oiii2.850 (5)F—Oxiii3.129 (5)
Ba—Oiv2.850 (5)F—Oxiv3.129 (5)
Ba—Ov2.850 (5)F—Oxv3.129 (5)
Ba—Ovi2.850 (5)F—Oxvi3.129 (5)
Ba—Fvii3.0438 (13)F—Oxi3.129 (5)
Ba—Fviii3.0438 (13)F—Fi3.187 (5)
Ba—Fix3.0438 (13)F—Fxxiii3.187 (5)
Ba—Fx3.0438 (13)F—Fxxiv3.187 (5)
Ba—Fxi3.0438 (13)F—Cvii3.450 (6)
Ba—Fxii3.0438 (13)F—Cix3.450 (6)
Pb—F2.219 (7)F—Cxi3.450 (6)
Pb—Ovii2.6456 (10)F—Pbi4.464 (5)
Pb—Oxiii2.6456 (10)F—Pbxxiii4.464 (5)
Pb—Oxiv2.6456 (10)F—Pbxxiv4.464 (5)
Pb—Oxv2.6456 (10)F—Oxxv4.623 (5)
Pb—Oxvi2.6456 (10)F—Oix4.623 (5)
Pb—Oxi2.6456 (10)F—Oxxvi4.623 (5)
Pb—Oiii3.262 (5)F—Oxxvii4.999 (6)
Pb—Oi3.262 (5)F—Oxxviii4.999 (6)
Pb—Ov3.262 (5)F—Oxxix4.999 (6)
F—Baxvii3.0438 (13)F—Oxxx4.999 (6)
F—Baxviii3.0438 (13)O—C1.290 (5)
F—Baxix3.0438 (13)C—Oxxxi1.290 (5)
F—Oxx3.110 (8)C—Oxxxii1.290 (5)
F—Oxxi3.110 (8)
Oi—Ba—Oii180.0Oiii—Ba—Fxii64.03 (11)
Oi—Ba—Oiii62.41 (15)Oiv—Ba—Fxii115.97 (11)
Oii—Ba—Oiii117.59 (15)Ov—Ba—Fxii116.41 (16)
Oi—Ba—Oiv117.59 (15)Ovi—Ba—Fxii63.59 (16)
Oii—Ba—Oiv62.41 (15)Fvii—Ba—Fxii63.14 (8)
Oiii—Ba—Oiv180.0Fviii—Ba—Fxii116.86 (8)
Oi—Ba—Ov62.41 (15)Fix—Ba—Fxii63.14 (8)
Oii—Ba—Ov117.59 (15)Fx—Ba—Fxii116.86 (8)
Oiii—Ba—Ov62.41 (15)Fxi—Ba—Fxii180.0
Oiv—Ba—Ov117.59 (15)F—Pb—Ovii79.53 (10)
Oi—Ba—Ovi117.59 (15)F—Pb—Oxiii79.53 (10)
Oii—Ba—Ovi62.41 (15)Ovii—Pb—Oxiii116.78 (6)
Oiii—Ba—Ovi117.59 (15)F—Pb—Oxiv79.53 (10)
Oiv—Ba—Ovi62.41 (15)Ovii—Pb—Oxiv116.78 (6)
Ov—Ba—Ovi180.0Oxiii—Pb—Oxiv116.78 (6)
Oi—Ba—Fvii115.98 (11)F—Pb—Oxv79.53 (10)
Oii—Ba—Fvii64.02 (11)Ovii—Pb—Oxv67.9 (2)
Oiii—Ba—Fvii63.59 (16)Oxiii—Pb—Oxv49.9 (2)
Oiv—Ba—Fvii116.41 (16)Oxiv—Pb—Oxv157.2 (2)
Ov—Ba—Fvii115.97 (11)F—Pb—Oxvi79.53 (10)
Ovi—Ba—Fvii64.03 (11)Ovii—Pb—Oxvi49.9 (2)
Oi—Ba—Fviii64.02 (11)Oxiii—Pb—Oxvi157.2 (2)
Oii—Ba—Fviii115.98 (11)Oxiv—Pb—Oxvi67.9 (2)
Oiii—Ba—Fviii116.41 (16)Oxv—Pb—Oxvi116.78 (6)
Oiv—Ba—Fviii63.59 (16)F—Pb—Oxi79.53 (10)
Ov—Ba—Fviii64.03 (11)Ovii—Pb—Oxi157.2 (2)
Ovi—Ba—Fviii115.97 (11)Oxiii—Pb—Oxi67.9 (2)
Fvii—Ba—Fviii180.0Oxiv—Pb—Oxi49.9 (2)
Oi—Ba—Fix63.59 (16)Oxv—Pb—Oxi116.78 (6)
Oii—Ba—Fix116.41 (16)Oxvi—Pb—Oxi116.78 (6)
Oiii—Ba—Fix115.98 (11)F—Pb—Oiii148.49 (8)
Oiv—Ba—Fix64.02 (11)Ovii—Pb—Oiii71.98 (17)
Ov—Ba—Fix115.97 (11)Oxiii—Pb—Oiii125.31 (6)
Ovi—Ba—Fix64.03 (11)Oxiv—Pb—Oiii101.30 (10)
Fvii—Ba—Fix116.86 (8)Oxv—Pb—Oiii101.30 (10)
Fviii—Ba—Fix63.14 (8)Oxvi—Pb—Oiii71.98 (17)
Oi—Ba—Fx116.41 (16)Oxi—Pb—Oiii125.31 (6)
Oii—Ba—Fx63.59 (16)F—Pb—Oi148.49 (8)
Oiii—Ba—Fx64.02 (11)Ovii—Pb—Oi101.30 (10)
Oiv—Ba—Fx115.98 (11)Oxiii—Pb—Oi71.98 (17)
Ov—Ba—Fx64.03 (11)Oxiv—Pb—Oi125.31 (6)
Ovi—Ba—Fx115.97 (11)Oxv—Pb—Oi71.98 (17)
Fvii—Ba—Fx63.14 (8)Oxvi—Pb—Oi125.31 (6)
Fviii—Ba—Fx116.86 (8)Oxi—Pb—Oi101.30 (10)
Fix—Ba—Fx180.0Oiii—Pb—Oi53.83 (14)
Oi—Ba—Fxi115.97 (11)F—Pb—Ov148.49 (8)
Oii—Ba—Fxi64.03 (11)Ovii—Pb—Ov125.31 (6)
Oiii—Ba—Fxi115.97 (11)Oxiii—Pb—Ov101.30 (10)
Oiv—Ba—Fxi64.03 (11)Oxiv—Pb—Ov71.98 (16)
Ov—Ba—Fxi63.59 (16)Oxv—Pb—Ov125.31 (6)
Ovi—Ba—Fxi116.41 (16)Oxvi—Pb—Ov101.30 (10)
Fvii—Ba—Fxi116.86 (8)Oxi—Pb—Ov71.98 (16)
Fviii—Ba—Fxi63.14 (8)Oiii—Pb—Ov53.83 (14)
Fix—Ba—Fxi116.86 (8)Oi—Pb—Ov53.83 (14)
Fx—Ba—Fxi63.14 (8)O—C—Oxxxi119.96 (4)
Oi—Ba—Fxii64.03 (11)O—C—Oxxxii119.96 (4)
Oii—Ba—Fxii115.97 (11)Oxxxi—C—Oxxxii119.96 (4)
Symmetry codes: (i) x+1/3, y+2/3, z+2/3; (ii) x1/3, y2/3, z2/3; (iii) y2/3, x+y1/3, z+2/3; (iv) y+2/3, xy+1/3, z2/3; (v) xy+1/3, x1/3, z+2/3; (vi) x+y1/3, x+1/3, z2/3; (vii) x2/3, y1/3, z1/3; (viii) x+2/3, y+1/3, z+1/3; (ix) x+1/3, y+2/3, z1/3; (x) x1/3, y2/3, z+1/3; (xi) x+1/3, y1/3, z1/3; (xii) x1/3, y+1/3, z+1/3; (xiii) x+y+1/3, x+2/3, z1/3; (xiv) y+1/3, xy1/3, z1/3; (xv) y+1/3, xy+2/3, z1/3; (xvi) x+y2/3, x1/3, z1/3; (xvii) x+2/3, y+1/3, z+1/3; (xviii) x1/3, y2/3, z+1/3; (xix) x1/3, y+1/3, z+1/3; (xx) y, x+y, z+1; (xxi) xy, x, z+1; (xxii) x, y, z+1; (xxiii) x2/3, y1/3, z+2/3; (xxiv) x+1/3, y1/3, z+2/3; (xxv) y2/3, xy1/3, z1/3; (xxvi) x+y+1/3, x1/3, z1/3; (xxvii) x+1, y+1, z+1; (xxviii) xy, x1, z+1; (xxix) y1, x+y, z+1; (xxx) xy+1, x, z+1; (xxxi) y, xy, z; (xxxii) x+y, x, z.

Experimental details

Crystal data
Chemical formula(PbCO3)2BaF2
Mr709.74
Crystal system, space groupTrigonal, R3m
Temperature (K)293
a, c (Å)5.1865 (4), 23.4881 (8)
V3)547.18 (6)
Z3
Radiation typeMo Kα
µ (mm1)51.41
Crystal size (mm)0.22 × 0.13 × 0.05
Data collection
DiffractometerSiemens SMART CCD area-detector
diffractometer
Absorption correctionNumerical
(HABITUS; Herrendorf, 1993-97)
Tmin, Tmax0.013, 0.138
No. of measured, independent and
observed [I > 2σ(I)] reflections
2535, 237, 236
Rint0.069
(sin θ/λ)max1)0.698
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.020, 0.044, 1.34
No. of reflections237
No. of parameters19
w = 1/[σ2(Fo2) + (0.0071P)2 + 10.9202P]
where P = (Fo2 + 2Fc2)/3
Δρmax, Δρmin (e Å3)2.38, 1.32

Computer programs: SMART (Siemens, 1996), SAINT (Siemens, 1996), SAINT, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ATOMS (Dowty, 1998), SHELXL97.

Selected geometric parameters (Å, º) top
Ba—Oi2.850 (5)Pb—Oii2.6456 (10)
Ba—Fii3.0438 (13)Pb—Oiii3.262 (5)
Pb—F2.219 (7)C—Oiv1.290 (5)
O—C—Oiv119.96 (4)
Symmetry codes: (i) x+1/3, y+2/3, z+2/3; (ii) x2/3, y1/3, z1/3; (iii) y2/3, x+y1/3, z+2/3; (iv) y, xy, z.
 

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