Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S010827011204913X/sk3452sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S010827011204913X/sk3452Isup2.hkl |
CCDC reference: 925259
For related literature, see: Allen (2002); Arnaiz et al. (2010); Flack (1983); Hahn (2002); Halla & Zimmermann (1932); Harrison & Steel (1982); Higgitt et al. (2003); Niklasson et al. (2004); Plater et al. (2003); Schieweck et al. (2009); Sheldrick (1998); Spek (2009); Sugawara et al. (1951); Tétreault et al. (1998, 2003); Wilson (1949); Zhang et al. (2007).
The title compound can be easily obtained according to literature methods [see, for example, Zhang et al. (2007) and Arnaiz et al. (2010)]. In the present work, crystals of lead formate were obtained by fractional crystallization from a formic-acid-containing solution of lead palmitate. A few drops of formic acid were added to a saturated solution of lead palmitate, Pb[(OCO(CH2)14CH3]2, in MeOH. The mixture was refluxed for a few minutes and the white insoluble solid which formed was filtered off. The colourless saturated solution was collected in a small vial and crystallized by the diffusion method: the vial was placed in a screw-capped glass test tube containing a few millilitres of Et2O and left at room temperature for several days. A small number of white lead formate single crystals were collected from the solution.
H atoms were placed in idealized positions and refined as riding, with C—H = 0.93Å and Uiso(H) = 1.2Ueq(C). PLATON (Spek, 2009) was used for analysing and validating the symmetry, while the Flack parameter (Flack, 1983) was used to determine the absolute structure.
Data collection: CrysAlis CCD (Oxford Diffraction, 2005); cell refinement: CrysAlis RED (Oxford Diffraction, 2005); data reduction: CrysAlis RED (Oxford Diffraction, 2005); program(s) used to solve structure: WinGX (Farrugia, 1999) and SUPERFLIP (Palatinus & Chapuis, 2007); program(s) used to refine structure: WinGX (Farrugia, 1999) and SHELXL97 (Sheldrick, 2008); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: publCIF (Westrip, 2010).
Fig. 1. The first coordination sphere of O atoms around the central Pb2+
cation, showing the atomic labelling scheme and relevant bond distances in
Å. [Symmetry codes: (i) x + 1/2, -y + 1/2, -z + 2; (ii)
-x + 2, y + 1/2, -z + 3/2; (iii) -x + 2, y
- 1/2, -z + 3/2.] Fig. 2. The distorted eightfold coordination polyhedron around the Pb2+ cation. [Symmetry codes: (i) x + 1/2, -y + 1/2, -z + 2; (ii) -x + 2, y + 1/2, -z + 3/2; (iii) -x + 2, y - 1/2, -z + 3/2.] Fig. 3. The structure of (I), with displacement ellipsoids drawn at the 50% probability level, and a polymeric expansion showing the two µ4-bridging formate groups. [Symmetry codes: (i) x + 1/2, -y + 1/2, -z + 2; (ii) -x + 2, y + 1/2, -z + 3/2; (iii) -x + 2, y - 1/2, -z + 3/2; (iv) x - 1, y, z; (v) x + 1/2, -y + 1/2, -z + 1; (vi) x - 1/2, -y + 1/2, -z + 2; (vii) -x + 5/2, -y + 1, z - 1/2; (viii) -x + 1, y - 1/2, -z + 3/2.] Fig. 4. The crystal packing of (I), viewed down (from left to right) the a, b and c axes. |
[Pb(HCO2)2] | Dx = 4.657 Mg m−3 |
Mr = 297.24 | Mo Kα radiation, λ = 0.71073 Å |
Orthorhombic, P212121 | Cell parameters from 2211 reflections |
a = 6.5227 (8) Å | θ = 3.6–43.1° |
b = 7.4153 (8) Å | µ = 39.68 mm−1 |
c = 8.7646 (10) Å | T = 297 K |
V = 423.92 (8) Å3 | Block, colourless |
Z = 4 | 0.15 × 0.09 × 0.08 mm |
F(000) = 512 |
Stoe STADI IV diffractometer equipped with an Oxford Sapphire I CCD area detector | 1026 independent reflections |
Radiation source: fine-focus sealed tube | 867 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.086 |
ϕ and ω scans | θmax = 28.0°, θmin = 3.6° |
Absorption correction: numerical [X-RED (Stoe & Cie, 1999) and X-SHAPE (Stoe & Cie, 2001)] | h = −8→7 |
Tmin = 0.011, Tmax = 0.058 | k = −9→8 |
3678 measured reflections | l = −11→11 |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.035 | H-atom parameters constrained |
wR(F2) = 0.079 | w = 1/[σ2(Fo2) + (0.0321P)2] where P = (Fo2 + 2Fc2)/3 |
S = 1.00 | (Δ/σ)max < 0.001 |
1026 reflections | Δρmax = 1.30 e Å−3 |
65 parameters | Δρmin = −1.94 e Å−3 |
0 restraints | Absolute structure: Flack (1983), with 404 Bijvoet pairs |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: 0.03 (4) |
[Pb(HCO2)2] | V = 423.92 (8) Å3 |
Mr = 297.24 | Z = 4 |
Orthorhombic, P212121 | Mo Kα radiation |
a = 6.5227 (8) Å | µ = 39.68 mm−1 |
b = 7.4153 (8) Å | T = 297 K |
c = 8.7646 (10) Å | 0.15 × 0.09 × 0.08 mm |
Stoe STADI IV diffractometer equipped with an Oxford Sapphire I CCD area detector | 1026 independent reflections |
Absorption correction: numerical [X-RED (Stoe & Cie, 1999) and X-SHAPE (Stoe & Cie, 2001)] | 867 reflections with I > 2σ(I) |
Tmin = 0.011, Tmax = 0.058 | Rint = 0.086 |
3678 measured reflections |
R[F2 > 2σ(F2)] = 0.035 | H-atom parameters constrained |
wR(F2) = 0.079 | Δρmax = 1.30 e Å−3 |
S = 1.00 | Δρmin = −1.94 e Å−3 |
1026 reflections | Absolute structure: Flack (1983), with 404 Bijvoet pairs |
65 parameters | Absolute structure parameter: 0.03 (4) |
0 restraints |
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. |
x | y | z | Uiso*/Ueq | ||
Pb1 | 0.92919 (8) | 0.25999 (6) | 0.83375 (7) | 0.02668 (16) | |
O1 | 0.5193 (15) | 0.2353 (14) | 0.8629 (12) | 0.033 (2) | |
O2 | 1.2416 (17) | 0.0663 (13) | 0.8153 (18) | 0.041 (3) | |
O3 | 0.8524 (18) | 0.0793 (14) | 0.5921 (13) | 0.030 (2) | |
O4 | 1.144 (2) | 0.4259 (13) | 0.6077 (13) | 0.035 (3) | |
C1 | 0.421 (3) | 0.1095 (17) | 0.8001 (14) | 0.022 (3) | |
C2 | 1.247 (2) | 0.349 (2) | 0.5066 (19) | 0.028 (3) | |
H1 | 0.4957 | 0.0391 | 0.7322 | 0.027* | |
H2 | 1.2436 | 0.2234 | 0.5062 | 0.034* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Pb1 | 0.0267 (2) | 0.0235 (2) | 0.0298 (3) | 0.0009 (3) | −0.0014 (2) | −0.0018 (3) |
C1 | 0.030 (7) | 0.030 (6) | 0.008 (6) | 0.010 (7) | 0.002 (6) | 0.001 (4) |
O1 | 0.028 (5) | 0.028 (5) | 0.044 (6) | −0.001 (5) | 0.000 (4) | 0.011 (6) |
O4 | 0.043 (7) | 0.028 (5) | 0.034 (6) | −0.004 (5) | 0.018 (5) | −0.011 (5) |
O2 | 0.031 (7) | 0.026 (5) | 0.067 (9) | 0.004 (4) | 0.013 (6) | 0.004 (6) |
C2 | 0.028 (7) | 0.033 (8) | 0.024 (8) | 0.003 (6) | 0.001 (6) | 0.001 (7) |
O3 | 0.024 (6) | 0.032 (5) | 0.033 (6) | 0.002 (4) | −0.007 (5) | −0.001 (5) |
Pb1—O1 | 2.692 (10) | Pb1—O4iii | 2.575 (10) |
Pb1—O2 | 2.498 (11) | C1—O1 | 1.259 (17) |
Pb1—O3 | 2.556 (11) | C1—O2iv | 1.22 (2) |
Pb1—O4 | 2.722 (11) | C1—H1 | 0.9300 |
Pb1—O1i | 2.723 (10) | C2—O3v | 1.226 (19) |
Pb1—O2ii | 2.848 (12) | C2—O4 | 1.249 (19) |
Pb1—O3ii | 2.839 (10) | C2—H2 | 0.9300 |
O2—Pb1—O3 | 78.8 (4) | O2—Pb1—O2ii | 138.42 (19) |
O2—Pb1—O4iii | 67.2 (4) | O3—Pb1—O2ii | 87.8 (4) |
O3—Pb1—O4iii | 67.9 (4) | O4iii—Pb1—O2ii | 141.8 (4) |
O2—Pb1—O1 | 141.0 (3) | O1—Pb1—O2ii | 73.1 (3) |
O3—Pb1—O1 | 81.3 (3) | O4—Pb1—O2ii | 60.5 (4) |
O4iii—Pb1—O1 | 74.4 (4) | O1i—Pb1—O2ii | 121.5 (4) |
O2—Pb1—O4 | 78.0 (4) | O3ii—Pb1—O2ii | 68.7 (3) |
O3—Pb1—O4 | 74.6 (4) | O2iv—C1—O1 | 129.5 (14) |
O4iii—Pb1—O4 | 132.5 (3) | O2iv—C1—H1 | 115.3 |
O1—Pb1—O4 | 127.7 (4) | O1—C1—H1 | 115.3 |
O2—Pb1—O1i | 83.9 (4) | C1—O1—Pb1 | 121.0 (10) |
O3—Pb1—O1i | 149.1 (3) | C1—O1—Pb1vi | 109.0 (9) |
O4iii—Pb1—O1i | 81.8 (4) | Pb1—O1—Pb1vi | 107.8 (3) |
O1—Pb1—O1i | 97.0 (3) | C2—O4—Pb1ii | 133.0 (10) |
O4—Pb1—O1i | 126.4 (3) | C2—O4—Pb1 | 125.9 (9) |
O2—Pb1—O3ii | 94.9 (3) | Pb1ii—O4—Pb1 | 101.2 (3) |
O3—Pb1—O3ii | 136.5 (2) | C1vii—O2—Pb1 | 129.7 (9) |
O4iii—Pb1—O3ii | 148.3 (4) | O3v—C2—O4 | 127.0 (14) |
O1—Pb1—O3ii | 122.2 (3) | O3v—C2—H2 | 116.5 |
O4—Pb1—O3ii | 62.0 (3) | O4—C2—H2 | 116.5 |
O1i—Pb1—O3ii | 70.0 (3) | C2viii—O3—Pb1 | 117.8 (10) |
Symmetry codes: (i) x+1/2, −y+1/2, −z+2; (ii) −x+2, y+1/2, −z+3/2; (iii) −x+2, y−1/2, −z+3/2; (iv) x−1, y, z; (v) x+1/2, −y+1/2, −z+1; (vi) x−1/2, −y+1/2, −z+2; (vii) x+1, y, z; (viii) x−1/2, −y+1/2, −z+1. |
Experimental details
Crystal data | |
Chemical formula | [Pb(HCO2)2] |
Mr | 297.24 |
Crystal system, space group | Orthorhombic, P212121 |
Temperature (K) | 297 |
a, b, c (Å) | 6.5227 (8), 7.4153 (8), 8.7646 (10) |
V (Å3) | 423.92 (8) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 39.68 |
Crystal size (mm) | 0.15 × 0.09 × 0.08 |
Data collection | |
Diffractometer | Stoe STADI IV diffractometer equipped with an Oxford Sapphire I CCD area detector |
Absorption correction | Numerical [X-RED (Stoe & Cie, 1999) and X-SHAPE (Stoe & Cie, 2001)] |
Tmin, Tmax | 0.011, 0.058 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3678, 1026, 867 |
Rint | 0.086 |
(sin θ/λ)max (Å−1) | 0.660 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.035, 0.079, 1.00 |
No. of reflections | 1026 |
No. of parameters | 65 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 1.30, −1.94 |
Absolute structure | Flack (1983), with 404 Bijvoet pairs |
Absolute structure parameter | 0.03 (4) |
Computer programs: CrysAlis CCD (Oxford Diffraction, 2005), CrysAlis RED (Oxford Diffraction, 2005), WinGX (Farrugia, 1999) and SUPERFLIP (Palatinus & Chapuis, 2007), WinGX (Farrugia, 1999) and SHELXL97 (Sheldrick, 2008), Mercury (Macrae et al., 2008), publCIF (Westrip, 2010).
Pb1—O1 | 2.692 (10) | Pb1—O3ii | 2.839 (10) |
Pb1—O2 | 2.498 (11) | Pb1—O4iii | 2.575 (10) |
Pb1—O3 | 2.556 (11) | C1—O1 | 1.259 (17) |
Pb1—O4 | 2.722 (11) | C1—O2iv | 1.22 (2) |
Pb1—O1i | 2.723 (10) | C2—O3v | 1.226 (19) |
Pb1—O2ii | 2.848 (12) | C2—O4 | 1.249 (19) |
O2—Pb1—O3 | 78.8 (4) | O2—Pb1—O3ii | 94.9 (3) |
O2—Pb1—O4iii | 67.2 (4) | O3—Pb1—O3ii | 136.5 (2) |
O3—Pb1—O4iii | 67.9 (4) | O4iii—Pb1—O3ii | 148.3 (4) |
O2—Pb1—O1 | 141.0 (3) | O1—Pb1—O3ii | 122.2 (3) |
O3—Pb1—O1 | 81.3 (3) | O4—Pb1—O3ii | 62.0 (3) |
O4iii—Pb1—O1 | 74.4 (4) | O1i—Pb1—O3ii | 70.0 (3) |
O2—Pb1—O4 | 78.0 (4) | O2—Pb1—O2ii | 138.42 (19) |
O3—Pb1—O4 | 74.6 (4) | O3—Pb1—O2ii | 87.8 (4) |
O4iii—Pb1—O4 | 132.5 (3) | O4iii—Pb1—O2ii | 141.8 (4) |
O1—Pb1—O4 | 127.7 (4) | O1—Pb1—O2ii | 73.1 (3) |
O2—Pb1—O1i | 83.9 (4) | O4—Pb1—O2ii | 60.5 (4) |
O3—Pb1—O1i | 149.1 (3) | O1i—Pb1—O2ii | 121.5 (4) |
O4iii—Pb1—O1i | 81.8 (4) | O3ii—Pb1—O2ii | 68.7 (3) |
O1—Pb1—O1i | 97.0 (3) | O2iv—C1—O1 | 129.5 (14) |
O4—Pb1—O1i | 126.4 (3) | O3v—C2—O4 | 127.0 (14) |
Symmetry codes: (i) x+1/2, −y+1/2, −z+2; (ii) −x+2, y+1/2, −z+3/2; (iii) −x+2, y−1/2, −z+3/2; (iv) x−1, y, z; (v) x+1/2, −y+1/2, −z+1. |
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We have synthesized several lead carboxylates in order to characterize their structures, as part of a larger research project aiming to study the degradation phenomena of ancient pieces of art, and in particular paintings. Indeed, the formation and slow crystal growth of lead carboxylates within paint layers can eventually cause the formation of cracks and fractures that irreversibly damage the artifacts (Higgitt et al., 2003; Niklasson et al., 2004; Plater et al. 2003; Schieweck et al., 2009; Tétreault et al., 1998, 2003). Among the whole carboxylate homologous family, the simplest compound, lead(II) formate, Pb(HCOO)2, (I), has been widely investigated and characterized in the past, as witnessed by over 100 bibliographic references addressing its preparation and formation, thermodynamic properties and applications. Nevertheless, the published structural characterization is very old and incomplete. The first published crystal structure is probably that reported in 1932 by Halla & Zimmermann (1932), but the accessible information from the Cambridge Structural Database (CSD, Version?; Allen, 2002) is limited to just one entry, by Harrison & Steel (1982) (CSD refcode BIYLAW), which is incomplete since no atomic coordinates were provided in the paper and, moreover, it claims a different space group from the previous literature.
As a first and most relevant result of this study, our diffraction data clearly indicate the space group P212121, instead of the space group Pnma reported by Harrison & Steel (1982). The unit-cell dimensions are identical. Both space groups (P212121 and Pnma) possess 21 screw axes along the three crystallographic directions, hence showing systematic extinctions for odd index values in the reflections h00, 0k0 and 00l. Yet the additional conditions k+l = 2n for 0kl reflections, and even h values for hk0 reflections, must be fulfilled in the space group Pnma (Hahn, 2002). It is interesting to note that the Pb2+ sites in the structure of (I) obey the Pnma symmetry closely, although it is broken by the formate anions which conform only with the P212121 symmetry. Due to the dominating scattering power of Pb atoms, some reflections appear to be pseudo-extinct, and they were probably misinterpreted by Harrison & Steel (1982) as corresponding to the presence of additional n- and a-glide planes.
In the present analysis, E statistics on the collected data clearly suggested the absence of an inversion center, with a Sheldrick criterion |E2 - 1| = 0.666 (where E are the normalized structure factors, and 0.968 and 0.736 are the ideal values for a centric and an acentric random distribution, respectively) (Wilson, 1949; Sheldrick, 1998). Moreover, an attempt to solve the structure in space group Pnma produced an inadequate model where some atoms assumed forbidden bonding geometry, with inconsistently short distances between symmetry-equivalent atoms, and large and highly distorted displacement ellipsoids or, in some cases, nonpositive definite anisotropic displacement parameters. On the other hand, structure solution and refinement in P212121 were carried out successfully, leading to a final R1 value of 0.0354, which represents a better result than previous work [i.e. 0.0549 in Harrison & Steel (1982)]. Finally, the selected space group has been post-validated using PLATON (Spek, 2009), which did not suggest any other possible space group. The P212121 symmetry for lead formate is not actually completely new, as it had been suggested very early on by Sugawara et al. (1951). However, based on the atomic coordinates published by Sugawara et al. (1951), we obtained a structure totally inconsistent with the well known geometries of formate groups, being strongly distorted and characterized by unrealistic bond lengths.
Part of the crystal structure of (I) is shown in Fig. 3 and projections of unit-cell content are shown in Fig. 4. Selected geometric data are given in Table 1. The current structure in space group P212121 qualitatively resembles that reported by Harrison & Steel (1982) in terms of the general structural characteristics (i.e. the Pb coordination and the general behaviour of the Pb—O bonds). Our investigation confirms that (I) is a three-dimensional coordination polymer, where the formate anions act as tetradentate bridging groups between adjacent PbII cations, which exhibit a distorted eightfold coordination (Figs. 1 and 2). As observed previously (Harrison & Steel, 1982), the PbII cation forms three shorter and five longer bonds to the O atoms. Quantitatively, the bond lengths in both structures differ, as expected in view of the incorrect space-group assignment. The correctness of the currently assigned space group is clearly indicated by the value of the Flack (1983) parameter [x = 0.03 (4)].