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The title compound, catena-poly­[[(heptanoato-O,O')­lead(II)]-[mu]-heptanoato-O,O':O:O'], [Pb(C7H13O2)2], is a metallic soap which can be used as a corrosion inhibitor since it forms a passive film at the Pb surface. Its structure is characterized by two-dimensional layers parallel to the bc plane. The layers are packed through van der Waals interactions along the a direction and form blocks parallel to (001). The 6s2 lone pair of electrons on PbII is stereochemically active in this compound, which leads to a hemidirected octahedral geometry for the O-environment around the Pb atoms.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270101001615/os1131sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270101001615/os1131Isup2.hkl
Contains datablock I

CCDC reference: 164628

Comment top

Electrochemical studies have shown that aliphatic sodium carboxylate inhibits the corrosion of lead in aqueous solution (Rocca & Steinmetz, 2000). Particularly, the efficiency of this inhibition by these compounds, with the general formula CH3(CH2)n-2COONa (n = 7–11), depends on the chain length of the aliphatic group. The passivation of the metal was attributed to the growth of passive layers containing metallic soap, [Pb(CnH2n-1O2)2]. Metals such as Cu, Zn, Mg and Fe, for which the corrosion/passivation behaviour is under study in our laboratory, can be protected by their corresponding metallic soaps. The general aim of these studies concerns new protective treatments, which would be less polluting than the phosphatation or chromatation often used in metal protection. To optimize the treatments, for example by varying the chain length of the aliphatic carboxylate group, it is necessary to understand better the interactions between the surface of the metal, oxidized or not, and the metallic soap, which requires knowledge of the crystallographic structure formed by the hydrophobic and protecting metallic soap.

Crystallographic structures for two short linear chain carboxylates are known: lead formate, [Pb(CHO2)2], and lead acetate trihydrate, [Pb(C2H3O2)2]·3H2O (Harrisson & Steel, 1982). The former has a three-dimensional polymeric structure, while the latter is built up of parallel sheets and so adopts a two-dimensional character. The structure of the title compound, (I), is characterized by a lamellar building of sheets, formed by Pb—O bonds, parallel to the bc plane. The sheets are packed along the a direction by van der Waals interactions and consequently form blocks parallel to (001), as shown in Fig. 1. The Pb atoms are disposed on a zigzag chain through the middle of the sheets, running along the b direction. \sch

Fig. 2 shows the environment around Pb. Each Pb atom is surrounded by six O atoms, which form a very distorted polyhedron. The six O atoms belong to four different bidentate carboxylate groups. Carboxylate O11/O12 is chelating [Pb—O11i 2.583 (8) and Pb—O12i 2.735 (8) Å; symmetry code: (i) -x, -y, -z] and also bridges the adjacent Pb atoms along the b direction [Pb—O11 2.567 (7) and Pb—O12ii 2.620 (7) Å, and O11—Pb—O12ii 166.6 (3)°; symmetry code: (ii) x, 1 + y, z]. Carboxylate O21/O22 is only chelating and leads to the shortest Pb—O distances in the structure [Pb—O21 2.451 (8) and Pb—O22 2.410 (9) Å]. The average Pb—O distance is 2.56 Å, which is slightly smaller than the sum of the ionic radii (ionic radius for PbII = 1.19 Å when the coordination number = 6, and for O = 1.40 Å; Shannon, 1976). The six Pb—O bonds are directed on the same side of a globe surrounding the Pb atom, so that the coordination can be qualified as `hemidirected octahedral coordination' (Shimoni-Livny et al., 1998). This type of coordination arises for PbII when the 6 s2 lone pair is stereochemically active. There are voids in the Pb—O bonding distribution which make the lone pair position identifiable. The lone pair is approximately situated in the direction of the relatively short Pb—O21 bond.

The absence of structural water, contrary to the case of the equivalent acetate compound, which is in fact the trihydrate, was confirmed by thermo-gravimetric analysis measurements (no weight loss was observed between room temperature and 448 K) and micro-Raman spectroscopy (no signal due to water-molecule vibration was recorded in the wavenumber range 3100–3500 cm-1). The structures of both lead heptanoate and lead acetate have a two-dimensional character. The building of the sheets is similar, but the main differences in the lead acetate are the existence of hydrogen bonds formed by water molecules and the coordination number for the Pb atoms, which is increased up to eight by the O atoms of the water molecules.

Related literature top

For related literature, see: Rocca & Steinmetz (2000); Shannon (1976); Shimoni-Livny, Glusker & Bock (1998).

Experimental top

Crystals of the title compound were prepared by the reaction of a solution of lead nitrate with sodium heptanoate. The precipitates obtained were then washed in distilled water and dried. A small quantity of the product was recrystallized from ethanol for one month at room temperature. The colourless crystals were small plates with the (001) face well developed.

Refinement top

H atoms were geometrically placed but their parameters were not refined. Their individual isotropic displacement parameters were fixed, with Uiso = 1.2Ueq(C). C—H distances?

Computing details top

Data collection: COLLECT (Nonius, 1998); cell refinement: SCALEPACK in HKL (Otwinowski & Minor, 1997); data reduction: SCALEPACK and DENZO in HKL; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SIR97 (Altomare et al., 1998); molecular graphics: ATOMS (Dowty, 1995).

Figures top
[Figure 1] Fig. 1. The projection of the structure of (I) along [100]. Displacement ellipsoids are drawn at the 70% probability level. H atoms have been omitted for clarity.
[Figure 2] Fig. 2. The environment of the PbII ion in (I) showing the orientation of the linear heptanoate chains. Displacement ellipsoids are drawn at the 70% probability level (symmetry codes are as in Table 1).
catena-poly[[(heptanoato-O,O')lead(II)]-µ-heptanoato-O,O':O] top
Crystal data top
[Pb(C7H13O2)2]Z = 2
Mr = 465.2F(000) = 448
Triclinic, P1Dx = 1.890 Mg m3
a = 4.8574 (10) ÅMo Kα radiation, λ = 0.71073 Å
b = 7.3046 (10) ÅCell parameters from 41187 reflections
c = 23.1846 (10) Åθ = 1.0–31.0°
α = 91.61 (1)°µ = 10.32 mm1
β = 95.66 (1)°T = 293 K
γ = 90.99 (1)°Plate, colourless
V = 818.1 (2) Å30.15 × 0.13 × 0.01 mm
Data collection top
Nonius KappaCCD area-detector
diffractometer
2820 independent reflections
Radiation source: fine-focus sealed tube2419 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.078
Detector resolution: n pixels mm-1θmax = 24.8°, θmin = 1.8°
CCD scansh = 55
Absorption correction: empirical (using intensity measurements)
fitted by spherical harmonic functions (SORTAV; Blessing, 1995)
k = 88
Tmin = 0.22, Tmax = 0.90l = 027
16127 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)] = 0.042Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.132H-atom parameters constrained
S = 1.03Weighting scheme based on measured s.u.'s w = 1/[σ2(Fo2) + (0.0852P)2]
where P = (Fo2 + 2Fc2)/3
2820 reflections(Δ/σ)max < 0.001
172 parametersΔρmax = 1.12 e Å3
12 restraintsΔρmin = 2.15 e Å3
Crystal data top
[Pb(C7H13O2)2]γ = 90.99 (1)°
Mr = 465.2V = 818.1 (2) Å3
Triclinic, P1Z = 2
a = 4.8574 (10) ÅMo Kα radiation
b = 7.3046 (10) ŵ = 10.32 mm1
c = 23.1846 (10) ÅT = 293 K
α = 91.61 (1)°0.15 × 0.13 × 0.01 mm
β = 95.66 (1)°
Data collection top
Nonius KappaCCD area-detector
diffractometer
2820 independent reflections
Absorption correction: empirical (using intensity measurements)
fitted by spherical harmonic functions (SORTAV; Blessing, 1995)
2419 reflections with I > 2σ(I)
Tmin = 0.22, Tmax = 0.90Rint = 0.078
16127 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.04212 restraints
wR(F2) = 0.132H-atom parameters constrained
S = 1.03Δρmax = 1.12 e Å3
2820 reflectionsΔρmin = 2.15 e Å3
172 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
Pb0.20267 (8)0.25423 (5)0.032812 (17)0.03529 (19)
O110.1778 (18)0.0961 (10)0.0381 (4)0.055 (2)
O120.1725 (18)0.3910 (10)0.0500 (4)0.055 (2)
O210.2092 (17)0.2836 (14)0.0853 (4)0.057 (2)
O220.1744 (17)0.2309 (13)0.1356 (4)0.056 (2)
C110.259 (2)0.2354 (14)0.0661 (4)0.035 (2)
C120.461 (2)0.2100 (17)0.1202 (4)0.048 (3)
H12A0.54020.08690.12220.057*
H12B0.61040.29600.11890.057*
C130.307 (2)0.2425 (17)0.1738 (4)0.047 (3)
H13A0.14240.16880.17180.056*
H13B0.24940.37020.17400.056*
C140.489 (2)0.1935 (17)0.2297 (4)0.051 (3)
H14A0.53460.06370.23060.061*
H14B0.65990.25990.23000.061*
C150.350 (2)0.2380 (19)0.2844 (4)0.055 (3)
H15A0.17520.17560.28340.066*
H15B0.31120.36870.28440.066*
C160.529 (3)0.181 (2)0.3404 (5)0.067 (4)
H16A0.70410.24330.34110.080*
H16B0.56760.05060.34020.080*
C170.394 (4)0.225 (3)0.3954 (6)0.084 (5)
H17A0.20310.19220.39070.126*
H17B0.48770.15660.42780.126*
H17C0.40780.35360.40240.126*
C210.069 (2)0.2705 (14)0.1323 (4)0.037 (2)
C220.204 (2)0.3105 (17)0.1880 (4)0.044 (3)
H22A0.24510.43980.19020.053*
H22B0.37780.24230.18630.053*
C230.025 (2)0.2613 (17)0.2428 (4)0.045 (3)
H23A0.15320.32400.24370.054*
H23B0.00700.13050.24200.054*
C240.160 (2)0.3137 (19)0.2976 (4)0.048 (3)
H24A0.33820.25140.29650.058*
H24B0.19080.44450.29840.058*
C250.019 (3)0.2635 (19)0.3527 (4)0.054 (3)
H25A0.19600.32780.35400.064*
H25B0.05340.13310.35130.064*
C260.117 (3)0.312 (2)0.4079 (5)0.069 (4)
H26A0.29370.24690.40670.083*
H26B0.15210.44190.40920.083*
C270.064 (4)0.261 (3)0.4630 (6)0.098 (6)
H27A0.09210.13150.46270.147*
H27B0.02550.29690.49650.147*
H27C0.24020.32420.46420.147*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Pb0.0420 (3)0.0302 (3)0.0329 (3)0.00078 (16)0.00065 (17)0.00002 (16)
O110.066 (5)0.021 (4)0.070 (6)0.002 (3)0.033 (5)0.001 (4)
O120.066 (5)0.025 (4)0.069 (6)0.005 (3)0.023 (4)0.006 (4)
O210.041 (4)0.088 (7)0.043 (5)0.005 (4)0.003 (4)0.001 (5)
O220.038 (4)0.084 (6)0.048 (5)0.015 (4)0.009 (4)0.002 (5)
C110.044 (6)0.034 (6)0.026 (6)0.001 (4)0.002 (4)0.001 (4)
C120.051 (7)0.042 (6)0.047 (7)0.001 (5)0.008 (6)0.001 (5)
C130.053 (7)0.047 (6)0.035 (7)0.000 (5)0.016 (5)0.003 (5)
C140.054 (7)0.047 (7)0.051 (8)0.005 (6)0.003 (6)0.000 (6)
C150.057 (8)0.057 (8)0.050 (8)0.000 (6)0.005 (6)0.005 (6)
C160.076 (10)0.074 (10)0.049 (8)0.009 (8)0.002 (7)0.004 (7)
C170.113 (14)0.093 (12)0.045 (9)0.019 (11)0.003 (9)0.008 (8)
C210.047 (6)0.040 (6)0.021 (5)0.003 (5)0.010 (5)0.000 (4)
C220.049 (6)0.059 (7)0.025 (6)0.001 (5)0.001 (5)0.006 (5)
C230.046 (6)0.057 (7)0.031 (6)0.002 (5)0.002 (5)0.007 (5)
C240.047 (7)0.069 (8)0.028 (6)0.009 (6)0.001 (5)0.000 (6)
C250.069 (8)0.061 (8)0.031 (7)0.009 (6)0.007 (6)0.008 (6)
C260.088 (11)0.091 (11)0.029 (7)0.012 (9)0.010 (7)0.005 (7)
C270.130 (16)0.119 (16)0.047 (10)0.026 (13)0.019 (10)0.003 (10)
Geometric parameters (Å, º) top
Pb—O222.410 (9)O22—C211.217 (13)
Pb—O212.451 (8)C11—C121.521 (9)
Pb—O112.567 (7)C12—C131.533 (9)
Pb—O11i2.583 (8)C13—C141.525 (9)
Pb—O12ii2.620 (7)C14—C151.532 (9)
Pb—O12i2.735 (8)C15—C161.532 (9)
Pb—C212.769 (9)C16—C171.53 (2)
O11—C111.270 (12)C21—C221.528 (9)
O11—Pbi2.583 (8)C22—C231.522 (9)
O12—C111.239 (12)C23—C241.527 (9)
O12—Pbiii2.620 (7)C24—C251.529 (9)
O12—Pbi2.735 (8)C25—C261.532 (9)
O21—C211.235 (13)C26—C271.54 (2)
O22—Pb—O2152.4 (3)C11—O12—Pbiii156.0 (7)
O22—Pb—O1181.3 (3)C11—O12—Pbi92.1 (6)
O21—Pb—O1191.1 (3)Pbiii—O12—Pbi109.1 (3)
O22—Pb—O11i118.7 (3)C21—O21—Pb91.3 (6)
O21—Pb—O11i77.6 (3)C21—O22—Pb93.7 (7)
O11—Pb—O11i65.2 (3)O12—C11—O11120.5 (9)
O22—Pb—O12ii86.4 (3)O12—C11—C12120.0 (9)
O21—Pb—O12ii77.2 (3)O11—C11—C12119.5 (9)
O11—Pb—O12ii166.6 (3)C11—C12—C13109.0 (8)
O11i—Pb—O12ii117.4 (3)C14—C13—C12111.6 (9)
O22—Pb—O12i129.2 (3)C13—C14—C15113.2 (9)
O21—Pb—O12i78.1 (3)C16—C15—C14112.8 (9)
O11—Pb—O12i113.4 (2)C17—C16—C15113.6 (11)
O11i—Pb—O12i48.3 (2)O22—C21—O21122.0 (9)
O12ii—Pb—O12i70.9 (3)O22—C21—C22119.2 (9)
O22—Pb—C2126.0 (3)O21—C21—C22118.7 (9)
O21—Pb—C2126.5 (3)O22—C21—Pb60.3 (6)
O11—Pb—C2187.7 (3)O21—C21—Pb62.2 (5)
O11i—Pb—C2199.9 (3)C22—C21—Pb171.1 (8)
O12ii—Pb—C2178.9 (3)C23—C22—C21113.6 (8)
O12i—Pb—C21103.5 (3)C22—C23—C24111.9 (8)
C11—O11—Pb146.0 (7)C23—C24—C25112.1 (8)
C11—O11—Pbi98.6 (6)C24—C25—C26112.5 (9)
Pb—O11—Pbi114.8 (3)C25—C26—C27112.1 (11)
Symmetry codes: (i) x, y, z; (ii) x, y+1, z; (iii) x, y1, z.

Experimental details

Crystal data
Chemical formula[Pb(C7H13O2)2]
Mr465.2
Crystal system, space groupTriclinic, P1
Temperature (K)293
a, b, c (Å)4.8574 (10), 7.3046 (10), 23.1846 (10)
α, β, γ (°)91.61 (1), 95.66 (1), 90.99 (1)
V3)818.1 (2)
Z2
Radiation typeMo Kα
µ (mm1)10.32
Crystal size (mm)0.15 × 0.13 × 0.01
Data collection
DiffractometerNonius KappaCCD area-detector
diffractometer
Absorption correctionEmpirical (using intensity measurements)
fitted by spherical harmonic functions (SORTAV; Blessing, 1995)
Tmin, Tmax0.22, 0.90
No. of measured, independent and
observed [I > 2σ(I)] reflections
16127, 2820, 2419
Rint0.078
(sin θ/λ)max1)0.591
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.042, 0.132, 1.03
No. of reflections2820
No. of parameters172
No. of restraints12
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)1.12, 2.15

Computer programs: COLLECT (Nonius, 1998), SCALEPACK in HKL (Otwinowski & Minor, 1997), SCALEPACK and DENZO in HKL, SHELXS97 (Sheldrick, 1990), SIR97 (Altomare et al., 1998), ATOMS (Dowty, 1995).

Selected geometric parameters (Å, º) top
Pb—O222.410 (9)Pb—O12ii2.620 (7)
Pb—O212.451 (8)Pb—O12i2.735 (8)
Pb—O112.567 (7)O11—C111.270 (12)
Pb—O11i2.583 (8)O12—C111.239 (12)
O22—Pb—O2152.4 (3)O11—Pb—O12ii166.6 (3)
O22—Pb—O1181.3 (3)O11i—Pb—O12ii117.4 (3)
O21—Pb—O1191.1 (3)O22—Pb—O12i129.2 (3)
O22—Pb—O11i118.7 (3)O21—Pb—O12i78.1 (3)
O21—Pb—O11i77.6 (3)O11—Pb—O12i113.4 (2)
O11—Pb—O11i65.2 (3)O11i—Pb—O12i48.3 (2)
O22—Pb—O12ii86.4 (3)O12ii—Pb—O12i70.9 (3)
O21—Pb—O12ii77.2 (3)
Symmetry codes: (i) x, y, z; (ii) x, y+1, z.
 

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