Anhydrous polymeric zinc(II) octanoate

The structure of the title compound, poly­[zinc(II)-bis([mu]-octanoato-O:O')], [Zn(C₈H₁₅O₂)₂]_n, consists of polymeric sheets parallel to (100) in which tetrahedrally coordinated Zn²⁺ cations are connected by carboxyl­ate bridges in a syn-anti arrangement.

S1. Comment

The elucidation of the structure of the title compound, (I), follows that already performed for zinc heptanoate, (II) (Peultier et al., 1999). It was undertaken to characterize as well as possible these metal soaps which protect zinc surfaces against corrosion, and to understand the evolution of the structural properties in the Zn(C_nH_2n-1O₂)₂ series according to n, the number of C atoms in the aliphatic chain. \scheme

Compound (I) clearly shows the structural features of the previously known members of the series, namely, n = 2 (acetate; Clegg et al., 1987; Frada, 1992), n = 3 (propionate; Clegg et al., 1986), n = 4 (butanoate; Blair et al., 1993) and n = 6 (hexanoate; Segedin et al., 1999). The structure is layered, as shown in Fig. 1. Each Zn atom is tetrahedrally coordinated by O atoms belonging to four different octanoate groups (Fig. 2). The Zn tetrahedra are connected by syn-anti bridges of the octanoate groups, thus forming layers parallel to (100). The chains constituted by the C2n atoms form an angle of approximately 60°, confirming the tendency of these angles to decrease when n increases (Peultier et al., 1999).

It is mainly the stacking mode of the layers which varies according to n. For example, the addition of a C atom in going from zinc heptanoate [(II)] to zinc octanoate [(I)] results in the structure changing from one in which the planes containing the C2n chains of two adjacent layers form an angle of approximately 120° [(II)] to one in which they are parallel [(I)]. The structure of (I) (Pc) can be deduced from that of (II) [Pbc2₁, a = 4.7651 (6), b = 9.3404 (15) and c = 37.066 (6) Å] by carrying out a rotation of 180° of every other layer around the c axis, followed by a translation of 4.14 Å along the b axis. This modification in stacking involves the loss of the 2₁ axis parallel with the c axis and of the c glide mirror perpendicular to the b axis, but preserves the b glide mirror perpendicular to the a axis. According to the orientation used to describe the structure of (I), the element of symmetry which is preserved is a c glide mirror perpendicular to the monoclinic b axis, which for (I) leads to a noncentrosymmetric and monoclinic structure (Pc).

S2. Experimental

Anhydrous zinc(II) octanoate was synthesized after a weakly acidic solution of zinc nitrate (pH 5.5) was added to a solution of sodium octanoate in solvent?. The precipitate, (I), was washed with distilled water and dried. Finally, compound (I) was recrystallized from ethanol at room temperature. Colourless crystals appeared as small plates with well developed (100) faces.

Computing details

Data collection: COLLECT (Nonius, 1998); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN; program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ATOMS (Dowty, 1995); software used to prepare material for publication: WINWORD Version 5.0.

Figures

	Fig. 1. Projection of the structure of (I) along [010] (ATOMS for Windows; Dowty, 1995). Displacement ellipsoids are drawn at the 50% probability level. H atoms are omitted for clarity.
	Fig. 2. The Zn^II tetrahedral environment in (I) showing the orientation of the linear octanoate chains. Displacement ellipsoids are drawn at the 50% probability level (ATOMS for Windows; Dowty, 1995). Symmetry codes are as given in Table 1. H atoms are omitted for clarity.

poly[zinc(II)-bis(µ-octanoato-O:O')]

Crystal data

[Zn(C8H15O2)2]	F(000) = 376
Mr = 351.79	Dx = 1.301 Mg m^−3
Monoclinic, Pc	Mo Kα radiation, λ = 0.71073 Å
a = 21.093 (2) Å	Cell parameters from 62153 reflections
b = 4.6905 (3) Å	θ = 1.0–27.5°
c = 9.2544 (9) Å	µ = 1.38 mm^−1
β = 101.323 (3)°	T = 150 K
V = 897.78 (14) Å^3	Plate, colourless
Z = 2	0.30 × 0.20 × 0.02 mm

Data collection

Nonius CCD area detector diffractometer	2984 independent reflections
Radiation source: fine-focus sealed tube	2231 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.095
CCD scans	θmax = 24.7°, θmin = 2.0°
Absorption correction: empirical (using intensity measurements) fitted by spherical harmonic functions (SORTAV; Blessing, 1995)	h = −24→24
Tmin = 0.751, Tmax = 0.976	k = −5→5
14913 measured reflections	l = −10→10

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.058	H-atom parameters not refined
wR(F^2) = 0.167	Calculated w = 1/[σ^2(Fo^2) + (0.079P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.00	(Δ/σ)max = 0.007
2984 reflections	Δρmax = 0.57 e Å^−3
191 parameters	Δρmin = −0.66 e Å^−3
16 restraints	Absolute structure: Flack (1983)
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.02 (3)

Special details

Experimental. The crystal to detector distance was 39.6 (1) mm. 924 frames were recorded by the oscillation method with an exposure time of 120 s per frame.

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 (Ų)

	x	y	z	Uiso*/Ueq
Zn	0.00002 (6)	0.0581 (2)	−0.00046 (7)	0.0243 (3)
O11	−0.0219 (3)	−0.5357 (13)	−0.0340 (6)	0.0304 (17)
O12	−0.0795 (3)	−0.1493 (13)	−0.0857 (6)	0.0271 (15)
C11	−0.0714 (4)	−0.408 (2)	−0.1056 (9)	0.026 (2)
C12	−0.1212 (5)	−0.567 (2)	−0.2202 (10)	0.029 (2)
H12A	−0.0983	−0.6792	−0.2818	0.034*
H12B	−0.1446	−0.6988	−0.1691	0.034*
C13	−0.1695 (5)	−0.3768 (19)	−0.3184 (10)	0.031 (2)
H13A	−0.1468	−0.2530	−0.3751	0.037*
H13B	−0.1913	−0.2576	−0.2577	0.037*
C14	−0.2192 (5)	−0.551 (2)	−0.4226 (9)	0.033 (2)
H14A	−0.2406	−0.6799	−0.3654	0.040*
H14B	−0.1973	−0.6658	−0.4849	0.040*
C15	−0.2703 (4)	−0.367 (2)	−0.5201 (9)	0.031 (2)
H15A	−0.2906	−0.2448	−0.4579	0.037*
H15B	−0.2492	−0.2456	−0.5812	0.037*
C16	−0.3220 (4)	−0.542 (2)	−0.6186 (10)	0.035 (2)
H16A	−0.3428	−0.6639	−0.5570	0.042*
H16B	−0.3015	−0.6647	−0.6802	0.042*
C17	−0.3737 (4)	−0.364 (2)	−0.7173 (10)	0.039 (3)
H17A	−0.3941	−0.2402	−0.6560	0.047*
H17B	−0.3531	−0.2438	−0.7799	0.047*
C18	−0.4255 (5)	−0.544 (2)	−0.8140 (12)	0.051 (3)
H18A	−0.4082	−0.6263	−0.8930	0.076*
H18B	−0.4619	−0.4262	−0.8539	0.076*
H18C	−0.4390	−0.6936	−0.7559	0.076*
O21	0.0801 (3)	0.0793 (14)	0.4393 (6)	0.0314 (15)
O22	0.0214 (3)	0.0339 (13)	0.2158 (6)	0.0277 (15)
C21	0.0718 (4)	0.1216 (19)	0.3022 (9)	0.027 (2)
C22	0.1229 (5)	0.288 (2)	0.2438 (10)	0.032 (3)
H22A	0.1400	0.1680	0.1752	0.038*
H22B	0.1024	0.4510	0.1891	0.038*
C23	0.1787 (5)	0.394 (2)	0.3593 (10)	0.036 (3)
H23A	0.1981	0.2347	0.4190	0.043*
H23B	0.1628	0.5282	0.4236	0.043*
C24	0.2295 (4)	0.538 (2)	0.2896 (10)	0.036 (2)
H24A	0.2106	0.7026	0.2341	0.043*
H24B	0.2435	0.4065	0.2211	0.043*
C25	0.2878 (4)	0.632 (2)	0.4039 (10)	0.041 (3)
H25A	0.3049	0.4679	0.4630	0.049*
H25B	0.2738	0.7700	0.4690	0.049*
C26	0.3418 (4)	0.763 (2)	0.3369 (10)	0.042 (3)
H26A	0.3540	0.6278	0.2677	0.050*
H26B	0.3251	0.9318	0.2818	0.050*
C27	0.4020 (5)	0.844 (3)	0.4491 (10)	0.045 (3)
H27A	0.4182	0.6760	0.5051	0.055*
H27B	0.3899	0.9814	0.5173	0.055*
C28	0.4565 (5)	0.971 (3)	0.3830 (12)	0.063 (4)
H28A	0.4736	0.8277	0.3275	0.095*
H28B	0.4901	1.0393	0.4608	0.095*
H28C	0.4400	1.1270	0.3192	0.095*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Zn	0.0333 (5)	0.0212 (4)	0.0168 (4)	0.0002 (10)	0.0014 (3)	−0.0011 (10)
O11	0.049 (5)	0.015 (3)	0.021 (4)	−0.002 (3)	−0.007 (3)	−0.001 (3)
O12	0.036 (4)	0.014 (3)	0.030 (4)	−0.005 (3)	0.003 (3)	−0.006 (3)
C11	0.035 (5)	0.025 (6)	0.020 (5)	−0.004 (5)	0.007 (4)	0.004 (4)
C12	0.034 (5)	0.021 (5)	0.028 (5)	0.000 (5)	0.001 (4)	0.004 (5)
C13	0.038 (6)	0.020 (6)	0.032 (5)	0.001 (4)	0.003 (4)	0.001 (4)
C14	0.038 (6)	0.041 (6)	0.018 (5)	0.006 (5)	−0.003 (4)	−0.004 (5)
C15	0.033 (5)	0.035 (6)	0.023 (5)	0.002 (4)	0.002 (4)	0.002 (4)
C16	0.024 (5)	0.045 (6)	0.032 (5)	0.008 (5)	−0.002 (4)	0.002 (5)
C17	0.032 (6)	0.049 (7)	0.035 (6)	0.001 (5)	0.003 (5)	−0.001 (5)
C18	0.027 (6)	0.065 (8)	0.055 (7)	0.000 (6)	−0.006 (5)	0.009 (6)
O21	0.041 (4)	0.040 (4)	0.014 (3)	0.000 (3)	0.007 (3)	0.001 (3)
O22	0.037 (4)	0.031 (4)	0.015 (3)	−0.001 (3)	0.005 (3)	0.002 (3)
C21	0.027 (5)	0.033 (6)	0.020 (5)	0.003 (4)	0.000 (4)	−0.003 (4)
C22	0.038 (6)	0.026 (7)	0.031 (6)	−0.011 (5)	0.006 (5)	0.000 (5)
C23	0.039 (6)	0.044 (8)	0.023 (5)	0.002 (5)	0.004 (5)	0.002 (5)
C24	0.030 (5)	0.048 (7)	0.029 (5)	0.000 (5)	0.003 (4)	−0.001 (5)
C25	0.041 (6)	0.056 (8)	0.026 (6)	−0.008 (5)	0.002 (5)	0.001 (5)
C26	0.051 (7)	0.045 (7)	0.030 (5)	−0.011 (6)	0.006 (5)	0.004 (5)
C27	0.039 (6)	0.065 (8)	0.029 (6)	−0.011 (6)	−0.003 (5)	0.006 (5)
C28	0.043 (7)	0.096 (11)	0.045 (7)	−0.019 (7)	−0.006 (6)	0.000 (7)

Geometric parameters (Å, º)

Zn—O12	1.965 (6)	C18—H18B	0.9600
Zn—O22	1.966 (5)	C18—H18C	0.9600
Zn—O11^i	1.971 (6)	O21—C21	1.262 (10)
Zn—O21^ii	1.988 (6)	O21—Zn^iv	1.988 (6)
O11—C11	1.272 (11)	O22—C21	1.267 (10)
O11—Zn^iii	1.971 (6)	C21—C22	1.514 (11)
O12—C11	1.242 (11)	C22—C23	1.510 (11)
C11—C12	1.533 (11)	C22—H22A	0.9700
C12—C13	1.516 (11)	C22—H22B	0.9700
C12—H12A	0.9700	C23—C24	1.513 (12)
C12—H12B	0.9700	C23—H23A	0.9700
C13—C14	1.517 (11)	C23—H23B	0.9700
C13—H13A	0.9700	C24—C25	1.521 (11)
C13—H13B	0.9700	C24—H24A	0.9700
C14—C15	1.528 (11)	C24—H24B	0.9700
C14—H14A	0.9700	C25—C26	1.529 (8)
C14—H14B	0.9700	C25—H25A	0.9700
C15—C16	1.519 (11)	C25—H25B	0.9700
C15—H15A	0.9700	C26—C27	1.524 (11)
C15—H15B	0.9700	C26—H26A	0.9700
C16—C17	1.526 (11)	C26—H26B	0.9700
C16—H16A	0.9700	C27—C28	1.524 (12)
C16—H16B	0.9700	C27—H27A	0.9700
C17—C18	1.525 (11)	C27—H27B	0.9700
C17—H17A	0.9700	C28—H28A	0.9600
C17—H17B	0.9700	C28—H28B	0.9600
C18—H18A	0.9600	C28—H28C	0.9600
O12—Zn—O22	112.8 (3)	C17—C18—H18C	109.5
O12—Zn—O11^i	105.1 (3)	H18A—C18—H18C	109.5
O22—Zn—O11^i	102.5 (2)	H18B—C18—H18C	109.5
O12—Zn—O21^ii	115.6 (3)	C21—O21—Zn^iv	112.0 (6)
O22—Zn—O21^ii	103.2 (2)	C21—O22—Zn	128.3 (5)
O11^i—Zn—O21^ii	117.1 (3)	O21—C21—O22	121.1 (8)
C11—O11—Zn^iii	133.0 (6)	O21—C21—C22	118.2 (8)
C11—O12—Zn	114.3 (6)	O22—C21—C22	120.7 (7)
O12—C11—O11	120.4 (8)	C23—C22—C21	115.3 (8)
O12—C11—C12	118.9 (8)	C23—C22—H22A	108.4
O11—C11—C12	120.7 (8)	C21—C22—H22A	108.4
C13—C12—C11	114.5 (8)	C23—C22—H22B	108.5
C13—C12—H12A	108.6	C21—C22—H22B	108.5
C11—C12—H12A	108.6	H22A—C22—H22B	107.5
C13—C12—H12B	108.6	C22—C23—C24	111.3 (7)
C11—C12—H12B	108.6	C22—C23—H23A	109.4
H12A—C12—H12B	107.6	C24—C23—H23A	109.4
C12—C13—C14	111.3 (7)	C22—C23—H23B	109.4
C12—C13—H13A	109.4	C24—C23—H23B	109.4
C14—C13—H13A	109.4	H23A—C23—H23B	108.0
C12—C13—H13B	109.4	C23—C24—C25	112.0 (7)
C14—C13—H13B	109.4	C23—C24—H24A	109.2
H13A—C13—H13B	108.0	C25—C24—H24A	109.2
C13—C14—C15	112.9 (8)	C23—C24—H24B	109.2
C13—C14—H14A	109.0	C25—C24—H24B	109.2
C15—C14—H14A	109.0	H24A—C24—H24B	107.9
C13—C14—H14B	109.0	C24—C25—C26	113.5 (7)
C15—C14—H14B	109.0	C24—C25—H25A	108.9
H14A—C14—H14B	107.8	C26—C25—H25A	108.9
C16—C15—C14	112.9 (8)	C24—C25—H25B	108.9
C16—C15—H15A	109.0	C26—C25—H25B	108.9
C14—C15—H15A	109.0	H25A—C25—H25B	107.7
C16—C15—H15B	109.0	C27—C26—C25	114.4 (7)
C14—C15—H15B	109.0	C27—C26—H26A	108.7
H15A—C15—H15B	107.8	C25—C26—H26A	108.7
C15—C16—C17	114.0 (8)	C27—C26—H26B	108.7
C15—C16—H16A	108.7	C25—C26—H26B	108.7
C17—C16—H16A	108.7	H26A—C26—H26B	107.6
C15—C16—H16B	108.7	C26—C27—C28	114.7 (8)
C17—C16—H16B	108.7	C26—C27—H27A	108.6
H16A—C16—H16B	107.6	C28—C27—H27A	108.6
C18—C17—C16	113.1 (8)	C26—C27—H27B	108.6
C18—C17—H17A	109.0	C28—C27—H27B	108.6
C16—C17—H17A	109.0	H27A—C27—H27B	107.6
C18—C17—H17B	109.0	C27—C28—H28A	109.5
C16—C17—H17B	109.0	C27—C28—H28B	109.5
H17A—C17—H17B	107.8	H28A—C28—H28B	109.5
C17—C18—H18A	109.5	C27—C28—H28C	109.5
C17—C18—H18B	109.5	H28A—C28—H28C	109.5
H18A—C18—H18B	109.5	H28B—C28—H28C	109.5

Symmetry codes: (i) x, y+1, z; (ii) x, −y, z−1/2; (iii) x, y−1, z; (iv) x, −y, z+1/2.