Anhydrous polymeric zinc(II) penta­noate

Richard A Taylor; Henry A Ellis

doi:10.1107/S1600536808008283

. 2008 Jun 7;64(Pt 7):m895. doi: 10.1107/S1600536808008283

Anhydrous polymeric zinc(II) pentanoate

Richard A Taylor ^a, Henry A Ellis ^a,^*

PMCID: PMC2961895 PMID: 21202761

Abstract

The structure of the title compound, poly[di-μ-pentanoato-zinc(II)], [Zn{CH₃(CH₂)₃COO}₂]_n, consists of a three-dimensional polymeric layered network with sheets parallel to the (100) plane, in which tetrahedrally coordinated zinc(II) ions are connected by pentanoate bridges in a syn–anti arrangement. The hydrocarbon chains are in the fully extended all-trans conformation and are arranged in a tail-to-tail double bilayer.

Related literature

For related literature, see: Clegg et al. (1986 ▶); Blair et al. (1993 ▶); Dumbleton & Lomer (1965 ▶); Glover (1981 ▶); Goldschmied et al. (1977 ▶); Ishioka et al. (1998 ▶); Lacouture et al. (2000 ▶); Lewis & Lomer (1969 ▶); Lomer & Perera (1974 ▶); Peultier et al. (1999 ▶); Segedin et al. (1999 ▶).

Experimental

Crystal data

[Zn(C₅H₉O₂)₂]
M _r = 267.63
Monoclinic,
a = 9.389 (2) Å
b = 4.7820 (10) Å
c = 29.126 (7) Å
β = 104.256 (7)°
V = 1267.5 (5) Å³
Z = 4
Mo Kα radiation
μ = 1.93 mm⁻¹
T = 293 (2) K
0.30 × 0.30 × 0.05 mm

Data collection

Rigaku R-AXIS IIC image-plate diffractometer
Absorption correction: multi-scan (CrystalClear; Rigaku, 2000 ▶) T _min = 0.621, T _max = 1.000 (expected range = 0.564–0.908)
7493 measured reflections
2125 independent reflections
1965 reflections with I > 2σ(I)
R _int = 0.061

Refinement

R[F ² > 2σ(F ²)] = 0.062
wR(F ²) = 0.126
S = 1.17
2125 reflections
138 parameters
H-atom parameters constrained
Δρ_max = 0.32 e Å⁻³
Δρ_min = −0.52 e Å⁻³

Data collection: CrystalClear (Rigaku, 2000 ▶); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SIR92 (Altomare et al., 1994 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: Mercury (Macrae et al., 2006 ▶) and DIAMOND (Bergerhoff et al., 1996 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808008283/cf2188sup1.cif

e-64-0m895-sup1.cif^{(15.3KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808008283/cf2188Isup2.hkl

e-64-0m895-Isup2.hkl^{(401.4KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Selected geometric parameters (Å, °).

Zn1—O1	1.950 (3)
Zn1—O3	1.966 (3)
Zn1—O2ⁱ	1.947 (3)
Zn1—O4ⁱⁱ	1.963 (4)

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O2ⁱ—Zn1—O1	107.80 (15)
O2ⁱ—Zn1—O4ⁱⁱ	112.66 (15)
O1—Zn1—O4ⁱⁱ	116.62 (17)
O2ⁱ—Zn1—O3	113.19 (15)
O1—Zn1—O3	100.89 (15)
O4ⁱⁱ—Zn1—O3	105.21 (14)

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Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

The authors express thanks to Ms Susanne Olsson of the X-ray Crystallography Laboratory in the Department of Chemistry of the University of Gothenberg, Sweden, for her assistance with aspects of the single-crystal work.

supplementary crystallographic information

Comment

Long-chain metal carboxylates do not easily form crystals suitable for single-crystal X-ray analysis; usually, the crystals are thin needles that are fragile and, in many cases exhibit micro-twinning. Consequently, the few structures that have been reported are those of the short-chain homologues (Dumbleton & Lomer, 1965; Lewis & Lomer, 1969; Glover, 1981; Lomer & Perera, 1974; Ishioka et al., 1998). For the zinc(II) series those reported include anhydrous zinc(II) acetate (Clegg et al., 1986), propionate (Goldschmied et al., 1977), butanoate (Blair et al., 1993), hexanoate and heptanoate (Segedin et al., 1999; Peultier et al., 1999) and octanoate (Lacouture et al., 2000). The compounds are isostructural in the sense that the zinc ions have a tetrahedral geometry of oxygen atoms and are bridged by bidentate ligands. In this study, anhydrous zinc(II) pentanoate, (I), was investigated in order to elucidate its crystal structure.

The structure (Fig. 1) is four-coordinate, where each zinc ion is tetrahedrally coordinated by oxygen atoms from four different pentanoate ligands. The four pentanoate ligands around zinc are of the Z,E-type bridging bidentate mode; that is, they are bonded in a syn-anti arrangement to two tetrahedral zinc ions. Geometric data indicate that the Zn—O bond lengths are not equivalent and clearly point to unsymmetrical bonding around the zinc ion.

The alkyl chains of the pentanoate groups are in the fully extended all-trans conformation. There is excellent agreement of the C—C bond lengths and C—C—C angles with published values for hydrocarbon chains in a fully extended all-trans conformation (Lomer & Perera, 1974). There are four formula units in the unit cell and two distinct basal planes, resulting in a double bilayer lamella arrangement forming a polymeric network (Fig. 2) with an alternating packing of the hydrocarbon chains in neighbouring bilayers. When viewed down the b axis, the hydrocarbon chains, which are tilted with respect to the zinc basal planes, are in each bilayer aligned in different planes. The structure appears very different when viewed down the a axis (Fig. 3), where in one bilayer the chains appear to zigzag and cross at the bonds along the C—C axis. In the other bilayer the chains are tilted towards each other and appear to cross each other at carbon atom number 4.

The molecular packing (Fig. 4) highlights the distorted tetrahedra around the zinc ions. In one basal plane, the vertices of the tetrahedra alternate parallel and perpendicular to the vertical plane throughout and in the other basal plane the vertices alternate at the top and bottom throughout. This arrangement allows for alternating basal planes in the overall structure to be identical.

There is interaction between parallel sheets through bidentate bridging, resulting in a three-dimensional sheet-like/layered polymeric network where the chains are arranged tail-to-tail, arising from van der Waals interactions in sheets parallel to the ac plane.

Experimental

Single crystals of zinc(II) pentanoate were prepared from the reaction of zinc oxide (0.407 g) and n-pentanoic acid (5.0 cm³; >100% excess) in approximately 100 cm³ of ethanol. The white suspension was refluxed until the solution was transparent. The resulting hot, colorless solution was filtered by suction and the filtrate left to cool to room temperature. After about six days, long, thin, colourless, plate-like single crystals, some in clusters, crystallized from solution. The crystals were then removed, air-dried, and kept in sealed vials at ambient temperature.