Anhydrous polymeric zinc(II) penta­noate

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.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.009 Å
• R factor = 0.062
• wR factor = 0.126
• Data-to-parameter ratio = 15.4

checkCIF/PLATON results

No syntax errors found



Datablock: I


Alert level B
PLAT027_ALERT_3_B _diffrn_reflns_theta_full (too) Low ............      24.99 Deg.
PLAT029_ALERT_3_B _diffrn_measured_fraction_theta_full Low .......       0.95
PLAT220_ALERT_2_B Large Non-Solvent    C     Ueq(max)/Ueq(min) ...       3.97 Ratio

Alert level C
PLAT062_ALERT_4_C Rescale T(min) & T(max) by .....................       0.91
PLAT125_ALERT_4_C No _symmetry_space_group_name_Hall Given .......          ?
PLAT128_ALERT_4_C Non-standard setting of Space-group P21/c   ....      P21/a
PLAT222_ALERT_3_C Large Non-Solvent    H     Ueq(max)/Ueq(min) ...       3.78 Ratio
PLAT341_ALERT_3_C Low Bond Precision on C-C Bonds (x 1000) Ang ...          9
PLAT764_ALERT_4_C Overcomplete CIF Bond List Detected (Rep/Expd) .       1.12 Ratio

Alert level G
ABSTM02_ALERT_3_G  When printed, the submitted absorption T values will be
            replaced by the scaled T values. Since the ratio of scaled T's
            is identical to the ratio of reported T values, the scaling
            does not imply a change to the absorption corrections used in
            the study.
            Ratio of Tmax expected/reported      0.908
            Tmax scaled      0.908 Tmin scaled      0.564
PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature        293 K

   0 ALERT level A = In general: serious problem
   3 ALERT level B = Potentially serious problem
   6 ALERT level C = Check and explain
   2 ALERT level G = General alerts; check

   1 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   1 ALERT type 2 Indicator that the structure model may be wrong or deficient
   5 ALERT type 3 Indicator that the structure quality may be low
   4 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. 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.

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).

S2. 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.

S3. Refinement

H atoms were positioned geometrically and refined as riding, with C—H = 0.97 Å and U_iso(H) = 1.2U_eq(C) for methylene, and C—H = 0.96 Å and U_iso(H) = 1.5U_eq(C) for methyl groups. The crystal was weakly diffracting at high angles.

Computing details

Data collection: CrystalClear (Rigaku, 2000); cell refinement: CrystalClear (Rigaku, 2000); data reduction: CrystalClear (Rigaku, 2000); 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 (Sheldrick, 2008).

Figures

	Fig. 1. : Asymmetric unit of zinc(II) n-pentanoate: Displacement ellipsoids are drawn at the 75% probability level.
	Fig. 2. : Projection down the b axis. Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 3. : View down the a axis (hydrogen atoms omitted). Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 4. : Unit-cell contents, showing alternating tetrahedra of oxygen atoms around zinc ions in the zinc basal planes.

poly[di-µ-pentanoato-zinc(II)]

Crystal data

[Zn(C5H9O2)2]	Dx = 1.402 Mg m^−3
Mr = 267.63	Melting point: 425.5 K
Monoclinic, P21/a	Mo Kα radiation, λ = 0.71073 Å
a = 9.389 (2) Å	Cell parameters from 7493 reflections
b = 4.782 (1) Å	θ = 2.2–25.0°
c = 29.126 (7) Å	µ = 1.93 mm^−1
β = 104.256 (7)°	T = 293 K
V = 1267.5 (5) Å^3	Thin block, colourless
Z = 4	0.30 × 0.30 × 0.05 mm
F(000) = 560

Data collection

Rigaku R-AXIS IIC image-plate diffractometer	2125 independent reflections
Radiation source: rotating-anode X-ray tube	1965 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.062
Detector resolution: 105 pixels mm^-1	θmax = 25.0°, θmin = 2.2°
ϕ scans	h = −11→11
Absorption correction: multi-scan (CrystalClear; Rigaku, 2000)	k = −5→5
Tmin = 0.621, Tmax = 1.000	l = −34→34
7493 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.062	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.126	H-atom parameters constrained
S = 1.17	w = 1/[σ^2(Fo^2) + (0.0408P)^2 + 3.0707P] where P = (Fo^2 + 2Fc^2)/3
2125 reflections	(Δ/σ)max < 0.001
138 parameters	Δρmax = 0.32 e Å^−3
0 restraints	Δρmin = −0.52 e Å^−3

Special details

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
C1	0.7184 (5)	−0.3109 (10)	0.19302 (17)	0.0350 (10)
C2	0.7780 (6)	−0.1602 (11)	0.15666 (19)	0.0456 (13)
H2A	0.8636	−0.0544	0.1731	0.055*
H2B	0.7047	−0.0267	0.1407	0.055*
C3	0.8215 (6)	−0.3404 (11)	0.11919 (19)	0.0462 (13)
H3A	0.8985	−0.4689	0.1346	0.055*
H3B	0.7374	−0.4503	0.1029	0.055*
C4	0.8750 (7)	−0.1677 (13)	0.0835 (2)	0.0571 (15)
H4A	0.9595	−0.0591	0.1000	0.069*
H4B	0.7983	−0.0376	0.0686	0.069*
C5	0.9177 (9)	−0.3437 (17)	0.0453 (2)	0.081 (2)
H5A	0.9946	−0.4712	0.0599	0.122*
H5B	0.9517	−0.2233	0.0239	0.122*
H5C	0.8338	−0.4473	0.0282	0.122*
C6	0.4620 (5)	0.1354 (11)	0.29619 (18)	0.0405 (12)
C7	0.5718 (6)	−0.0210 (14)	0.3329 (2)	0.0569 (16)
H7A	0.6541	0.1024	0.3456	0.068*
H7B	0.6085	−0.1756	0.3176	0.068*
C8	0.5177 (7)	−0.1364 (17)	0.3739 (2)	0.0666 (18)
H8A	0.4695	0.0125	0.3870	0.080*
H8B	0.4450	−0.2800	0.3621	0.080*
C9	0.6363 (9)	−0.258 (2)	0.4128 (3)	0.097 (3)
H9A	0.7112	−0.1168	0.4237	0.116*
H9B	0.6817	−0.4123	0.4001	0.116*
C10	0.5825 (11)	−0.362 (3)	0.4546 (3)	0.139 (4)
H10A	0.5363	−0.2109	0.4672	0.208*
H10B	0.6642	−0.4303	0.4787	0.208*
H10C	0.5128	−0.5099	0.4446	0.208*
O1	0.6932 (4)	−0.1838 (7)	0.22800 (13)	0.0486 (9)
O2	0.6954 (4)	−0.5724 (7)	0.18803 (12)	0.0438 (9)
O3	0.4976 (4)	0.2344 (7)	0.26038 (12)	0.0431 (8)
O4	0.3333 (4)	0.1625 (8)	0.30100 (13)	0.0480 (9)
Zn1	0.68833 (6)	0.21140 (11)	0.24407 (2)	0.0358 (2)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.040 (3)	0.031 (3)	0.038 (3)	0.000 (2)	0.017 (2)	0.001 (2)
C2	0.065 (4)	0.032 (3)	0.049 (3)	−0.004 (2)	0.032 (3)	0.000 (2)
C3	0.061 (4)	0.035 (3)	0.049 (3)	0.001 (2)	0.027 (3)	−0.006 (2)
C4	0.071 (4)	0.058 (4)	0.050 (3)	0.000 (3)	0.031 (3)	0.001 (3)
C5	0.110 (6)	0.092 (6)	0.059 (4)	−0.004 (5)	0.052 (4)	−0.008 (4)
C6	0.038 (3)	0.037 (3)	0.051 (3)	−0.001 (2)	0.020 (2)	−0.004 (2)
C7	0.045 (3)	0.077 (4)	0.051 (3)	0.011 (3)	0.017 (3)	0.018 (3)
C8	0.051 (4)	0.093 (5)	0.057 (4)	−0.003 (3)	0.017 (3)	0.022 (4)
C9	0.076 (5)	0.144 (9)	0.070 (5)	0.010 (5)	0.015 (4)	0.047 (5)
C10	0.121 (9)	0.214 (13)	0.081 (6)	0.009 (8)	0.025 (6)	0.073 (7)
O1	0.073 (3)	0.0289 (18)	0.055 (2)	−0.0028 (17)	0.037 (2)	−0.0019 (16)
O2	0.058 (2)	0.0271 (18)	0.051 (2)	−0.0039 (15)	0.0227 (18)	0.0000 (16)
O3	0.040 (2)	0.047 (2)	0.0457 (19)	0.0031 (15)	0.0176 (16)	0.0053 (16)
O4	0.036 (2)	0.064 (3)	0.050 (2)	0.0026 (17)	0.0219 (17)	0.0016 (18)
Zn1	0.0426 (4)	0.0295 (3)	0.0410 (3)	−0.0012 (2)	0.0210 (2)	−0.0022 (3)

Geometric parameters (Å, º)

C1—O1	1.258 (6)	C7—C8	1.512 (8)
C1—O2	1.271 (6)	C7—H7A	0.970
C1—C2	1.498 (6)	C7—H7B	0.970
C2—C3	1.523 (7)	C8—C9	1.496 (9)
C2—H2A	0.970	C8—H8A	0.970
C2—H2B	0.970	C8—H8B	0.970
C3—C4	1.506 (7)	C9—C10	1.515 (10)
C3—H3A	0.970	C9—H9A	0.970
C3—H3B	0.970	C9—H9B	0.970
C4—C5	1.525 (8)	C10—H10A	0.960
C4—H4A	0.970	C10—H10B	0.960
C4—H4B	0.970	C10—H10C	0.960
C5—H5A	0.960	Zn1—O1	1.950 (3)
C5—H5B	0.960	O2—Zn1^i	1.947 (3)
C5—H5C	0.960	Zn1—O3	1.966 (3)
C6—O4	1.256 (6)	O4—Zn1^ii	1.963 (4)
C6—O3	1.263 (6)	Zn1—O2^iii	1.947 (3)
C6—C7	1.491 (7)	Zn1—O4^iv	1.963 (4)
O1—C1—O2	120.5 (4)	C8—C7—H7A	108.2
O1—C1—C2	121.2 (4)	C6—C7—H7B	108.2
O2—C1—C2	118.4 (4)	C8—C7—H7B	108.2
C1—C2—C3	116.5 (4)	H7A—C7—H7B	107.4
C1—C2—H2A	108.2	C9—C8—C7	114.0 (6)
C3—C2—H2A	108.2	C9—C8—H8A	108.8
C1—C2—H2B	108.2	C7—C8—H8A	108.8
C3—C2—H2B	108.2	C9—C8—H8B	108.8
H2A—C2—H2B	107.3	C7—C8—H8B	108.8
C4—C3—C2	112.2 (4)	H8A—C8—H8B	107.7
C4—C3—H3A	109.2	C8—C9—C10	113.7 (7)
C2—C3—H3A	109.2	C8—C9—H9A	108.8
C4—C3—H3B	109.2	C10—C9—H9A	108.8
C2—C3—H3B	109.2	C8—C9—H9B	108.8
H3A—C3—H3B	107.9	C10—C9—H9B	108.8
C3—C4—C5	113.1 (5)	H9A—C9—H9B	107.7
C3—C4—H4A	109.0	C9—C10—H10A	109.5
C5—C4—H4A	109.0	C9—C10—H10B	109.5
C3—C4—H4B	109.0	H10A—C10—H10B	109.5
C5—C4—H4B	109.0	C9—C10—H10C	109.5
H4A—C4—H4B	107.8	H10A—C10—H10C	109.5
C4—C5—H5A	109.5	H10B—C10—H10C	109.5
C4—C5—H5B	109.5	C1—O1—Zn1	133.1 (3)
H5A—C5—H5B	109.5	C1—O2—Zn1^i	117.8 (3)
C4—C5—H5C	109.5	C6—O3—Zn1	128.3 (3)
H5A—C5—H5C	109.5	C6—O4—Zn1^ii	115.0 (3)
H5B—C5—H5C	109.5	O2^iii—Zn1—O1	107.80 (15)
O4—C6—O3	120.7 (5)	O2^iii—Zn1—O4^iv	112.66 (15)
O4—C6—C7	119.0 (5)	O1—Zn1—O4^iv	116.62 (17)
O3—C6—C7	120.3 (4)	O2^iii—Zn1—O3	113.19 (15)
C6—C7—C8	116.2 (5)	O1—Zn1—O3	100.89 (15)
C6—C7—H7A	108.2	O4^iv—Zn1—O3	105.21 (14)

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