catena-Poly­[[di­aqua­di­chloro­iron(II)]-μ-1,4-dioxane-κ²O:O′]

The crystal structure of the title compound, [FeCl₂(C₄H₈O₂)(H₂O)₂]_n, contains six-coordinate Fe^II atoms in approximately octahedral environments. The Fe^II atoms have symmetry, i.e. all pairs of identical ligands are trans. The structure consists of polymeric chains made up of dioxane mol­ecules, in the chair conformation with symmetry, linking the Fe^II centers. The chains are crosslinked by O—H...Cl hydrogen bonds.

S1. Comment

For many years, crystal engineering has utilized the hydrogen bond for the formation of extended networks, thus creating structures with a variety of pore shapes and sizes able to accommodate various guest molecules. Many of the networks that have been reported are neutral. An obvious alternative to neutral frameworks are ionic ones, in particular, cationic frameworks. These could then play host to a variety of negatively charged species of various sizes. It has been suggested that a metal-cation–dioxane network could achieve this (Hasch et al., 2000). A number of structures have been reported involving alkali-metal–dioxane networks (Taube et al., 1993; Eaborn et al., 1997; Kühl et al., 1999, 2000; Hasche et al., 2000). These structures indicate the variety of structures obtainable as a result of variations in the coordination at the metal center; thus, one-dimensional chains, two-dimensional sheets, and three-dimensional networks have all been observed. The only other known extended dioxane–metal structures are chains with hard metal centers, for example, Al^III (Boardman et al., 1983), Ga^III (Boardman et al., 1984), Mg^II (Parvez et al., 1988), Cd^II (Almond et al., 1991), Tl^III (Jeffs et al., 1983), Nd^III (Taube et al., 1996), and Fe^II (Müller et al., 1997). Recently, another type of chain structure has been reported where 1,4-dioxane links 1,2-diiodotetrafluoroethane molecules by coordination to the two I atoms (Chu et al., 2001).

While attempting to extend our work on lithium-containing cationic networks to include iron(II)-containing anions by the reaction of LiCl and FeCl₂ in dioxane, only the lithium-free title compound, (I), a one-dimensional polymeric structure, was obtained. This compound contains a pseudo-octahedral six-coordinate Fe^II cation with 1 symmetry, coordinated by two trans Cl^- ions and two trans water molecules. The final two coordination sites are occupied by 1,4-dioxane rings bound through O atoms, as shown in Fig. 1. The O atoms of the dioxane ring, which adopts a chair conformation, bind to two Fe^II atoms on either side, with a bond distance of 2.1830 (17) Å. This coordination results in the formation of chains parallel to a and these chains build the backbone of the crystal structure, similar to the case in catena-[[bis(2,2,6,6-tetramethylheptane-3,5-dionato)iron(II)]-µ-1,4-dioxane] (Müller et al., 1997). In the present case, the iron–dioxane chains are crosslinked by O_water···Cl hydrogen bonding (Fig. 2). The hydrogen bonding involves the H atoms located on the coordinated water molecules and the coordinated Cl^- ions on the Fe^II atoms of two adjacent chains. Each water molecule hydrogen bonds to two Cl^- ions from two adjacent Fe^II centers, and each chloride ion accepts two hydrogen bonds from two adjacent Fe^II centers, i.e. an approximately square arrangement with the two Cl and two O atoms at opposite corners, each side representing a hydrogen bond, and each corner bound to a different Fe^II atom; an approximately planar FeOClH layer is thus formed perpendicular to the Fe—O_dioxane vector within the polymer chain.

S2. Experimental

Anhydrous iron(II) chloride (0.50 g) and lithium chloride (0.50 g) were placed in a 100 ml beaker. 1,4-Dioxane (50 ml) was added and the solution was heated and stirred for 2 h. After filtering off unreacted starting material, the resulting solution was separated in 5 ml vials for evaporation and crystallization.

Computing details

Data collection: SMART (Bruker, 1999); cell refinement: SAINT (Bruker, 1999); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXL97; software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. One polymeric chain in (I) parallel to a.
	Fig. 2. The hydrogen-bonded layer perpendicular to the Fe—Odioxane vector in the polymer chains of (I).

catena-diaqua-dichloro-(µ-1,4-dioxane-O,O')-iron(II)

Crystal data

[FeCl2(C4H8O2)(H2O)2]	F(000) = 256
Mr = 250.89	Dx = 1.811 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 6.8590 (18) Å	Cell parameters from 1309 reflections
b = 9.273 (2) Å	θ = 3.3–29.2°
c = 7.925 (2) Å	µ = 2.19 mm^−1
β = 114.082 (5)°	T = 100 K
V = 460.2 (2) Å^3	Irregular, red–brown
Z = 2	0.20 × 0.20 × 0.15 mm

Data collection

Bruker SMART CCD diffractometer	1058 independent reflections
Radiation source: fine-focus sealed tube	965 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.021
ω scans	θmax = 29.2°, θmin = 3.3°
Absorption correction: empirical (using intensity measurements) multipole expansion (Blessing, 1995; Sheldrick, 1996)	h = −9→7
Tmin = 0.364, Tmax = 0.659	k = −5→12
1799 measured reflections	l = −10→9

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)] = 0.035	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.094	All H-atom parameters refined
S = 1.05	w = 1/[σ^2(Fo^2) + (0.0666P)^2 + 0.1903P] where P = (Fo^2 + 2Fc^2)/3
1058 reflections	(Δ/σ)max < 0.001
76 parameters	Δρmax = 0.92 e Å^−3
0 restraints	Δρmin = −0.67 e Å^−3

Special details

Experimental. The decay correction was applied simultaneously with the absorption correction in SADABS. No formal measure of the extent of decay is printed out by this program. The final unit cell is obtained from the refinement of the XYZ weighted centroids of reflections above 15 σ(I).

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
Fe1	0.0000	0.5000	0.0000	0.01226 (17)
Cl1	0.03854 (8)	0.23836 (5)	−0.02603 (7)	0.01541 (18)
O2	0.1774 (3)	0.48894 (17)	0.2862 (3)	0.0173 (4)
H1A	0.240 (6)	0.561 (4)	0.343 (5)	0.031 (9)*
H1B	0.268 (7)	0.425 (4)	0.327 (5)	0.033 (9)*
O1	0.2847 (3)	0.54151 (18)	−0.0509 (2)	0.0168 (4)
C1	0.3476 (4)	0.4532 (2)	−0.1708 (3)	0.0172 (4)
H2A	0.225 (5)	0.388 (3)	−0.237 (4)	0.016 (7)*
H2B	0.379 (6)	0.518 (3)	−0.254 (5)	0.026 (9)*
C2	0.4591 (4)	0.6350 (2)	0.0583 (4)	0.0178 (5)
H3A	0.492 (5)	0.697 (4)	−0.028 (4)	0.022 (8)*
H3B	0.406 (5)	0.690 (3)	0.140 (4)	0.022 (7)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Fe1	0.0110 (3)	0.0113 (3)	0.0139 (3)	0.00039 (15)	0.00445 (19)	0.00011 (14)
Cl1	0.0147 (3)	0.0115 (3)	0.0183 (3)	0.00052 (17)	0.0050 (2)	−0.00036 (17)
O2	0.0167 (9)	0.0136 (7)	0.0181 (9)	0.0005 (6)	0.0034 (7)	−0.0013 (6)
O1	0.0125 (8)	0.0181 (7)	0.0211 (8)	−0.0019 (6)	0.0082 (6)	−0.0052 (6)
C1	0.0164 (11)	0.0201 (10)	0.0167 (10)	−0.0007 (9)	0.0084 (9)	−0.0028 (9)
C2	0.0149 (11)	0.0166 (11)	0.0230 (11)	−0.0030 (8)	0.0090 (9)	−0.0026 (8)

Geometric parameters (Å, º)

Fe1—O1	2.1830 (17)	O1—C2	1.444 (3)
Fe1—O1^i	2.1830 (17)	O1—C1	1.448 (3)
Fe1—O2^i	2.0934 (19)	C1—C2^ii	1.502 (3)
Fe1—O2	2.0934 (19)	C1—H2A	0.99 (3)
Fe1—Cl1^i	2.4583 (8)	C1—H2B	0.98 (3)
Fe1—Cl1	2.4583 (8)	C2—C1^ii	1.502 (3)
O2—H1A	0.82 (4)	C2—H3A	0.99 (3)
O2—H1B	0.83 (4)	C2—H3B	1.00 (3)
O1—Fe1—O1^i	180.0	H1A—O2—H1B	103 (4)
O1—Fe1—Cl1^i	88.65 (5)	C2—O1—C1	109.67 (18)
O1^i—Fe1—Cl1^i	91.35 (5)	C2—O1—Fe1	125.44 (13)
O1—Fe1—Cl1	91.35 (5)	C1—O1—Fe1	123.40 (14)
O1^i—Fe1—Cl1	88.65 (5)	O1—C1—C2^ii	110.2 (2)
O2^i—Fe1—O2	180.0	O1—C1—H2A	105.9 (17)
O2^i—Fe1—O1	87.69 (7)	C2^ii—C1—H2A	109.5 (16)
O2—Fe1—O1	92.31 (7)	O1—C1—H2B	107.4 (19)
O2^i—Fe1—O1^i	92.31 (7)	C2^ii—C1—H2B	110 (2)
O2—Fe1—O1^i	87.69 (7)	H2A—C1—H2B	113 (3)
O2^i—Fe1—Cl1^i	90.44 (4)	O1—C2—C1^ii	110.13 (18)
O2—Fe1—Cl1^i	89.56 (4)	O1—C2—H3A	107.6 (18)
O2^i—Fe1—Cl1	89.56 (4)	C1^ii—C2—H3A	109.5 (18)
O2—Fe1—Cl1	90.44 (4)	O1—C2—H3B	105.1 (19)
Cl1^i—Fe1—Cl1	180.0	C1^ii—C2—H3B	111.1 (18)
Fe1—O2—H1A	120 (3)	H3A—C2—H3B	113 (3)
Fe1—O2—H1B	118 (3)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H1A···Cl1^iii	0.82 (4)	2.31 (4)	3.1202 (19)	171 (4)
O2—H1B···Cl1^iv	0.83 (4)	2.31 (4)	3.1280 (19)	173 (3)

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