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Acta Cryst. (2008). E64, m497    [ doi:10.1107/S1600536808005102 ]

Tetrakis([mu]-pivalato-[kappa]2O:O')bis[(2-methylpyridine-[kappa]N)iron(II)](Fe-Fe)

J. Overgaard, G. A. Timco and F. K. Larsen

Abstract top

The asymmetric unit of the title compound, [Fe2(C5H9O2)4(C6H7N)2], contains one unique Fe-atom site located close to a centre of symmetry which generates the molecular dimer. The two Fe atoms are bridged by four carboxylate groups and are each coordinated by a molecule of 2-picoline. Electron counting and the 18-electron rule suggest that a chemical single bond is likely to exist between the two Fe atoms, which are separated by a distance of 2.8576 (4) Å. This bond completes an approximately octahedral coordination environment around each Fe atom.

Comment top

In a systematic study of the reactions of iron powder with simple carboxylates and aromatic amines to prepare iron(II) carboxylates, the title compound, (1) (Fig. 1) resulted, under ambient reaction conditions. Both monomeric molecular complexes (Celengil-Cetin et al., 2000) and extended iron(II) carboxylates have previously been prepared (Weber, 1980) using similar methods.

In the present study, the iron atoms are only coordinated to five ligands each, with a total donation of 10 electrons. This gives a total of 16 electrons on both Fe, thus a Fe—Fe bond needs to be present to fill the outer orbitals on Fe. The relatively short Fe(1)—Fe(1) interaction distance (d(Fe(1)–Fe(1)) = 2.8576 (4) Å) is likely evidence for such iron-iron bond.

Related literature top

For related literature, see: Celengil-Cetin et al. (2000); Weber (1980); Johnson (1976).

Experimental top

Iron powder (1.0 g) was refluxed in a solution of 2-picoline (C6H7N, 10.0 ml), pivalic acid (4.0 g) and water (1.0 ml) for 5 h under an inert atmosphere. The obtained yellow solution was filtered while hot under an inert atmosphere and the filtrate afforded green crystals upon cooling slowly at room temperature.

Refinement top

The methyl hydrogen atoms were constrained to tetrahedral geometry with C—H distances of 0.98 Å and Uiso(H) = 1.5Ueq(C). The positions of each set of three of the H atoms of the methyl groups constrained to tetrahedral geometry were refined so as to optimize the overlap with the observed electron density (AFIX 137). The H atoms bonded to the aromatic C atoms were constrained to ride on their parent atom in a distance of 0.95 Å in an ideal geometry and with Uiso(H) = 1.2 Ueq(C).

Computing details top

Data collection: SMART (Bruker, 1998); cell refinement: SMART (Bruker, 1998); data reduction: SAINT-Plus (Bruker, 1998); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XP in SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. ORTEPdrawing (Johnson, 1976) of (1) showing the atomic labelling scheme. Hydrogen atoms are omitted for clarity. The thermal ellipsoids show 50% probability surfaces.
Tetrakis(µ-pivalato-κ2O:O')bis[(2-methylpyridine-κN)iron(II)] top
Crystal data top
[Fe2(C5H9O2)4(C6H7N)2]Z = 1
Mr = 702.44F000 = 372
Triclinic, P1Dx = 1.284 Mg m−3
a = 9.5387 (8) ÅMo Kα radiation
λ = 0.71073 Å
b = 10.5403 (9) ÅCell parameters from 2580 reflections
c = 10.5546 (9) Åθ = 2.9–32.7º
α = 64.138 (2)ºµ = 0.85 mm−1
β = 83.600 (2)ºT = 120 (2) K
γ = 72.090 (2)ºPrism, green
V = 908.30 (13) Å30.30 × 0.25 × 0.20 mm
Data collection top
Bruker SMART 1000 CCD area-detector
diffractometer		4949 independent reflections
Radiation source: fine-focus sealed tube4259 reflections with I > 2σ(I)
Monochromator: graphiteRint = 0.032
Detector resolution: 12.0 pixels mm-1θmax = 33.8º
T = 120(2) Kθmin = 2.2º
ω scansh = −11→12
Absorption correction: gaussian
(SADABS; Sheldrick, 2003)		k = −13→16
Tmin = 0.762, Tmax = 0.863l = −14→12
8222 measured reflections
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.035H-atom parameters constrained
wR(F2) = 0.101  w = 1/[σ2(Fo2) + (0.0621P)2 + 0.0412P]
where P = (Fo2 + 2Fc2)/3
S = 1.11(Δ/σ)max < 0.001
4949 reflectionsΔρmax = 0.56 e Å−3
206 parametersΔρmin = −0.48 e Å−3
Primary atom site location: structure-invariant direct methodsExtinction correction: none
Crystal data top
[Fe2(C5H9O2)4(C6H7N)2]γ = 72.090 (2)º
Mr = 702.44V = 908.30 (13) Å3
Triclinic, P1Z = 1
a = 9.5387 (8) ÅMo Kα
b = 10.5403 (9) ŵ = 0.85 mm−1
c = 10.5546 (9) ÅT = 120 (2) K
α = 64.138 (2)º0.30 × 0.25 × 0.20 mm
β = 83.600 (2)º
Data collection top
Bruker SMART 1000 CCD area-detector
diffractometer		4949 independent reflections
Absorption correction: gaussian
(SADABS; Sheldrick, 2003)		4259 reflections with I > 2σ(I)
Tmin = 0.762, Tmax = 0.863Rint = 0.032
8222 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.035206 parameters
wR(F2) = 0.101H-atom parameters constrained
S = 1.11Δρmax = 0.56 e Å−3
4949 reflectionsΔρmin = −0.48 e Å−3
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
Fe1−0.03369 (2)−0.11318 (2)−0.02000 (2)0.02183 (8)
O10.16294 (13)−0.13551 (14)−0.12201 (14)0.0380 (3)
O20.20582 (14)0.04754 (14)−0.09692 (13)0.0355 (3)
O30.08500 (15)−0.25206 (16)0.16687 (14)0.0443 (3)
O40.12814 (14)−0.07109 (13)0.19692 (12)0.0360 (3)
C10.23705 (16)−0.04856 (16)−0.14308 (15)0.0246 (3)
C20.37218 (19)−0.05517 (19)−0.23535 (17)0.0327 (3)
C30.4232 (3)−0.2015 (3)−0.2491 (3)0.0555 (6)
H3A0.3466−0.2079−0.29870.083*
H3B0.4415−0.2836−0.15510.083*
H3C0.5142−0.2064−0.30230.083*
C40.3273 (4)0.0754 (3)−0.3758 (2)0.1009 (14)
H4A0.29950.1665−0.36290.151*
H4B0.24320.0693−0.41610.151*
H4C0.41010.0753−0.43970.151*
C50.4987 (2)−0.0447 (3)−0.1668 (3)0.0671 (7)
H5A0.46590.0437−0.14910.101*
H5B0.5823−0.0389−0.230.101*
H5C0.5288−0.1321−0.07750.101*
C60.14310 (16)−0.20469 (18)0.23159 (15)0.0271 (3)
C70.24543 (19)−0.31837 (17)0.35736 (15)0.0303 (3)
C80.3883 (2)−0.3772 (3)0.2947 (2)0.0602 (6)
H8A0.4266−0.29530.23160.09*
H8B0.3695−0.4270.24150.09*
H8C0.461−0.44730.37060.09*
C90.1777 (4)−0.4420 (3)0.4476 (2)0.0679 (8)
H9A0.2495−0.52090.52030.102*
H9B0.1501−0.4810.38810.102*
H9C0.0897−0.40360.49240.102*
C100.2741 (2)−0.2478 (2)0.44773 (18)0.0409 (4)
H10A0.3193−0.16940.39040.061*
H10B0.3407−0.32270.5270.061*
H10C0.1806−0.20620.48370.061*
N1−0.12992 (14)−0.26829 (14)−0.02513 (14)0.0262 (3)
C1A−0.12609 (18)−0.30575 (18)−0.13207 (18)0.0300 (3)
C1B−0.1759 (2)−0.4233 (2)−0.1168 (2)0.0386 (4)
H1BA−0.171−0.4493−0.19320.046*
C1C−0.2317 (2)−0.5006 (2)0.0088 (2)0.0424 (4)
H1CA−0.2643−0.58150.02070.051*
C1D−0.2402 (2)−0.4603 (2)0.1183 (2)0.0414 (4)
H1DA−0.2815−0.51080.20530.05*
C1E−0.18751 (19)−0.34521 (18)0.09860 (19)0.0336 (3)
H1EA−0.1915−0.31850.17430.04*
C1F−0.0673 (2)−0.2167 (2)−0.26681 (18)0.0397 (4)
H1FA0.0329−0.2192−0.25050.06*
H1FB−0.1305−0.1146−0.3040.06*
H1FC−0.0653−0.2573−0.33490.06*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Fe10.01980 (12)0.02218 (11)0.02716 (12)−0.00602 (8)−0.00176 (8)−0.01322 (8)
O10.0264 (6)0.0324 (6)0.0575 (8)−0.0128 (5)0.0049 (5)−0.0193 (6)
O20.0342 (7)0.0406 (7)0.0408 (6)−0.0122 (5)0.0116 (5)−0.0268 (5)
O30.0387 (7)0.0543 (8)0.0456 (7)−0.0036 (6)−0.0154 (6)−0.0291 (6)
O40.0388 (7)0.0291 (6)0.0288 (5)−0.0013 (5)−0.0068 (5)−0.0061 (4)
C10.0199 (7)0.0263 (7)0.0239 (6)−0.0055 (5)0.0008 (5)−0.0081 (5)
C20.0295 (8)0.0347 (8)0.0314 (8)−0.0075 (7)0.0112 (6)−0.0154 (6)
C30.0481 (12)0.0612 (14)0.0708 (14)−0.0102 (11)0.0179 (11)−0.0477 (12)
C40.102 (2)0.085 (2)0.0341 (11)0.0216 (17)0.0300 (13)0.0076 (12)
C50.0283 (10)0.0836 (18)0.110 (2)−0.0247 (11)0.0200 (12)−0.0580 (17)
C60.0203 (7)0.0364 (8)0.0215 (6)−0.0050 (6)0.0007 (5)−0.0116 (6)
C70.0361 (9)0.0281 (7)0.0224 (6)−0.0077 (6)−0.0070 (6)−0.0061 (5)
C80.0391 (11)0.0744 (16)0.0519 (12)0.0178 (11)−0.0188 (9)−0.0318 (11)
C90.125 (2)0.0509 (13)0.0361 (10)−0.0530 (15)0.0006 (12)−0.0069 (9)
C100.0517 (11)0.0413 (9)0.0287 (8)−0.0139 (8)−0.0127 (7)−0.0108 (7)
N10.0215 (6)0.0253 (6)0.0350 (7)−0.0048 (5)−0.0023 (5)−0.0163 (5)
C1A0.0244 (7)0.0309 (7)0.0388 (8)−0.0025 (6)−0.0056 (6)−0.0206 (6)
C1B0.0306 (9)0.0334 (8)0.0588 (11)−0.0045 (7)−0.0072 (8)−0.0270 (8)
C1C0.0331 (9)0.0320 (8)0.0685 (13)−0.0079 (7)−0.0033 (9)−0.0269 (9)
C1D0.0367 (10)0.0317 (8)0.0540 (11)−0.0134 (7)0.0088 (8)−0.0158 (8)
C1E0.0286 (8)0.0300 (8)0.0428 (9)−0.0083 (7)0.0031 (7)−0.0167 (7)
C1F0.0470 (11)0.0437 (10)0.0353 (8)−0.0130 (8)−0.0012 (8)−0.0224 (8)
Geometric parameters (Å, °) top
Fe1—O4i2.0508 (11)C7—C81.522 (3)
Fe1—O12.0571 (13)C7—C91.523 (3)
Fe1—O32.0675 (13)C7—C101.529 (2)
Fe1—O2i2.0717 (11)C8—H8A0.98
Fe1—N12.1284 (13)C8—H8B0.98
Fe1—Fe1i2.8576 (4)C8—H8C0.98
O1—C11.2548 (19)C9—H9A0.98
O2—C11.2508 (19)C9—H9B0.98
O2—Fe1i2.0717 (11)C9—H9C0.98
O3—C61.255 (2)C10—H10A0.98
O4—C61.255 (2)C10—H10B0.98
O4—Fe1i2.0508 (11)C10—H10C0.98
C1—C21.529 (2)N1—C1A1.342 (2)
C2—C41.508 (3)N1—C1E1.362 (2)
C2—C51.529 (3)C1A—C1B1.399 (2)
C2—C31.535 (3)C1A—C1F1.483 (2)
C3—H3A0.98C1B—C1C1.368 (3)
C3—H3B0.98C1B—H1BA0.95
C3—H3C0.98C1C—C1D1.382 (3)
C4—H4A0.98C1C—H1CA0.95
C4—H4B0.98C1D—C1E1.378 (2)
C4—H4C0.98C1D—H1DA0.95
C5—H5A0.98C1E—H1EA0.95
C5—H5B0.98C1F—H1FA0.98
C5—H5C0.98C1F—H1FB0.98
C6—C71.527 (2)C1F—H1FC0.98
O4i—Fe1—O189.37 (5)C8—C7—C9110.6 (2)
O4i—Fe1—O3162.10 (6)C8—C7—C6105.56 (13)
O1—Fe1—O387.58 (6)C9—C7—C6110.04 (16)
O4i—Fe1—O2i89.38 (5)C8—C7—C10110.31 (17)
O1—Fe1—O2i161.85 (5)C9—C7—C10109.23 (15)
O3—Fe1—O2i88.07 (5)C6—C7—C10111.10 (14)
O4i—Fe1—N1101.37 (5)C7—C8—H8A109.5
O1—Fe1—N1107.04 (5)C7—C8—H8B109.5
O3—Fe1—N196.39 (5)H8A—C8—H8B109.5
O2i—Fe1—N190.95 (5)C7—C8—H8C109.5
O4i—Fe1—Fe1i77.91 (4)H8A—C8—H8C109.5
O1—Fe1—Fe1i86.43 (4)H8B—C8—H8C109.5
O3—Fe1—Fe1i84.30 (4)C7—C9—H9A109.5
O2i—Fe1—Fe1i75.61 (4)C7—C9—H9B109.5
N1—Fe1—Fe1i166.53 (4)H9A—C9—H9B109.5
C1—O1—Fe1119.93 (11)C7—C9—H9C109.5
C1—O2—Fe1i133.33 (11)H9A—C9—H9C109.5
C6—O3—Fe1121.86 (12)H9B—C9—H9C109.5
C6—O4—Fe1i130.76 (11)C7—C10—H10A109.5
O2—C1—O1124.45 (15)C7—C10—H10B109.5
O2—C1—C2116.85 (14)H10A—C10—H10B109.5
O1—C1—C2118.67 (15)C7—C10—H10C109.5
C4—C2—C5110.6 (2)H10A—C10—H10C109.5
C4—C2—C1106.23 (16)H10B—C10—H10C109.5
C5—C2—C1109.10 (15)C1A—N1—C1E118.33 (14)
C4—C2—C3112.1 (2)C1A—N1—Fe1126.41 (11)
C5—C2—C3107.82 (18)C1E—N1—Fe1114.92 (11)
C1—C2—C3111.00 (15)N1—C1A—C1B121.33 (16)
C2—C3—H3A109.5N1—C1A—C1F116.98 (15)
C2—C3—H3B109.5C1B—C1A—C1F121.69 (16)
H3A—C3—H3B109.5C1C—C1B—C1A119.52 (17)
C2—C3—H3C109.5C1C—C1B—H1BA120.2
H3A—C3—H3C109.5C1A—C1B—H1BA120.2
H3B—C3—H3C109.5C1B—C1C—C1D119.66 (17)
C2—C4—H4A109.5C1B—C1C—H1CA120.2
C2—C4—H4B109.5C1D—C1C—H1CA120.2
H4A—C4—H4B109.5C1E—C1D—C1C118.50 (17)
C2—C4—H4C109.5C1E—C1D—H1DA120.8
H4A—C4—H4C109.5C1C—C1D—H1DA120.8
H4B—C4—H4C109.5N1—C1E—C1D122.61 (17)
C2—C5—H5A109.5N1—C1E—H1EA118.7
C2—C5—H5B109.5C1D—C1E—H1EA118.7
H5A—C5—H5B109.5C1A—C1F—H1FA109.5
C2—C5—H5C109.5C1A—C1F—H1FB109.5
H5A—C5—H5C109.5H1FA—C1F—H1FB109.5
H5B—C5—H5C109.5C1A—C1F—H1FC109.5
O3—C6—O4124.77 (15)H1FA—C1F—H1FC109.5
O3—C6—C7117.45 (15)H1FB—C1F—H1FC109.5
O4—C6—C7117.70 (14)
O4i—Fe1—O1—C172.98 (13)O3—C6—C7—C9−43.7 (2)
O3—Fe1—O1—C1−89.39 (13)O4—C6—C7—C9139.25 (18)
O2i—Fe1—O1—C1−13.1 (2)O3—C6—C7—C10−164.77 (15)
N1—Fe1—O1—C1174.67 (12)O4—C6—C7—C1018.2 (2)
Fe1i—Fe1—O1—C1−4.95 (12)O4i—Fe1—N1—C1A55.44 (13)
O4i—Fe1—O3—C65.7 (3)O1—Fe1—N1—C1A−37.42 (14)
O1—Fe1—O3—C686.11 (14)O3—Fe1—N1—C1A−126.84 (13)
O2i—Fe1—O3—C6−76.26 (14)O2i—Fe1—N1—C1A145.00 (13)
N1—Fe1—O3—C6−167.00 (14)Fe1i—Fe1—N1—C1A140.97 (14)
Fe1i—Fe1—O3—C6−0.53 (13)O4i—Fe1—N1—C1E−131.33 (11)
Fe1i—O2—C1—O1−1.9 (3)O1—Fe1—N1—C1E135.81 (11)
Fe1i—O2—C1—C2175.95 (10)O3—Fe1—N1—C1E46.39 (12)
Fe1—O1—C1—O25.5 (2)O2i—Fe1—N1—C1E−41.77 (12)
Fe1—O1—C1—C2−172.25 (10)Fe1i—Fe1—N1—C1E−45.8 (2)
O2—C1—C2—C4−74.1 (2)C1E—N1—C1A—C1B−1.8 (2)
O1—C1—C2—C4103.8 (2)Fe1—N1—C1A—C1B171.27 (12)
O2—C1—C2—C545.1 (2)C1E—N1—C1A—C1F178.04 (15)
O1—C1—C2—C5−136.93 (18)Fe1—N1—C1A—C1F−8.9 (2)
O2—C1—C2—C3163.78 (17)N1—C1A—C1B—C1C0.9 (3)
O1—C1—C2—C3−18.3 (2)C1F—C1A—C1B—C1C−178.84 (17)
Fe1—O3—C6—O45.0 (2)C1A—C1B—C1C—C1D1.0 (3)
Fe1—O3—C6—C7−171.88 (11)C1B—C1C—C1D—C1E−2.0 (3)
Fe1i—O4—C6—O3−8.7 (3)C1A—N1—C1E—C1D0.7 (2)
Fe1i—O4—C6—C7168.15 (11)Fe1—N1—C1E—C1D−173.13 (14)
O3—C6—C7—C875.6 (2)C1C—C1D—C1E—N11.2 (3)
O4—C6—C7—C8−101.42 (19)
Symmetry codes: (i) −x, −y, −z.
Table 1
Selected geometric parameters (Å) top
Fe1—O4i2.0508 (11)Fe1—Fe1i2.8576 (4)
Fe1—O12.0571 (13)O1—C11.2548 (19)
Fe1—O32.0675 (13)O2—C11.2508 (19)
Fe1—O2i2.0717 (11)O3—C61.255 (2)
Fe1—N12.1284 (13)O4—C61.255 (2)
Symmetry codes: (i) −x, −y, −z.
Acknowledgements top

GAT thanks the Danish Research Council (DANSYNC) for financial support.

references
References top

Bruker (1998). SMART and SAINT-Plus. Bruker AXS Inc., Madison, Wisconsin, USA.

Celengil-Cetin, R., Staples, R. J. & Stavropoulos, P. (2000). Inorg. Chem. 39, 5838–5846.

Johnson, C. K. (1976). ORTEPII. Report ORNL-5138. Oak Ridge National Laboratory, Tennessee, USA.

Sheldrick, G. M. (2003). SADABS. University of Göttingen, Germany.

Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.

Weber, G. (1980). Acta Cryst. B36, 3107–3109.