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The novel title double-butterfly Fe/S cluster complex, [Fe4(C4H8S2)2(CO)12], which is structurally similar to the active site of the Fe-only hydrogenases, contains two inversion-related Fe2S2(CO)6 subcluster cores connected by two equivalent butyl chains to afford a 16-membered macrocycle. The formation of the 16-membered macrocycle has an influence on the C-S-Fe angles, while the Fe-Fe and Fe-S bond lengths remain similar to those in related complexes.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270107041674/sq3090sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270107041674/sq3090Isup2.hkl
Contains datablock I

CCDC reference: 669157

Comment top

Recently, with the shortage of fossil fuels, hydrogen, as a kind of much-needed and clean energy, has attracted growing attention. Unfortunately, because of its high cost, it has become a bottleneck that has limited its wide application. Consequently, scientists have been looking for a new route to prepare H2, and the Fe-only hydrogenases, as effective enzymes for production of molecular hydrogen in biological systems, have become of particular interest (Georgakaki et al., 2003; Artero & Fontecave, 2005). With advances in X-ray crystallographic and spectroscopic techniques for macromolecules, the detailed structures of the Fe-only hydrogenases have been determined (Peters et al., 1998; Nicolet et al., 1999). The active site is composed of an Fe2S2 core that is bound to a cuboidal Fe4S4 cluster via the cysteine S atom. To enhance the efficiency and activity of the Fe-only hydrogenases, scientists have designed and simulated many kinds of models of the active site (Gao et al., 2007; Song et al., 2006; Schwartz et al., 2006). On the basis of our previous work on the Fe2S2 core of the Fe-only hydrogenases (Hu et al., 2006, 2007; Cheng et al., 2005; Si et al., 2007), we have successfully prepared a new double-butterfly Fe/S cluster complex containing a 16-membered macrocycle formed by the linking of two Fe2S2(CO)6 subcluster cores through two butyl chains.

The title compound, (I), is a centrosymmetric double-butterfly cluster complex with two identical butterfly Fe2S2(CO)6 subcluster cores linked together through two identical butyl chains (Fig. 1). The resulting 16-membered macrocycle thus includes four Fe atoms, four S atoms and eight C atoms. This kind of complex with a macrocycle is relatively rare; reported examples include [{Fe2(CO)5(µ-SCH2)2NCH2CH2N(µ-SCH2)2Fe2(CO)5}(Ph2PCH2)2], (II) (Gao et al., 2006), with a 14-membered macrocycle, [Fe2(CO)6]2[µ-SCH2(CH2OCH2)2CH2S-µ]2, (III) (Song et al., 2004) with a 24-membered macrocycle, and [Fe2(CO)6]2[µ-SCH2(CH2OCH2)3CH2S-µ]2, (IV) (Song et al., 2004), with a 30-membered macrocycle. Complex (II) is different from (I) and the other complexes in that the bridges between the iron fragments are different so the complex is not symmetrical. Although (III) and (IV) are very similar to (I) structurally, they form macrocycles through long ether chains [–CH2(CH2OCH2)nCH2–, with n = 2 and 3, respectively], while (I) gives a new synthetic route to form such a macrocycle by alkyl chains.

The formation of the macrocycle has a slight lengthening influence on the Fe1—Fe2 distance (Table 1) as compared to those of [{(µ-pdt)Fe2}(CO)6], (V) [2.5103 (11) Å; pdt is propane-1,3-dithiolate; Lyon et al., 1999], and (III) [2.5130 (14) Å], while lying between the Fe1—Fe2 [2.5197 (8) Å] and Fe3—Fe4 [2.5387 (8) Å] distances in (II). The average Fe—S bond length in (I) [2.2599 (12) Å] is slightly longer than that in (V) [2.2516 (10) Å; Lyon et al., 1999]. The C—S—Fe angles in (I) show small variations (Table 2) compared to those of [{(Et2NCsc/Desktop/publCIF/symbols/dbnd.png" height="12" />CNEt2)Fe2S2}(CO)6] [C1—S1—Fe1 = 104.0 (2)°, C1—S2—Fe1 = 102.02 (19)°, C2—S2—Fe1 = 103.70 (19)° and C2—S2—Fe2 = 102.73 (19)°; Siebenlist et al., 2002]. Compared with S1—Fe—S2 [85.27 (4)°] in (V), the S—Fe—S angles of (I) [S2—Fe1—S1 = 80.37 (4)° and S2—Fe2—S1 = 80.30 (5)°] are smaller because of the different sizes of the macrocycle. In addition, the C7—S2···S1 angle is 160.0°, which shows that the C7—S2 bond is approximately equatorial with respect to the line connecting the wingtip atoms S1 and S2, while C10—S1···S2 is 100.1°, which shows that the C10—S1 bond is axial with respect to the span between the wingtip S atoms. By contrast, both C—S···S angles in [Fe2(SPh-2-OMe)2(CO)6] are ca 160°, which indicates that both the C—S bonds are equatorial with respect to the S···S line across the wingtips (Si et al., 2005).

Related literature top

For related literature, see: Artero & Fontecave (2005); Cheng et al. (2005); Gao et al. (2006, 2007); Georgakaki et al. (2003); Hu et al. (2006, 2007); Lyon et al. (1999); Nicolet et al. (1999); Peters et al. (1998); Schwartz et al. (2006); Si et al. (2005, 2007); Siebenlist et al. (2002); Song et al. (2004, 2006).

Experimental top

All reactions were carried out under dry oxygen-free N2 using standard Schlenk techniques. Tetrahydrofuran (THF) and n-hexane were dried and distilled prior to use according to standard methods. Commercially available chemicals such as 1,4-butanedithiol and Fe3(CO)12 were reagent grade and used as received. Fe3(CO)12 (3 mmol, 1.5 g) was dissolved in dry THF (50 ml) under an N2 atmosphere and 1,4-butanedithiol (3 mmol, 0.353 ml) was added. The solution was stirred at 343 K for 90 min and the color changed from dark green to dark red. After cooling to room temperature, the majority of the solvent was evaporated under vacuum, and the remaining solution was purified through silica gel. A red fraction was collected, and (I) was obtained as dark-red crystals from hexane (yield 7%). Elemental analysis calculated for C20H16Fe4O12S4: C 30.03, H 2.02%; found: C 30.97, H 2.15%. IR (KBr pellet, cm−1): νCO 2070 (m), 2030 (s), 1984 (vs). m/z 823.1 (M + Na+).

Refinement top

H atoms were placed at idealized positions [C—H = 0.97 Å and Uiso(H) = 1.2Ueq(C)] and treated as riding atoms.

Computing details top

Data collection: CrystalClear (Rigaku, 2000); cell refinement: CrystalClear (Rigaku, 2000); data reduction: CrystalClear (Rigaku, 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1997); software used to prepare material for publication: SHELXTL (Bruker, 1997).

Figures top
[Figure 1] Fig. 1. The molecular structure of (I), shown with 20% probability displacement ellipsoids.
Bis(µ4-butane-1,4-dithiolato)bis[hexacarbonyldiiron(II)(Fe—Fe)] top
Crystal data top
[Fe4(C4H8S2)2(CO)12]Z = 1
Mr = 799.97F(000) = 400
Triclinic, P1Dx = 1.771 Mg m3
Hall symbol: -p 1Mo Kα radiation, λ = 0.71073 Å
a = 7.765 (4) ÅCell parameters from 1725 reflections
b = 9.712 (5) Åθ = 2.9–27.5°
c = 11.036 (6) ŵ = 2.23 mm1
α = 82.445 (17)°T = 295 K
β = 74.035 (17)°Needle, red
γ = 69.718 (16)°0.5 × 0.3 × 0.15 mm
V = 750.0 (7) Å3
Data collection top
Mercury CCD
diffractometer
3378 independent reflections
Radiation source: fine-focus sealed tube2413 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.020
ω scansθmax = 27.5°, θmin = 2.9°
Absorption correction: empirical (using intensity measurements)
(SADABS; Sheldrick, 1996)
h = 910
Tmin = 0.46, Tmax = 0.72k = 1212
5772 measured reflectionsl = 1414
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.037Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.106H-atom parameters constrained
S = 1.00 w = 1/[σ2(Fo2) + (0.0619P)2]
where P = (Fo2 + 2Fc2)/3
3378 reflections(Δ/σ)max = 0.001
181 parametersΔρmax = 0.56 e Å3
0 restraintsΔρmin = 0.46 e Å3
Crystal data top
[Fe4(C4H8S2)2(CO)12]γ = 69.718 (16)°
Mr = 799.97V = 750.0 (7) Å3
Triclinic, P1Z = 1
a = 7.765 (4) ÅMo Kα radiation
b = 9.712 (5) ŵ = 2.23 mm1
c = 11.036 (6) ÅT = 295 K
α = 82.445 (17)°0.5 × 0.3 × 0.15 mm
β = 74.035 (17)°
Data collection top
Mercury CCD
diffractometer
3378 independent reflections
Absorption correction: empirical (using intensity measurements)
(SADABS; Sheldrick, 1996)
2413 reflections with I > 2σ(I)
Tmin = 0.46, Tmax = 0.72Rint = 0.020
5772 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0370 restraints
wR(F2) = 0.106H-atom parameters constrained
S = 1.00Δρmax = 0.56 e Å3
3378 reflectionsΔρmin = 0.46 e Å3
181 parameters
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
Fe10.34173 (7)0.31415 (4)0.77669 (4)0.04095 (15)
Fe20.69927 (7)0.21204 (5)0.72228 (4)0.04236 (15)
S20.50730 (11)0.08216 (7)0.82326 (6)0.03454 (18)
S10.52384 (13)0.35871 (8)0.88656 (7)0.0416 (2)
C70.5016 (5)0.0585 (3)0.7294 (3)0.0413 (7)
H7A0.37790.07100.75650.050*
H7B0.52120.02580.64130.050*
C10.2931 (5)0.2614 (4)0.6441 (3)0.0495 (8)
C100.5316 (5)0.2553 (3)1.0382 (3)0.0423 (7)
H10A0.60610.15331.02180.051*
H10B0.59550.29361.08310.051*
C90.6592 (5)0.2620 (3)0.8791 (3)0.0440 (8)
H9A0.74300.36300.87770.053*
H9B0.71140.20410.91480.053*
O10.2625 (5)0.2254 (3)0.5594 (3)0.0770 (9)
O20.0292 (4)0.3481 (4)0.9547 (3)0.0822 (10)
O60.7862 (5)0.0808 (4)0.4793 (3)0.0834 (10)
C60.7523 (6)0.1308 (4)0.5742 (3)0.0554 (9)
O51.0214 (5)0.0291 (4)0.8226 (3)0.0953 (11)
C80.6527 (5)0.2050 (3)0.7432 (3)0.0479 (8)
H8A0.77540.19620.69940.057*
H8B0.63310.27800.70120.057*
C50.9024 (6)0.1019 (4)0.7795 (4)0.0575 (9)
C20.1147 (6)0.3357 (4)0.8874 (4)0.0544 (9)
O40.8230 (6)0.4581 (4)0.5958 (4)0.1114 (14)
C40.7740 (7)0.3627 (4)0.6451 (4)0.0674 (11)
C30.3007 (7)0.5007 (4)0.7156 (4)0.0756 (14)
O30.2732 (8)0.6173 (4)0.6779 (5)0.142 (2)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Fe10.0534 (3)0.0293 (2)0.0364 (2)0.0048 (2)0.0161 (2)0.00211 (17)
Fe20.0514 (3)0.0349 (2)0.0372 (3)0.0143 (2)0.0042 (2)0.00335 (18)
S20.0461 (4)0.0261 (3)0.0307 (4)0.0090 (3)0.0111 (3)0.0029 (3)
S10.0606 (5)0.0283 (3)0.0368 (4)0.0148 (3)0.0122 (3)0.0028 (3)
C70.060 (2)0.0318 (14)0.0353 (16)0.0125 (14)0.0177 (14)0.0052 (12)
C10.063 (2)0.0383 (16)0.0415 (18)0.0057 (15)0.0199 (16)0.0024 (13)
C100.059 (2)0.0325 (14)0.0364 (16)0.0141 (14)0.0148 (14)0.0025 (12)
C90.055 (2)0.0313 (14)0.0369 (16)0.0038 (14)0.0096 (14)0.0029 (12)
O10.109 (3)0.0724 (18)0.0545 (16)0.0150 (17)0.0439 (17)0.0098 (14)
O20.0488 (18)0.104 (3)0.081 (2)0.0092 (17)0.0047 (16)0.0265 (19)
O60.115 (3)0.080 (2)0.0482 (16)0.0342 (19)0.0018 (16)0.0221 (15)
C60.069 (3)0.0471 (18)0.0422 (19)0.0165 (18)0.0038 (17)0.0030 (15)
O50.057 (2)0.114 (3)0.105 (3)0.007 (2)0.0306 (19)0.006 (2)
C80.066 (2)0.0332 (15)0.0350 (16)0.0055 (15)0.0091 (15)0.0077 (12)
C50.050 (2)0.059 (2)0.064 (2)0.0206 (19)0.0083 (18)0.0071 (18)
C20.055 (2)0.0510 (19)0.052 (2)0.0013 (17)0.0217 (18)0.0162 (16)
O40.131 (3)0.068 (2)0.118 (3)0.054 (2)0.021 (2)0.005 (2)
C40.081 (3)0.053 (2)0.057 (2)0.027 (2)0.008 (2)0.0021 (18)
C30.120 (4)0.0385 (19)0.074 (3)0.014 (2)0.054 (3)0.0102 (18)
O30.240 (6)0.0489 (18)0.164 (4)0.041 (3)0.121 (4)0.044 (2)
Geometric parameters (Å, º) top
Fe1—C11.784 (4)C1—O11.148 (4)
Fe1—C31.798 (4)C10—C9i1.495 (5)
Fe1—C21.808 (4)C10—H10A0.9700
Fe1—S22.2460 (12)C10—H10B0.9700
Fe1—S12.2721 (12)C9—C10i1.495 (5)
Fe1—Fe22.5263 (14)C9—C81.537 (4)
Fe2—C41.786 (4)C9—H9A0.9700
Fe2—C61.791 (4)C9—H9B0.9700
Fe2—C51.798 (4)O2—C21.135 (5)
Fe2—S22.2528 (12)O6—C61.137 (4)
Fe2—S12.2687 (13)O5—C51.131 (5)
S2—C71.838 (3)C8—H8A0.9700
S1—C101.840 (3)C8—H8B0.9700
C7—C81.519 (4)O4—C41.140 (5)
C7—H7A0.9700C3—O31.122 (5)
C7—H7B0.9700
C1—Fe1—C391.90 (18)C10—S1—Fe2111.11 (11)
C1—Fe1—C298.62 (17)C10—S1—Fe1115.56 (12)
C3—Fe1—C299.2 (2)Fe2—S1—Fe167.61 (4)
C1—Fe1—S292.69 (11)C8—C7—S2111.7 (2)
C3—Fe1—S2157.92 (18)C8—C7—H7A109.3
C2—Fe1—S2101.43 (12)S2—C7—H7A109.3
C1—Fe1—S1155.84 (13)C8—C7—H7B109.3
C3—Fe1—S186.68 (15)S2—C7—H7B109.3
C2—Fe1—S1105.42 (12)H7A—C7—H7B107.9
S2—Fe1—S180.37 (4)O1—C1—Fe1179.0 (3)
C1—Fe1—Fe2100.85 (12)C9i—C10—S1113.9 (2)
C3—Fe1—Fe2101.96 (18)C9i—C10—H10A108.8
C2—Fe1—Fe2150.58 (11)S1—C10—H10A108.8
S2—Fe1—Fe255.97 (3)C9i—C10—H10B108.8
S1—Fe1—Fe256.13 (4)S1—C10—H10B108.8
C4—Fe2—C691.01 (19)H10A—C10—H10B107.7
C4—Fe2—C5101.3 (2)C10i—C9—C8112.8 (3)
C6—Fe2—C5100.67 (18)C10i—C9—H9A109.0
C4—Fe2—S2160.19 (15)C8—C9—H9A109.0
C6—Fe2—S293.70 (13)C10i—C9—H9B109.0
C5—Fe2—S296.68 (13)C8—C9—H9B109.0
C4—Fe2—S187.98 (14)H9A—C9—H9B107.8
C6—Fe2—S1157.32 (13)O6—C6—Fe2179.1 (4)
C5—Fe2—S1101.74 (13)C7—C8—C9115.9 (3)
S2—Fe2—S180.30 (5)C7—C8—H8A108.3
C4—Fe2—Fe1104.48 (15)C9—C8—H8A108.3
C6—Fe2—Fe1102.33 (13)C7—C8—H8B108.3
C5—Fe2—Fe1144.83 (13)C9—C8—H8B108.3
S2—Fe2—Fe155.71 (4)H8A—C8—H8B107.4
S1—Fe2—Fe156.26 (3)O5—C5—Fe2175.0 (4)
C7—S2—Fe1115.19 (10)O2—C2—Fe1178.3 (3)
C7—S2—Fe2114.89 (12)O4—C4—Fe2179.5 (5)
Fe1—S2—Fe268.33 (4)O3—C3—Fe1179.3 (6)
Symmetry code: (i) x+1, y, z+2.

Experimental details

Crystal data
Chemical formula[Fe4(C4H8S2)2(CO)12]
Mr799.97
Crystal system, space groupTriclinic, P1
Temperature (K)295
a, b, c (Å)7.765 (4), 9.712 (5), 11.036 (6)
α, β, γ (°)82.445 (17), 74.035 (17), 69.718 (16)
V3)750.0 (7)
Z1
Radiation typeMo Kα
µ (mm1)2.23
Crystal size (mm)0.5 × 0.3 × 0.15
Data collection
DiffractometerMercury CCD
diffractometer
Absorption correctionEmpirical (using intensity measurements)
(SADABS; Sheldrick, 1996)
Tmin, Tmax0.46, 0.72
No. of measured, independent and
observed [I > 2σ(I)] reflections
5772, 3378, 2413
Rint0.020
(sin θ/λ)max1)0.649
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.037, 0.106, 1.00
No. of reflections3378
No. of parameters181
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.56, 0.46

Computer programs: CrystalClear (Rigaku, 2000), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), SHELXTL (Bruker, 1997).

Selected geometric parameters (Å, º) top
Fe1—C11.784 (4)Fe2—C41.786 (4)
Fe1—C31.798 (4)Fe2—C61.791 (4)
Fe1—C21.808 (4)Fe2—C51.798 (4)
Fe1—S22.2460 (12)Fe2—S22.2528 (12)
Fe1—S12.2721 (12)Fe2—S12.2687 (13)
Fe1—Fe22.5263 (14)
C7—S2—Fe1115.19 (10)C10—S1—Fe2111.11 (11)
C7—S2—Fe2114.89 (12)C10—S1—Fe1115.56 (12)
 

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