[μ-3-(Methyl­sulfan­yl)benzene-1,2-di­thiol­ato-1:2κ⁴S,S′:S,S′]bis­[tri­carbonyl­iron(I)]

The title compound, [Fe₂(C₇H₆S₃)(CO)₆], was prepared as a biomimic for the active site of [FeFe]-hydrogenases. The central Fe₂S₂ core is in a butterfly conformation and each Fe^I atom has a pseudo-square-pyramidal coordination by three O atoms and two S atoms. The Fe—Fe distance is 2.471 (2) Å and the dihedral angle between the two Fe—S—Fe planes is 78.96 (7)°. The least-squares plane through the –S(C₇H₆S)S– bridge nearly bis­ects the mol­ecular structure: except for the two Fe(CO)₃ units, all atoms are in this plane with an average deviation from the plane of 0.028 (3) Å. In the crystal, the mol­ecules are linked into chains along [001] by C—H...π(arene) inter­actions.

Key indicators

• Single-crystal X-ray study
• T = 295 K
• Mean [sigma](C-C) = 0.005 Å
• R factor = 0.036
• wR factor = 0.084
• Data-to-parameter ratio = 13.9

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT148_ALERT_3_C su on the      a  - Axis is (Too) Large ........      0.017 Ang.
PLAT148_ALERT_3_C su on the      b  - Axis is (Too) Large ........     0.0080 Ang.
PLAT232_ALERT_2_C Hirshfeld Test Diff (M-X)  Fe1    --  C2      ..        5.3 su
PLAT232_ALERT_2_C Hirshfeld Test Diff (M-X)  Fe2    --  C4      ..        6.3 su
PLAT232_ALERT_2_C Hirshfeld Test Diff (M-X)  Fe2    --  C6      ..        6.3 su
PLAT906_ALERT_3_C Large K value in the Analysis of Variance ......      2.350
PLAT910_ALERT_3_C Missing # of FCF Reflections Below Th(Min) .....          1
PLAT911_ALERT_3_C Missing # FCF Refl Between THmin & STh/L=  0.595         14
PLAT913_ALERT_3_C Missing # of Very Strong Reflections in FCF ....          1

Alert level G
PLAT005_ALERT_5_G No _iucr_refine_instructions_details  in the CIF          ?
PLAT909_ALERT_3_G Percentage of Observed Data at Theta(Max) still          35 Perc.
PLAT961_ALERT_5_G Dataset Contains no Negative Intensities .......          !

   0 ALERT level A = Most likely a serious problem - resolve or explain
   0 ALERT level B = A potentially serious problem, consider carefully
   9 ALERT level C = Check. Ensure it is not caused by an omission or oversight
   3 ALERT level G = General information/check it is not something unexpected

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

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S1. Comment

[FeFe]-hydrogenases are important enzymes in numerous microorganisms, which can catalyse hydrogen evolution or uptake. Crystallographic and IR spectroscopic studies on the two types of [FeFe]Hases, CpI (Clostridium pasteurianum) and DdH (Desulfovibrio desulfuricans), revealed that the active site of [FeFe]-hydrogenases is comprised of a 2Fe2S butterfly structure, which contains diatomic ligands CO and CN^-, a cysteinyl-S ligand connecting to a 4Fe4S subcluster, and a three-atom linker (–CH₂XCH₂–, X = CH₂,NH or O) bridged between the two S atoms of the Fe₂S₂ H-cluster (Capon et al., 2009, Tard & Pickett, 2009). It was found that the introduction of a rigid and conjugate bridge to the Fe₂S₂ complexes could make the electrochemical properties of the complexes apparently different from the Fe₂S₂ complexes with flexible bridges (Capon et al., 2009).

The structure of the title compound resembles the active site of [FeFe]-hydrogenases, with a butterfly architectonic 2Fe2S core and the usual distorted square-pyramidal geometry around the iron center (Wang et al., 2005, Dong et al., 2006). The length of the Fe–Fe bond [2.471 (2) Å] is slightly shorter than those in the structures of natural enzymes (ca 2.6 Å) (Peters et al., 1998, Nicolet et al., 1999). The dihedral angle between two Fe–S–Fe planes is 78.96 (7) °. The rigid dithiolate bridge is a special feature for the title compound. The molecular structure has an internal pseudo-mirror plane passing through the aromatic ring. The calculated plane of the SRS bridge is nearly a bisecting plane of the molecular structure. Except for two Fe(CO)₃ units all atoms are in the plane with the average deviation of 0.0280 Å. The deviations of the iron atoms from the SRS basal plane are 1.266 (5) Å for Fe(1) and 1.205 (5) Å for Fe(2). The molecular structure of the title compound is shown in Figure 1.

Related literature

For general background to [FeFe]-hydrogenases, see: Capon et al. (2009); Tard & Pickett (2009). For the crystal structure of the natural enzyme, see: Peters et al. (1998); Nicolet et al. (1999). For related structures and the synthesis, see: Maiolo et al. (1981); Wang et al. (2005); Dong et al. (2006).

S2. Experimental

All reactions and operations related to the title compound were carried out under a dry, prepurified nitrogen atmosphere with standard Schlenk techniques. All solvents were dried and distilled prior to use according to standard methods. The starting material 3-(methylthio)benzene-1,2-dilthiol was prepared by a similar procedure according to the literature (Maiolo et al., 1981). 3-(Methylthio)benzene-1,2-dilthiol (1 mmol, 0.188 g) and freshly synthesized Fe₃(CO)₁₂ (1 mmol, 0.503 g) were refluxed in toluene under N₂ atmosphere for 3 h. The color of the solution changed gradually from dark green to dark red. The solvent was removed under reduced pressure. The residue was purified by column chromatography on silica gel using hexane as eluent to give the title compound as a red solid (0.294 g, 63%). A single-crystal suitable for X-ray study was obtained by slow evaporation of CH₂Cl₂/hexane (1:10, v/v) solution at room temperature. IR (CH₂Cl₂, cm^-1): ν(CO) 2075 (m), 2045 (s), 1999 (versus); ¹H NMR (400 MHz, CDCl₃): δ 6.92 (s, 1H, C₆H₃), 6.60 (s, 1H, C₆H₃), 6.53 (s, 1H, C₆H₃), 2.41 (s, 3H, SCH₃).

S3. Refinement

Hydrogen atoms were positioned geometrically and refined as riding atoms, with C–H = 0.93 (CH) and 0.96 (CH₃) Å and with U_iso(H) = 1.2 (1.5 for methyl) U_eq(C).

Computing details

Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT-Plus (Bruker, 2007); data reduction: SAINT-Plus (Bruker, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

Fig. 1. Molecular structure of the title compound, with displacement ellipsoids drawn at the 30% probability level.

[µ-3-(Methylsulfanyl)benzene-1,2-dithiolato-1:2κ⁴S,S':S,S']bis[tricarbonyliron(I)]

Crystal data

[Fe2(C7H6S3)(CO)6]	F(000) = 928
Mr = 466.06	Dx = 1.801 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 2629 reflections
a = 16.531 (17) Å	θ = 2.5–27.1°
b = 7.975 (8) Å	µ = 2.08 mm^−1
c = 13.047 (13) Å	T = 295 K
β = 92.055 (13)°	Block, red
V = 1719 (3) Å^3	0.39 × 0.24 × 0.08 mm
Z = 4

Data collection

Bruker APEXII CCD diffractometer	3024 independent reflections
Radiation source: fine-focus sealed tube	2098 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.055
φ and ω scans	θmax = 25.0°, θmin = 2.5°
Absorption correction: multi-scan (SADABS; Bruker, 2001)	h = −19→18
Tmin = 0.555, Tmax = 0.847	k = −9→9
8260 measured reflections	l = −15→13

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)] = 0.036	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.084	H-atom parameters constrained
S = 0.97	w = 1/[σ^2(Fo^2) + (0.0341P)^2] where P = (Fo^2 + 2Fc^2)/3
3024 reflections	(Δ/σ)max < 0.001
217 parameters	Δρmax = 0.44 e Å^−3
0 restraints	Δρmin = −0.31 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
Fe1	0.17590 (2)	0.29795 (7)	0.64150 (4)	0.04642 (17)
Fe2	0.18906 (3)	0.54555 (7)	0.52941 (4)	0.04814 (18)
S3	0.46296 (5)	0.53167 (12)	0.73543 (7)	0.0462 (2)
S2	0.22860 (5)	0.28468 (12)	0.48479 (7)	0.0475 (2)
S1	0.27674 (5)	0.48911 (12)	0.66349 (7)	0.0446 (2)
C8	0.35707 (16)	0.3899 (4)	0.5983 (2)	0.0354 (7)
C10	0.3893 (2)	0.2051 (4)	0.4606 (3)	0.0481 (9)
H10A	0.3730	0.1375	0.4055	0.058*
C2	0.0831 (2)	0.2118 (5)	0.5909 (3)	0.0560 (10)
C9	0.33421 (18)	0.2915 (4)	0.5159 (3)	0.0401 (8)
C5	0.1075 (2)	0.5260 (5)	0.4373 (4)	0.0605 (11)
C1	0.21760 (19)	0.1120 (6)	0.6991 (3)	0.0564 (10)
C7	0.43793 (17)	0.4062 (4)	0.6280 (3)	0.0377 (8)
C11	0.4698 (2)	0.2221 (5)	0.4897 (3)	0.0514 (9)
H11A	0.5086	0.1648	0.4535	0.062*
C12	0.49397 (19)	0.3216 (4)	0.5709 (3)	0.0449 (9)
H12A	0.5488	0.3324	0.5879	0.054*
O2	0.02428 (15)	0.1593 (4)	0.5570 (3)	0.0859 (10)
O1	0.24308 (17)	−0.0076 (4)	0.7338 (3)	0.0867 (11)
C4	0.2506 (2)	0.6882 (6)	0.4606 (4)	0.0700 (12)
O5	0.05695 (18)	0.5075 (4)	0.3771 (3)	0.0918 (11)
O6	0.09707 (19)	0.7802 (4)	0.6518 (3)	0.0961 (12)
O4	0.2905 (2)	0.7821 (5)	0.4201 (3)	0.1088 (13)
O3	0.09360 (19)	0.4359 (5)	0.8164 (3)	0.0994 (12)
C6	0.1338 (2)	0.6903 (5)	0.6042 (4)	0.0643 (12)
C3	0.1254 (2)	0.3805 (6)	0.7494 (4)	0.0631 (11)
C13	0.57037 (19)	0.5072 (4)	0.7506 (3)	0.0543 (10)
H13A	0.5900	0.5721	0.8082	0.082*
H13B	0.5956	0.5454	0.6897	0.082*
H13C	0.5831	0.3911	0.7619	0.082*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Fe1	0.0379 (3)	0.0561 (4)	0.0452 (3)	−0.0011 (2)	0.0000 (2)	0.0002 (3)
Fe2	0.0429 (3)	0.0491 (4)	0.0522 (4)	0.0050 (2)	−0.0029 (2)	−0.0011 (3)
S3	0.0421 (4)	0.0487 (6)	0.0479 (6)	−0.0040 (4)	0.0011 (4)	−0.0067 (5)
S2	0.0480 (4)	0.0519 (6)	0.0422 (6)	−0.0004 (4)	−0.0046 (4)	−0.0077 (5)
S1	0.0379 (4)	0.0538 (6)	0.0423 (6)	0.0033 (4)	0.0016 (4)	−0.0123 (4)
C8	0.0392 (15)	0.036 (2)	0.0313 (19)	0.0026 (15)	0.0060 (13)	−0.0023 (16)
C10	0.061 (2)	0.046 (2)	0.038 (2)	0.0035 (18)	0.0044 (17)	−0.0051 (18)
C2	0.052 (2)	0.058 (3)	0.057 (3)	0.0055 (19)	−0.0012 (18)	0.002 (2)
C9	0.0433 (16)	0.040 (2)	0.037 (2)	0.0048 (15)	0.0035 (14)	0.0003 (17)
C5	0.052 (2)	0.061 (3)	0.068 (3)	0.0124 (19)	−0.001 (2)	−0.002 (2)
C1	0.0372 (17)	0.070 (3)	0.061 (3)	−0.0023 (19)	−0.0012 (17)	−0.001 (2)
C7	0.0405 (16)	0.0300 (19)	0.043 (2)	−0.0003 (14)	0.0051 (14)	0.0067 (16)
C11	0.056 (2)	0.050 (2)	0.050 (3)	0.0106 (18)	0.0194 (17)	0.003 (2)
C12	0.0416 (17)	0.046 (2)	0.048 (2)	0.0045 (16)	0.0079 (15)	0.0058 (19)
O2	0.0549 (15)	0.087 (2)	0.115 (3)	−0.0205 (15)	−0.0156 (17)	−0.004 (2)
O1	0.0665 (18)	0.085 (2)	0.108 (3)	0.0094 (17)	−0.0127 (18)	0.028 (2)
C4	0.062 (2)	0.069 (3)	0.079 (3)	0.006 (2)	−0.005 (2)	0.006 (3)
O5	0.0720 (19)	0.109 (3)	0.092 (3)	0.0123 (17)	−0.034 (2)	−0.008 (2)
O6	0.083 (2)	0.088 (3)	0.117 (3)	0.0311 (18)	−0.0015 (19)	−0.043 (2)
O4	0.101 (2)	0.096 (3)	0.130 (4)	−0.025 (2)	0.021 (2)	0.030 (3)
O3	0.087 (2)	0.145 (3)	0.068 (3)	0.028 (2)	0.0250 (19)	−0.007 (2)
C6	0.048 (2)	0.064 (3)	0.080 (3)	0.004 (2)	−0.011 (2)	−0.005 (3)
C3	0.0422 (19)	0.087 (3)	0.060 (3)	0.005 (2)	0.0038 (19)	0.007 (3)
C13	0.0432 (18)	0.055 (3)	0.064 (3)	−0.0049 (16)	−0.0044 (17)	−0.001 (2)

Geometric parameters (Å, º)

Fe1—C1	1.789 (5)	C8—C9	1.373 (4)
Fe1—C2	1.786 (4)	C10—C9	1.368 (5)
Fe1—C3	1.788 (5)	C10—C11	1.378 (5)
Fe1—Fe2	2.471 (2)	C10—H10A	0.9300
Fe1—S1	2.2695 (19)	C11—C12	1.372 (5)
Fe1—S2	2.253 (2)	C11—H11A	0.9300
Fe2—C4	1.789 (5)	C12—H12A	0.9300
Fe2—C5	1.781 (4)	C13—H13A	0.9600
Fe2—C6	1.784 (5)	C13—H13B	0.9600
Fe2—S1	2.2763 (19)	C13—H13C	0.9600
Fe2—S2	2.263 (2)	O3—C3	1.127 (5)
C1—O1	1.131 (4)	O6—C6	1.139 (5)
C2—O2	1.133 (4)	S1—C8	1.787 (3)
C4—O4	1.140 (5)	S2—C9	1.779 (3)
C5—O5	1.135 (5)	S3—C7	1.759 (4)
C7—C12	1.385 (5)	S3—C13	1.790 (4)
C8—C7	1.385 (4)
C2—Fe1—C3	90.77 (19)	C8—S1—Fe1	101.39 (13)
C2—Fe1—C1	98.59 (17)	C8—S1—Fe2	100.67 (13)
C3—Fe1—C1	99.1 (2)	Fe1—S1—Fe2	65.86 (5)
C2—Fe1—S2	90.09 (15)	C9—C8—C7	120.6 (3)
C3—Fe1—S2	159.76 (15)	C9—C8—S1	115.9 (2)
C1—Fe1—S2	100.74 (14)	C7—C8—S1	123.4 (2)
C2—Fe1—S1	157.30 (13)	C9—C10—C11	117.3 (3)
C3—Fe1—S1	90.84 (14)	C9—C10—H10A	121.3
C1—Fe1—S1	103.50 (13)	C11—C10—H10A	121.3
S2—Fe1—S1	80.80 (5)	O2—C2—Fe1	178.5 (4)
C2—Fe1—Fe2	100.45 (13)	C10—C9—C8	122.1 (3)
C3—Fe1—Fe2	103.00 (16)	C10—C9—S2	122.0 (3)
C1—Fe1—Fe2	150.44 (12)	C8—C9—S2	115.9 (2)
S2—Fe1—Fe2	57.01 (5)	O5—C5—Fe2	177.1 (4)
S1—Fe1—Fe2	57.20 (5)	O1—C1—Fe1	178.4 (4)
C5—Fe2—C6	92.06 (19)	C8—C7—C12	117.4 (3)
C5—Fe2—C4	98.5 (2)	C8—C7—S3	118.3 (2)
C6—Fe2—C4	100.1 (2)	C12—C7—S3	124.3 (2)
C5—Fe2—S2	87.98 (13)	C12—C11—C10	121.5 (3)
C6—Fe2—S2	153.34 (15)	C12—C11—H11A	119.3
C4—Fe2—S2	106.31 (16)	C10—C11—H11A	119.3
C5—Fe2—S1	161.32 (14)	C11—C12—C7	121.0 (3)
C6—Fe2—S1	91.81 (15)	C11—C12—H12A	119.5
C4—Fe2—S1	98.82 (15)	C7—C12—H12A	119.5
S2—Fe2—S1	80.45 (5)	O4—C4—Fe2	177.5 (5)
C5—Fe2—Fe1	104.41 (14)	O6—C6—Fe2	178.4 (4)
C6—Fe2—Fe1	97.78 (16)	O3—C3—Fe1	178.5 (5)
C4—Fe2—Fe1	150.30 (13)	S3—C13—H13A	109.5
S2—Fe2—Fe1	56.64 (3)	S3—C13—H13B	109.5
S1—Fe2—Fe1	56.94 (5)	H13A—C13—H13B	109.5
C7—S3—C13	103.30 (16)	S3—C13—H13C	109.5
C9—S2—Fe1	101.52 (13)	H13A—C13—H13C	109.5
C9—S2—Fe2	101.73 (12)	H13B—C13—H13C	109.5
Fe1—S2—Fe2	66.35 (4)

Hydrogen-bond geometry (Å, º)

Cg1 is the centroid of the C7–C12 ring.

D—H···A	D—H	H···A	D···A	D—H···A
C13—H13A···Cg1^i	0.96	2.69	3.590 (5)	157

Symmetry code: (i) −x+1, y+1/2, −z+3/2.