Penta­carbonyl-1[kappa]²C,2[kappa]³C-(4-iodo­phenyl isocyanide-1[kappa]C)([mu]-propane-1,3-dithiol­ato-1:2[kappa]⁴S,S':S,S')iron(I)(Fe-Fe)

In the title compound, [Fe₂(C₇H₄IN)(C₃H₆S₂)(CO)₅], the Fe-Fe distance of 2.5156 (11) Å compares well with that in related model structures. The phenyl isocyanide ligand is in the basal position and trans to the S atoms of the propane­dithiol­ate ligand due to steric hindrance. The crystal structure features C-H...O inter­actions.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.009 Å
• R factor = 0.051
• wR factor = 0.110
• Data-to-parameter ratio = 13.8

checkCIF/PLATON results

No syntax errors found



Alert level C
THETM01_ALERT_3_C  The value of sine(theta_max)/wavelength is less than 0.590
            Calculated sin(theta_max)/wavelength =    0.5824
PLAT023_ALERT_3_C Resolution (too) Low [sin(theta)/Lambda < 0.6]..      24.45 Deg.
PLAT342_ALERT_3_C Low Bond Precision on  C-C Bonds ...............     0.0085 Ang
PLAT911_ALERT_3_C Missing # FCF Refl Between THmin & STh/L=  0.582         46

Alert level G
PLAT003_ALERT_2_G Number of Uiso or Uij Restrained Atom Sites ....         19
PLAT005_ALERT_5_G No _iucr_refine_instructions_details in CIF ....          ?
PLAT083_ALERT_2_G SHELXL Second Parameter in WGHT Unusually Large.      16.87
PLAT128_ALERT_4_G Alternate Setting of Space-group P21/c   .......      P21/n
PLAT194_ALERT_1_G Missing _cell_measurement_reflns_used datum ....          ?
PLAT195_ALERT_1_G Missing _cell_measurement_theta_max   datum ....          ?
PLAT196_ALERT_1_G Missing _cell_measurement_theta_min   datum ....          ?
PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_G Check the Reported   _diffrn_ambient_temperature        293 K
PLAT860_ALERT_3_G Note: Number of Least-Squares Restraints .......        219
PLAT909_ALERT_3_G Percentage of Observed Data at Theta(Max) still          73 Perc.

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

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

---

S1. Comment

The iron-only Hydrogenases ([Fe]H₂ase) in microorganisms can catalyze the reversible reduction of protons to hydrogen according to the reaction: 2H⁺+2 e^-=H₂. (Cammack et al. 1999, Nicolet et al. 2000, Frey et al. 2002) The active site of [Fe]H₂ase is consisted of a 2Fe₂S linked to a [4Fe₄S] cluster by a bridged cysteine sulfur (Peters et al. 1998, Nicolet et al. 1999). In the 2Fe₂S unit, the two iron atoms are coordinated by CO and CN– ligands. We have prepared the title complex as a structural model for the iron-only hydrogenases active site. Herein we report its crystal structure.

The molecular structure of the title complex is shown in Fig.1 and selected bond distances are listed in Table 1. The crystal packing diagram reveals that molecules of the title compound form layers in the yz plane (Fig. 2) and the intermolecular interactions present in the structure are listed in Table 2. The Fe—Fe distance of 2.5157 (14) Å compares well with that in the (µ-PDT) Fe₂ (CO)₆ analogous structure (Lyon et al., 1999). The phenyl isocyanide ligand is in the basal position and trans to the sulfur atoms of the propanedithiolate ligand due to the steric hindrance. The Fe—CN distance of 1.87 Å is longer than Fe—CO distance of 1.79–1.81 Å, suggesting the strong electron σ-donating of the isocyanide ligand with iron center. The π-π conjugation between CN triple bond and phenyl ring is somewhat interrupted in the solid state, as the angle of C(9) N(1) C(10) is 169.8 (9)°, indicating a slight distorting from linearity.

Related literature

The title compound was prepared as a model for the iron-only hydrogenase ([Fe]H₂ase) active site. Iron-only hydrogenase in micro-organisms can catalyse the reversible reduction of protons to hydrogen, see: Cammack (1999); Frey (2002); Nicolet et al. (2000). For the active site of [Fe]H₂ase , see: Nicolet et al. (1999); Peters et al. (1998). For an analogous structure, see: Lyon et al. (1999). For the preparation of the starting material [Fe₂(S₂C₃H₆)(CO)₆], see: Winter et al. (1982).

S2. Experimental

A solution of Fe₂(S₂C₃H₆)(CO)₆ (Winter et al. 1982) (1.5 g, 3.88 mmol) in 100 ml MeCN was treated with a solution of Me₃NO.2H₂O (433 mg, 3.9 mmol) in 30 ml of MeCN followed by a solution of p- benzylisocyanide (895 mg, 3.9 mmol) in 30 ml of MeCN at ambient temperature. After 2 h at this temperature, the solvent was removed in vacuo, and the resulting red residue was purified on silica gel to give title compound as a red solid (1.94 g, 85% yield). Single crystals of the title compound for X-ray analysis were grown by slow evaporation. A near saturated solution of the title compound was prepared in a CH₂Cl₂ -hexane (1:5 v/v) solution. The solution was then being left in a glass tube that has a perforated cap at ambient temperature. After one week, some of the crystals grow on the side of the tube.

S3. Refinement

Carbon-bound H atoms were positioned geometrically, with C—H = 0.97Å for methylene and 0.93 Å for aromatic, and refined using a riding model, with U_iso (H) = 1.2 U_eq (C). The hydroxyl H atom was positioned geometrically and freely refined.

Data collection: SMART (Bruker, 2000); cell refinement: SAINT (Bruker, 2000); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Computing details

Data collection: SMART (Bruker, 2000); cell refinement: SAINT (Bruker, 2000); data reduction: SAINT (Bruker, 2000); 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: SHELXTL (Sheldrick, 2008).

Figures

	Fig. 1. View of the title compound, with the atomic numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. A packing diagram for the title compound viewed along the [001] axis (H atoms are omitted for clarity)

Pentacarbonyl-1κ²C,2κ³C-(4-iodophenyl isocyanide-1κC)(µ-propane-1,3-dithiolato-1:2κ⁴S,S': S,S')iron(I)(Fe—Fe)

Crystal data

[Fe2(C7H4IN)(C3H6S2)(CO)5]	Z = 4
Mr = 586.96	F(000) = 1136
Monoclinic, P21/n	Dx = 1.948 Mg m^−3
Hall symbol: -P 2yn	Mo Kα radiation, λ = 0.71073 Å
a = 7.7290 (3) Å	µ = 3.23 mm^−1
b = 11.7215 (5) Å	T = 293 K
c = 22.3974 (10) Å	Cuboid, red
β = 99.466 (1)°	0.15 × 0.14 × 0.12 mm
V = 2001.47 (15) Å^3

Data collection

Bruker Smart APEX CCD area-detector diffractometer	3254 independent reflections
Radiation source: fine-focus sealed tube	2913 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.018
phi and ω scans	θmax = 24.5°, θmin = 1.8°
Absorption correction: multi-scan (SADABS; Bruker, 2000)	h = −6→9
Tmin = 0.630, Tmax = 0.680	k = −13→10
5430 measured reflections	l = −22→25

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)] = 0.051	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.110	H-atom parameters constrained
S = 1.09	w = 1/[σ^2(Fo^2) + (0.0001P)^2 + 16.8715P] where P = (Fo^2 + 2Fc^2)/3
3254 reflections	(Δ/σ)max = 0.002
235 parameters	Δρmax = 0.78 e Å^−3
219 restraints	Δρmin = −0.64 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
N1	0.3432 (6)	0.7795 (5)	0.9391 (2)	0.0648 (15)
I1	0.13693 (6)	1.11048 (4)	1.135787 (19)	0.07267 (14)
Fe1	0.09353 (10)	0.48170 (7)	0.86223 (4)	0.0473 (2)
S1	0.28437 (19)	0.42518 (11)	0.80138 (7)	0.0531 (4)
O1	−0.0108 (7)	0.6147 (5)	0.9623 (2)	0.0910 (16)
C1	0.0272 (8)	0.5622 (5)	0.9234 (3)	0.0599 (14)
Fe2	0.36277 (9)	0.59245 (6)	0.84823 (3)	0.04142 (18)
S2	0.08546 (16)	0.64796 (11)	0.80994 (6)	0.0403 (3)
O2	0.2466 (8)	0.2970 (5)	0.9430 (3)	0.124 (2)
C2	0.1834 (9)	0.3696 (6)	0.9117 (3)	0.0699 (14)
O3	−0.2423 (6)	0.3742 (5)	0.8099 (2)	0.0927 (17)
C3	−0.1125 (8)	0.4154 (5)	0.8299 (3)	0.0605 (13)
O4	0.6000 (6)	0.6782 (4)	0.7683 (2)	0.0833 (14)
C4	0.1905 (9)	0.4428 (5)	0.7209 (3)	0.0649 (14)
H4A	0.2723	0.4100	0.6972	0.078*
H4B	0.0839	0.3978	0.7129	0.078*
O5	0.6200 (6)	0.4745 (5)	0.9381 (2)	0.0909 (17)
C5	0.1472 (9)	0.5607 (6)	0.6976 (3)	0.0666 (15)
H5A	0.2554	0.6040	0.7012	0.080*
H5B	0.0990	0.5555	0.6549	0.080*
C6	0.0215 (8)	0.6253 (5)	0.7284 (2)	0.0564 (14)
H6A	−0.0898	0.5852	0.7217	0.068*
H6B	0.0024	0.6993	0.7091	0.068*
C7	0.5080 (8)	0.6483 (5)	0.8004 (3)	0.0553 (13)
C8	0.5211 (8)	0.5203 (5)	0.9022 (3)	0.0580 (14)
C9	0.3564 (7)	0.7105 (5)	0.9038 (3)	0.0524 (12)
C10	0.3002 (8)	0.8540 (5)	0.9841 (2)	0.0542 (12)
C11	0.2862 (8)	0.9692 (5)	0.9732 (3)	0.0573 (12)
H11A	0.3087	0.9986	0.9366	0.069*
C12	0.2389 (8)	1.0414 (5)	1.0164 (3)	0.0576 (13)
H12A	0.2269	1.1193	1.0087	0.069*
C13	0.2097 (7)	0.9983 (5)	1.0706 (2)	0.0512 (12)
C14	0.2235 (9)	0.8808 (5)	1.0821 (3)	0.0616 (13)
C15	0.2705 (8)	0.8104 (5)	1.0382 (3)	0.0614 (13)
H15A	0.2822	0.7324	1.0455	0.074*
H14A	0.1991	0.8516	1.1182	0.074*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.057 (3)	0.073 (3)	0.062 (3)	0.007 (3)	0.004 (2)	−0.029 (3)
I1	0.0759 (3)	0.0804 (3)	0.0617 (2)	0.0098 (2)	0.0113 (2)	−0.0295 (2)
Fe1	0.0490 (4)	0.0437 (4)	0.0540 (4)	−0.0003 (3)	0.0224 (3)	0.0047 (3)
S1	0.0550 (7)	0.0342 (7)	0.0756 (9)	0.0039 (6)	0.0268 (7)	−0.0082 (6)
O1	0.118 (3)	0.100 (4)	0.067 (3)	−0.016 (3)	0.051 (2)	−0.017 (3)
C1	0.058 (3)	0.064 (3)	0.062 (3)	0.002 (2)	0.024 (2)	0.004 (2)
Fe2	0.0412 (4)	0.0367 (4)	0.0491 (4)	0.0025 (3)	0.0154 (3)	−0.0058 (3)
S2	0.0453 (6)	0.0367 (6)	0.0408 (6)	0.0046 (5)	0.0126 (5)	−0.0034 (5)
O2	0.130 (4)	0.111 (4)	0.138 (4)	0.038 (3)	0.048 (3)	0.072 (3)
C2	0.071 (3)	0.065 (3)	0.078 (3)	0.007 (2)	0.026 (2)	0.019 (2)
O3	0.071 (3)	0.095 (4)	0.117 (4)	−0.030 (3)	0.033 (3)	−0.032 (3)
C3	0.061 (2)	0.058 (3)	0.069 (3)	−0.005 (2)	0.029 (2)	−0.007 (2)
O4	0.082 (3)	0.079 (3)	0.100 (3)	−0.022 (3)	0.050 (2)	−0.004 (3)
C4	0.075 (3)	0.063 (3)	0.061 (3)	−0.002 (2)	0.023 (2)	−0.020 (2)
O5	0.077 (3)	0.089 (3)	0.101 (4)	0.022 (3)	−0.002 (3)	0.013 (3)
C5	0.074 (3)	0.075 (3)	0.052 (3)	−0.002 (3)	0.016 (2)	−0.012 (3)
C6	0.064 (3)	0.061 (3)	0.045 (2)	−0.004 (3)	0.010 (2)	−0.008 (2)
C7	0.059 (2)	0.050 (2)	0.062 (2)	−0.005 (2)	0.022 (2)	−0.011 (2)
C8	0.055 (3)	0.052 (3)	0.069 (3)	0.006 (2)	0.018 (2)	−0.005 (2)
C9	0.054 (2)	0.051 (2)	0.054 (2)	0.006 (2)	0.013 (2)	−0.007 (2)
C10	0.062 (2)	0.053 (2)	0.046 (2)	0.006 (2)	0.006 (2)	−0.013 (2)
C11	0.071 (2)	0.053 (2)	0.049 (2)	0.000 (2)	0.013 (2)	−0.007 (2)
C12	0.073 (3)	0.049 (2)	0.050 (2)	0.005 (2)	0.010 (2)	−0.004 (2)
C13	0.061 (2)	0.050 (2)	0.041 (2)	0.008 (2)	0.005 (2)	−0.009 (2)
C14	0.081 (3)	0.055 (2)	0.047 (2)	0.004 (2)	0.004 (2)	−0.004 (2)
C15	0.078 (2)	0.049 (2)	0.055 (2)	0.007 (2)	0.002 (2)	−0.007 (2)

Geometric parameters (Å, º)

N1—C9	1.148 (7)	C4—C5	1.495 (9)
N1—C10	1.413 (7)	C4—H4A	0.9700
I1—C13	2.109 (5)	C4—H4B	0.9700
Fe1—C2	1.785 (7)	O5—C8	1.148 (7)
Fe1—C1	1.805 (6)	C5—C6	1.488 (9)
Fe1—C3	1.812 (6)	C5—H5A	0.9700
Fe1—S1	2.2656 (17)	C5—H5B	0.9700
Fe1—S2	2.2692 (15)	C6—H6A	0.9700
Fe1—Fe2	2.5156 (11)	C6—H6B	0.9700
S1—C4	1.841 (6)	C10—C15	1.370 (8)
S1—Fe2	2.2590 (16)	C10—C11	1.373 (8)
O1—C1	1.144 (7)	C11—C12	1.380 (8)
Fe2—C8	1.785 (6)	C11—H11A	0.9300
Fe2—C7	1.797 (6)	C12—C13	1.369 (8)
Fe2—C9	1.867 (6)	C12—H12A	0.9300
Fe2—S2	2.2689 (14)	C13—C14	1.401 (8)
S2—C6	1.831 (5)	C14—C15	1.376 (8)
O2—C2	1.157 (8)	C14—H14A	0.9272
O3—C3	1.137 (7)	C15—H15A	0.9300
O4—C7	1.146 (7)
C9—N1—C10	170.0 (6)	C5—C4—S1	118.4 (4)
C2—Fe1—C1	92.5 (3)	C5—C4—H4A	107.7
C2—Fe1—C3	99.2 (3)	S1—C4—H4A	107.7
C1—Fe1—C3	100.8 (3)	C5—C4—H4B	107.7
C2—Fe1—S1	86.2 (2)	S1—C4—H4B	107.7
C1—Fe1—S1	154.6 (2)	H4A—C4—H4B	107.1
C3—Fe1—S1	104.5 (2)	C6—C5—C4	115.8 (6)
C2—Fe1—S2	158.1 (2)	C6—C5—H5A	108.3
C1—Fe1—S2	87.5 (2)	C4—C5—H5A	108.3
C3—Fe1—S2	102.4 (2)	C6—C5—H5B	108.3
S1—Fe1—S2	84.61 (5)	C4—C5—H5B	108.3
C2—Fe1—Fe2	102.2 (2)	H5A—C5—H5B	107.4
C1—Fe1—Fe2	99.7 (2)	C5—C6—S2	116.5 (4)
C3—Fe1—Fe2	149.5 (2)	C5—C6—H6A	108.2
S1—Fe1—Fe2	56.10 (4)	S2—C6—H6A	108.2
S2—Fe1—Fe2	56.33 (4)	C5—C6—H6B	108.2
C4—S1—Fe2	112.9 (2)	S2—C6—H6B	108.2
C4—S1—Fe1	111.4 (2)	H6A—C6—H6B	107.3
Fe2—S1—Fe1	67.56 (5)	O4—C7—Fe2	176.2 (5)
O1—C1—Fe1	178.2 (6)	O5—C8—Fe2	178.0 (6)
C8—Fe2—C7	98.6 (3)	N1—C9—Fe2	175.5 (6)
C8—Fe2—C9	89.5 (3)	C15—C10—C11	120.3 (5)
C7—Fe2—C9	102.4 (3)	C15—C10—N1	119.6 (5)
C8—Fe2—S1	90.3 (2)	C11—C10—N1	120.1 (5)
C7—Fe2—S1	100.69 (19)	C10—C11—C12	120.0 (6)
C9—Fe2—S1	156.70 (19)	C10—C11—H11A	120.0
C8—Fe2—S2	153.1 (2)	C12—C11—H11A	120.0
C7—Fe2—S2	108.30 (19)	C13—C12—C11	119.8 (6)
C9—Fe2—S2	84.98 (17)	C13—C12—H12A	120.1
S1—Fe2—S2	84.77 (5)	C11—C12—H12A	120.1
C8—Fe2—Fe1	99.2 (2)	C12—C13—C14	120.5 (5)
C7—Fe2—Fe1	150.77 (19)	C12—C13—I1	119.0 (4)
C9—Fe2—Fe1	100.75 (18)	C14—C13—I1	120.5 (4)
S1—Fe2—Fe1	56.35 (5)	C15—C14—C13	118.7 (6)
S2—Fe2—Fe1	56.34 (4)	C15—C14—H14A	121.2
C6—S2—Fe1	111.7 (2)	C13—C14—H14A	120.1
C6—S2—Fe2	114.7 (2)	C10—C15—C14	120.7 (6)
Fe1—S2—Fe2	67.33 (4)	C10—C15—H15A	119.7
O2—C2—Fe1	177.7 (7)	C14—C15—H15A	119.7
O3—C3—Fe1	179.5 (6)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C12—H12A···O2^i	0.93	2.57	3.423 (9)	153
C15—H15A···O5^ii	0.93	2.55	3.464 (8)	168

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