Heptacarbonylbis(μ-propane-1,3-dithiolato)triiron(I,II)(2 Fe—Fe)

The trinuclear title compound, [Fe3(C3H6S2)2(CO)7], is a mixed-valent FeI/FeII complex and crystallizes with two molecules of similar configuration in the asymmetric unit. The three Fe atoms in each molecule display a bent arrangement [Fe—Fe—Fe = 156.22 (4) and 157.06 (3)°]. Both outer FeI atoms are six-coordinated in a distorted ocahedral coordination geometry defined by the bridging FeII atom, three carbonyl C atoms and two bridging S atoms. The coordination number of the central FeII atom is seven and includes bonding to the two outer FeI atoms, four bridging S atoms and one carbonyl C atom. The resulting coordination polyhedron might be described as a highly distorted monocapped trigonal prism. In the crystal packing, the molecules exhibit a chain-like arrangement parallel to [100] and [001], and the resulting layers are stacked along [010]. The cohesion of the structure is dominated by van der Waals interactions.

The trinuclear title compound, [Fe 3 (C 3 H 6 S 2 ) 2 (CO) 7 ], is a mixed-valent Fe I /Fe II complex and crystallizes with two molecules of similar configuration in the asymmetric unit. The three Fe atoms in each molecule display a bent arrangement  and 157.06 (3) ]. Both outer Fe I atoms are six-coordinated in a distorted ocahedral coordination geometry defined by the bridging Fe II atom, three carbonyl C atoms and two bridging S atoms. The coordination number of the central Fe II atom is seven and includes bonding to the two outer Fe I atoms, four bridging S atoms and one carbonyl C atom. The resulting coordination polyhedron might be described as a highly distorted monocapped trigonal prism. In the crystal packing, the molecules exhibit a chain-like arrangement parallel to [100] and [001], and the resulting layers are stacked along [010]. The cohesion of the structure is dominated by van der Waals interactions.

Experimental
We thank NNSF of China (Nos. 21173219 and 21203195) and the NSF of Fujian Province (2011 J01063) for supporting this work.
Supporting information for this paper is available from the IUCr electronic archives (Reference: WM5007).

Figure 1
The molecular structure of (I) with displacement ellipsoids drawn at the 30% probability level. Only one of the two independent molecules is displayed, and H atoms have been omitted for clarity.

Heptacarbonylbis(µ-propane-1,3-dithiolato)triiron(I,II)(2 Fe-Fe)
where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.43 e Å −3 Δρ min = −0.56 e Å −3 Absolute structure: Flack (1983), 4075 Friedel pairs Absolute structure parameter: 0.016 (13) 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 F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.