Bis(triethylammonium) bis(μ-pyrazine-2,3-dithiolato)bis(pyrazine-2,3-dithiolato)diferrate(III) methanol disolvate

In the title compound, (C6H16N)2[Fe2(C4H2N2S2)4]·2CH4O, the [FeIII(pdt)2]− anion (pdt is pyrazine-2,3-dithiolate) forms a centrosymmetric dimer supported by two FeIII—S bonds [Fe—S = 2.4787 (4) Å]. In the crystal structure, dimers form a one-dimensional stack along the b axis via π–π stacking interactions, the interplanar separation between adjacent dimers being 3.51 (2) Å. The methanol solvent molecule is involved in two hydrogen bonds in which the hydroxyl group acts as a hydrogen-bond donor to the N atom of a pdt ligand and the O atom acts as an acceptor for the NH group of the triethylammonium cation.

The pdt ligand has been selected to examine the effect of introducing N(imine) donor in close proximity to the active center of the HE reaction. The HE activity of (I) will be separately reported elsewhere (Yamaguchi et al., unpublished results).
The [Fe III (pdt) 2 ]anions form a dimer in the crystal with an inversion center located at the center of the dimer (Figure 1).
Although a dark-brown solid immediately precipitated, the suspension was stirred at room temperature for 18 h. The dark-brown solid deposited was collected by filtration and washed with THF. The crude material was re-dissolved in a minimum amount of methanol followed by filtration for the removal of insoluble materials. Standing of the filtrate at room temperature for several days afforded the black needles of (I), which were collected by filtration, washed with cold methanol, and dried in vacuo. Yield: 0.098 g (41%). Single crystals of (I) suitable for X-ray crystallography were grown by slow diffusion of diethyl ether into a methanol solution of (I). Analysis calculated for C 30 H 48 Fe 2 N 10 O 2 S 8 : C, 37.97; H,

S3. Refinement
All H atoms were placed in idealized position (ring C-H = 0.95 Å, methyl C-H = 0.98 Å, methylene C-H = 0.99 Å, hydroxyl O-H = 0.84 Å and tertiary N-H = 0.93 Å), and included in the refinement in a riding-model approximation, with U iso (H) = 1.2U eq (ring C, methylene C and tertiary N) and U iso (H) = 1.5U eq (methyl C and hydroxyl O). In the final Fourier map, the highest peak was located 0.99 Å from atom S4. The deepest hole was located 0.53 Å from atom Fe1.
Hydrogen atoms are omitted for clarity. Thermal ellipsoids are drawn at the 50% probability.     A view perpendicular to the plane defined by atoms S1-S2/C1-C4/N1-N2 which has a weak π-stack to the plane defined by atoms S1 ii , C1 ii , and N1 ii [Symmetry code: (ii) 1 -x, 1 -y, -z]. Hydrogen atoms are omitted for clarity. Thermal ellipsoids are drawn at the 50% probability.