Hexakis(dimethylformamide-κO)manganese(II) μ-oxido-bis[trichloridoferrate(III)]

The title compound, [Mn(C3H7NO)6][Fe2Cl6O], was obtained unintentionally as a product of an attempted synthesis of heterometallic complexes with Schiff base ligands using manganese powder and FeCl3·6H2O as starting materials. In the [Fe2OCl6]2− anion, the O atom and the Fe atom occupy positions with site symmetry and 3, respectively, resulting in a linear Fe—O—Fe angle and a staggered conformation. The octahedrally surrounded cation (site symmetry ) and the [Fe2Cl6O]2− anion are alternately stacked along [001].

The title compound, [Mn(C 3 H 7 NO) 6 ][Fe 2 Cl 6 O], was obtained unintentionally as a product of an attempted synthesis of heterometallic complexes with Schiff base ligands using manganese powder and FeCl 3 Á6H 2 O as starting materials. In the [Fe 2 OCl 6 ] 2À anion, the O atom and the Fe atom occupy positions with site symmetry 3 and 3, respectively, resulting in a linear Fe-O-Fe angle and a staggered conformation. The octahedrally surrounded cation (site symmetry 3) and the [Fe 2 Cl 6 O] 2À anion are alternately stacked along [001].

Comment
Continuing our research on direct synthesis of bimetallic complexes with Schiff base ligands, i.e. one-pot synthesis with the use of metal powders or their oxides as starting materials (Garnovskii et al., 1999), we present here a new Mn II /Fe III complex, which was obtained as a by-product during the investigation of the system: Mn 0 -FeCl 3 .6H 2 O -salicylic aldehyde -glycine -Et 3 N -dmf (dimethylformamide).
The crystal structure of the title complex, (I), is shown in Fig. 1 (Khutornoi et al., 2002)]. An additional argument for Mn in the cation as the correct metal, but not its Fe analogue, is the analysis of crystallographic data for 10 structures containing [Fe(dmf) 6 ] 2+ (Albanati et al., 2007;Baumgartner, 1986;Li et al., 2007a,b;Lode & Krautscheid, 2000;Müller et al., 1989a,b;Qiutian et al., 1983;Silva et al., 2008;Young et al., 1989) where Fe-O bond lengths in the range of 1.99 -2.16 Å with an average value of 2.11 Å are found. Moreover, no Fe II complexes with a regular octahedral dmf environment have been found.
The [Fe 2 OCl 6 ] 2anion possesses D 3d geometry with Fe and O atoms in special positions (3 and 3, respectively) that force the Fe-O-Fe angle to be linear and the anion to adopt a staggered conformation (Fig. 2). The Fe 3+ atom has a distorted tetrahedral coordination with an Fe1-O1S distances of 1.7758 (5) (Brown & Altermatt, 1985)].
The described complex (I) can be supposed as isostructural to [Mg(dmf) 6 ][Fe 2 OCl 6 ] (Juang et al., 1984) but interestingly the volume of the unit cell in case of the manganese complex is ca 200 Å 3 less than that of the magnesium complex.

Experimental
Salicylic aldehyde (0.31 g, 2.5 mmol), glycine (0.19 g, 2.5 mmol) and triethylamine (0.35 mmol, 2.5 mmol) were dissolved in dimethylformamide (dmf; 25 ml) in this order, and stirred at 323 -333 K (10 min). Then, manganese powder (0.14 supplementary materials sup-2 g, 2.5 mmol) and FeCl 3 .6H 2 O (0.68 g, 2.5 mmol) were added to the hot yellow solution with stirring for 3 h, until total dissolution of manganese was observed. The resulting solution was filtered and subsequently pale pink crystals suitable for X-ray crystallography were separated after eight days at successive addition of a Pr i OH. Yield: 0.23 g, 21.5% (per iron). Elemental analysis for C 18  443(w). The compound is sparingly soluble in dimethylsulfoxide (dmso), dmf, and H 2 O. In the IR spectrum of (I), the band corresponding to ν(CO) in dmf is shifted to the region of longer wavelenghts (1629 cm -1 ) relative to this band in the spectrum of noncoordinating dmf (1675 cm -1 ).

Refinement
The carbonyl H atom was found from a difference Fourier map and was refined freely. Methyl H atoms were allowed to ride on their attached atoms with C-H = 0.98 (1)Å and U iso (H)= 1.5Ueq(C). The highest remaining difference Fourier peak is located 0.87 Å from atom O1S. Fig. 1. Parts of the structure of (I), with atom labels and 50% probability displacement ellipsoids. Hydrogen atoms were omitted for clarity.   Fig. 1; hydrogen atoms were omitted for clarity.