Dimeric (2-cyanophenolato-κO){2,2′-[ethylenebis(nitrilomethylidyne)]diphenolato-κ4 O,N,N′,O′}manganese(III) monohydrate

The molecules of the title compound, [Mn(C7H4NO)(C16H14N2O2)]·H2O, form dimers in the solid state across a crystallographic inversion center. The bridging Mn2O2 group is built of phenoxy groups, and is asymmetric, with an Mn—O distances of 1.9002 (13) and 2.6236 (14) Å. A substantial cavity between the two Mn atoms [Mn⋯Mn = 3.5082 (4) Å] is produced by the formation of the dimer. In the crystal, an extended network of O—H⋯O hydrogen-bonding interactions stabilizes the structure.


Comment
Tetradentate Schiff base complexes of transition metals were involved in a large research activity during the last ten years.
The complexes of manganese(III) are currently used in catalysis (Ourari et al., 2006;Ourari et al., 2008;Srinivasan et al., 1986;Salomao et al., 2007) and in electrocatalysis reactions (Moutet, et al., 1997). In the present paper, we describe the synthesis and structural study of the dimeric 2-cyanophenoxy{2,2-[ethylenebis-(nitrilomethylidyne)]diphenolato}manganese(III) monohydrate. The metal fragment in this complex is similar to those described by Mirkhani et al., 2006;Oyaizu et al., 2000;Zhang et al., 2009), where the manganese(III) is chelated by an imidazole moiety, arylcarboxylate group and azide ion, respectively. In the title compound, the manganese(III) atom is chelated by the Schiff base ligand via two N and two O atoms, and is additionally coordinated by a cyanophenoxy group (Fig. 1), forming a distorted MnN 2 O 3 square pyramidal arrangement (Table 1). The Schiff base lies in the equatorial plane, and the cyanophenoxy group is in the axial coordination site. The manganese(III) atom is diplaced out of the salen N 2 O 2 plane by 0.18Å towards the cyanophenoxy group and confirms that the coordination geometry around the manganese is susceptible to the nature of the axial ligand as described by Oyaizu et al., 2000. In the crystal packing, 2-cyanophenoxy{2,2-[ethylenebis-(nitrilomethylidyne)]diphenolato} -manganese(III) monohydrate forms a solid-state dimer in which the Mn(salen) moiety is linked to its neighbor by two shared cyanophenoxy oxygen atoms. So each manganese(III) achieves a distorted octahedral geometry ( Table 1). The Mn-Mn distance is 3.5082 (4)Å. An extended network of O-H···O (Table 2) hydrogen-bonding interactions stabilizes the solid state ( Fig. 2). Each dimer is linked to four neighbor dimers via hydrogen water molecule bonds to give layers parallel to (001) plane.

Experimental
Reagent grade 2-hydroxybenzaldehyde (Aldrich), 1,2-diaminoethane (Fluka) and manganese(II) acetate tetrahydrate (Fluka) were obtained commercially. All the solvents used were of reagent grade. The symmetrical Schiff base was prepared in one step synthesis according to the method described by Trivedi et al., 1992. The ligand was obtained by refluxing a mixture of 2 mmol of 2-hydroxybenzaldehyde and 1 mmol of 1,2-diaminoethane in 25 ml of ethanol for 30 min. A methanolic solution (15 ml) of Mn(Ac) 2 , 4H 2 O (1 mmol) was added dropwise to the resulting yellow solution containing the ligand.
The reaction mixture was stirred continuously for 24 hours under air atmosphere and the mixture was filtered. The filtrate was concentrated to ca. 20 ml under reduced pressure, kept for several weeks at ambient temperature. The brown crystals were collected by filtration and were washed thoroughly with a minimum amount of methanol and dried in air. Yield: (78%).

Refinement
H atoms were positined geometrically, using a riding model with C-H = 0.96 Å (U iso (H) = 1.5) (including free rotation about C-C and C-N bond) for methyl groups and with C-H = 0.93 and 0.97 Å (1.2 for aromatic and methylene groups) times U eq (C). Hydrogen atoms bonded to the water oxygen were freely refined.
supplementary materials sup-2 The difference between 4732 independent reflections and 4601 reflections used in the refinement is 131 reflections. These are omitted, in refinement, as bad reflections. Fig. 1. The molecular structure of the title compound with atom labels and 35% probability displacement ellipsoids for non-H atoms. Symmetry codes: i = 1-x, 1-y, 2-z; ii = 0.5+x, 0.5-y, 1+z. (