Di-μ-benzoato-di-μ-ethanolato-tetrakis[μ3-5-(hydroxymethyl)-2-methyl-4-(oxidomethyl)pyridin-1-ium-3-olato]tetrakis[μ3-5-(hydroxymethyl)-2-methyl-4-(oxidomethyl)pyridin-3-olato]di-μ3-oxido-heptamanganese(II,III) ethanol octasolvate

The synthesis and structure of a heptanuclear cage-like complex, which includes six MnIII ions and one MnII ion, are presented.

The PNH 2 ligand is comprised of aliphatic and aromatic alkoxide groups, and those in principle can adopt both bridging and chelating modes while binding with metals. The partially labeled molecular structure of the title compound is shown in Fig. 1. The core of the centrosymmetric complex ( Fig. 2), is comprised of three triangular Mn 3 units connected via the Mn3 atom at the center of this cage-like structure. The core consists of six Mn III (Mn1,Mn2,Mn4) ions and one Mn II (Mn3) ion. The central Mn3 ion is connected to Mn1 and Mn2 via a 3 -O oxido ion (O2) and to Mn4 via 3 -O atoms (O1, O4) coming from the alkoxide arm of a PN 2À group that is chelating to Mn4. Apart from that, Mn1 and Mn2 are connected via a bridging -O atom from the ethoxide group (O5) and a carboxylate group (O11, O12). Mn1 is further connected to Mn4 via a bridging -O (O3) from the alkoxide arm of a PNH À group and a 3 -O atom (O1) from the alkoxide arm of a PN 2À group. Similarly, Mn2 is connected to Mn4 via a bridging -O (O10) from the alkoxide arms of the PNH À group and a 3 -O atom (O4) from the alkoxide arm of a PN 2À group. The neutral complex is thus comprised of six Mn III ions, one Mn II ion, two oxide ions, two ethoxide ions, two carboxylate ions, four doubly deprotonated, and four singly deprotonated ligands. All Mn ions possess octahedral environments. Bond-valence sum (BVS) calculations (Brese & O'Keeffe, 1991) show that one of the alkoxide arms of all eight PNH 2 ligands is deprotonated; however, four of the ligands, namely PNH À , exist in the zwitterionic form where the aromatic amine functionality is protonated. BVS calculations also confirmed that Mn1, Mn2, and Mn4 are Mn III ions.
Inspection of the crystal packing of the complex shows that the Mn 7 unit relates to its four neighboring units by O-HÁ Á ÁN hydrogen bonds involving the aromatic amine (N1, N3) group of the ligand PN 2À with the neighboring O atoms (O15, O14)

Figure 1
A view of the molecular structure of the title compound, with selected atoms labeled. Hydrogen atoms and solvent molecules are omitted for clarity. Displacement ellipsoids are drawn at the 50% probability level.
from the PNH À ligand (Fig. 3). In addition to the hydrogen bonds between neighboring molecules, there is also an O-HÁ Á ÁO hydrogen bond between two OH groups on adjacent ligands (O17, O13). Table 1 gives details of these hydrogenbonding interactions. The solid-state structural analysis of such complexes can give us valuable insights on potential uses of such materials for catalytic, magnetic and/or biological activity.
The crystal structure has large voids present in which highly disordered solvent molecules (ethanol) sit. A solvent mask was calculated and 181 electrons were found in a volume of 843 Å 3 in one void per triclinic unit cell. This is consistent with the presence of seven ethanol molecules per formula unit, which accounts for 182 electrons per unit cell. Additionally, one ethanol molecule O16/C42/C43 was found to be ordered in the crystal.

Synthesis and crystallization
The reaction was carried out in presence of air. To a stirred solution of Mn(C 6 H 5 COO) 2 (0.17 g, 1.0 mmol) in 12 ml of ethanol, pyridoxine (PNH 2 , 0.10 g, 1.0 mmol) was added at 343 K. The solution turned from pink to light brown after the addition of the PNH 2 , which is an indication of oxidation of Mn II to Mn III by the atmospheric O 2 . After 30 min, TMAOH (0.09 g, 1.0 mmol) was added to the stirred solution. Heating was ceased and the reaction was set to stir for 3 h, after which the dark-brown solution was filtered and set for slow diffusion with Et 2 O. X-ray quality crystals grew after two weeks with a yield of 23%. The crystals were stored in the mother solvent until X-ray study.