Bis[N-(pyridin-2-ylcarbonyl)pyridine-2-carboxamidato]iron(III) perchlorate monohydrate

The structure of the title salt complex, [Fe(C12H8N3O2)2]ClO4·H2O, contains one FeIII cation, two N-(pyridin-2-ylcarbonyl)pyridine-2-carboxamidate (bpca−) anions, one perchlorate anion and one water molecule. The FeIII cation has an approximate octahedral geometry, defined by six N atoms from two bpca− anions. The nearly parallel [dihedral angle = 1.50 (1)°] bpca− anions form two-dimensional supermolecules along the a axis by the way of weak π–π stacking inteactirons [centroid–centroid distances = 3.948 (2), 4.000 (2), 3.948 (2), 3.911 (2), 3.897 (2), 3.984 (2) and 3.929 (2) Å]. Intra- and intermolecular C—H⋯O hydrogen bonding occurs. The water molecule [occupancies 0.520 (5) and 0.480 (5)], two carbonyl O atoms [occupancies 0.622 (7) and 0.378 (7)] and the four perchlorate O atoms [occupancies 0.887 (4) and 0.113 (4)] are each disordered over two positions.

As a continuation of our studies related to the behaviour of the bpca ligand with Fe III ions, we have synthesized the title salt complex [Fe(bpca) 2 (ClO 4 ) . H 2 O]. As shown in Fig. 1, each asymmetric unit contains one Fe III cation, two bpcaanions, one perchlorate anion and one lattice water molecule. The bpca ligands are nearly parallel in the structure and form two-dimensional supermolecules by the way of weak π-π stacking inteactions [centroid to centroid distances = 3.9475Å, 3.9997Å, 3.9488Å, 3.9107Å, 3.8973Å, 3.9838Å and 3.9287Å, respectively]. The bond lengths for Fe-N vary from 1.902 (2)Å to 1.979 (2)Å, and the angles for N-Fe-N are between 81.65 (9)° and 178.54 (10)°. These bond lengths and angles are in agreement with those found in similar related Fe III compounds (Wocadlo et al., 1993).

Experimental
A mixture of methanol and water (1:1, 2 ml) was gently layered on the top of a solution of Fe(ClO 4 ) 3 .6H 2 O (46.2 mg, 0.1 mmol) in water (3 ml). A solution of Hbpca = bis(2-pyridylcarbonyl)amine (22.7 mg, 0.1 mmol), in methanol (10 ml) was added carefully as the third layer. Red crystals suitable for X-ray diffraction were obtained after 3 weeks, washed with ethanol and ether, and dried in air.

Refinement
Lattice water OW1 and OW1' atoms were disordered over two positions with approximate part occupancies of 0.520 (5) and 0.480 (5). Hydrogen atoms on OW1 and OW1' were also treated using the above two part model. The carbonyl oxygen atoms, O1A and O1B, were disordered over two positions with approximate part occupancies of 0.622 (7) and 0.378 (7).
The four perchlorate oxygen atoms O5, O6, O7 and O8 were also disordered with approximate part occupancies of 0.887 (4) and 0.113 (4). All of the remaining H atoms were placed in calculated positions and then refined using the riding model with Atom-H lengths of 0.93Å (CH). Isotropic displacement parameters for these atoms were set to 1.2 (CH) times U eq of the parent atom.
supplementary materials sup-2 Figures Fig. 1. The molecular structure for title salt with isplacement ellipsoids at the 30% probability level. OW1 and OW1' atoms were disordered over two positions with approximate part occupancies of 0.520 (5) and 0.480 (5). Hydrogen atoms on OW1 and OW1' were also treated using the above two part model. O1A and O1B, were disordered over two positions with approximate part occupancies of 0.622 (7) and 0.378 (7). O5, O6, O7 and O8 were disordered with approximate part occupancies of 0.887 (4) and 0.113 (4).