Tris(1,10-phenanthroline-κ2 N,N′)iron(II) bis(1,1,3,3-tetracyano-2-ethoxypropenide) hemihydrate

In the title hydrated molecular salt, [Fe(C12H8N2)3](C9H5N4O)2·0.5H2O, the water molecule site is half-occupied. The Fe—N bond lengths within the octahedral tris-chelate [Fe(phen)3]2+ ion (phen is 1,10-phenantroline) are indicative of a low-spin d 6 electronic configuration for the metal ion. The C—N, C—C and C—O bond lengths in the polynitrile anions indicate extensive electronic delocalization. In the crystal, the components are linked through O—H⋯N hydrogen bonds, forming [100] chains, as well as through Coulombic interactions.

In the title hydrated molecular salt, [Fe(C 12 H 8 N 2 ) 3 ](C 9 H 5 -N 4 O) 2 Á0.5H 2 O, the water molecule site is half-occupied. The Fe-N bond lengths within the octahedral tris-chelate [Fe(phen)3] 2+ ion (phen is 1,10-phenantroline) are indicative of a low-spin d 6 electronic configuration for the metal ion. The C-N, C-C and C-O bond lengths in the polynitrile anions indicate extensive electronic delocalization. In the crystal, the components are linked through O-HÁ Á ÁN hydrogen bonds, forming [100] chains, as well as through Coulombic interactions.
Six nitrogen atoms from three bidentate phen ligands form a distorted octahedron around the iron atom with a mean Fe1 -N bond length of 1.972 (18) Å. The main distortion from the octahedral geometry is observed in the values of the angles subtended by phen at the metal atom (82.36 (7)°, 82.50 (8)° and 83.02 (8)° for N1-Fe1-N2, N4-Fe1-N3 and N6-Fe1-N5, respectively) which deviate significantly from the ideal value of 90°. Each phenanthroline ligand is coplanar to within 0.04 Å. The average value of dihedral angle between pairs of phenanthroline planes is 82,1(3)°. The carbon-carbon and carbon-nitrogen intra-ring bond lengths agree with those observed in other metal complexes with chelating phen (Hoshina et al., 2000;Aparici Plaza et al., 2007;Cai & Zhan, 2012).
Examination of the intermolecular contacts in the crystal structure of (I) reveals that the main contacts are associated with O-H···N hydrogen bonds involving the water H atoms and those of the N atoms of the CN groups of the tcnoet anions containing atoms O1 (Table 1). In the crystal, this leads to the formation of an infinite one-dimensional {[(H 2 O) (tcnoet) 2 ] 2-} n anionic chains (Fig. 2), which interact with the cationic entities [Fe(phen) 3 ] 2+ and the tcnoet anions involving atoms O2 via coulombic forces.
Due to the presence of the supplementary π electron systems of the cyano groups, the tcnoet ligands of (I) present a strong electronic delocalization, as indicated by C-N, C-C and C-O bond lengths.

Refinement
Carbon-bound H-atoms were placed in calculated positions (C-H 0.93 to 0.97 Å) and were included in the refinement in the riding model approximation, with U(H) set to 1.2 to 1.5 U(C).
The water H-atoms were placed in calculated positions on the basis of hydrogen bonding and their temperature factors tied by a factor of 1.5 times. As the oxygen atom displayed extremely large temperature factors, the refinement of its occupancy was attempted. This refined to nearly 0.5; the occupancy was then set to exactly 0.5.
The two ethyl groups are disordered over two positions in a 1:1 ratio. The C-C distance was restrained to 1.54±0.01 Å.
For each group, the pair of O-C distances were restrained to within 0.01 Å of each other. The anisotropic temperature factors of the C atoms of the groups as well as those of the water molecule were tightly restrained to be nearly isotropic.

Figure 1
The molecular structure of (I) at the 30% probability level; hydrogen atoms are drawn as spheres of arbitrary radius. The disorder in the ethyl groups is not shown.   Table 1; symmetry code: (i) x + 1, y, z.]