Bis(ethanol-κO)bis(pyridine-3-carbaldehyde-κN thiosemicarbazone)bis(thiocyanato-κN)iron(II)–pyridine-3-carbaldehyde thiosemicarbazone (1/2)

The crystal structure of the title FeII complex, [Fe(NCS)2(C7H8N4S)2(CH3CH2OH)2]·2C7H8N4S, based on the Schiff base ligand pyridine-3-carbaldehyde thiosemicarbazone (pct), results from the cocrystallization of an FeII coordination compound together with two of the pct ligands. The complex unit is mononuclear, with the central FeII ion located on a crystallographic centre of inversion and coordinated by four N atoms from two pct ligands and two thiocyanate anions. The slightly distorted octahedral coordination is completed by two O atoms from ethanol molecules. The crystal packing is accomplished intermolecular N—H⋯S hydrogen bonds.

The structure of the title compound, (I), consists of discrete [Fe(C 7 H 8 N 4 S) 2 (SCN) 2 (C 2 H 5 OH) 2 ] neutral units and uncoordinated pct molecules. The two semicarbazone ligands are planar, and each binds to Fe II via the pyridine N atom. Therefore, pct acts as a monodentate ligand with the sulphur and nitrogen atoms of the semicarbazone subunit remaining uncoordinated. In addition to pct, the central Fe II is coordinated by two SCNanions and two C 2 H 5 OH molecules via the N and O atoms, respectively. (Fig. 1) The molecules are held together by intermolecular hydrogen bonding interactions. The imino nitrogen N3 acts as a hydrogen donor site towards S3 of the uncoordinated pct molecule forming intermolecular N3-H3···S3 hydrogen bonds.
S3 also accepts a hydrogen bond from N9 of a neighboring uncoordinated pct to form N9-H9B···S3 hydrogen bonds. In addition, the SCNalso is involved in the construction of the hydrogen bond network by establishing an interaction between the terminal S atoms accept and the hydrogen atom at N4 to form N4-H4A···S2 and N4-H4B···S1 hydrogen bonds (Table 1, Fig. 2).

S2. Experimental
A mixture of 0.5 mmol FeCl 2 × 6 H 2 O, 1.0 mmol of (NH 4 )SCN and 10 ml water-ethanol (1:2 v/v) was stirred for ca. 2 hrs at 343 K. Then 1.0 mmol pct in 10 ml water-ethanol mixture (1:2 v/v) was added. The mixture was further stirred for another 2 h, then filtered. The resultant filtrate was left to stand for slow evaporation at room temperature. Dark green single crystals of (I) suitable for X-ray structure analysis were obtained after a period of one week (yield 63%).

S3. Refinement
Hydrogen atoms attached to carbon atoms and nitrogen atoms were positioned geometrically and treated as riding, with C -H = 0.93 Å, N-H = 0.86 Å, and U iso (H) = 1.2U eq (C or N). The H atom attached to the hydroxy group of the ethanol ligand was located from difference density maps and was refined with distance restraints of O-H = 0.82 (1) Å.  The structure of (I) × pct, symmetry code: (i) -x + 2, -y, -z + 1.

Figure 2
Three-dimensional supramolecular network constructed by hydrogen bonding interactions (dashed lines).

Crystal data
[Fe(NCS) 2 (C 7 H 8 N 4 S) 2 (C 2 H 6 O) 2 ]·2C 7 H 8 N 4 S M r = 985.08 Triclinic, P1 Hall symbol: -P 1 a = 8.916 (4) Å b = 9.556 (5) Å c = 14.538 (7)   Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq