[2,2′-(2,6,9,13-Tetraazatetradecane-1,14-diyl)diphenolato]iron(III) iodide

The title FeIII complex, [Fe(C22H32N4O2)]I, contains a six-coordinate FeN4O2 cation in which the ligand is a reduced Schiff base resulting from the NaBH4 reduction of the condensation product between salicylaldehyde and 1,5,8,12-tetraazadodecane. In spite of the increased flexibility of the saturated backbone of the ligand compared to the Schiff base from which it was synthesized, the complex adopts a cis-FeN4O2 conformation for the phenolic O-atom donors, which contrasts with the trans conformation adopted by the analogous ClO4 − salt [Yisgedu et al. (2009 ▶). J. Chem. Crystallogr. 39, 315–319]. In addition to extensive N—H⋯I hydrogen bonding between the amine H atoms and the anion there is a weak C—H⋯I interaction.


Experimental
Crystal data [Fe(C 22 [2,6,9, & Lions, 1947). The first such report of an Fe complex of a linear FeN 4 O 2 ligand derived from the Schiff base condensation of salicylaldehyde and triethylenetetraamine was in 1955 (Das Sarma & Bailar, 1955). However, this interest lapsed for several years until the discovery that such complexes exhibited spin-crossover magnetic behavior (Sinn et al., 1978).
Hexadentate linear FeN 4 O 2 ligands derived from the Schiff base condensation of salicylaldehyde and linear tetramines can be characterized by the number of linking carbon atoms in the tetramine backbone (from 222 to 333). The structures of Fe complexes of Sal222 (Sinn et al., 1978;Hayami et al., 1997;Floquet et al., 2004;Dorbes et al., 2005;Bera et al., 2005;Nishida et al., 1987;Salmon et al., 1999;McPartlin et al., 1978;Maeda et al., 1991;Boinnard et al., 1994), Sal232 (Hayami et al., 1997), Sal323 (Hayami et al., 1997Ito, et al., 1983), and Sal333 (Ito, et al., 1983) derivatives have been reported. When chelating to Fe, as the number of carbon atoms in the tetramine backbone increases from 6 to 9, the conformation adopted by the ligand changes from a cis-FeN 4 O 2 to a trans-FeN 4 O 2 arrangement for the phenolic O donors. All structurally characterized Fe complexes with Sal222 have adopted the cis-FeN 4 O 2 conformation while all those with either Sal323 or Sal333 have adopted the trans-FeN 4 O 2 conformation. For Sal232, both conformations have been observed (Hayami et al., 1997). Further, it has been observed that, in addition to the usual reduction in metal ligand bond distances when going from high spin to low spin, the angles subtended at the Fe center reflect the magnetic properties of the compound (Hayami et al., 1997;Nishida et al., 1987) with low-spin compounds having such angles closer to 90° and 180°.
Despite the interest shown in salicylaldimine complexes with Fe III due to their interesting structural and magnetic properties, there have been very few structures reported on related complexes where the C=N imine groups have been reduced to C-N-H amine groups (Harpstrite et al., 2003;Yisgedu et al., 2009). One of these is the perchlorate analog of the title compound (Harpstrite et al., 2003). As expected, due to increased flexibility of the saturated amine, compared to the more rigid Schiff base, and also the length of the carbon backbone, this compound has adopted a trans-FeN 4 O 2 conformation.
To further characterize such compounds and determine the conformation adopted the structure of an Fe III complex of the iodide salt of reduced Sal323 is reported. In addition to extensive hydrogen bonding between the amine H atoms and the anion there is a weak C-H···I interaction (see table 1).

Experimental
Synthesis of ligand: The procedure for the synthesis of the ligand 1,12-bis(2-hydroxybenzyl)-1,4,8,12-tetraazaundecane (H 2 L) (Yisgedu et al., 2009) is as follows: A solution of 6.1 g (50 mmol) of salicylaldehyde in 10 ml ethanol was added drop-wise to a solution of 4.0 g (25 mmol) of 1,5,8,12-tetraazadodecane in 15 ml of ethanol. A deep yellow solution was obtained and was stirred for half an hour. To this yellow solution was added a NaBH 4 solution (3.0 g NaBH 4 , 0.4 g NaOH, and 40 ml H 2 O). The volume of the solution was reduced to 20 ml and extracted with chloroform (3 x 40 ml). The extracts were combined and dried with Na 2 SO 4 . The Na 2 SO 4 was filtered and the filtrate concentrated to a colorless thick oil (8.1 g, 87%).  supplementary materials sup-3 [2,6,9,