Crystal structure of bis(N-(2-aminoethyl)salicylaldiminato)iron(III) isothiocyanide, [Fe(C9H11N2O)2][NCS]

Abstract

C19H22FeN5O2S, triclinic, P1 (no. 2), a = 9.613(1) Å, b = 9.913(1) Å, c = 10.869(2) Å, a = 84.958(2)°, b = 89.047(2)°, g = 86.098(1)°, V = 1029.3 Å 3 , Z = 2, Rgt(F) = 0.038, wRref(F 2 ) = 0.099, T = 291 K. Source of materialThe mixture of FeCl 2 · 4H 2 O (0.122 g, 0.5 mmol) and NH 4 SCN (0.192 g, 1 mmol) were refluxed in anhydrous methanol (15 mL) at a temperature of 60°C for 50 min, then were added 20 mL methanol solution of freshly distilled salicylaldehyde and ethylenediamine simultaneously. The mixture was stirred for 5 h, then filtered. The resulting clear solution was diffused with ethyl ether vapor at room temperature under ambient for three weeks. Blocklike dark-red crystals were formed and collected by filtration and dried in air (yield 0.202 g, 46 %). DiscussionIron complexes play an important role in biological field, catalysis application and earth chemistry research [1][2][3][4]. Schiff base complexes containing different central metal atoms such as Zn, Cu, Ni and Ru have been studied in great detail for their various crystallographic features, enzymatic reactions and magnetic properties [5][6][7]. To the best of our knowledge, the iron(III) salicylaldehyde Schiff base complexes have been seldom reported [8,9]. At the same time, the study of octahedron complexes involving an aromatic Schiff base as the primary ligand, isothiocyanato ion as secondary ligand can serve as a useful model for gaining a better understanding of enzyme-metal ion-substrate complexes, which plays an important role in metalloenzyme-catalyzed biochemical reactions.Based on the studies of the iron complexes and the salicylaldehyde Schiff base, in the present ferrum enzyme imitational investigation, an octahedral complex of iron(III) ion with sal-en Schiff base as ligand has been template synthesized and characterized. The asymmetric unit of the crystal structure consists of a discrete [Fe(sal-en)2] + cation and a counter isothiocyanato anion ( figure, top). The central iron(III) ion is six-coordinated (FeN4O2 ) and the coordination polyhedron can be described as an distorted octahedron formed by the four nitrogen atoms of the ethylenediamine molecule part, and two hydroxyl oxygen atoms from salicylaldehyde molecule part. In the complex, the salicylaldehyde-ethylenediamine Schiff base molecule acts as tridentate chelate ligand, obviously, only one of the amidocyanogen group of the ethylenediamine was involved in the reaction to salicylaldehyde to obtain the sal-en Schiff base during the template synthesis. N1, N3, O2, N2 are occupied at equatorial positions, O1, N4, are occupied at apical positions, Fe1, N1, N2, C8, N9 form a cyclopental ring, and Fe1, O1, N1, N2, C1, C2 form a cyclohexal ring. All the atoms of two six-membered rings are almost at the

When the Metal Makes the Difference: Template Syntheses of Tridentate and Tetradentate Salen-Type Schiff Base Ligands and Related Complexes

“…Other metal ions that favor an octahedral coordination, such as iron(III) [107][108][109][110], chromium(III) [111][112][113][114][115][116][117], and cobalt(III) [44,85,[116][117][118][119][120][121][122][123][124][125][126], are known to show a reactivity for obtaining [M( G L) 2 ](X) species with various X − anions, similarly to nickel(II). Differently from before, these metals allow to obtaining N 2 O tridentate Schiff base ligands with diamines bearing two carbon atoms connecting the amine groups (en, pn, etc.…”

“…It is noteworthy that the reaction of [Fe(salen)(Cl)] with en in ethanol leads to its conversion to [Fe( H L) 2 ](Cl) [108] where the initial kinetic template effect brings en within the coordination sphere of iron(III), and then the thermodynamic template effect allows the formation of the most stable product. The anion X − in the final product can be the same as in the iron source (Cl − [107,108]) or different for the addition of a different anion (SCN − [109,110]) (Figure 7a). It is also important to highlight a peculiar structural difference: meridional coordination of G L − is preferred when short en is employed [107][108][109] while facial coordination is present in the compound with the long 2,2-dimethyl-1,3-diaminopropane [110].…”

“…aldehydes (H-salH [109], 2-hydroxy-1-naphthalaldehyde [110], and 2-mercaptobenzaldehyde [107]), diamines with two or three methylene units (en [107,109] and 2,2-dimethyl-1,3-diaminopropane [110]), and variable iron sources (FeCl3 [107], hydrated Fe(ClO4)3 [110], FeCl2 with concomitant oxidation to iron(III) [107]). It is noteworthy that the reaction of [Fe(salen)(Cl)] with en in ethanol leads to its conversion to [Fe( H L)2](Cl) [108] where the initial kinetic template effect brings en within the coordination sphere of iron(III), and then the thermodynamic template effect allows the formation of the most stable product.…”

“…The anion X  in the final product can be the same as in the iron source (Cl  [107,108]) or different for the addition of a different anion (SCN  [109,110]) (Figure 7a). It is also important to highlight a peculiar structural difference: meridional coordination of G L  is preferred when short en is employed [107][108][109] while facial coordination is present in the compound with the long 2,2-dimethyl-1,3-diaminopropane [110]. The template effect of chromium(III) has been exploited with two different approaches, one by reacting the precursor [Cr(H-sal)3] with en or pn, similarly to nickel(II) [37], and addition of the sodium salt with anions such as I  , Br  , ClO4  , and NO3  [112,117], Equation (8a), and the second by hydrolytic conversion of H2salen in the presence of [Cr(urea)6](Cl)32H2O [115], Equation (8b).…”