Coexistence of two distinct axial ligands and their thermo-induced substitution in trans-[FeL2(NCS)2][FeL2(CH3OH)2](NCS)2 (L = 4-amino-3-(p-chlorophenyl)-5-(2-pyridyl)-1,2,4-triazole)

A novel iron(II) complex, trans-[FeL2(NCS)2][FeL2(CH3OH)2](NCS)2 (1) with 4-amino-3-(p-chlorophenyl)-5-(2-pyridyl)-1,2,4-triazole (L) has been successfully synthesized and characterized. X-ray crystallography analysis shows that 1 is the first example in the mononuclear triazole-based complexes consisting of two distinct molecules: trans-[FeL2(NCS)2] and trans-[FeL2(CH3OH)2](NCS)2 with each octahedral iron(II) center coordinated axial by two NCS− ions in Fe1 but two MeOH molecules in Fe2. Moreover, 1 can lose two MeOH molecules at 220 °C to form trans-[FeL2(NCS)2] (2) which can be transformed to 1 when recrystallizing 2 in methanol. Both 1 and 2 are high-spin species in the range of 1.8–300 K.

Graphical abstractA novel iron(II) complex, trans-[FeL2(NCS)2][FeL2(CH3OH)2](NCS)2 (1) has been synthesized and structurally characterized by single-crystal X-ray diffraction. 1 is the first mononuclear triazole-based octahedral complex with two trans-coordinated NCS- ions and MeOH molecules. 1 reveals an interesting substitution of axial ligand NCS– for CH3OH when heated at 220 °C.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A new asymmetrical 3,5-disubstituted 1,2,4-triazole and its iron(II) complexes. ► Their structures were characterized by IR, ESI-MS, EA and X-ray crystallography. ► The first mononuclear triazole-based complex with two trans-positions NCS– and MeOH. ► A substitution of axial ligand NCS– for CH3OH in the complex occurs at 220 °C.