Complexes Fe(HTrz)3B_(10)H_(10) · H2O and Fe(NH2Trz)3B_(10)H_(10) · H2O (HTrz = 1,2,4-Triazole and NH2Trz = 4-Amino-1,2,4-Triazole). The Spin Transition ~1A_1 ←→ ~5T_2 in Fe(HTrz)3B_(10)H_(10) · H2O

摘要

Methods for the synthesis of iron(II) complexes with 1,2,4-triazole (HTrz) and 4-amino-1,2,4-tria-zole (NH2Trz) containing the decahydro-closo-decaborate ion [B_(10)H_(10)]~2- were developed. The empirical formulas of the complexes were Fe(HTrz)3B_(10)H_(10) · H2O (I) and Fe(NH2Trz)3B_(10)H_(10) · H2O (II). The complexes were examined by static magnetic susceptibility measurements (2-300 K) and Moessbauer, IR, and electronic spectroscopy. Complex I exhibits the reversible spin transition ~1A_1 ←→ ~5T_2 and pink ←→ white thermo-chromism. The temperatures of the forward and reverse transitions in complex I were 246 and 233 K, respectively. Complex II remained in the high-spin state over the whole temperature range. The sharp decrease in its effective magnetic moment at T < 78 K was attributed to antiferromagnetic exchange interactions between Fe~(2+) ions.