Abstract
The employment of a strategy based on nucleophilic substitution, rather than Schiff base condensation, for the preparation of 1,2,4‐triazole‐based ligands has been investigated and has led to the synthesis of two new ligands, 4‐amino‐3,5‐bis{[N‐(2‐pyridylmethyl)‐N‐(4‐toluenesulfonyl)amino]methyl}‐4__H__‐1,2,4‐triazole (TsPMAT, 14) and 4‐amino‐3,5‐bis{[(2‐pyridylmethyl)amino]methyl}‐4__H__‐1,2,4‐triazole (PMAT, 15). These are the first examples of bis(terdentate) ligands incorporating the 1,2,4‐triazole unit. TsPMAT (14) forms a dinuclear 2:2 complex with Co(BF~4~)~2~⋅6 H~2~O even when reacted in a metal‐to‐ligand molar ratio of 2:1. Similarly, the reaction of PMAT (15) with Mn(ClO~4~)~2~⋅6 H~2~O or M(BF~4~)~2~⋅6 H~2~O (M=Fe, Co, Ni, Zn) in a ligand‐to‐metal molar ratio of 1:1 has afforded a series of complexes with the general formula [M^II^~2~(PMAT)~2~]X~4~. The metal centres in these complexes of TsPMAT (14) and PMAT (15) are encapsulated by two ligand molecules and doubly bridged by the N~2~ units of the 1,2,4‐triazole moieties, which gives rise to N~6~ coordination spheres that are strongly distorted from octahedral, as evidenced by the X‐ray crystal structure analyses of Co^II^~2~(TsPMAT)~2~~4~⋅6 MeCN (24⋅6 MeCN) and Fe^II^~2~(PMAT)~2~~4~⋅DMF (27⋅DMF). Studies of the magnetic properties of Co^II^~2~(TsPMAT)~2~~4~⋅4 H~2~O (24⋅4 H~2~O), Mn^II^~2~(PMAT)~2~~4~ (26), and Co^II^~2~(PMAT)~2~~4~ (28) have revealed weak antiferromagnetic coupling (J=−3.3, −0.16, and −2.4 cm^−1^, respectively) between the two metal centres in these complexes.