Synthesis and some first-row transition-metal complexes of the 1,2,4-triazole-based bis(terdentate) ligands TsPMAT and PMAT

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-pyridyl-methyl)-N-(4-toluenesulfonyl)amino]-methyl]-4H-1,2,4-triazole(TsPMAT, 14) and 4-amino-3,5-bis{[(2-pyridylmethyl)amino]methyl}-4H-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)center dot 6H(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)center dot 6H(2)O or M(BF(4))(2)center dot 6H(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(2)(II)(PMAT)(2)]X(4). The metal centres in these complexes of TsPMAT (14) and PMAT (15) are encapsulated by two ligand molecules i and doubly bridged by the N(6) 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(2)(II)(TsPMAT)(2)] (BF(4))(4)center dot 6MeCN (24.6MeCN) and [Fe(2)(II)-(PMAT)(2)](BF(4))(4)center dot DMF (27 center dot DMF). Studies of the magnetic properties Of [CO(2)(II)(TsPMAT)(2)](BF(4))(4)-4H(2)O (24.4H20), [Mnr'2(PMAT)11(ClO1)1 (26), and [CO(2)(II)(PMAT)21(BF(4))(4) (28) have revealed weak antiferromagnetic coupling (J=-3.3, -0.16, and -2.4cm-', respectively) between the two metal centres in these complexes.