Synthesis and Some First‐Row Transition‐Metal Complexes of the 1,2,4‐Triazole‐Based Bis(terdentate) Ligands TsPMAT and PMAT

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}-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(BF4)2.6 H2O even when reacted in a metal-to-ligand molar ratio of 2:1. Similarly, the reaction of PMAT (15) with Mn(ClO4)2.6H2O or M(BF4)2.6 H2O (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]X4. The metal centres in these complexes of TsPMAT (14) and PMAT (15) are encapsulated by two ligand molecules and doubly bridged by the N2 units of the 1,2,4-triazole moieties, which gives rise to N6 coordination spheres that are strongly distorted from octahedral, as evidenced by the X-ray crystal structure analyses of [Co(II) (2)(TsPMAT)(2)](BF(4))(4)6 MeCN (246 MeCN) and [Fe(II) 2(PMAT)2](BF4)4DMF (27DMF). Studies of the magnetic properties of [Co(II) 2(TsPMAT)2](BF4)4.4 H2O (244 H2O), [Mn(II) 2(PMAT)2](ClO4)4 (26), and [Co(II) 2(PMAT)2](BF4)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.

Probing the Dinucleating Behaviour of a Bis‐Bidentate Ligand: Synthesis and Characterisation of Some Di‐ and Mononuclear Cobalt(II), Nickel(II), Copper(II) and Zinc(II) Complexes of 3,5‐Di(2‐pyridyl)‐4‐(1H‐pyrrol‐1‐yl)‐4H‐1,2,4‐triazole

“…The best fit parameters are given in Table 5. The magnitude of the coupling between the two cobalt(ii) centres in the ClO 4 -complex 4 (J = -3.1 cm -1 ) and the BF 4 -complex 7 (J = -3.1 cm -1 ) was similar to the corresponding value observed for [Co II 2 (TsPMAT) 2 ](BF 4 ) 4 ·4H 2 O (J = -3.3 cm -1 ) [51] and was only slightly less than that reported for related complexes of other 4-substituted 3,5-di(2-pyridyl)-4H-1,2,4-triazoles. [5,32] The room temperature effective magnetic moment of 2.82 μ B per nickel(ii) centre for the ClO 4 -complex 9 (Figure 8) was reduced from the typical uncoupled value of ca.…”

“…There is only one report in the literature dealing with 3,5-di(2-pyridyl)-4-(1H-pyrrol-1-yl)-4H-1,2,4-triazole (pldpt, 3) ( Figure 1) and it describes the structural characterisation of the dinuclear complex [Co [ 44] Overall it appears that the factors which combine to determine the nature of the products of such a complexation reaction, in particular whether a di-or mononuclear complex is formed as the main product, include the reaction stoichiometry, the choice of the counterions and the solvent used, as well as the influence of the N 4 substituent on the electronic structure and conformation of the respective ligand and on the relative solubility of the various possible product complexes. Systematic studies aimed at investigating the relative importance of these factors are currently lacking but clearly desirable so we are beginning to address this as part of our ongoing studies which are directed towards the synthesis and characterisation of dinuclear 1,2,4-triazole-bridged complexes of such ligands, [2,3,30,32,33,[45][46][47][48][49][50][51] with a particular interest in iron(ii) complexes. [52] Given that to date dinuclear 1,2,4-triazolebridged complexes are far less common than the corresponding mononuclear complexes, here we target the controlled formation of further examples of dinuclear complexes of pldpt (3) by employing a metal-to-ligand molar ratio of 1:1 in the complexation reactions and varying the solvents and counterions.…”

Electrochemical, quantum chemical, and molecular dynamics studies on the interaction of 4‐amino‐4H,3,5‐di(methoxy)‐1,2,4‐triazole (ATD), BATD, and DBATD on copper metal in 1N H2SO4

“…The resulting solution was heated at 120 8C for 6 h. Then the reflux condenser was replaced with a downward condenser and the reaction mixture was heated at 160 8C for a further 18 h allowing excess hydrazine and water to distil off. After cooling, the resulting yellowish crystalline solid was recrystallized from water to give analytically pure ATD [13,14]. BATD was prepared by the condensation of ATD with benzaldehyde (E. Merck) (1:1 molar ratio) using alcohol as the solvent.…”

Mössbauer spectroscopy in molecular magnetism

“…[Fe II 2 (PMAT) 2 ](BF 4 ) 4 · DMF (6) The dinuclear complex [Fe II 2 (PMAT) 2 ](BF 4 ) 4 · DMF (6), where PMAT is 4-amino-3,5-bis{[(2-pyridylmethyl)amino]methyl}-4H-1,2,4-triazole, exhibiting thermal spin transition (ST), was reported in 2005 [20,21]. At ca.…”