6533b7d9fe1ef96bd126cba2

RESEARCH PRODUCT

New Reactivity of 4‐Amino‐3,5‐bis(pyridin‐2‐yl)‐1,2,4‐triazole: Synthesis and Structure of a Mononuclear Species, a Dinuclear Species, and a Novel Tetranuclear Nickel(II) Rectangle Box, and Magnetic Properties of the Dinuclear and Tetranuclear Complexes

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Reactions of Ni(O 2 CMe) 2 ·4H 2 O or NiCl 2 ·6H 2 O, 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole (abpt) and NaN 3 or KSCN in different molar ratios heated under reflux or hydrothermal conditions generate a mononuclear species with dimorphous phases, a dinuclear species incorporating an in situ deaminated [bpt-H] - ligand and a tetranuclear rectangle box incorporating an unprecedented μ:η 1 :η 2 :η 1 coordination mode of the deprotonated [abpt-H] - ligand. Structural analysis reveals that a pair of [Ni 2 (μ 1,1 -N 3 )(μ-OAc)] motifs in [Ni 4 (abpt) 2 -(abpt-H)(N3) 5 (Ο 2 CMe) 2 ]·5H 2 O (1) are bridged by two abpt and one [abpt-H] - units into a rectangle box. [Ni 2 (bpt-H) 2 -(SCN) 2 (H 2 O) 2 ]·2H 2 O (2) is a neutral centrosymmetric dinuclear Ni" complex doubly bridged by abpt ligands. The complex [Ni(abpt) 2 (N 3 ) 2 ] (3) is a neutral centrosymmetric mononuclear Ni" complex and crystallizes in polymorphous phases, showing an interesting example of temperature-induced polymorphism. Variable-temperature magnetic susceptibility measurements reveal that the ferromagnetic interaction via the (μ 1,1 -N 3 ) 2 (μ-OAc) and (μ 1,1 -N 3 )(μ 1,1 -NH abpt-H )(μ-OAC) bridges slightly dominates over the antiferromagnetic interaction via the abpt bridges, therefore indicative of an overall ferromagnetic coupling between Ni ΙΙ centers in 1, and a moderate antiferromagnetic interaction occurs in 2.