Synthesis and co-ordination chemistry of a novel dinucleating chelating triazole ligand. The crystal structure of bis-µ-[4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole-N′, µ-N1,µ-N2,N″,]-bis[aquachloro-nickel(II)] dichloride tetrahydrate

Abstract

Reaction of 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole (abpt) with nickel(II) and cobalt (II) salts produces dinuclear co-ordination compounds. One of the compounds, [Ni₂(abpt)₂Cl₂(H₂O)₂]Cl₂·4H₂O, crystallizes in the triclinic space group P with a= 6.840(2), b= 10.199(4), c= 12.480(3)Å, α= 78.62(3), β= 76.47(2), γ= 84.17(3)°, and Z= 1. Refinement based on 4 015 independent reflections yielded a value for R′ of 0.034. The dinuclear Ni₂(abpt)₂ unit is almost planar. The nickel ions are co-ordinated by four nitrogen atoms with N–Ni–N angles of 93.00(4), 76.74(4), 113.67(4), and 76.47(4)° and Ni–N distances of 2.013(1), 2.029(1), 2.155(1), and 2.164(1)Å. The axial ligands are a water molecule and a chloride ion. The co-ordination of the metal centres is rhombically distorted octahedral. The uncommon ligand-field spectrum is interpreted along with these findings. Variable-temperature magnetic susceptibility measurements for analogous compounds of Ni^II and Co^II with BF₄^–, Cl^–, or Br^– anions revealed that a relatively weak antiferromagnetic exchange is present in these compounds.