Structures and Magnetic Properties of Nickel Thiocyanato Coordination Compounds with 2‐Chloropyrazine as a Neutral Coligand

Abstract

AbstractReaction of Ni(NCS)2 with 2‐chloropyrazine in different molar ratios and solvents at room temperature leads to five new coordination polymers. In the crystal structures of Ni(NCS)2(2‐chloropyrazine)4·2‐chloropyrazine solvate (1) and Ni(NCS)2(2‐chloropyrazine)4 (2) the nickel cations are octahedrally coordinated by two terminal N‐bonded thiocyanato anions and four 2‐chloropyrazine ligands into discrete complexes. In the crystal structures of the Ni(NCS)2(2‐chloropyrazine)2(CH3OH)2·(CH3OH)2 solvate (3) and Ni(NCS)2(2‐chloropyrazine)2(CH3OH)2 (4) each nickel(II) cation is coordinated by two terminal N‐bonded thiocyanato anions, two 2‐chloropyrazine ligands and two O‐bonded methanol molecules in a slightly distorted octahedron. On heating, compounds 1 and 2 transform into the ligand‐deficient 1:2 compound 5, which can also be crystallized from solution. In the crystal structure of [Ni(NCS)2(2‐chloropyrazine)2]n (5) each nickel(II) cation is coordinated by two N‐bonded and two S‐bonded thiocyanato anions as well as two 2‐chloropyrazine ligands. The nickel cations are linked into dimers by pairs of μ‐1,3‐bridging thiocyanato anions that are further linked into chains and finally into layers by single μ‐1,3‐bridging thiocyanato anions. Magnetic measurements of compound 1 and 2 show only Curie or Curie–Weiss paramagnetism, whereas in the ligand‐deficient compound 5 a metamagnetic transition is observed at a critical field of HC = 14 kOe. The results of the magnetic measurements are compared with those of related nickel compounds with different coligands.