Synthesis, structures and magnetic properties of new Fe(II) and Co(II) thiocyanato coordination compounds with 2-chloropyrazine as Co-ligand

Investigations on the synthesis of coordination compounds based on Fe(NCS)(2) and Co(NCS)(2) with 2-chloropyrazine as ligand leads to the formation of five new compounds. Fe(NCS)(2)(2-chloropyrazine)(4) (1-Fe), Co(NCS)(2)(2-chloropyrazine)(4) (1-Co) and Fe(NCS)(2)(2-chloropyrazine)(4)center dot 2-chloropyrazine solvate (2-Fe) consists of discrete complexes in which the metal cations are octahedrally coordinated and in which the thiocyanato anions are only terminal coordinated. On heating 1-Fe and 1-Co transform into new coordination polymers of composition [Fe(NCS)(2)(2-chloropyrazine)(2)](n) (3-Fe) and [Co(NCS)(2)(2-chloropyrazine)(2)](n) (3-Co) which are isotypic. No access to large and phase pure amounts of these compounds was found in solution but the structure of 3-Co was determined from a crystal obtained in one batch by accident. In the crystal structure of 3-Co and 3-Fe the metal(II) cations are coordinated by two N-bonded as well as two S-bonded thiocyanato anions and two 2-chloropyrazine ligands and are linked by mu-1,3-bridging anions into layers. Magnetic measurements of 1-Fe and 1-Co show only Curie-or Curie-Weiss paramagnetism, whereas for 3-Fe antiferromagnetic ordering and for 3-Co metamagnetic behavior is observed. (C) 2013 Elsevier B. V. All rights reserved.