Synthesis, Thermal and Magnetic Properties of New Coordination Compounds based on Mn(NCS)2with 2-Chloropyrazine and 2-Methylpyrazine as neutral Co-Ligand

Formation of di- and polynuclear Mn(II) thiocyanate pyrazole complexes in solution and in the solid state

Reaction of Mn(NCS)2 with pyrazole leads to the formation of three compounds with the compositions Mn(NCS)2(pyrazole)4 (1), [Mn(NCS)2]2(pyrazole)6 (2) and Mn(NCS)2(pyrazole)2 (3). Compound 1, already reported in the literature, consists of discrete complexes, in which the Mn(II) cations are octahedrally coordinated by four pyrazole ligands and two terminally N-bonded thiocyanate anions. In compound 2 each of the two Mn(II) cations are coordinated octahedrally by three pyrazole ligands and one terminal as well as two bridging thiocyanate anions, which link the metal cations into dimers. In compound 3 also octahedrally coordinated Mn(II) cations are present but they are linked into chains via centrosymmetric pairs of μ-1,3-bridging thiocyanate anions. Upon heating compound 1 loses the pyrazole co-ligands stepwise and is transformed into the chain compound 3 via the dimer 2 that is formed as an intermediate. Magnetic measurements on compounds 2 and 3 reveal dominating antiferromagnetic interactions, as already observed for 1D Mn(NCS)2 coordination compounds with pyridine based co-ligands.