Synthesis, Crystal Structures, and Properties of Mn(NCS)_2 Coordination Compounds with 4-Picoline as Coligand and Crystal Structure of Mn(NCS)_2

摘要

Reaction of Mn(NCS)_2 with 4-picoline (4-methylpyridine) leads to the formation of [Mn(NCS)_2(4-picoline)4]·0.67·4-picoline· 0.33·H_2O (1-Mn) reported in literature, Mn(NCS)_2(4-picoline)2(H2O)2 (2-Mn/H2O), and of [Mn(NCS)_2(4-picoline)2]n (2-Mn/I). 1-Mn and 2-Mn/H_2O consist of discrete complexes, in which the metal cations are octahedrally coordinated, whereas in 2-Mn/I the metal cations are linked by pairs of μ-1,3-bridging thiocyanate anions into corrugated chains. Measurements using thermogravimetry and differential scanning calorimetry as well as temperature dependent X-ray powder diffraction on 1-Mn and 2-Mn/H_2O reveal that upon heating both compounds transform into [Mn(NCS)_2(4-picoline)]n (3-Mn) via 2-Mn/I as intermediate. 3-Mn shows a very rare chain topology in which the metal cations are linked by μ-1,3,3 (N,S,S) coordinating anionic ligands which was never observed before with MnII. From these investigations there is no hint that a further modification of 2-Mn can be prepared as recently observed for [M(NCS)_2(4-picoline)2]n (M = Fe, Cd) and such a form is also not available if the metastable forms of the FeII or CdII compounds were used as template during thermal decomposition. Magnetic investigations on 2-Mn/H_2O show only paramagnetic behavior, whereas for 2-Mn/I antiferromagnetic ordering is observed. Finally, the crystal structure of Mn(NCS)_2 was determined from XRPD data, which shows that it is strongly related to that of 3-Mn.