Thermal Decomposition Reactions for the Exploration of New Coordination Polymers based on Mn(NCS)2 and Pyridazine

Abstract

AbstractReaction of different ratios of manganese(II) thiocyanate with pyridazine in water at room temperature leads always to the formation of the pyridazine‐rich 1:4 compound (1:4 = ratio between metal and neutral co‐ligand) Mn(NCS)2(pyridazine)4 (1). In the crystal structure of 1, the Mn2+ cations are coordinated by two nitrogen atoms of terminal N‐bonded thiocyanato anions and four nitrogen atoms of pyridazine ligands within slightly distorted octahedra. However, in one reaction single crystals of the new compound Mn3(NCS)6(pyridazine)4(H2O)·(pyridazine) (2) were obtained. In its crystal structure the manganese atoms are linked into chains by µ‐1, 3 and µ‐1, 1 bridging thiocyanato anions as well as bridging pyridazine ligands. Heating rate dependent DTA‐TG measurements of 1 reveal a multi‐step thermal decomposition, in which three new pyridazine‐deficient compounds of composition Mn(NCS)2(pyridazine)3 (3), Mn(NCS)2(pyridazine)2 (4) and Mn(NCS)2(pyridazine) (5‐Mn) are formed. IR‐spectroscopic investigations indicate that on heating more condensed coordination networks with µ‐1, 3‐ and µ‐1, 1‐bridging thiocyanato anions has formed. Magnetic measurements show only Curie‐Weiss paramagnetism for compounds 1, 3 and 4, whereas in the 1:1 compound 5 an antiferromagnetic ordering is observed at TN = 14 K. Surprisingly, the most pyridazine deficient compound 5 transforms into 2 after storage for several weeks.