Zn(NCS)2‐3‐cyanopyridine Coordination Compounds: Synthesis, Crystal Structures, and Thermal Properties

Abstract

The reaction of different stoichiometric amounts of Zn(NCS)2 with 3‐cyanopyridine in different solvents leads to the formation of several new coordination compounds, which were structurally characterized and investigated for their thermal behavior. In Zn(NCS)2(3‐cyanopyridine)4 (1) and Zn(NCS)2(3‐cyanopyridine)2(H2O)2·(3‐cyanopyridine)2 (2) the zinc cations are octahedrally coordinated by two terminally N‐bonded thiocyanate anions and four 3‐cyanopyridine (1) or two 3‐cyanopyridine and two water molecules (2) within slightly distorted octahedra. Zn(NCS)2(3‐cyanopyridine)2 (3) and Zn(NCS)2(3‐cyanopyridine)2·(H2O)0.5 (3‐H2O) also form discrete complexes but with tetrahedrally coordinated Zn cations. Upon heating compound 1 decomposes without the formation of any intermediate compound. In contrast, compound 2 loses the water molecules in the first step and transforms into compound 1. Surprisingly, upon further heating a second TG step is observed, in which compound 3 is formed as an intermediate, which is not observed if compound 1 is heated directly. The tetrahedral complex 3 melts leading to the formation of an amorphous phase. If the hemihydrate 3‐H2O is heated, it transforms into 3 via melting and crystallization but there are hints that a metastable phase might form as intermediate on water removal.