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

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 (H 2 O) 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 · (H 2 O) 0.5 ( 3‐H 2 O ) 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‐H 2 O 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.