Solid-State 1D → 3D Transformation of Polynitrile-Based Coordination Polymers by Dehydration Reaction

In crystal structures of two chain coordination polymers [M(tcnopr3OH)2(H2O)2] (M = NiII and CoII; tcnopr3OH- = [(NC)2CC(O(CH2)3OH)C(CN)2]-) based on a N,O or N,N′-bridge polynitrile ligand, the parallel chains are connected via, respectively, C≡N…H-O and O-H…O hydrogen bonds between uncoordinated functional groups of the ligand, and coordinated water molecules. At heating, both solids underwent dehydration accompanied with degradation of their single crystals. Powder X-ray diffraction showed that non-isostructural triclinic single crystals transformed to isostructural monoclinic compounds. The solid-state reaction yielded 3D coordination polymers [M(tcnopr3OH)2] (M = NiII and CoII) based on a N,N′,O-connected tcnopr3OH- as proved by powder X-ray diffraction and infrared spectroscopy. Although previously tens of complexes based on tcnopr3OH and similar anions were synthesized and X-ray characterized, none of these contains a tridentate polynitrile ligand. Thus, this study provides evidence that solid-state reactions allow obtaining novel coordination modes of polynitrile ligands. The possible pathways for the transformation are discussed on the bases of the topological approach. Applicability of the topological approach to predict possible networks of solid-state reaction products based on crystal structures of initial compounds is demonstrated.