Crystal Structures and Melting Behaviors of 2D and 3D Anionic Coordination Polymers Containing Organometallic Ionic Liquid Components

Although coordination polymers generally do not melt, several that do melt have been synthesized recently and have drawn much attention. In this study, two‐ and three‐dimensional coordination polymers that melt were synthesized, [Ru(Cp)(C6H5R)][M{C(CN)3}2] (R=H, Me, Et; M=K, Rb; Cp=C5H5), which are complex salts comprising M[C(CN)3] and organometallic ionic liquids [Ru(Cp)(C6H5R)][C(CN)3]. They have anionic [M{C(CN)3}2]n− coordination polymer frameworks, whose dimensionalities depend on the size of the organometallic cation inside. Their melting points decreased with increasing cation substituent length and size of the alkali metal ion (Tm=102–239 °C), and these low‐melting‐point coordination polymers exhibited incongruent melting, forming mixtures of solid M[C(CN)3] and ionic liquid upon melting. Using the same method, coordination polymers were synthesized with various bridging ligands, [Co(Cp)2][MX2] (X=B(CN)4, C(CN)3, N(CN)2; M=K, Na), as well as a paramagnetic coordination polymer, [Fe(Cp)2][K{C(CN)3}2].