Ni3 vs Ni30. A Truncated Octahedron Metal-Organic Cage Constructed with [Ni5(CN)4]6+ Squares and Tripodal Tris-tacn Ligands that are Large and Flexible

Reactions of trinickel complex of tripodal tris-tacn ligand N(CH2-m-C6H4-CH2tacn)3 (L, tacn = 1,4,7-triazacyclononane) in acetonitrile-methanol solution with and without phosphate led to two complexes of distinct nuclearities, [(NiIICl)3(CH3OH)3(HPO4)L](PF6) (Ni3, 1) and [(NiII5(CN)4(H2O)8Cl)6L8]Cl30 (Ni30, 2). Ligand L takes upward and downward conformation in the structure of 1 and 2, respectively. It is proposed that phosphate directs the upward conformation of Ni3L to form 1. In the absence of phosphate, Ni3L assembles with cyanide ions, which are formed via Ni-catalyzed C−CN bond cleavage of acetonitrile, to give nano-sized Ni30 cage. Complex 2 represents a discrete truncated octahedron cage assembled with [Ni5(CN)4]6+ squares and large and flexible triangular ligands, which is scarcely observed for self-assembled metal-organic cages. Magnetic properties of 1 and 2 were examined, showing intriguing magnetic properties.