Bulletin of the Chemical Society of Japan The Best Article of the Month賞 p-tert-Butylthiacalix[6]arene as a Clustering Ligand. Syntheses and Structures of CoII5, NiII4, and Mixed-metal MIINiII4 (M = Mn, Co, and Cu) Cluster Complexes, and a Novel Metal-induced Cluster Core Rearrangement.