Highly Stable Molecular Borromean Rings

A series of Cp*Rh-based molecular Borromean rings (BRs) are prepared from naphthazarine or metallaligand. Some of as-synthesized BRs display high stability and are formed in high yields in solution. The reason is related to the length ratio of the long-arm linker and short-arm linker, where smaller aspect ratios of the metallarectangles promote improved stability and yields of the BRs in solution. Increasing the width of the metallaligand or pyridyl ligand hinders the formation of BRs and leads to unoccupied monomeric rectangles, which were further used as catalysts for the acyl transfer reaction between N-acetylimidazole and (4-(pyridin-4-yl)phenyl) methanol.