ルテニウムピラー[5]アレーン錯体の合成と物性

概要

Pillar[n]arenes (n = 5–15) first reported by Ogoshi in 2008 are macrocyclic compounds composed of electron-rich dialkoxybenzene units connected by methylene bridges at the para-positions.1 Especially, pillar[5]arenes show interesting host properties derived from their rigid pentagonal flamework. For example, they can selectively form host–guest complexes with only linear n-alkanes, while do not with cyclic and branched alkanes. 2 Since it is expected that πcomplexation of pillar[n]arenes with cationic transition metals reduces electron density of the cavity, such πmetalated pillar[n]arenes would have unique host properties different from those of unmodified pillar[n]arenes. In fact, pillar[5]arene complexes bearing one, two or three [Cp*M]2+ (Cp* = η 5 -C5Me5; M = Rh, Ir) units, have been synthesized and revealed to uptake one of the counteranions inside the cavity through anion–π interactions. 3 On the other hand, our group independently has synthesized [Cp*M(η 6 - pillar[5]arene)][BF4]2 (M = Rh, Ir) which show strong interaction with polar solvents such as CH3NO2 and acetone. In this study, the author reports the synthesis of novel Ru–pillar[5]arenes whose ruthenium units have mono- and dicationic charges. The host–guest chemistry of the dicationic Ru complex is also demonstrated.

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