A Remarkable Organometallic Transformation on a Cage-Incarcerated Dinuclear Ruthenium Complex

摘要

Multinuclear metal complexes promote organometallic transformations in a manner different from that of mononuclear complexes. Although a variety of transformations on multi-nuclear metal centers have been reported, they are mostly thermal reactions and surprisingly, in contrast to the rich photochemistry of mononuclear complexes, photochemical transformations on multinuclear metal complexes have been largely unexplored. This is because metal-metal bonds are in general photolabile and quite apt to undergo photocleavage prior to desired transformations across the multimetal centers. Recently, we have shown that a photolabile Ru2 dinuclear complex [(indenyl)Ru(CO)2]2 gains photostability toward ambient light through encapsulation in coordination cage 1 because the Ru—Ru bond cleavage is suppressed by the cage effect, We thus expect that cage 1 enables the photochemical transformation on the dinuclear center without Ru—Ru bond photocleavage. Herein we report that [(Me4Cp)Ru(CO)2]2 (2; Cp = cyclopentadienyl) encapsulated in cage 1 undergoes photosubstitution of a CO ligand with alkyne 3, without Ru—Ru bond cleavage, to form Ru-alkyne π complex 4 (Scheme 1). We show that this π complex is a cage-trapped metastable species and, when ejected from the cage, it is further converted to diruthenacyclopentenone framework 5 by intramolecular CO insertion.The overall reaction provides the first example of a photochemical organometallic transformation of a Ru2 dinuclear complex that occurs across the two metal centers.