Binuclear ruthenium macrocycles formed via the weak-link approach

The weak-link approach for the synthesis of metallomacrocycles has been used to synthesize a series of novel Ru(II) macrocycles in high yield. RUCl2(PPh3)(3) has been reacted with two different phosphino-alkyl-ether hemilabile ligands, 1,4-(PPh2(CH2)(2)O)(2)C6H4 and 1,4-(PPh2(CH2)(2)OCH2)(2)C6H4. The hemilabile bidentate ligand coordinates to Ru(II) centers through both the P and O atoms to form bimetallic condensed intermediates. The weak Ru-O bonds have been selectively cleaved with CO, 1,2-diaminopropane, and pyridine to yield large open macrocycles. This is the first example of the weak-link approach employed to synthesize macrocycles with Ru, and metal centers in general that have more than four coordination sites.