Understanding C–H Bond Activation on a Diruthenium(I) Platform

Abstract

Activation of the C–H bond at the axial site of a [RuI–RuI] platform has been achieved. Room-temperature treatment of 2-(R-phenyl)-1,8-naphthyridine (R = H, F, OMe) with [Ru2(CO)4(CH3CN)6][BF4]2 in CH2Cl2 affords the corresponding diruthenium(I) complexes, which carry two ligands, one of which is orthometalated and the second ligand engages an axial site via a Ru···C–H interaction. Reaction with 2-(2-N-methylpyrrolyl)-1,8-naphthyridine under identical conditions affords another orthometalated/nonmetalated (om/nm) complex. At low temperature (4 °C), however, a nonmetalated complex is isolated that reveals axial Ru···C–H interactions involving both ligands at sites trans to the Ru–Ru bond. A nonmetalated (nm/nm) complex was characterized for 2-pyrrolyl-1,8-naphthyridine at room temperature. Orthometalation of both ligands on a single [Ru–Ru] platform could not be accomplished even at elevated temperature. X-ray metrical parameters clearly distinguish between the orthometalated and nonmetalated ligands. NMR ...