Ligand assisted homolytic cleavage of the Ru–Ru single bond in [Ru2(CO)4]2+ core and the chemical consequence

The Ru–Ru single bond in [Ru2(CO)4(MeCN)6][BF4]2 remains intact in the reaction with 2-i-propyl-1,8-naphthyridine (iPrNP) and the isolated product is the cis-[Ru2(iPrNP)2(CO)4(OTf)2] (1) obtained via crystallization in the presence of [n-Bu4N][OTf]. The 2-t-butyl-1,8-naphthyridine (tBuNP), on the contrary, leads to the oxidative cleavage of the Ru–Ru single bond resulting in the trans-[Ru(tBuNP)2(MeCN)2][BF4]2[NC(Me)C(Me)N] (2). The anti-[NC(Me)C(Me)N]2− is the product of the two-electron reductive coupling of two acetonitrile molecules. The phenoxo appendage in 2-(2-hydroxyphenyl)-1,8-naphthyridine (hpNP) brings the identical effect of the scission of the Ru–Ru bond but the process is non-oxidative and the product obtained is the cis-[Ru(hpNP)2(CO)2][BF4] (3). The bis-(diphenylphosphino)methane (dppm) in dichloromethane oxidatively cleave the Ru–Ru bond leading to chloro bridged [Ru(μ-Cl)(dppm)(CO)(MeCN)]2[BF4]2 (4). All the complexes have been characterized by the spectroscopic and electrochemical measurements and their structures have been established by X-ray diffraction study.

Graphical abstractThe reaction of 2-i-propyl-1,8-naphthyridine (iPrNP) with [Ru2(CO)4(MeCN)6][BF4]2 and subsequent crystallization in [n-Bu4N][OTf] provide the Ru–Ru singly bonded cis-[Ru2(iPrNP)2(CO)4(OTf)2] whereas the t-butyl appendage in tBuNP leads to the oxidative cleavage of the Ru–Ru bond resulting in the trans-[Ru(tBuNP)2(MeCN)2][BF4]2[NC(Me)C(Me)N]. The dianion anti-[NC(Me)C(Me)N]2− is the product of the two-electron reductive coupling of two acetonitrile molecules.Figure optionsDownload full-size imageDownload as PowerPoint slide