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 [Ru-2(CO)(4)(MeCN)(6)][BF4](2) remains intact in the reaction with 2-i-propyl-1,8-naphthyridine ((PrNP)-Pr-i) and the isolated product is the cis-[Ru-2((PrNP)-Pr-i)(2)(CO)(4)(OTf)(2)] (1) obtained via crystallization in the presence of [n-Bu4N][OTf]. The 2-t-butyl-1,8-naphthyridine ((BuNP)-Bu-t), on the contrary, leads to the oxidative cleavage of the Ru-Ru single bond resulting in the trans-[Ru((BuNP)-Bu-t)(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(mu-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. (c) 2006 Elsevier B.V. All rights reserved.