Different Degrees of Electron Delocalization in Mixed Valence Ru-Ru-Ru Compounds by Cyanido-/Isocyanido-Bridge Isomerism

The two stable pairs of trimetallic compounds trans-[Cp*(dppe)Ru(-NC)Ru(dmap)(4)(-CN)Ru(dppe)Cp*][PF6](n) (1[PF6](n), n=2, 3; Cp*=1,2,3,4,5-pentamethylcyclopentadiene; dppe=1,2-bis-(diphenylphosphino)ethane; dmap= 4-dimethylaminopyridine) and trans-[Cp*(dppe)Ru(-CN)Ru(dmap)(4)(-NC)Ru(dppe)Cp*][PF6](n) (2[PF6](n), n=2, 3), which demonstrate cyanide/isocyanide isomerism, have been synthesized and fully characterized. 1(3+)[PF6](3) and 2(3+)[PF6](3) are the one-electron oxidation products of 1(2+)[PF6](2) and 2(2+)[PF6](2), respectively. The results suggest that 1[PF6](3) is a classIII mixed valence compound, whereas 2[PF6](3) might be an unusually symmetrical classII-III mixed valence compound composed of the two asymmetrical delocalized Ru-III-NC-Ru-II mixed valence subunits.