Bonding and substituent effects in electron-rich mononuclear ruthenium σ-arylacetylides of the formula [(η2-dppe)(η5-C5Me5)Ru(CC)-1,4-(C6H4)X][PF6]n (n = 0, 1; X = NO2, CN, F, H, OMe, NH2)

This study reports the isolation and the structural (X-ray), UV-vis, and NMR characterization of a series of electron-rich Ru(II) acetylide complexes of the formula (eta(2)-dppe)(eta(5)-C5Me5)Ru(C equivalent to X)-1,4-(C6H4)X (1a-f; X = NO2, CN, F, H, OMe, NH2) and (eta(2)-dppe)(eta(5)-C5Me5)Ru(C equivalent to C)-1,3-(C6H4)F (1c-m), as well as the spectroscopic (near-IR and ESR) in situ characterization of the corresponding elusive Ru(III) radical cations. The spectroscopic data are discussed in connection with DFT computations, and a consistent picture of the electronic structure of these Ru(11) and Ru(111) acetylide complexes is proposed. Notably, the strong reactivity of the Ru(Ill) radicals evidenced in this contribution constitutes a major difference with the relative stability of the known iron analogues.