Bonding and Substituent Effects in Electron-Rich Mononuclear Ruthenium σ-Arylacetylides of the Formula [(η²-dppe)(η⁵-C₅Me₅)Ru(C⋮C)-1,4-(C₆H₄)X][PF₆]<i>_n</i>(<i>n</i>= 0, 1; X = NO₂, CN, F, H, OMe, NH₂)

Abstract

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 (η2-dppe)(η5-C5Me5)Ru(C⋮C)-1,4-(C6H4)X (1a−f; X = NO2, CN, F, H, OMe, NH2) and (η2-dppe)(η5-C5Me5)Ru(C⋮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(II) and Ru(III) acetylide complexes is proposed. Notably, the strong reactivity of the Ru(III) radicals evidenced in this contribution constitutes a major difference with the relative stability of the known iron analogues.