Chemical oxidation of tris(2-diphenylphosphinebenzenethiolato) ruthenate (II) [Ru-1](-) with ferrocenium hexafluorophosphate in the presence of ethylene yields [(2-diphenylphosphinebenzenethiolato)(ethane-1,2-diylbis(thio-2,1-phenylene)diphenylphosphine)ruthenium(II)] hexafluorophosphate, [Ru-1 center dot C2H4]PF6, from addition of the alkene across cis sulfur sites. The [Ru-1 center dot C2H4]+ complex displays a single redox couple at +794 mV versus ferrocenium/ferrocene. H-1 NMR of [Ru-1 center dot C2H4](+) displays ethylene resonances at (delta = 1.29 (td, 1H), 1.59 (td, 1H), 2.78 (dd, 1H), and 3.03 (dd, 1H). In the presence of base [Ru-1 center dot C2H4] is selectively deprotonated at the pseudoequatorial proton on the carbon a to the sulfur trans to phosphorus, yielding the vinyl metallosulfonium derivative [Ru-1 center dot C2H3]. 1H and P-31 NMR spectra of [Ru-1 center dot C2H3] are temperature dependent, associated with inversion of the sulfur lone pair at the vinyl metallosulfonium. The activation energy for the fluxional process calculated using density functional theory (B3LYP/LANL2DZ+6-31g) of 14.36 kcal/mol is consistent with the experimentally determined value of 13.08 kcal/mol. The complex [Ru-1 center dot C2H3] crystallizes as yellow blocks in the triclinic space group P-1 with unit cell dimensions of a = 11.2718(5) angstrom, b =12.0524(3) angstrom, c = 23.6075(10) angstrom, alpha = 101.715(3)degrees, beta = 98.154(4), and gamma = 105.209(3)degrees. Addition of hydrochloric acid to [Ru-1-C2H3] regenerates [Ru-1-C2H4]. Addition of DCI confirms the selectivity of this reverse reaction.