Selective and Reversible Base-Induced Elimination of a Ruthenium Dithioether Yields a Vinyl Metallosulfonium Complex

Abstract

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·C(2)H(4)]PF(6), from addition of the alkene across cis sulfur sites. The [Ru-1·C(2)H(4)](+) complex displays a single redox couple at +794 mV versus ferrocenium/ferrocene. (1)H NMR of [Ru-1·C(2)H(4)](+) displays ethylene resonances at δ = 1.29 (td, 1H), 1.59 (td, 1H), 2.78 (dd, 1H), and 3.03 (dd, 1H). In the presence of base [Ru-1·C(2)H(4)](+) is selectively deprotonated at the pseudoequatorial proton on the carbon α to the sulfur trans to phosphorus, yielding the vinyl metallosulfonium derivative [Ru-1·C(2)H(3)]. (1)H and (31)P NMR spectra of [Ru-1·C(2)H(3)] 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·C(2)H(3)] crystallizes as yellow blocks in the triclinic space group P-1 with unit cell dimensions of a = 11.2718(5) Å, b =12.0524(3) Å, c = 23.6075(10) Å, α = 101.715(3)°, β = 98.154(4)°, and γ = 105.209(3)°. Addition of hydrochloric acid to [Ru-1·C(2)H(3)] regenerates [Ru-1·C(2)H(4)](+). Addition of DCl confirms the selectivity of this reverse reaction.