Gas-phase bond strength and atomic connectivity studies of the unsymmetrical two-center three-electron ion, [Et(2)S therefore SMe(2)](+)

A computational and experimental study of the unsymmetrical 2c-3e bond in [Et(2)S therefore SMe(2)](+) is presented. For the first time, MS/MS collision-induced dissociation experiments provide strong experimental support of the atomic connectivity in a gas-phase S therefore S 2c-3e association adduct. The strongest peak in the collision-induced dissociation spectrum corresponds to Et(2)S(+), consistent with the lower ionization potential of Et(2)S compared to Me(2)S and the proposed structure. High-pressure equilibrium mass spectrometry experiments yield a reaction enthalpy of -104 kJ/mol for the equilibrium reaction Et(2)S(+) + Me(2)S reversible arrow [Et(2)S therefore SMe(2)](+) at 506 K. Correcting this value to 0 K using ab initio molecular parameters results in a bond energy of 107 kJ/mol which can be compared to a calculated value of 107.9 kJ/mol at the B3LYP/6-31G(d)//B3LYP/6-31G(d)+ZPC level. Studies on a competing reaction, Et(2)S(+) + Et(2)S reversible arrow [Et(2)S therefore SEt(2)](+), yield an experimental bond enthalpy of 119 kJ/mol at 506 IC and a calculated bond energy of 121.3 kJ/mol, in excellent agreement with previously reported values.