Theoretical Study on the Gas Phase Reaction: B₂H^-₃+CS₂ →B₂H₃S^-+CS

The mechanism for the gas phase ion-molecule reaction B₂H^-₃+CS₂ →B₂H₃S^-+CS has been investigated theoretically by using the B3LYP/6-311++G(d,p) and the high-level electron-correlation CCSD(T)/6-311++G(d,p) single-point levels. It is shown that the B₂H^-₃ anion may attack the carbon atom of CS₂ to form a three-membered-ring intermediate followed by a H-shift and subsequently a CS-extrusion steps to reach the final dissociation product H₃BBS^-+CS. The reaction is largely exothermic and no activation energy is needed for this three-membered-ring mechanism. On the other hand, an activation barrier is found for the sulfur atom abstraction reaction initiated by the sulfur-attack of B₂H^-₃ towards CS₂. The calculated results presented in this paper may be helpful for understanding the chemical behavior of electron-deficient boron hydride anions such as B₂H^-₃ , B₃H^-₆ and B₄H^-₇, etc..