Acta Phys. -Chim. Sin. ›› 2006, Vol. 22 ›› Issue (01): 59-64.doi: 10.3866/PKU.WHXB20060112

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Theoretical Study of Gas-phase Reaction of CrO2+ with H2

CHEN Xiao-xia; WANG Yong-cheng; Geng Zhiy-Yuan; GAO Li-guo; FANG Ran; ZHANG Xing-hui   

  • Received:2005-06-10 Revised:2005-08-19 Published:2006-01-15
  • Contact: WANG Yong-cheng

Abstract: The gas-phase reaction of CrO2+(2A1/4A″) with H2 to yield CrO+(2Σg/5Σg) and H2O is selected as a representative system of activation of H—H σ bond by MO2+. The reaction mechanism has been investigated with density functional theory (DFT) at the UB3LYP/6-311++G(3df, 3pd)//6-311G(2d, p) level. The geometries for reactants, the transition states, and the products were completely optimized. All the transition states were verified by the vibrational analysis and the intrinsic reaction coordinate calculations. The H—H bond has been activated by CrO2+(2A1) on the doublet PES(potential energy surface) while dihydrogen transfer from Cr to O (in longer Cr—O) on the quartet PES. The involving potential energy curve-crossing, with dramatically affecs reaction mechanism and reaction rate, has been discussed in detail. The crossing points (CPs) are localized by means of the Hammond postulate and the intrinsic reaction coordinate (IRC) approach. The formation of the transition metal dihydrogen complex (H2)CrO2+(2IM1 and 4IM1) involves donation of the H2 σ bonding orbital to the metal and the back-donation by the metal electron to the H2 σ* antibonding orbital, as illustrated by the fragment molecular orbital(FMO). In addition, the orbital analysis on the activation of the H—H bond and dihydrogen transfer has been carried out by FMO.

Key words: Activation H—H bond, Potential energy surfaces crossing, Fragment molecular orbital