C–C versus C–H bond activation of propyne by Y: A DFT study

A DFT study on the mechanism of the gas phase reaction of ground-state Y (4d15s2,2D) with 2-butyne

“…Especially, our previous calculations on Y + propyne ? CH 3 + YCCH reactions indicate that the energy barriers obtained at this level agree well with the experimentally observed threshold energy [19].…”

“…This is consistent with the C2AC3 bond distance, 1.351 Å, which is 0.148 Å longer than the bond length in the free 2-butyne molecule. The similar situation was also found in the reaction of Y, Zr with C 2 H 4 [12,16], C 2 H 2 [17], C 3 H 4 [19].…”

“…Our calculations confirmed this mechanism. However, it was also pointed out that such mechanism cannot explain the observation of YCCH + CH 3 in the reaction of Y with allene, CH 2 @C@CH 2 [19]. Instead, we found a novel mechanism which can explain the experimental results and this mechanism can be described as: p-complex ?…”

“…In this pathway, the collision between 2-butyne and Y forms the initial strongly bound p-complex IM1 with C 2v symmetry. The binding energy of this complex was calculated to be 153.3 kJ/mol, slightly weaker than that calculated for Y-propyne complex, 167.6 kJ/mol [19]. Natural bond orbital (NBO) analysis suggests that the C2AC3 bond has been weakened to double bond, meanwhile a pair of r-bonds, YAC2 and YAC3, have been almost formed.…”

“…For other metal atoms, such product channel was not observed. To rationalize the experimental results, very recently, we performed a theoretical study on the reaction of Y with propyne [19]. In this study, four reaction pathways leading to H 2 -elimination were identified and three isomers, Y(HCCCH), Y(CCCH 2 ) and YACCCH 2 , were assigned to the experimentally observed H 2 -elimination product YC 3 H 2 .…”