Mechanisms for H2 and CH3 elimination in the gas phase reaction of propyne with Zr: A DFT study

The reaction of ground-state Zr with propyne has been investigated using B3LYP method. Four H2 elimination pathways were identified. Three isomers, Zr(HCCCH), Zr(CCCH2) and Zr–CCCH2 were identified for the experimentally observed product ZrC3H2. For elimination of CH3, besides the previously proposed direct sp–sp3 C–C bond insertion mechanism, a novel C–C bond activation mechanism was also elucidated. The two different CH3 elimination mechanisms also lead to two isomers (Zr–CCH and Zr(CC)H) for the product ZrC2H. Our calculations found that the formation of Zr–CCH and Zr(CC)H is highly endothermic by 88.3 and 83.5 kJ/mol, respectively, at B3LYP/TZVP + RECP level, which rationalizes the absence of the products (ZrC2H + CH3) in experiment.