The reaction of ground-state Zr with propyne has been investigated using B3LYP method. Four H-2 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-sp(3) 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. (c) 2009 Elsevier B.V. All rights reserved.