Activation of CH4 and H2 molecules by cationic zirconium(IV) complexes: A DFT study

Reactions of methane and hydrogen molecules with [(η5-C5H5)2ZrCH3]+ and (η5-C5H5)2ZrH3]+ cations were studied using nonempirical density functional theory (DFT). In all cases, the reactions begin with the formation of agostic complexes between the substrate molecules and1 or2. Transformation of these intermediates into transition states when moving along the reaction coordinate requires only slight changes in the geometry. The dihydrogen molecule reacts with1 exothermically (−8.8 kcal mol−1) and barrierlessly to form2 and CH4. Exchange of σ-bonded ligands in the1−CH4 system proceeds through a symmetric transition state with an activation energy of 15.0 kcal mol−1. According to calculations, organometallic ZrIV complexes are promising for activation of C−H and H−H bonds under mild conditions.