Vibrational Spectroscopy of Intermediates and C-H Activation Products of Sequential Zr Reactions with CH.

Vibrational spectra of the entrance channel complexes Zr(CH)(Ar) ( = 1-2) and Zr(CH) ( = 3-4) and the reaction products ZrCH, ZrCH, ZrCH, and ZrCH in the C-H stretching region (2550-3100 cm) are obtained using photofragment spectroscopy. The experimental spectra and simulations based on calculations at the B3LYP/aug-cc-pVTZ level of theory work together to identify the structures of the ions. The = 1-3 entrance channel complexes show peaks around 2800 and 3000 cm which indicates methane η hydrogen coordination, while the = 4 complex has two peaks around 2800 cm indicative of methane η hydrogen coordination. Observation of the low-frequency C-H stretch of an agostic carbene group, as well as the high-frequency H-H stretch, also confirms production of (H)ZrCH(CH) ( = 1-2) exit channel complexes. The observed C-H activation products formally correspond to loss of H from Zr(CH) and loss of H, H, and H + H from Zr(CH). Comparison of experiment and simulations indicates that the activation products are Zr(CH)(CH), Zr(CH)(CH), Zr(CH)(CH), and HZrCH+(CH) and/or ZrCH(CH).