Short-Lived Orthobenzyne Complexes with Early Transition Metals of Group IV. First Direct Characterization and Electronic Cartography by Coupling FVT/UV-PES with Calculations
Résumé
Short‐lived eta2‐benzyne metallocene complexes [Cp2M(eta2‐c‐C6H4)] with Gp IV metals are important intermediates in organic chemistry, their olefin insertion products being building block for aromatic and heterocyclic compounds. For the first time, an electronic cartography of these short‐lived species has been obtained through the determination of their ionization potentials. They have been directly characterized in gas phase by UV‐Photoelectron Spectroscopy by monitoring in‐situ the thermal beta‐H abstraction of benzene from Cp2MPh2. The metal impacts more strongly the energetic position of the sigmaMC orbitals than the piCCbenzyne orbital (HOMO). This study has been supported by DFT calculations and by NBO, AIM, ELF, EDA analyses. Electronic structure of the transient Cp2Ti(eta2‐c‐C6H4) complex is peculiar and slightly differs from that of their zirconium and hafnium analogous. It results in a combination between metallacycle and pi‐complex, whereas with Hf and Zr the metallacycle structure appears to be more representative.