Observation and Characterization of CH 3 CH 2 -MH, (CH 2 ) 2 -MH 2 , CH 2 ═CH-MH 3 , and CH 3 -C≡MH 3 - Produced by Reactions of Group 5 Metal Atoms with Ethane.

The primary products in reactions of laser-ablated group 5 metal atoms with ethane were identified in argon matrix IR spectra and characterized via density functional theory computations. The second- and third-row transition metals Nb and Ta produced insertion, metallacyclopropane, vinyl trihydrido, and anionic ethylidyne complexes (CH3 CH2 -MH, (CH2 )2 -MH2 , CH2 ═CH-MH3 , and CH3 C≡MH3 - ), while the first-row transition metal V yielded only the insertion and metallacyclopropane products. The energetically higher ethylidenes and neutral ethylidynes (CH3 CH═MH2 and CH3 C[Formula: see text]MH3 ) were not detected. The unique anionic ethylidynes are the most stable anionic species in the Nb and Ta systems. Evidently back-donation from the metal center to the C-C π* orbital is stronger than that in the group 6 metal analogue but weaker than that in the corresponding group 4 metal complex. The C-M bond for the Nb and Ta ethylidyne anions is a true triple bond.