Observation and Characterization of CH₃CH₂–MH,\n(CH₂)₂–MH₂, CH₂CH–MH₃, and CH₃–CMH₃^– Produced\nby Reactions of Group 5 Metal Atoms with Ethane

Abstract

The primary products in reactions\nof laser-ablated group 5 metal\natoms with ethane were identified in argon matrix IR spectra and characterized\nvia density functional theory computations. The second- and third-row\ntransition metals Nb and Ta produced insertion, metallacyclopropane,\nvinyl trihydrido, and anionic ethylidyne complexes (CH₃CH₂–MH, (CH₂)₂–MH₂, CH₂CH–MH₃, and CH₃CMH₃^–), while the first-row\ntransition metal V yielded only the insertion and metallacyclopropane\nproducts. The energetically higher ethylidenes and neutral ethylidynes\n(CH₃CHMH₂ and CH₃C≐MH₃) were not detected. The unique\nanionic ethylidynes are the most stable anionic species in the Nb\nand Ta systems. Evidently back-donation from the metal center to the\nC–C π* orbital is stronger than that in the group 6 metal\nanalogue but weaker than that in the corresponding group 4 metal complex.\nThe C–M bond for the Nb and Ta ethylidyne anions is a true\ntriple bond.