Reactions of Actinide Metal Atoms with Ethane: Computation and Observation of New Th and U Ethylidene Dihydride, Metallacyclopropane Dihydride, and Vinyl Metal Trihydride Complexes

A combined computational and experimental investigation provides evidence that excited thorium and uranium atoms activate ethane to form the vinyl metal trihydride, metallacyclopropane dihydride, and ethylidene metal dihydride for thorium and the latter complex and the inserted ethyl metal hydride for uranium. These products are trapped in solid argon and identified through deuterium isotopic substitution and vibrational frequencies calculated by densitiy functional theory. Comparisons are made with group 4 and methane reaction products. Numerous calculations using several methods show that these simple ethylidene complexes are more distorted by the agostic interaction than the corresponding methylidene species. This enhanced agostic interaction probably arises from methyl hydrogen to α-H repulsions, which leads to a substantial decrease in the α-H to Th agostic interaction distance, and contributes to our understanding of agostic distortion in organometallic complexes.