An IR Matrix Isolation and DFT Theoretical Study of the First Steps of the Ti(0) Ethylene Reaction: Vinyl Titanium Hydride and Titanacyclopropene

Two new species have been formed by codeposition of ground-state Ti atoms and ethylene molecules in excess argon at low temperature, followed by selective electronic excitation of the Ti atoms. The two products are identified as H 2 Ti(C 2 H 2 ) (titanacyclopropene) and HTi(C 2 H 3 ) (vinyltitanium monohydride) based on IR spectroscopy with various isotopic precursors ( 12 C 2 H 4, 13 C 2 H 4, C 2 D 4, CH 2 CD 2, and the natural Ti isotopes), vibrational analysis, and density functional theory (DFT) calculations. Theoretical results are also presented for a Ti(C 2 H 4 ) π-complex structure, not observed in this study. Although DFT predicts a strongly bound Ti(C 2 H 4 ) system having a stability similar to H 2 Ti(C 2 H 2 ) and HTi(C 2 H 3 ), this molecule is not observed in our experiments. It is found that Ti atoms react with ethylene when in the first excited states ( 3 F, 3 D, or 3 G) to form first an insertion product and next, after a 1,2-hydrogen shift, the dihydrotitanacyclopropene.