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 at oms and ethylene molecules in excess argon at low temperature, followe d by selective electronic excitation of the Ti atoms. The two products are identified as H2Ti(C2H2) (titanacyclopropene) and HTi(C2H3) (viny ltitanium monohydride) based on IR spectroscopy with various isotopic precursors ((C2H4)-C-12, (C2H4)-C-13, C2D4, CH2CD2, and the natural Ti isotopes), vibrational analysis, and density functional theory (DFT) calculations. Theoretical results are also presented for a Ti(C2H4) pi -complex structure, nor observed in this study. Although DFT predicts a strongly bound Ti(C2H4) system having a stability similar to H2Ti(C2 H2) and HTi(C2H3), this molecule is not observed in our experiments. I t is found that Ti atoms react with ethylene when in the first excited states (F-3, D-3, or (3)G) to form first an insertion product and nex t, after a 1,2-hydrogen shift, the dihydrotitanacyclopropene.