GAS-PHASE KINETICS OF NEUTRAL TRANSITION-METAL ATOMS - REACTIONS OF Y THROUGH MO WITH ALKANES AND ALKENES AT 300-K

We survey the reactivity of ground-state, neutral transition metal atoms from the left-hand side of the 4d series (Y through Mo) with eight alkanes and alkenes. Effective bimolecular rate constants are measured in 0.5-0.8 Torr of He in a fast flow reactor at 300 K with laser-induced fluorescence detection. None of the four ground-state metal atoms reacts with linear alkanes. Mo reacts slowly and Y, Zr, and Nb react rapidly with alkenes. From the absence of a measureable pressure dependence of the rate constant over the limited He range of 0.5-0.8 Torr, we infer that bimolecular elimination chemistry occurs. We relate the pattern of reactivity to recent ab initio calculations of the geometry and binding energy of M-C2H4 and H-M-C2H3 for 4d-series transition metals.