Methane activation by titanium(1+): electronic and translational energy dependence

Abstract

The reaction of Ti/sup +/ with methane is studied as a function of translational energy in a guided ion beam tandem mass spectrometer. The effect of electronic excitation is also studied by varying the conditions for forming Ti/sup +/. The a/sup 2/F excited state is found to form the two main products, TiH/sup +/ and TiCH/sub 2//sup +/, substantially more efficiently than the a/sup 4/F ground and b/sup 4/F first excited states. The results indicate that reaction occurs primarily through a doublet H-Ti/sup +/-CH/sub 3/ intermediate. The reactivities of the different electronic states of Ti/sup +/ can be explained by using simple molecular orbital concepts and spin conversation. The thresholds for these reactions and for related reactions in other systems are interpreted to give D/sup 0/(Ti/sup +/-H) = 54.2 +/- 2.5, D/sup 0/(Ti/sup +/-CH/sub 3/) = 57.5 +/- 2.8, D/sup 0/(Ti/sup +/-CH/sub 2/) = 93.4 +/- 3.5, and D/sup 0/(Ti/sup +/-CH) = 121 +/- 4, all in kcal/mol.