C-H- and N-H-activation by gaseous Rh2+ and PtRh+ cluster ions

The gas-phase reactions of the cluster ions Rh-2(+) and PtRh+ with methane and ammonia are studied by Fourier-transform ion-cyclotron-resonance mass spectrometry. The dehydrogenation reactions observed closely resemble processes previously found for Pt-2(+). In the presence of ammonia. the carbene species Rh2CH2+ and PtRhCH2+ formed in the primary dehydrogenation of methane yield the carbide complexes Rh2C+(NH3) and PtRhC+(NH3), respectively. Again, this behavior is analogous to that of the corresponding platinum cluster. The generation of carbide complexes in the gas phase mimics unwanted soot formation in the heterogeneous DEGUSSA process which employs platinum and rhodium for the catalytic conversion of methane and ammonia to hydrogen cyanide. (C) 2004 Elsevier B.V. All rights reserved.