Ligand-induced selectivity switch: The gas-phase reactions of "bare" and ligated iron(I) and cobalt(I) cations with n-propyltrimethylsilane

The unimolecular and bimolecular gas-phase reactivities of the model compound n-propyltrimethylsilane with "naked" transition-metal ions Fe+ and Co+ versus the one of the ligated complexes Fe(L)(+) and Co(L)(+) (L = HCN, CD3CN, (CD3)(2)CO) have been investigated by tandem and Fourier transform ion cyclotron resonance mass spectrometry. The present study focuses on the changes in product selectivity upon coordination of the metal center to a spectator ligand L which serves to moderate the intrinsic reactivity of the metal. The bare metal cations Fe+ and Co+ suffer from a lack of selectivity, and C-H, C-C, and C-Si bond-activation processes compete with each other in the reactions of Fe+ and Co+ with n-propyltrimethylsilane. In marked contrast, the gas-phase chemistry of the ligated complexes of the two metal ions differs significantly in that Fe(L)(+) predominantly activates C-H and C-C bonds while Co(L)(+) favors C-H and C-Si bond activation.