Isomerization of 1-butene on Mo(VI)ISiO2, W(VI)/SiO2, and Cr(VI)/SiO2 was investigated by steady-state flow reactor studies and Fourier transform infrared spectroscopy. (eta(5)-C5H5)(2)M-2(CO)(6) or M(eta(3)-C3H5)(4) (M = MO, W) were used as precursors in preparing Mo(VI)/SiO2 and W(VI)/SiO2 catalysts. Cr(NO3)(3) was used to prepare Cr(VI)/SiO2. Isomerization proceeds by a Bronsted catalyzed pathway involving alkoxide intermediates and an oxidative dehydrogenation pathway involving allylic intermediates. Flow reactor experiments revealed that two pathways for isomerization could be observed with Mo(VI)/SiO2 : through the alkoxide intermediate at T < 523 K and through the allylic intermediate at T > 573 K. W(VI)/SiO2 catalysts were more active for isomerization than Mo(VI)/SiO2 catalysts, but the demarcation of the two pathways was not as clear. Only the oxidative dehydrogenation pathway for isomerization was observed for the Cr(VI)/SiO2 catalysts at T > 473 K. In IR studies, alkoxide intermediates were observed following adsorption of 1-butene on Mo(VI)/SiO2 and W(VI)/SiO2 catalysts at 300 K; complete desorption of the surface alkoxide occurred by 523 K. The surface species observed for adsorption of 1-butene on Cr(VI)/SiO2 at 300 K were typical of allylic C-H abstraction; these surface species transform into deep oxidation products on heating, resulting in a surface that is poisoned. Pyridine adsorption studies reveal traces of Bronsted acidity on Mo(VI)/SiO2, W(VI)/SiO2, and Cr(VI)/SiO2. Bronsted acidity would account for the alkoxide mechanism of 1-butene isomerization. The reason that these Bronsted acid sites are most active for 1-butene isomerization on W(VI)/SiO2 and inactive on Cr(VI)/SiO2 is discussed.