Infrared spectroscopy, coupled with matrix isolation and theoretical calculations, has been used to reexamine the photochemical reaction of C2H2 with CrCl2O2, as well as to extend the study to the reaction of C2H2 with OVCl3. Two sets of product bands were observed, even at very high sample dilutions, and were assigned on the basis of density functional calculations to the eta(1) end-on complex of ketene with Cl2CrO and the eta(2)(C=C) side-on complex, contrary to a previous report. Isomerization of the less stable eta(1) complex to the more stable eta(2) (C=C) complex was observed upon continued irradiation of the matrix with light of lambda > 300 nm. A second possible eta(2) complex (side-on to the C=O bond) was not observed, nor was evidence obtained for the five-membered metallocycle, which was calculated to be approximately as stable as the eta(1) complex. The photochemical reaction of C2H2 with OVCl3 followed a very similar course, although with lower overall yield.