Infrared spectroscopic evidence is presented showing that photolysis of a variety of ring-substituted half-sandwich tetracarbonylvanadium complexes (ring: eta5-C5Me5, eta5-C5H4Me, eta5-indenyl, eta5-C5Cl5) in Ar and CH4 matrices at high dilution at ca. 12 K affords reversible CO ejection and partial ring dechelation. For the eta5-C5H4Me and eta5-C5Cl5, compounds, further photolysis led to dicarbonyl species. In N2 MatriCes reversible ring dechelation was aw observed but the CO loss species reacted with N2 to yield mono- and bis(dinitrogen) species. In CO matrices reversible ring dechelation was still observed but there was no evidence for CO uptake by these species resulting in complete ejection of the cyclopentadienyl rings. In 02 matrices photolysis of (eta5-C5Me5)V(CO)4 led to the formation of (eta5-C5Me5)V(CO)3(02) with a side-on bonded 02 ligand, ag confirmed using an O-18(2) matrix. In Ar matrices doped with H2S and tetrahydrofuran (THF), there was no evidence for uptake of the donor ligands. In poly(vinyl chloride) films photolysis Of (eta5-C5Me5)V(CO)4 also gave both the CO loss and the ring dechelation product at 12 K, but as the film was warmed, bands were observed which were consistent with the formation Of (eta5-C5Me5)V(CO)3(THF). The photoreactions at 12 K are discussed and compared to those of (eta5-C5H5)V(CO)4 and related to the preparative and mechanistic thermal and photochemical reactions at ambient temperatures. It is apparent that more credence should be given to ring dechelation/ring slippage pathways when reaction mechanisms are discussed.