The matrix isolation technique has been combined with infrared spectroscopy to isolate, identify, and characterize the initial intermediates in the thermal and photochemical reactions of OVCl3 with CH3SH. The thermal reaction proceeds through formation of a 1:1 complex that is characterized by perturbations to the -VCl3, -V=O, and S-H stretching modes, as well as the -CH3 rocking and bending modes. The photochemical reaction leads to HCl elimination from the initial 1:1 complex, and formation of Cl2V(O)SCH3. Additional support for the species identification and vibrational band assignments comes from isotopic substitution. Density functional calculations (B3LYP/6-311G+(d, 2p)) were carried out to confirm the experimental band assignments for this latter species. Efforts to study the thermal reaction beyond formation of the initial complex were unsuccessful, despite pyrolysis at temperatures as high as 300 degreesC prior to sample deposition.