The pressure-tuning Raman spectra of the two methylbenzoate complexes, (g 6 -C 6 H 5 CO 2 CH 3 )Cr(CO) 2 (CX) (X ¼ O, S), have been examined up to $35 kbar. Structural changes occurred for both complexes in the 10-15 kbar pressure range, most probably as the result of second-order phase transitions. From the observed pressure dependences, replacement of a CO group in the piano-stool (g 6 -C 6 H 5 CO 2 CH 3 )Cr(CO) 3 molecule by a CS group has a marked influence on the Cr-arene ring vibrational modes, and the arene ring clearly plays a role in determining the nature of the Cr-CO and Cr-CS bonding interactions.