The benzylic deprotonation of tricarbonyl(eta(6)-1-tertbutoxycarbonyl-2,3-dimethylbenzene)chromium occurs preferentially at the ortho position, whereas the meta position is still reactive but to a lesser extent. X-ray study of the title compound, [Cr(CO)(3)(C10H10O2)], obtained in a very good yield, confirms this result and shows a strong hydrogen bond between neighbouring carboxy groups, The acid group and the phenyl ring are coplanar and the torsion angle between the phenyl ring and the vinyl group is 61.2 degrees(4).