Infrared, far-infrared and Raman spectra of Re2(O2CCH3)4X2 (X=Cl, Br) and Re2(O2CCD3)4Cl2 have been recorded. Assignments of the vibrational spectra of Os2(O2CCH3)4Cl2 and its deuterated derivative have been completed together with the Re complexes on the basis of normal-coordinate analysis. Force constant calculation was made for the acetate ion as well as for a four-atomic unit (with the CH3 and CD3 groups considered as point masses) using optimized masses of 16.7, 17.8, 20.5 and 21.6 for 12CH3, 13CH3, 12CD3 and 13CD3 groups, respectively. The force constants of the acetate ion have been adopted to the starting force field of the M2(O2CCH3)4X2 type complexes. The metal–halide (0.889, 0.997 and 1.286Ncm−1) and metal–metal stretching (3.32, 3.34 and 3.57Ncm−1) force constants were obtained for Re2(O2CCH3)4Cl2Re2(O2CCH3)4Br2 and Os2(O2CCH3)4Cl2 complexes, respectively. It was shown that the so-called diatomic approximation in most cases overestimates the M–M stretching force constants by 30–40%. Much better correlation has been obtained to fit these force constants, which produced values very close to those obtained by full normal-coordinate calculations. The Re–Re stretching force constants showed a reasonable correlation with the Re–Re bond distances for 18 rhenium complexes.