Raman and infrared spectroscopic and theoretical studies of dinuclear rhenium and osmium complexes, M2(O2CCH3)4X2 (MÂ =Â Re, Os; XÂ =Â Cl, Br)

Infrared, far-infrared and Raman spectra of Re2(O2CCH3)4X2 (X = Cl, Br) and Re2(O2CCD3)4Cl2 have been recorded and fully assigned together with Os2(O2CCH3)4Cl2 and its deuterated derivative on the basis of IR and Raman activities, isotope shifts and normal-coordinate analysis It as shown that the metal-metal bond strength increases as ReCl < ReBr < OsCl, while metal-oxygen stretching force constants exhibit an opposite tendency. The Re-Re stretching force constants showed a reasonable correlation with the Re-Re bond distances for 18 rhenium complexes.