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

Hajba, László and Mink, János and Kühn, F. E. (2006) Raman and infrared spectroscopic and theoretical studies of dinuclear rhenium and osmium complexes,M2(O2CCH3)(4)X2 (M = Re, Os; X = Cl, Br). INORGANICA CHIMICA ACTA, 359 (15). pp. 4741-4756. ISSN 0020-1693

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Abstract

Infrared, far-infrared and Raman spectra of Re-2(O2CCH3)(4)X-2 (X = Cl, Br) and Re-2(O2CCD3)(4)Cl-2 have been recorded. Assignments of the vibrational spectra Of OS2(O2CCH3)(4)Cl-2 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 (CH3)-C-12, (CH3)-C-13, (CD3)-C-12 and (CD3)-C-13 groups, respectively. The force constants of the acetate ion have been adopted to the starting force field of the M-2(O2CCH3)IXI type complexes. The metal-halide (0. 889, 0.997 and 1.286 N cm(-1)) and inetal-metal stretching (3.32, 3.34 and 3.57 N cm(-1)) force constants were obtained for Re-2(O2CCH3)(4)Cl2Re2(O2CCH3)(4)Br-2, and OS2(O2CCH3)(4)Cl-2 complexes, respectively. It was shown that the socalled 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.

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