EVIDENCES OF ELECTRONIC EFFECTS IN THE VIBRATIONAL-SPECTRA OF SOME RHODIUM(II) CARBOXYLATE COMPLEXES

A series of dirhodium tetracarboxylate complexes, containing triphenyl phosphine as axial ligand was investigated by electronic and Raman spe ctroscopy, aiming to detect the influence of electronic effects of the carboxylate substituents on the nu1[nu(rhRh)[ and nu2[nu(RhO)] modes. When pairs of complexes with similar molecular weights are compared, as in the case of the cyclopentanecarboxylate and trifluoroacetate com plexes, the striking difference in the inductive character of the two species results in substantial shifts of the nu1 and nu2 modes as a co nsequence of variations in the corresponding force constants rather th an a simple mass effect as previously observed for non-substituted rho dium-carboxylates.