Vibrational spectroscopy studies and density functional theory calculations on square-planar vinylidene, carbonyl and ethylene rhodium(I) complexes

Density functional theory (DFT) calculations have been carried out for trans-[RhF(CCH2)(PMe3)2] (5), trans-[RhF(CO)(PMe3)2] (6) and trans-[RhF(C2H4)(PMe3)2] (7) which serve as model compounds for the analysis of the vibrational structure of related rhodium (I) compounds. The calculated structures were in good agreement with the geometries determined from the experimental data of related compounds. The calculated vibrational modes have been used to classify the bands found in the Raman spectra of the rhodium (I) complexes: trans-[RhF(CCH2)(PiPr3)2] (1), trans-[RhF(13C13CH2)(PiPr3)2] (2), trans-[RhF(CO)(PiPr3)2] (3) and trans-[RhF(C2H4)(PiPr3)2] (4). The comparison of the vibrational behavior of the vinylidene complexes 1 and 2 allow for a characterization of the RhC stretching mode. The IR and FT-Raman spectra of complexes 1–4 exhibit one vibrational mode between 425 and 465 cm−1 with strong to medium intensity. This band can be assigned to the ν(RhF) mode.