Synthesis and spectroscopic properties of Re(R)(CO)3(α-diimine) (R = alkyl; α-diimine = R'-pyCa, R'-DAB) complexes. Crystal structure of Re(Me)(CO)3(iPr-DAB)

Article abstract of DOI:10.1016/0022-328X(95)05392-3

The synthesis, structure and spectroscopic properties of several complexes of the type Re(R)(CO)3(α-diimine) (R = alkyl) are reported.The structure of Re(Me)(CO)3(ⁱPr-DAB) has been determined by a single-crystal X-ray diffraction study.The molecule has a distorted octahedral geometry, with the three carbonyls in a fac-geometry.The complexes possess strong absorption bands in the visible region which are assigned to MLCT transitions with the aid of resonance Raman spectroscopy; the Raman spectra do not provide any evidence for a ?(Re-R) <*> ?^*(α-diimine) transition within this absorption band.The UV-vis spectrum of Re(Bz)(CO)3(ⁱPr-DAB) (Bz = benzyl) shows a distinct shoulder at the low-energy side of the visible band, which is attributed to the interaction between the d?(Re)-orbitals and the ?-orbitals of the benzyl group.The UV-photoelectron spectrum of Re(Me)(CO)3(ⁱPr-DAB) shows that ?(Re-Me) has a higher ionization potential than the d?(Re)-orbitals, a result that is of importance for the interpretation of the photochemical behaviour of this complex. Keywords: Raman spectroscopy; Crystal structure; Rhenium; Photoelectron spectroscopy; Diimine; Alkyl