New rhenium(I) compounds containing the donor-acceptor diphosphine ligands 2-(ferrocenylidene)-4,5-bis(diphenylphosphino)4-cyclopenten-1,3-dione (fbpcd) and 2-(3-ferrocenylprop-2-ynylidene)-4,5-bis(diphenylphosphino)4-cyclopenten- 1,3-dione (fpbpcd): Elec

The diphosphine ligands fbpcd and fpbpcd react with BrRe(CO)3(THF)2 to furnish the diphosphine-substituted compounds fac-BrRe(CO)3(fbpcd) (2) and fac-BrRe(CO)3(fpbpcd) (3), respectively. The more highly conjugated fpbpcd ligand was prepared from 3-ferrocenylpropynal and 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) via a Knoevenagel condensation. 2 and 3 have been isolated and fully characterized by a combination of IR and NMR spectroscopies, mass spectrometry, and X-ray diffraction analysis in the case of 3. Cyclic voltammetric studies reveal well-defined 0/1+ and 0/1− redox couples for both new rhenium compounds, and the nature of the HOMO and LUMO levels is discussed relative to MO calculations at the extended Hückel level.