Synthesis and spectroelectrochemistry of transition metal carbonyls with 1,1′-bis(phosphino)metallocene ligands

The oxidative electrochemistry of group VI and group VII metal carbonyl compounds containing 1,1′-bis(phosphino)ferrocene ligands with the general formula [M(CO)4(P∩P)] (M = Cr, Mo, or W, P∩P = 1,1′-bis(diisopropylphosphino)ferrocene (dippf) or 1,1′-bis(dicyclohexylphosphino)ferrocene (dcpf)) and [M(CO)3Br(P∩P)] (M = Mn, P∩P = 1,1′-bis(diphenylphosphino)ferrocene (dppf) or dippf; M = Re, P∩P = dppf, dippf or dcpf) was investigated. Two reversible waves were observed in the electrochemistry of the Cr compounds, while the other compounds exhibited one wave with varying reversibility. The compounds were examined using spectroelectrochemistry, which was particularly useful in assigning the two waves in the Cr species. In addition, the X-ray structures of [Cr(CO)4(dippf)], [Cr(CO)4(dcpf)] and [Mn(CO)3Br(dippf)] were determined. The %Vbur values for dippf, dcpf and other bidentate phosphines have been calculated for these pseudo-octahedral Cr and Mn compounds and these structural studies have been supplemented by DFT optimized geometries for the Cr complexes.