1,1′-Bis(diphenylphosphino)ferrocene bridging two mono(cyclopentadienyl) cobalt moieties: Synthesis, structure, electrochemistry and DFT studies

Reaction of [Co(η5-C5H5)(CO)2], 1, with 1,1′-bis(diphenylphosphino)ferrocene (dppf) yields the new trinuclear complex [Co(η5-C5H5)(CO)]2(μ-dppf), 2, which was structurally characterised by single crystal X-ray diffraction and showed two Co(η5-C5H5)(CO) moieties covalently linked by a dppf bridge. Electrochemical studies in dichloromethane revealed that both Co(I) and Fe(II) in the precursors were oxidized to Co(II)/Co(III) and Fe(III), respectively. On the other hand, in 2 the two first oxidation waves were assigned to Co, the Fe(II) centre requiring a higher potential than in free dppf. DFT calculations showed that the HOMOs of 2 were localised in the Co fragments, owing to the destabilisation of the Co(η5-C5H5)(CO) orbitals after binding dppf.

Graphical abstract[Co(η5-C5H5)(CO)2] reacts with dppf to form the trinuclear [Co(η5-C5H5)(CO)]2(μ-dppf). This complex oxidizes at Co(I), as reflected in the HOMO shown in the picture.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Formation of a trinuclear complex with dppf bridging two Co(I) centres. ► Electrochemistry studies show several oxidation processes. ► DFT calculations show the localisation of the HOMO in cobalt.