New ferrocenyl heterometallic complexes of 2,7-diethynylfluoren-9-one

A new series of rigid-rod alkynylferrocenyl precursors with central fluoren-9-one bridge, 2-bromo-7-(2-ferrocenylethynyl)fluoren-9-one (1b), 2-trimethylsilylethynyl-7-(2-ferrocenylethynyl)fluoren-9-one (2) and 2-ethynyl-7-(2-ferrocenylethynyl)fluoren-9-one (3), have been prepared in moderate to good yields. The ferrocenylacetylene complex 3 can provide a direct access to novel heterometallic complexes, trans-[(η ⁵ -C ₅ H ₅ ) Fe(η ⁵ -C ₅ H ₄ ) C≡CRC≡CPt(PEt ₃ ) ₂ Ph] (4), trans-[(η ⁵ -C ₅ H ₅ ) Fe(η ⁵ -C ₅ H ₄ ) C≡CRC≡CPt(PBu ₃ ) ₂ C≡CRC≡C (η ⁵ -C ₅ H ₄ )Fe(η ⁵ - C ₅ H ₅ )] (5), [(η ⁵ -C ₅ H ₅ )Fe(η ⁵ - C ₅ H ₄ ) C≡CRC≡CAu(PPh ₃ )] (6) and [(η ⁵ -C ₅ H ₅ )Fe(η ⁵ - C ₅ H ₄ )C≡CRC≡CHgMe] (7) (R=fluoren-9-one-2,7-diyl), following the CuI-catalyzed dehydrohalogenation reactions with the appropriate metal chloride compounds. All the new complexes have been characterized by FTIR, ¹ H-NMR and UV-vis spectroscopies and fast atom bombardment mass spectrometry. The solid state molecular structures of 3, 5, 6 and 7 have been established by X-ray crystallography. The redox chemistry of these mixed-metal species has been investigated by cyclic voltammetry and oxidation of the ferrocenyl moiety is facilitated by the presence of the heavy metal centre and increased conjugation in the chain through the ethynyl and fluorenone linkage units.