Synthesis, characterisation and properties of platinum(II) acetylide complexes of ferrocenylfluorene: novel soluble donor–acceptor heterometallic materials ‡

Abstract

Two new bis(acetylide)-functionalised ferrocenylfluorene complexes, 9-ferrocenylmethylene-2,7-bis(trimethylsilylethynyl)fluorene 1 and -2,7-bis(ethynyl)fluorene 2, have been prepared in good yield by condensation of ferrocenecarbaldehyde with 2,7-bis(trimethylsilylethynyl)fluorene and the subsequent desilylation of 1. Treatment of trans-[PtPh(Cl)(PEt₃)₂] with half an equivalent of 2 in CH₂Cl₂–NHPrⁱ₂, in the presence of CuI, at room temperature, gives the dimeric platinum(II) complex trans-[Ph(Et₃P)₂Pt–C[triple bond, length half m-dash]CRC[triple bond, length half m-dash]C–Pt(PEt₃)₂Ph] 3 (R = 9-ferrocenylmethylenefluorene-2,7-diyl) in 56% yield. Soluble polymeric trans-[{-Pt(PBuⁿ₃)₂-C[triple bond, length half m-dash]CRC[triple bond, length half m-dash]C-}_n] 4 has been obtained in good yield by the CuI-catalysed dehydrohalogenation of trans-[Pt(PBuⁿ₃)₂Cl₂] with 2 (1∶1 molar ratio) in an amine solvent. Optical measurements on the thin films indicated that there is a significant reduction in the bandgap value for polymer 4 (2.1 eV) as compared to that of trans-[{-Pt(PBuⁿ₃)₂-C[triple bond, length half m-dash]CRC[triple bond, length half m-dash]C-}_n] 5 (R = fluorene-2,7-diyl) (2.9 eV) without the ferrocenyl moiety, featuring the importance of donor–acceptor interaction in such conjugated systems. All the new compounds have been characterised by analytical, spectroscopic and electrochemical methods, and the single-crystal structures of 2, 3 and 5 have been established.

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