Chemical and electrochemical oxidation studies on new copper(I) ferrocenyl-functionalised β-diketonates

• Three new ferrocene (Fc)-containing copper(I) β-diketonates have been prepared.
• Chemical oxidation of 3a led to [Cu(FcCOCHCOCH3)(μ-OEt)]2 and [CuII(FcCOCHCOCH3)2].
• Structures of [Cu(FcCOCHCOFc)(PPh3)2] and [Cu(FcCOCHCOCH3)(μ-OEt)]2 were solved.
• Electrochemical oxidation led to [CuII(FcCOCHCOR)2] and [CuI(PPh3)4]+.
• Structural rearrangements follow Cu(I) oxidation before ferrocenyls are oxidised.

A two-step synthetic methodology for the preparation of bis(triphenylphosphine) copper(I) β-diketonates, [Cu(FcCOCHCOR)(PPh3)2] (R = CH3 (3a), CF3 (3b) and Fc = Fe(η5-C5H4)(η5-C5H5)) (3c)) is reported using K[FcCOCHCOR] and [CuCl(PPh3)2] (2) as the key starting materials. Organometallics 3a–3c are stable under inert gas atmosphere. However, in ethanol and air it was shown that 3a decomposes to the dimeric μ-ethoxy copper(II) β-diketonate [Cu(FcCOCHCOCH3)(μ-OEt)]2 (4) and [Cu(FcCOCHCOCH3)2] (5a), respectively. The molecular structures of 3c and [Cu(FcCOCHCOCH3)(μ-OEt)]2 (4) in the solid state are reported showing that the coordination geometry about copper(I) for 3c is best described as a somewhat distorted tetrahedron, while the copper(II) ions in 4 possess a square-planar environment constructed from two chelated FcCOCHCOCH3− ligands and two OEt groups. From an electrochemical study in CH2Cl2/0.1 mol dm−3 [nBu4N][B(C6F5)4], it was found that upon the anaerobic electrochemical irreversible oxidation of the Cu(I) centres to Cu(II), complexes 3a–3c lost both PPh3 ligands and formed square planar [CuII(FcCOCHCOR)2] complexes 5a–5cbefore the ferrocenyl centres are oxidised; homoleptic, cationic [CuI(PPh3)4]+ (6) is also formed. The CuI ion of 6 is oxidised after the ferrocenyl centres of 5a–5c.

The synthesis of new ferrocenyl-containing copper(I) β-diketonates of type [Cu(FcCOCHCOR)(PPh3)2] (R = CH3, CF3, Fc), their reactivity towards electrochemical (all R) and chemical oxidations (R = CH3) to produce copper(II) complexes [Cu(FcCOCHCOCH3)2] and [Cu(FcCOCHCOCH3)(μ-OEt)]2 are discussed; the solid state structures of the latter complex and [Cu(FcCOCHCOFc)(PPh3)2] are reported.Figure optionsDownload as PowerPoint slide