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

摘要

A two-step synthetic methodology for the preparation of bis(triphenylphosphine) copper(I) β-diketonates, [Cu(FcCOCHCOR)(PPh_3)_2] (R =CH_3 (3a), CF_3 (3b) and Fc = Fe(η~5-C_5H_4)(η~5-C_5H_5)) (3c)) is reported using K[FcCOCHCOR] and [CuCl(PPh_3)_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(FcCOCHCOCH_3)(l-OEt)]_2 (4) and [Cu(FcCOCHCOCH3)2] (5a), respectively. The molecular structures of 3c and [Cu(FcCOCHCOCH3)(l-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 FcCOCHCOCH_3~- ligands and two OEt groups. From an electrochemical study in CH_2Cl_2/0.1 mol dm~(-3) [~nBu_4N][B(C_6F_5)_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 [Cu~(II)(FcCOCHCOR)_2] complexes 5a-5c before the ferrocenyl centres are oxidised; homoleptic, cationic [Cu~I(PPh_3)_4]~+ (6) is also formed. The Cu~I ion of 6 is oxidised after the ferrocenyl centres of 5a-5c.