ISOMERISM AND REDOX PROPERTIES OF 1-FERROCENYL-1,3-BUTANEDIONATE COMPLEXES

The ferrocenyl diketone [(C5H5)Fe(C5H4)COCH2COCH3] has been used to fo rm neutral metal complexes of the 1-ferrocenyl-1,3-butanedionate ligan d [(C5H5)Fe(C5H4)COCHCOCH3](-): the aluminium complex of this ligand, [Al{(C5H5)Fe(C5H4)COCHCOCH3}(3)], has been characterised by H-1 and C- 13 NMR as a 2:3 mixture of fac and mer isomers, having C-3 and C-1 mol ecular symmetry respectively. Electrochemical studies show that each p eripheral 1-ferrocenyl-1,3-butanedionate ligand L of both (ML2)-L-II ( M = Co, Ni, Cu) and (ML3)-L-III (M = Al, Cr, Mn, Fe) complexes undergo es reversible one-electron oxidation at potential values essentially o verlapping each other. This means that the central metal ions prevent any electronic communication between the two or three ferrocene fragme nts. In addition to these reversible ferrocene-centred oxidations, the re are reversible one-electron reductions centred at M for MnL3 and Fe L3 (but not for CrL3 or AlL3), but the metal-centre reductions of (ML2 )-L-II are irreversible owing to further reactions following reduction . (C) 1998 Elsevier Science Ltd. All rights reserved.