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Synthetic ferroverdins, NaFe(RQ) afford trinuclear M[Fe(RQ)] upon reaction with bivalent ions (M). A probable bonding mode is considered. Ferric ions oxidise ferroverdin to ferriverdin, Fe(RQ). Both fac and mer isomers can be observed for ferro- and ferriverdins but at equilibrium the preferred isomers are fac for ferro- and mer for ferriverdin. Mismatch in geometry with oxidation state gets spontaneously corrected by isomerisation. Equilibrium constants, isomerisation rates, redox potentials and EPR spectra are examined. A study on the pattern of isomer population as a function of oxidation for other 3d analogues of ferro- and ferriverdin is initiated. [ABSTRACT FROM AUTHOR]

The g-tensor theory of low-spin d configuration in octahedral fields having axial (tetragonal or trigonal) and rhombic distorsions is summarised. Illustrations taken from literature concern the following ruthenium(III) species: Ru(HO) (trigonal), Ru(bpy) (trigonal), the Creutz-Taube cation (axial + rhombic) and RuCl(HL) (L) (axial + rhombic: HL = isonitrosoketone). The rationalisation of distorsion parameters in terms of bonding is considered. [ABSTRACT FROM AUTHOR]

The structure and selected reactions of the title compounds are reviewed. Some highlights are as follows (L = conjugate base of phenylazoacetaldoxime). While PtL exist in cis and trans forms, PdL occurs only in the trans form. In the crystalline state cis-PtL consists of weakly held dimers (Pt. Pt 3.151 A) but trans-PtL consists of stacks of discrete molecules in the solid state. Trans- PdL displays a surprisingly large tetrahedral distorsion. The different metal-ligand bonds undergo selective cleavage by different reagents. Thus HCl and tertiary phosphines respectively cleave the M-N (oxime) and M-N (azo) bonds. Phosphine cleavage leads to interesting situations such as cone angle-dependent equilibria and fluxional behaviour. A rich redox chemistry consisting of successive reductions of the azo groups and of the metal are revealed electrochemically. Cis-PtL unlike trans- PtL undergoes a facile one-electron oxidation at low potentials. Another very curious reaction of cis-PtL is the process in which an aromatic ring is thermally hydroxylated at the expense of an oximato oxygen atom. The meaning and significance of the observations are discussed. [ABSTRACT FROM AUTHOR]