Chemical oxidation of (TMP)Mn(III)(Cl) (TMP = the tetramesitylporphyrinato dianion) by Fe(ClO(4))(3) leads to the porphyrin-oxidized product (TMP(*)(+))Mn(III)(ClO(4))(2). Magnetic measurements and EPR spectroscopy show that the total spin of the complex changes from S = (5)/(2) at high temperature to S = (3)/(2) at low temperature. Ligand exchange of the perchlorato ligands in (TMP(*)(+))Mn(III)(ClO(4))(2) by chloride anions is accompanied by a change of the oxidation site from porphyrin to metal, resulting in (TMP)Mn(IV)(Cl)(2). This high-valent-metal complex can effect chlorine atom transfer to olefins, as well as to dimedone and chlorodimedone, natural substrates of chloroperoxidases.

Oxidation of trans-I−NiIIL, or NiIILout, by •OH radicals was carried out by irradiating N2O saturated solutions containing the complex, prepared by mixing equimolar concentrations of the metal ion and the ligand at pH 3.50. The intermediate thus formed has a strong absorption band at 310 nm and is stable for hours. That this unstable complex is a nickel(III) species was verified by EPR spectroscopy and its chemical reduction with ascorbic acid, which was found to be instantaneous. The most striking feature of the oxidation by •OH radicals, which are powerful single electron oxidizing agents, is that it produces a nickel(III) species which is different from the electrochemically produced one as manifested by their absorption spectra and EPR signals. The radiolytically produced nickel(III) species undergoes decarboxylation leading to the production of CO2, CH2O, NiIIL‘ and NiIIL (L‘ = the new ligand produced after oxidative degradation of one of the N-acetate groups of the ligand). The electrochemical oxidation of trans-I−NiIIL, or NiII outL, proceeds via the degradation of two of the acetate arms on average. The yield of CH2O is ∼2.0 mol per mole of the nickel(II) complex in electrochemical oxidations. These observations point out that the two techniques produce different nickel(III) complexes which do not interconvert. The mechanisms leading to the production of NiIIL‘ (oxidation by •OH radicals, radiolytically) and NiIIL‘‘ (electrochemically) differ from that proposed in the literature.

The synthesis and the crystal structure of the first compound containing Nb(3) triangular clusters bonded to fluorine ligands are presented in this work. The structure of Nb(3)IF(7)L(NbL(2))(0.25) with L = O and F, determined by single-crystal X-ray diffraction, is based on a Nb(3)I(i)F(i)(3)F(a)(8)L(a) unit and a NbL(6) octahedron (tetragonal, space group I4/m, a = 13.8638(3) A, c = 8.9183(2) A, V = 1714.14(7) A(3), Z = 8). Two crystallographic positions (noted L5 and L6) are randomly occupied by fluorine and oxygen with two different F:O occupancies. These L ligands build an octahedral site for a single niobium atom, located between the units. The four L5 ligands of the NbL(6) octahedron are shared with four Nb(3) cluster units, while the two other L6 ligands are terminal. The Nb(3) cluster is face-capped by one iodine and edge-bridged by three fluorine ligands. Two of the three niobium atoms constituting the cluster are bonded to three additional apical fluorine ligands, while the third one is bonded to two fluorines and one L5 ligand. The Nb(3) cluster is linked to six adjacent ones via all the apical fluorine ligands. The developed formula of the unit is therefore Nb(3)I(i)F(i)(3)F(a)(-)(a)(8/2)L(a) according to the Schäfer and Schnering notation. The oxidation state of the single niobium and the random distribution of fluorine and oxygen on the two L sites will be discussed on the basis of structural analysis, the bond valence method, and IR and EPR measurements. The structural results will be compared to those of previously reported niobium compounds containing NbF(6) or Nb(F,O)(6) octahedra.