Pascal Michaud

Improved synthesis and electronic structure of the 19-and 20-electron complexes [Fe(η6-C6Me6)2]n+, n= 1,0

The 19- and 20-electron complexes [Fe(η6-C6Me6)2]n(n= 1,0) are best synthesized by Na/Hg reduction of [Fe(η6-C6Me6)2]2[PF6–]2; the extremely negative value of the quadrupole splitting for [Fe(η6-C6Me6)2], comparison of Mossbauer parameters of [Fe(η6-C6Me6)2]n+(n= 0,1,2), and the temperature dependence of the quadrupole splitting for [Fe(η6-C6Me6)2]+ indicate high metal character for the antibonding e1* orbital and rhombic distortion of the Jahn–Teller-active FeI complex.

N–H activation by O2via O2˙– in FeI(η5-C5H5)(η6-C6Me5NH2) and subsequent formation of an amino-acid zwitterion by mild reaction with CO2

The thermally unstable complex FeI(cp)(C6Me5NH2), (cp =η5C5H5) reacts with 1/4 mol of O2 at –10 ° C in toluene to give FeII(cp)(η5C6Me5NH), the N–H being activated by O2, consistent with an electron transfer mechanism O2→ O2˙–; the latter complex reacts with CO2(20 °C, 1 atm) providing Fe+(cp)(η6-C6Me5NHCO2–).

Single electron reduction of tetracyanoquinodimethane, TCNQ, and phenazine and two electron reduction of TCNQ by organo-iron electron reservoir complexes

cp(C6Me6)FeI, (1), (cp = C5H5) reacts with one equivalent of phenazine and tetracyanoquinodimethane, TCNQ, to give the single electron transfer salts cp(C6Me6)Fe+, phenazine–, (2), and cp(C6Me6)Fe+, TCNQ–, (3), whereas addition of TCNQ to 2 equivalents of (1) or cp(PriPh)FeI gives the crystalline salts {cp(arene)Fe+}2 TCNQ2–, (4) and (5); (C6Me6)2Fe0, (7), also reacts with one equivalent of these acceptors to give (C6Me6)2Fe+, phenazine–, (8) and (C6Me6)2Fe+ TCNQ–, (9).

Influence of the nature and presence of the solvent on H atom abstraction by O2 and electron transfer O2 → O2⨪ during the aerobic oxidation of electronrich Fe(I) sandwiches

Abstract We have recently designed organometallic electron reservoirs η 5 -C 5 R 5 Fe(I)η 6 -C 6 R′ 6 to serve as powerful electron-tranfers reagents in stoichiometric (activation of CH bonds by O 2 and catalytic (redox catalysis of NO − 3 → NH 3 ) process [1, 2]. We wish to emphasize here dramatic roles of the nature and presence of the solvent on the reactions of CpFe(I)C 6 R 6 with O 2 (Cp = C 5 H 5 or C 5 Me 5 , R = H Me or Et). In pentane CpFe(I)C 6 Me 6 reacts instantaneously with air at 20 °C with the loss of a H atom from CH 3 group according to eqn. 1: In DME, however, simple electron transfer proceeds, according to eqn. 2: Evidence is given as eqn. w being the first step of eqn. 1, so that the H atom abstraction is an electron transfer to O 2 followed by deprotonation by superoxide radical anion O 2 −. In the solid state, aerobic oxidation occurs according to eqn. 1 at the surface of mono or polycrystalline samples with complete lattice rearrangement. CpFe(I)C 6 H 6−n Me n (n = 1 to 5) react with O 2 in pentane (or without O 2 in the solid state) without H atom abstraction nor even electron transfer to O 2 despite the large difference (1 volt) between the organometallic redox potential and that of O 2 /O 2 −. Instead, dimerization is observed (eqn. 3) whereas in DME electron transfer proceeds as in eqn. 2. The Mossbauer spectra of the Fe(I) sandwiches and of those of the various oxidized Fe(II) forms afford following the aerobic process in the solid state. This helps delineating the role of the solvent in sandwich-sandwich and sandwich-O 2 interactions.