Spectral and bonding properties of bis(N,N-disubstituted-dithiocarbamato)iron(III)dihalide complexes studied by experimental and EHMO quantum-chemical methods

Abstract

. Can. J. Chem. 63, 3249 (1985). A new series of homobinuclear iron(II1) halobisdithiocarbamate complexes antiferromagnetically coupled through a molecular halogen bridging unit has been synthesised and studied. The complexes have been characterized chemically and by spectroscopic methods and magnetic susceptibility measurements. The volatility characteristics and thermogravimetric analysis data for the new compounds are also studied. Finally, quantum-chemical calculations have been used to provide a qualitative guide to the possible pathways for the superexchange processes observed in these molecular magnetic systems, as well as to interpret their electronic spectra. [Traduit par le journal]

Thermal decomposition of some homobinuclear dihalide-bridged iron(III) complexes

“…The dihalide-bridged iron(Ill) complexes were prepared as previously reported [1,2]; they were recrystallized several times from methylene chloridecyclohexane mixtures, and dried under vacuum. The thermal decomposition was carried out on a TGS-2 Perkin-Elmer thermobalance at a heating rate of 5 deg/min, in the temperature range 20-1000 ~ with a sample mass of 5 mg and ~-A120 3 as reference.…”

“…The apparent activation energies were determined by graphical methods and the TTN temperatures were calculated from the TG profiles. Finally, a possible mechanism of the decomposition is suggested on the basis of the pyrolysis and mass spectral data.In previous papers, results have been reported on the reactions of molecular halogens (X~) with the square-pyramidal complexes [Fe(S2CNR2)2X] (X = CI, Br, I) [1][2][3]. The salient feature of these reactions is the effect of the alkyl substituent in the dithiocarbamato ligand on the composition of the products obtained [4,5].…”

“…In this paper, we focus our attention on the binuclear iron(Ill) complexes formulated [2] as [Fe(S2CNR2)2X]2(/~-X~), where R = Me, Et, pri; X' = Br, I. M6ssbauer and magnetic measurements on this very interesting class of compounds, as well as an X-ray crystal structure determination [6] of another derivative of this series containing the pyrrolidinyldithiocarbamato ligand, have established the presence of the molecular halogen in the form of a bridging unit mediating the formation of weakly coupled dimers with antiferromagnetic interaction. In particular, the molecular halogen interacts weakly in an end-on fashion with the halide ligand of the mononuclear complexes, forming an extended tetratomic bridging unit, {X-X'-X'-X} 2-, between the two paramagnetic centres.…”

Mass spectral and thermogravimetric studies of some iron(III) binuclear complexes with bridging thiuram disulfide ligands

“…Fragmentation patterns are given and possible mechanisms are discussed.In addition to the variety of products formed [1][2][3][4] during the reaction of iron(Ill) halobisdithiocarbamates, [Fe(Rzdtc)2X ], with halogens, X' 2, some novel homobinuclear iron(Ill) complexes with two different coordination spheres around the magnetic centers have also been synthesized and studied [5], The formation of these products, formulated as Fe2(R2dtc)2(tds~ [R = Me; R 2 = Pyrr; X = CI, Br; and X' = Br, I], depends on the natures of both the molecular halogen and the reagent complex, as well as on the reaction conditions. In particular, the proposed mechanism [5] which accounts for the synthesis of these compounds involves as a first step the formation of the corresponding dihalide-bridged dimers, [Fe(R2dtc)zX]2(/I-X'2).…”

“…In particular, the proposed mechanism [5] which accounts for the synthesis of these compounds involves as a first step the formation of the corresponding dihalide-bridged dimers, [Fe(R2dtc)zX]2(/I-X'2). Analogous iron(Ill) complexes have already been isolated and their structures were established on the basis of spectroscopic [1, 3,4] and X-ray crystal structure [6] determination methods, as well as the results of thermoanalytical studies [7]. Depending on the redox capacities of both the halogens and the dithiocarbamato ligands, an intramolecular electron transfer could take place resulting in the oxidation of half of the dithiocarbamate groups into thiuram disulfide.…”