Thermal studies by TG and DTG on some homobinuclear dihalide-bridged iron(Ill) complexes of the general type [Fe(S2CNR2)2X]2~-X~) were carried out in air and nitrogen atmospheres. 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 respect, a general mechanism accounting for the variety of products formed has been proposed [3].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. Consequently, the binuclear complexes have been proved [7] to be potential carriers of activated molecular halogens and therefore very reactive in halogentransfer reactions.As an extension of our previous work [8][9][10] on thermal studies of metal diothiocarbamate complexes, a thermal investigation of the dihalide-bridged

. 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]

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In the presence of a catalytic amount of iron(iii) halogenobisdithiocarbamates, the addition of molecular halogens to alkenes occurs rapidly to afford cis-addition products.

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