Synthesis and structure of iron (III) and iron (II) complexes in S4P2 environment created by diethyldithiocarbamate and 1,2-bis(diphenylphosphino)ethane chelation: Investigation of the electronic structure of the complexes by Mössbauer and magnetic studies

Iron (II) and iron (III) complexes, [FeII(DEDTC)2(dppe)] · CH2Cl2 (1), [FeII(ETXANT)2(dppe)] (2) (DEDTC = diethyldithiocarbamate, ETXANT = ethyl xanthate, dppe = 1,2-bis (diphenylphosphino) ethane), and [FeIII(DEDTC)2(dppe)] [FeIIICl4] (3) have been synthesized and characterized. Since 3 contains two magnetic centers, an anion metathesis reaction has been conducted to replace the tetrahedral FeCl4− by a non-magnetic BPh4− ion producing [FeIII(DEDTC)2(dppe)]BPh4 (4) for the sake of unequivocal understanding of the magnetic behavior of the cation of 3. With the similar end in view, the well-known FeCl4− ion, the counter anion of 3, is trapped as PPh4[FeIIICl4] (5) and its magnetic property from 298 to 2 K has been studied. Besides the spectroscopic (IR, UV–Vis, NMR, EPR, Mass and XPS) characterization of the appropriate compounds, especially 2, others viz. 1, 3 and 4 have been structurally characterized by X-ray crystallography. While FeII complexes, 1 and 2, are diamagnetic, the FeIII systems, namely the cations of 3, and 4 behave as low-spin (S = 1/2) paramagnetic species from 298 to 50 K. Below 50 K 3 shows gradual increase of χMT up to 2 K suggesting ferromagnetic behavior while 4 exhibits gradual decrease of magnetic moment from 60 to 2 K, indicating the occurrence of weak antiferromagnetic interaction. These conclusions are supported by the Mössbauer studies of 3 and 4. The Mössbauer pattern of 1 exhibits a doublet site for diamagnetic (2–400 K) FeII. The compounds 1, 2 and 4 encompass interesting cyclic voltammetric responses involving FeII, FeIII and FeIV.The authors namely T.K.J., D.P.K., S.D. and R.B. thank Department of Science and Technology (DST), Govt. of India for financial assistance in the form of a Project (Project No. SR/S1/IC-12/2002). T.K.J. thanks DST and D.P.K. thank CSIR, Govt. of India, for fellowship. The magnetic and Mössbauer studies have been supported by the Centre Franco-Indien pour 1a promotion de 1a Recherche Avancee/Indo-French Centre for the Promotion of Advanced Research under Project No. 3108-3.Peer Reviewe