Synthesis and structure of iron (III) and iron (II) complexes in S_4P_2 environment created by diethyldithiocarbamate and 1,2-bis(diphenylphosphino)ethane chelation: Investigation of the electronic structure of the complexes by M_ssbauer and magnetic studies

摘要

Iron (II) and iron (III) complexes, [Fe~(II)(DEDTC)_2(dppe)]_¤CH_2Cl_2 (1), [Fe~(II)(ETXANT)_2(dppe)] (2) (DED_TC = diethyldithiocarbamate, ETXANT = ethyl xanthate, dppe = 1,2-bis (diphenylphosphino) ethane), and [Fe~(III)(DEDTC)_2(dppe)] [Fe~(III)CI_4 (3) have been synthesized and characterized. Since 3 contains two magnetic centers, an anion metathesis reaction has been conducted to replace the tetrahedral FeCI_4~- by a non-magnetic BPh_4~- ion producing [Fe~(III)(DEDTC)_2(dppe)]BPh_4 (4) for the sake of unequivocal under_standing of the magnetic behavior of the cation of 3. With the similar end in view, the well-known FeCI_4- ion, the counter anion of 3, is trapped as PPMFe~(III)Cl_4] (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 Fe~(II) complexes, 1 and 2, are diamagnetic, the Fe~(III) 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 X_MT 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 M_ssbauer studies of 3 and 4. The M_ssbauer pattern of 1 exhibits a doublet site for diamagnetic (2-400 K) Fe~(II). The compounds 1, 2 and 4 encompass interesting cyclic voltammetric responses involving Fe~(II), Fe~(III) and Fe~(IV).