Transition Metal Tetrathiosquarates: One-Dimensional Linking in the Fe(II) salt FeC4S4·6 H2O
Résumé
The addition of a solution of tetrathiosquarate using K2C4S4·H2O to an aqueous solution of Fe(II) chloride yields mainly an insoluble, brown-black, amorphous material, but from the filtrate the Fe(II) salt FeC4S4·6H2O can be isolated as dark red crystals in low overall yield. The crystal structure determination shows the presence of C4S42– ions, which act each as bidentate chelating ligands towards two Fe2+ ions forming linear one-dimensional chains [Fe(H2O)2(C4S4)]n with two aqua ligands coordinated in trans positions of the octahedral FeS4(OH2)2 coordination polyhedron. Additional water molecules link the chains via O–H···O bridges to a three dimensional network. The C4S42– ions are planar but show substantial distortion from ideal D4h symmetry caused by the chelating coordination. The infrared and Raman spectra show bands typical for the molecular building units. The single-crystal vis/nir absorption spectrum of FeC4S4·6H2O reveals a weak absorption around nue = 6100 cm–1 which is assigned to the transition 5T2g → 5Eg. Above 14000 cm–1 the spectrum is completely dark, in agreement with the deep red colour of the compound. The magnetic properties of FeC4S4·6H2O show the expected single-ion effects for high-spin Fe(II) centers in a tetragonally distorted coordination environment and antiferromagnetic coupling within the coordination polymer. The quantitative analysis results of the susceptibility data concur with the ligand field parameters estimated from optical spectroscopy studies.
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