Orbital ground states and crystal field splittings in some octahedrally coordinated high-spin ferrous complexes

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The iron(II) sulfonates Fe(CF3SO3)2 and Fe(p-CH3C6H4SO3)2 have been prepared and on the basis of vibrational and electronic spectra and magnetic and MÖssbauer data have been assigned a layer lattice structure involving hexacoordinated iron(II) and terdentate bridging anions. The FeO6 chromophore in these compounds is distorted by a trigonal elongation along the C3 axis. Fe(CH3SO3)2 has been obtained in two isomeric forms, one having a trigonal elongation of the FeO6 chromophore, the other a trigonal compression. No structural isomerism has been found for the other iron(II) sulfonates; however, evidence for such isomerism in methanesulfonates of cobalt(II) and zinc(II) is presented. While Fe(CF3SO3)2 and Fe(p-CH3C6H4SO3)2 appear to be magnetically dilute the presence of antiferromagnetic coupling in both forms of Fe(CH3SO3)2 is indicated. The iron(III) sulfonates, Fe(CF3SO3)3, Fe(p-CH3C6H4SO3)3, and Fe(CH3SO3)3, have been prepared and all three are magnetically concentrated exhibiting magnetic moments which are significantly less than 5.92 BM and which decrease with decreasing temperature.

Section: Methodsmentioning

confidence: 99%

Synthesis and structural studies of iron(II) and iron(III) sulfonates

Haynes¹,

Sams²,

Thompson³

1981

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“…Electronic spectra (3.8-30 kK) were recorded on samples mulled in Nujol using a Cary 14 spectrophotometer. 5 7~e Mossbauer spectra were obtained as reported previously (30). Samples were contained in Nylon holders sealed with epoxy resin.…”

Section: Spectroscopymentioning

confidence: 99%

Structural, magnetic, and spectroscopic studies of tetrakis(pyridine) complexes of iron(II) sulfonates

Haynes¹,

Rettig²,

Sams³

et al. 1986

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. 64, 429 (1986).The iron(I1) complexes Fe(NC5H5)4(RS03)2 where R = CF3, CH,, and p-CH3C6H4 have been prepared and their crystal structures determined by single crystal X-ray diffraction. Cryst$ of trans-bis(methanesulfonato-O)tetrakis(pyridine)iron(II) are monoclinic, a = 16.524(2), b = 9.1 127(6), c = 18.684(2) A, P = 109.903(6)", Z = 4, space group Pn. The structure was solved by conventional heavy-atom methods and was refined by full-matrix least-squares procedures to R = 0.034 and R,, = 0.038 for 4243 reflections with I 2 3u(4. Crystals of trans-bis(trifluoromethanesulfonato-O)tetrakis(pyridine)iron(II) are monoclinic, a = 10.456(1), b = 9.2981(8), c = 14.625(2) A, P = 96.372(6)", Z = 2, space group Pn. Structure solved and refined as above to R = 0.036, and R,, = 0.037 for 1483 reflections with 1 2 3u(4. Crystals of transbis(p-toluenesulfonato-O)tetrakis(pyridine)iron(II) are orthorhombic, a = 40.818(2), b = 9.8722(6), c = 17.3544(7) A, Z = 8, space group Fdd2. The structure was solved by Patterson and Fourier syntheses and was refined by full-matrix least-squares procedures to R = 0.030 and R,, = 0.032 for 1851 reflections with 1 2 3u(l). All three structures show discrete octahedral molecules with monodentate trans-coordinated sulfonate groups. Two crystallographically independent molecules are observed in the R = CH3 structure, the difference between them involving the orientation of the CH3S03 groups with respect to the 0-Fe-0 vector. The FeN402 chromophore in each compoundo is a tetragonally compressed octahedron (approximate D4,, Dans le trois structures, on retrouve des molCcules octaCdriques individuelles avec des groupements sulfonates monodentates coordonntes en trans. Dans la structure oh R=CH3, on observe deux moltcules qui sont cristallographiquement indtpendantes; la difftrence entre les deux implique I'orientation des groupements CH3S03 par rapport au vecteur 0-Fe-0.Dans chacun des composts, le chromophore FeN402 est un octatdre qui est comprimt d'une faqon tttragonale (symttrie approximative D4)!) et dans lequel les distances Fe-N moyennes sont 2,21, 2.23 et 2,24 A alors que les distances Fe---0 sont 2,11, 2,06 et 2,08 a respectivement pour les derives CF3, CH3 et p-CH3C6H4. On a CtudiC les composts en faisant appel aux spectroscopies vibrationnelles, tlectroniques et de Mossbauer, i des mesures de susceptibilitt magnttique et i la calorimttrie de balayage difftrentiel. Les valeurs des dtdoublements quadrupolaires obtenus a partir des spectres de Mossbauer indiquent que les trois composts existent dans un ttat fondamental 5B2,; on a analysC les donnCes de susceptibilitC magnttique (de 3 10a 4,2 K) i l'aide des modtles tant de champ cristallin que de dtdoublement i champ ztro en faisant I'hypothtse que 1'Ctat fondamental est bien celui-18.[Traduit par le journal] IntroductionWe had earlier utilized spectroscopic and magnetic techThe study of the coordinating properties of sulfonate anions, niques to investigate the coordination of Sulfonate anions in RS03-, is of interest for a number of re...

“…A detailed fit of the temperature dependence of the Mossbauer quadrupole splitting in terms of a crystal field model which included spin-orbit and spin-spin coupling, showed that the axial crystal field splitting 3Ds was 455 cm-I (2), with the ground doublet separated by 110 cm-' from the next lowest lying spin-orbit-split state. spectrum broaden asymmetrically, signaling the onset of paramagnetic hyperfine splitting (1,2). Mossbauer measurements at 4.2 K in applied magnetic fields ranging from 1 to 50 kG have unequivocally confirmed the existence of slow spin relaxation in the complex (3).…”

Section: Inkrodlactionmentioning

confidence: 91%

“…in which the sain-lattice relaxation rate at low In a recent study (1,2) of some octahe-temperatures is slow compared to the nuclear drally coordinated high-spin iron(I1) complexes, Larmor precession frequency. Thus, at temperaFe(pyO),(ClO,), (pyO = C,H,E\IO) was found tures below 30 K the two lines of the Mossbauer to have an unusual orbital ground state.…”

Section: Inkrodlactionmentioning

confidence: 99%

“…Electronic spectra over the range 5-33 kK were obtained on samples mulled in NLIJO~ and hexachlorobutadiene, using a Cary model 14 spectrophotometer. Magnetic susceptibility and S7Fe Mossbauer spectra were measured as fully described elsewhere (2). The Doppler velocity scale was calibrated with a metallic iron foil absorber, and isomer shifts are quoted relative to the centroid of the iron foil spectrum.…”

Section: Inkrodlactionmentioning

confidence: 99%

See 1 more Smart Citation

Orbital ground state, crystal field splittings, and magnetic hyperfine interactions in iron(II) fluorosulphate

Sams¹,

Thompson²,

Tsin³

1977

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Magnetic susceptibilities between 80 and 300 K and 57Fe Mössbauer parameters between 4.2 and 295 K are reported for Fe(SO3F)2. These data have been analysed via a crystal field model including spin–orbit and spin–spin coupling. The compound is trigonally distorted by an elongation along the [111] axis of the FeO6 octahedron, and the ground state is the orbital doublet [Formula: see text]. The quadrupole coupling constant e2qQ is positive, and no rhombic distortion could be detected. The electronic spectrum shows a splitting of the 5Eg excited level, presumably by a dynamic Jahn–Teller effect, and [Formula: see text] Attempts to fit a low-temperature magnetic perturbation Mössbauer spectrum using a pseudo-spin Hamiltonian were only partially successful, but suggest that the g tensor is highly anisotropic with [Formula: see text] and that the internal hyperfine field is small. Spin relaxation in Fe(SO3F)2 is fast at all temperatures down to 4.2 K and in applied magnetic fields of up to 5.0 T.