83679-04-3Relevant academic research and scientific papers
FeCl3-phosphine adducts with trigonal-bipyramidal geometry. Influence of the phosphine on the spin state
Walker, J. David,Poli, Rinaldo
, p. 1793 - 1801 (2008/10/08)
Anhydrous FeCl interacts with phosphine ligands in various solvents and in various molar ratios to afford the adducts FeCl3(PR3)n (R = Ph, c-C6H11, n = 1, 2; R = Me, n = 1-3). The 1:1 adducts could only be characterized by low-temperature EPR spectroscopy. They are high-spin (S = 5/2) mononuclear compounds with a tetrahedral geometry. They decompose in aromatic hydrocarbons and halogenated hydrocarbons by complex pathways, including oxidation of the solvent C-H bonds. The 1:2 adducts were isolated and fully characterized. The PPh3 and PMe3 adducts were also characterized crystallographically. FeCl3(PPh3)2: orthorhombic, space group Pbca, a = 17.934 (2) ?, b = 17.075 (3) ?, c = 22.403 (3) ?, V = 6860 (3) ?3, Z = 8, dc = 1.33 g·cm-3, μ(Cu Kα) = 67.90 cm-1, R = 0.066, Rw = 0.066 for 199 parameters and 1916 observations with Fo2 > 3σ(Fo2). FeCl3(PMe3)2: orthorhombic, space group Pnma, a = 9.846 (2) ?, b = 10.680 (3) ?, c = 13.439 (7) ?, V = 1413 (1) ?3, Z = 4, dc = 1.48 g·cm-3, μ(Cu Kα) = 156.99 cm-1, R = 0.053, Rw = 0.066 for 64 parameters and 558 observations with Fo2 > 3σ(Fo2). Both compounds show a trigonal-bipyramidal structure with the two phosphine ligands in the axial positions. All bond parameters are comparable with the notable exception of the Fe-P bond lengths, which are (average) 2.64 ? in the PPh3 and 2.335 ? in the PMe3 derivative. Other properties of these compounds also differ: FeCl3(PPh3)2 is a high-spin (S = 5/2) compound, as shown by magnetic susceptibility and EPR studies. FeCl3(PMe3)2 is EPR silent at liquid-nitrogen temperature and shows a temperature-dependent magnetic moment in solution, consistent with an equilibrium between S = 5/2 and S = 3/2 spin states, the latter being the ground state. A temperature-independent (in the 10-300 K range) magnetic susceptibility corresponding to three unpaired electrons is observed in the solid state. FeCl3(PMe3)3 can only be obtained in equilibrium with the 1:2 adduct in the presence of a large excess of PMe3. Its EPR spectrum is consistent with a low-spin (S = 1/2) state and an octahedral coordination geometry with a meridional configuration. Visible spectroscopic properties and a qualitative MO diagram for these species are also discussed.
1H-NMR- AND MOESSBAUER INVESTIGATIONS ON THE ION PAIRS OF TETRACHLOROFERRATE(III) ANION WITH QUATERNARY PHOSPHONIUM CATIONS
Vincze, L.,Papp, S.
, p. 153 - 162 (2007/10/02)
Paramagnetic ion pairs were investigated by 1H-NMR and Moessbauer spectroscopy in chloroform and dimethyl sulphoxide.It has been shown that the chemical shifts of 1H-NMR peaks arise from a combination of contact and pseudocontact interactions of opposite sign, and the ratio of interactions was definitely influenced by the extent of solvation.On the basis of Moessbauer measurements it was shown that the change of the cation size had an effect on the electron delocalization and symmetry conditions of iron(III) in solid samples, too.In concentrated frozen solutions of ion pairs, different interactions were indicated by Moessbauer spectros copy in chloroform and dimethyl sulphoxide, in accordance with 1H-NMR results.However, in dilute solution such an anion-solvent interaction was observed directly, which could be shown by the NMR method only indirectly.
