Relation Between Magnetism and Structure of Iron(III) Complexes Exhibiting an S =3/2 ⇌ S = 5/2 Spin State Equilibrium. Structures of Chloroform and Water Solvated Tris( 4-morpholinecarbodithioato-S,S′ )iron(III) and -manganese(III)
The crystal and molecular structures of tris(1-morpholinecarbodithioato-S,S′)iron(III) crystallized from chloroform (FeM·CHCl3) and toluene (FeM·tol) and the manganese analogue crystallized from chloroform (MnM·CHCl3) were determined by single-crystal x-ray diffraction using computer techniques. Crystal data: FeM·CHCl3, Fe(S2CNC4H8O)3· CHCl3, P1̄, Z = 2, a = 9.209 (4) Å, b = 10.716 (4) Å, c = 14.512 (9) Å, a = 101.40 (6)°, β= 97.02 (6)°, γ = 90.61 (6)°, V = 1392 Å3, R = 4.0%, 2934 reflections; MnM·CHCl3, Mn(S2CNC4H8O)3·CHCl 3, P1̄, Z = 2, a = 13.60 (1) Å, b = 11.009 (5) Å, c = 11.733 (5) Å, α = 117.09 (4)°, β= 99.89 (6)°, 7 = 107.72 (5)°, V = 1387 Å3, R = 4.0%, 2576 reflections; FeM·tol, Fe(S2CNC4H8O)3·H 2O, P1̄, Z = 2, a = 9.292 (3) Å, b = 10.454 (4) Å, c = 13.646 (8) Å, α = 100.30 (3)°, β= 95.37 (4)°, γ = 106.19(3)°, V = 1238 Å3, R = 3.9%, 3316 reflections. Like the previously studied dichloromethane solvate, FeM·CHCl3 and FeM·tol exhibit a spin state equilibrium between S = 3/2 and S = 5/2 states. It now appears that with hydrogen bonding solvates (CH2Cl2 in FeM·CH2Cl2, CHCl3 in FeM·CHCl3, and H2O in FeM·tol), the magnetic moment is raised compared to that of the desolvated FeM, and an 5 = 3/2 ground state is produced, whereas FeM shows only S = 1/2 and S = 5/2 states. A possible mechanism for this, involving solvent hydrogen bonding to ligand sulfur atoms, is discussed. It is likely that S = 1/2, S = 3/2, and S = 5/2 states are all low lying in these and related complexes. In view of this and the extreme solvent sensitivity, many of the earlier literature data for such complexes should be taken with caution. The average metal-ligand bond lengths in the iron complexes increase as the moments increase. 〈Fe-S〉 is 2.317 (1), 2.416 (1), 2.430 (4), and 2.443 (1) Å in C6H6, CHCl3, CH2Cl2, and H2O solvates, respectively, the latter being the greatest (Fe-S) distance ever observed in a ferric dithiocarbamate. The manganese environment in MnM·CHCl3 exhibits strong tetragonal distortion in addition to the trigonal distortion that occurs in all tris(dithiocarbamate) complexes. Near liquid helium temperature, there is some evidence of the intermolecular antiferromagnetic interaction expected to occur in the manganese and iron complexes, via the electron spin density delocalized onto the ligands.
R. J. Butcher and E. Sinn, "Relation Between Magnetism and Structure of Iron(III) Complexes Exhibiting an S =3/2 ⇌ S = 5/2 Spin State Equilibrium. Structures of Chloroform and Water Solvated Tris( 4-morpholinecarbodithioato-S,S′ )iron(III) and -manganese(III)," Journal of the American Chemical Society, American Chemical Society (ACS), Jan 1976.
The definitive version is available at https://doi.org/10.1021/ja00433a018
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© 1976 American Chemical Society (ACS), All rights reserved.