Structures, magnetic properties, and reactivity studies of salts containing the dinuclear anion [M2Cl6](2-) (M = Mn, Fe, Co) Academic Article uri icon

abstract

  • Salts of the edge-sharing bitetrahedral anion [N 2Cl 6] 2- with M = Mn, Fe, and Co were prepared in high yields by reaction of MCl 2 with 1 equiv of chloride ion. The anion [Fe 2Cl 6] 2- was isolated with five different cations, namely, [PPh 4] + (1), [Et 4N] + (2), [ppn] + (3), [AsPh 4] + (4), and [H-TMPP] + (5) ([H-TMPP] + = tris(2,4,6-trimethoxyphenyl)phosphonium; [ppn] + = bis(triphenylphosphonium)iminium chloride). The Mn and Co compounds were isolated as [ppn] + salts, [ppn] 2[Co 2Cl 6] (6) and [ppn] 2Mn 2Cl 6] (7). The compounds were characterized by single-crystal X-ray analysis and subjected to variable-temperature and field-dependent magnetic measurements. These magnetic data were analyzed from a spin Hamiltonian that contains an isotropic exchange term supplemented by a zero-field-splitting term to account for the single-ion anisotropy of the interacting spins. By using this approach, the [Fe 2Cl 6] 2- salts (1-5) were shown to exhibit magnetic behavior dominated by single-ion anisotropy of the spin S = 2 of the tetrahedral Fe(II) ions (D 5 cm -1). The Co(II) compound (6) was found to exhibit considerable single-ion anisotropy of the spin S = 3/2 tetrahedral Co(II) centers (D = 29 cm -1) and stronger antiferromagnetic coupling than the Fe compounds. In the absence of complicating factors such as ZFS effects, as is the case for the Mn(II) derivative (7) it was possible to discern weak intermolecular as well as intramolecular antiferromagnetic interactions. Reactions between 2,2-bipyrimidine (2,2-bpym) and salts of [Fe 2Cl 6] 2- yielded two neutral compounds, namely, Fe 2Cl 4((2,2-bpym) 3 (8) and [Et 4N]Cl[Fe 2Cl 4(MeOH) 4(-2,2-bpym)] (9). In contrast to the previously described Fe(II) compounds, the Fe(II) center is octahedral in 8 and 9. The electronic ground state of this ion is orbitally degenerate and therefore highly anisotropic. An analysis of the magnetic data confirmed these predictions and revealed that the bridging ligand mediates antiferromagnetic exchange of 1 cm -1 and that the D parameter is large and negative (D -17 cm -1). 1999 American Chemical Society.

published proceedings

  • INORGANIC CHEMISTRY

altmetric score

  • 3

author list (cited authors)

  • Sun, J. S., Zhao, H. H., Xiang, O. Y., Clerac, R., Smith, J. A., Clemente-Juan, J. M., ... Dunbar, K. R.

citation count

  • 51

complete list of authors

  • Sun, JS||Zhao, HH||Xiang, OY||Clerac, R||Smith, JA||Clemente-Juan, JM||Gomez-Garcia, C||Coronado, E||Dunbar, KR

publication date

  • December 1999