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Structures and Properties of Dibridged (μ-Oxo)diiron(III) Complexes. Effects of the Fe-O-Fe Angle
Inorganic Chemistry
  • Richard E. Norman, University of Minnesota - Twin Cities
  • Richard C. Holz, Marquette University
  • Stephane Menage, University of Minnesota - Twin Cities
  • Charles J. O'Connor, University of New Orleans
  • Jian H. Zhang, University of New Orleans
  • Lawrence Que, Jr., University of Minnesota - Twin Cities
Document Type
Article
Publication Date
11-1-1990
Disciplines
Abstract
A series of (μ-oxo)diiron(lll) complexes of tris(2-pyridylmethy1)amine (TPA), [Fe2(TPA)2O(L)] (CIO4)n, were synthesized and characterized where L represents the bridging ligands carbonate, hydrogen maleate, diphenyl phosphate, diphenylphosphinate, maleate, and phthalate. Together with the linear dichloride complex, this series of compounds provides a unique opportunity to systematically study the effects of the Fe-0-Fe angle (125-180°) on the electronic spectral and magnetic properties of the (μ-oxo)diiron(lll) core. [Fe2(TPA)2O(CO3)](CIO4)2.2CH3OH (1) crystallizes in the monoclinic space group P21/c with a = 11.282 (7) Å, b = 18.253 (9) Å, c = 20.390 (7) Å, and β= 95.02 (4)°. The structure was determined at -50°C from 4544 out of a total of 8154 reflections with R = 0.068 and Rw = 0.080. [Fe2(TPA)2O(maleateH)](C104)3.2CH3COCH3(4) crystallizes in the monoclinic space group P21/n with a = 21.604 (6)°, b = 11.76 (1) Å, c = 22.150 (7) Å, and β = 115.62 (3)°. The structure was determined at -50°C from 4832 out of a total of 7043 reflections with R = 0.072 and Rw = 0.089. [Fe2(TPA)2O(phthalate)](C104)2CH3OH.H2O(9) crystallizes in the monoclinic space group PI with a = 12.170 (5) Å, b = 12.982 (9) Å, c = 17.070 (7) Å, ∞=115.62 (3)°, and γ=62.76 (6)°. The structure was determined at -32°C from 3592 out of a total of 8329 reflections with R = 0.059 and Rw = 0.069. X-ray crystallographic studies of 1,4, and 9 establish the presence of a doubly bridged diiron core in which complexes 1 and 4 contain distinct iron centers bridged by μ-1,3-carboxylates while 9 exhibits a symmetric diiron core bridged by a μp-1,6-phthalate. These studies also reveal that the (μ-oxo)diiron(III) core expands on going from 1 to 4 to 9 due to the increasing bites of the bridging ligands. The Fe-0-Fe bond angles of 1, 4, and 9 are 125.4, 131.0, and 143.4°, respectively, while the Fe-Fe distances are 3.196, 3.261, and 3.402 Å, respectively. 1H NMR spectra indicate that the iron(ll1) centers of 1 and 4 remain distinct in solution while 9 retains its symmetric structure. While the magnetic properties of the complexes appear to be independent of the Fe-O-Fe angle, the visible absorption features of the complexes systematically blue shift as the Fe-0-Fe angle increases. The latter trend suggests that the visible bands are dominated by oxo-to-Fe(1II) charge-transfer transitions.
Comments

Inorganic Chemistry, Vol. 29, No. 23 (November 1990): 4629-4637. DOI.

Richard Holz was affiliated with University of Minnesota at the time of publication.

Citation Information
Richard E. Norman, Richard C. Holz, Stephane Menage, Charles J. O'Connor, et al.. "Structures and Properties of Dibridged (μ-Oxo)diiron(III) Complexes. Effects of the Fe-O-Fe Angle" Inorganic Chemistry (1990) ISSN: 0020-1669
Available at: http://works.bepress.com/richard_holz/24/