Redox Pairs of Diiron and Iron-Cobalt Complexes with High-Spin Ground States.
A series of iron and iron-cobalt bimetallic complexes were isolated: LFe2Cl (1), LFe2(2), Li(THF)3[LFe2Cl](Li(THF)3[2-Cl]), LFeCoCl (3), and LFeCo (4), where L is a trianionic tris(phosphineamido)amine ligand. As elucidated by single-crystal X-ray diffraction studies and quantum-chemical calculations, the FeIIFeIIand FeIICoIIcomplexes, 1 and 3, respectively, have weak metal-metal interactions (the metal-metal distances are 2.63 and 2.59 Å, respectively) with a partial bond order of 0.5. The formally mixed-valent complexes, FeIIFeI(3) and FeIICoI(4), have short metal-metal bonds (2.32 and 2.26 Å, respectively) with a formal bond order of 1.5. On the basis of magnetic susceptibility measurements, complexes 1-4 are all paramagnetic with high-spin ground states, S = 3-4, which are proposed to arise from ferromagnetic coupling of the two metals' spins through a direct exchange mechanism. Zero- and applied-field Mössbauer spectra corroborate the presence of distinct oxidation and spin states for the iron sites. The reduction potentials of 1 and 3 are -1.48 and -1.60 V (vs Fc+/Fc), respectively. Other characterization data are also reported for this series of complexes, electronic absorption spectra and anomalous X-ray scattering data.
Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, United States.
Deanna L
DL
Miller
Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, United States.
Randall B
RB
Siedschlag
Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, United States.
Laura J
LJ
Clouston
Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, United States.
Victor G
VG
Young
ChemMatCARS, University of Chicago , Argonne, Illinois 60439, United States.
Yu-Sheng
YS
Chen
Max Planck Institut für Chemische Energiekonversion , Stiftstraße 34-36, 45470 Mülheim an der Ruhr, Germany.
Eckhard
E
Bill
Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, United States.|Supercomputing Institute and Chemical Theory Center, University of Minnesota , Minneapolis, Minnesota 55455, United States.
Laura
L
Gagliardi
Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, United States.
Connie C
CC
Lu