TY - JOUR
T1 - Mixed-valent dicobalt and iron-cobalt complexes with high-spin configurations and short metal-metal bonds
AU - Zall, Christopher M.
AU - Clouston, Laura J.
AU - Young, Victor G.
AU - Ding, Keying
AU - Kim, Hyun Jung
AU - Zherebetskyy, Danylo
AU - Chen, Yu Sheng
AU - Bill, Eckhard
AU - Gagliardi, Laura
AU - Lu, Connie C.
PY - 2013/8/19
Y1 - 2013/8/19
N2 - Cobalt-cobalt and iron-cobalt bonds are investigated in coordination complexes with formally mixed-valent [M2]3+ cores. The trigonal dicobalt tris(diphenylformamidinate) compound, Co2(DPhF) 3, which was previously reported by Cotton, Murillo, and co-workers (Inorg. Chim. Acta 1996, 249, 9), is shown to have an energetically isolated, high-spin sextet ground-state by magnetic susceptibility and electron paramagnetic resonance (EPR) spectroscopy. A new tris(amidinato)amine ligand platform is introduced. By tethering three amidinate donors to an apical amine, this platform offers two distinct metal-binding sites. Using the phenyl-substituted variant (abbreviated as LPh), the isolation of a dicobalt homobimetallic and an iron-cobalt heterobimetallic are demonstrated. The new [Co2]3+ and [FeCo]3+ cores have high-spin sextet and septet ground states, respectively. Their solid-state structures reveal short metal-metal bond distances of 2.29 Å for Co-Co and 2.18 Å for Fe-Co; the latter is the shortest distance for an iron-cobalt bond to date. To assign the positions of iron and cobalt atoms as well as to determine if Fe/Co mixing is occurring, X-ray anomalous scattering experiments were performed, spanning the Fe and Co absorption energies. These studies show only a minor amount of metal-site mixing in this complex, and that FeCoL Ph is more precisely described as (Fe0.94(1)Co 0.06(1))(Co0.95(1)Fe0.05(1))LPh. The iron-cobalt heterobimetallic has been further characterized by Mössbauer spectroscopy. Its isomer shift of 0.65 mm/s and quadrupole splitting of 0.64 mm/s are comparable to the related diiron complex, Fe2(DPhF) 3. On the basis of spectroscopic data and theoretical calculations, it is proposed that the formal [M2]3+ cores are fully delocalized.
AB - Cobalt-cobalt and iron-cobalt bonds are investigated in coordination complexes with formally mixed-valent [M2]3+ cores. The trigonal dicobalt tris(diphenylformamidinate) compound, Co2(DPhF) 3, which was previously reported by Cotton, Murillo, and co-workers (Inorg. Chim. Acta 1996, 249, 9), is shown to have an energetically isolated, high-spin sextet ground-state by magnetic susceptibility and electron paramagnetic resonance (EPR) spectroscopy. A new tris(amidinato)amine ligand platform is introduced. By tethering three amidinate donors to an apical amine, this platform offers two distinct metal-binding sites. Using the phenyl-substituted variant (abbreviated as LPh), the isolation of a dicobalt homobimetallic and an iron-cobalt heterobimetallic are demonstrated. The new [Co2]3+ and [FeCo]3+ cores have high-spin sextet and septet ground states, respectively. Their solid-state structures reveal short metal-metal bond distances of 2.29 Å for Co-Co and 2.18 Å for Fe-Co; the latter is the shortest distance for an iron-cobalt bond to date. To assign the positions of iron and cobalt atoms as well as to determine if Fe/Co mixing is occurring, X-ray anomalous scattering experiments were performed, spanning the Fe and Co absorption energies. These studies show only a minor amount of metal-site mixing in this complex, and that FeCoL Ph is more precisely described as (Fe0.94(1)Co 0.06(1))(Co0.95(1)Fe0.05(1))LPh. The iron-cobalt heterobimetallic has been further characterized by Mössbauer spectroscopy. Its isomer shift of 0.65 mm/s and quadrupole splitting of 0.64 mm/s are comparable to the related diiron complex, Fe2(DPhF) 3. On the basis of spectroscopic data and theoretical calculations, it is proposed that the formal [M2]3+ cores are fully delocalized.
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U2 - 10.1021/ic400292g
DO - 10.1021/ic400292g
M3 - Article
C2 - 23902538
AN - SCOPUS:84882664892
VL - 52
SP - 9216
EP - 9228
JO - Inorganic Chemistry
JF - Inorganic Chemistry
SN - 0020-1669
IS - 16
ER -