Chemistry of iron(III) complexes of N,N′-bis(2-hydroxyphenyl)-pyridine-2,6-dicarboxamide: seven-coordinate iron(III) complexes ligated to deprotonated carboxamido nitrogens

The Coordination Chemistry of FeCl3 and FeCl2 to Bis[2‐(2,3‐dihydroxyphenyl)‐6‐pyridylmethyl](2‐pyridylmethyl)amine: Access to a Diiron(III) Compound with an Unusual Pentagonal‐Bipyramidal/Square‐Pyramidal Environment

“…In most of these cases, the ligands are potentially penta-or even heptadentate. [39][40][41] The occurrence of such a geometry in our case was unexpected, and means that, to the best of our knowledge, compound 3 is the only example of a seven-coordinate ironA C H T U N G T R E N N U N G (iii) derivative in the chemistry of TPAs.…”

Change in the Spin State of an FeIII Center upon One N‐to‐O Switch in the Coordination of a 2,6‐Pyridinedicarboxamido Unit: The Effect of Methyl Thioether and Methyl Ether Appendages at the Ligand Periphery

“…[5,11] Interestingly, the bond lengths of 1 compare well with those noted for high spin (vide infra) Fe III complexes that contain one 2,6-pyridinedicarboxamido unit in the primary coordination sphere. [6,10,15] The CϪO bond length of the O-bound carbonyl group [1.286 (4) III complexes with FeN 6 chromophores arising from coordination of two 2,6-pyridinedicarboxamido units. [5,11] However, these bonds are consistently shorter than those in 1 due to the low spin nature of the Fe III center in 2 (vide infra).…”

“…[5,6,9,11,15] Recent work in this laboratory has afforded a variety of Fe III complexes based on this tridentate moiety in the first coordination sphere. [5,6,10] For example, coordination of the pentadentate ligand POPyH 4 to Fe III (H represents dissociable amide protons) results in high-spin, seven-coordinate, pentagonal bipyramidal complexes with the entire ligand in the basal plane and with two exogenous axial ligands (structure i, Figure 2). [6] In contrast, the Fe III complex of the similar pentadentate ligand PyPSH 4 is high spin, five-coordinate with a distorted trigonal bipyramidal geometry due to the steric bulk of the thiolato sulfur (structure ii, Figure 2).…”

“…[5,6,10] For example, coordination of the pentadentate ligand POPyH 4 to Fe III (H represents dissociable amide protons) results in high-spin, seven-coordinate, pentagonal bipyramidal complexes with the entire ligand in the basal plane and with two exogenous axial ligands (structure i, Figure 2). [6] In contrast, the Fe III complex of the similar pentadentate ligand PyPSH 4 is high spin, five-coordinate with a distorted trigonal bipyramidal geometry due to the steric bulk of the thiolato sulfur (structure ii, Figure 2). [10] It is interesting to note that the potentially pentadentate ligands Py 3 PH 2 and MePy 3 PH 2 invariably afford six-coordinate bis complexes in which the two ligands are coordinated to the Fe III center through the 2,6-pyridinedicarboxamido moiety with unbound pendant Figure 1.…”

Ambidentate behavior of pentadentate N,N′-bis(2-hydroxyphenyl)-pyridine-2,6-dicarboxamide towards transition metal(II) salts

“…Iron(III) complexes of the title ligand have been reported and reveal that the ligand can behave as (i) a pentadentate ligand via pyridine nitrogen, doubly deprotonated amide nitrogen and doubly deprotonated phenolic oxygen with sodium hydride at 60°C, and (ii) as a bidentate ligand through two phenolic oxygens via deprotonation with sodium hydroxide at room temperature [11].…”