Molecular structure of the methoxy-iron(III) derivative of 5,15-(o,o′(2-methyl-2′-hydroxy-3,3′-diamidobiphenyl)-diphenyl)-porphyrin and CO binding properties of iron(II)-pyridine complexes of 2,2′-substituted biphenyl strapped porphyrins

Mechanistic Comparison of Cyclic Ester Polymerizations by Novel Iron(III)−Alkoxide Complexes: Single vs Multiple Site Catalysis

“…The iron−oxygen (Fe1−O1) bond distances are 1.802(3) (R = Et) and 1.8417(12) Å (R = CHPh 2 ), which fall in the middle of the range reported for other mononuclear iron(III)−alkoxides (1.77−1.89 Å) . The Fe−O−C angles are 141.5(7)° (R = Et) and 127.6(1)° (R = CHPh 2 ), consistent with the absence of multiple Fe−OR bonding that has been identified in some complexes with more Lewis acidic Fe(III) ions supported by neutral N-donors. 12b,g

2 Representations of the X-ray crystal structures of (a) L 2 FeOEt, (b) L 2 FeOCHPh 2 , and (c) Fe 2 (OCHPh 2 ) 6 . All atoms are shown as 50% thermal ellipsoids, with solvent and hydrogen atoms omitted for clarity.

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“…Thus inspired, we turned our attention toward designing a mononuclear complex L x FeOR with which to perform comparative mechanistic studies. Here we report the synthesis and full characterization of rare examples of well-defined complexes of this type, L 2 FeOR (L = N , N ‘ -bis(trimethylsilyl)benzamidinate, R = Et and CHPh 2 ), as well as a homoleptic dinuclear analogue with one of the same alkoxides, Fe 2 (OCHPh 2 ) 6 . Direct comparison of the reactivity of the compounds that contain the same Ph 2 HCO - initiators in the polymerization of LA and ε-caprolactone (CL) (Figure ) revealed unexpected differences in kinetic behavior that raise issues of importance for the design of new cyclic ester polymerization catalysts.…”

Reactivity of a (μ-Oxo)(μ-hydroxo)diiron(III) Diamond Core with Water, Urea, Substituted Ureas, and Acetamide

“…The presence of a terminal ethoxy ligand in the structure is confirmed by a short iron−oxygen (Fe1−O2) bond distance of 1.82 Å [EtOH would lead to a weaker binding with d (Fe−O) of about 2.15 Å]. − Very few other examples of mononuclear iron(III) alkoxide complexes have been structurally characterized and reported in the literature. Most of the known structures were obtained for heme iron(III) complexes with a methoxy group bound to the metal center in the axial position − and, to our knowledge, only four structures for mononuclear non-heme iron(III) alkoxide complexes − have been reported. The iron−oxygen bond distance in complex 2 is elongated as compared to the other non-heme iron complexes (1.77−1.80 Å) 56-58 but shorter than most Fe−OR distances found in heme complexes (about 1.84 Å). − The Fe−O−C angle (142°) is consistent with the absence of multiple Fe−OEt bonding, which would lead to a linear arrangement of Fe−O−R. − Complex 2 is also one of the few structurally characterized iron complexes with a neutral urea ligand, with previous determinations limited to [Fe(urea) 6 ] 3+ and [Fe(urea) 6 ] 2+ .…”

The crystal structure of halofantrine–ferriprotoporphyrin IX and the mechanism of action of arylmethanol antimalarials

“…The Cambridge Structural Database (CSD) was surveyed for five-coordinate Fe(III) alkoxide complexes. Five molecules that are structurally similar to the Hf-Fe(III)PPIX structure were selected [31][32][33][34][35], as was the Hf-Fe(III)PPIX complex itself from the current work. For this type of study the force field is considered correct if the absolute difference between the crystal structure averages and the values returned by the force field agree within 0.01 Å for bond lengths, 2°for bond angles and 4°for torsion angles [29,30].…”