title: Nonheme Fe(IV) Oxo Complexes of Two New Pentadentate Ligands and Their Hydrogen-Atom and Oxygen-Atom Transfer Reactions.
abstract: Two new pentadentate {N5} donor ligands based on the N4Py (N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine) framework have been synthesized, viz. [N-(1-methyl-2-benzimidazolyl)methyl-N-(2-pyridyl)methyl-N-(bis-2-pyridyl methyl)amine] (L(1)) and [N-bis(1-methyl-2-benzimidazolyl)methyl-N-(bis-2-pyridylmethyl)amine] (L(2)), where one or two pyridyl arms of N4Py have been replaced by corresponding (N-methyl)benzimidazolyl-containing arms. The complexes [Fe(II)(CH3CN)(L)](2+) (L = L(1) (1); L(2) (2)) were synthesized, and reaction of these ferrous complexes with iodosylbenzene led to the formation of the ferryl complexes [Fe(IV)(O)(L)](2+) (L = L(1) (3); L(2) (4)), which were characterized by UV-vis spectroscopy, high resolution mass spectrometry, and Mössbauer spectroscopy. Complexes 3 and 4 are relatively stable with half-lives at room temperature of 40 h (L = L(1)) and 2.5 h (L = L(2)). The redox potentials of 1 and 2, as well as the visible spectra of 3 and 4, indicate that the ligand field weakens as ligand pyridyl substituents are progressively substituted by (N-methyl)benzimidazolyl moieties. The reactivities of 3 and 4 in hydrogen-atom transfer (HAT) and oxygen-atom transfer (OAT) reactions show that both complexes exhibit enhanced reactivities when compared to the analogous N4Py complex ([Fe(IV)(O)(N4Py)](2+)), and that the normalized HAT rates increase by approximately 1 order of magnitude for each replacement of a pyridyl moiety; i.e., [Fe(IV)(O)(L(2))](2+) exhibits the highest rates. The second-order HAT rate constants can be directly related to the substrate C-H bond dissociation energies. Computational modeling of the HAT reactions indicates that the reaction proceeds via a high spin transition state.
authors.affiliation: †Chemical Physics, Department of Chemistry, Lund University, Box 124, SE-221 00, Lund, Sweden.
authors.forename: Mainak
authors.initials: M
authors.lastname: Mitra
authors.affiliation: ‡Department of Chemistry and Earth Sciences, College of Arts and Sciences, Qatar University, P.O. Box 2713, Doha, State of Qatar.
authors.forename: Hassan
authors.initials: H
authors.lastname: Nimir
authors.affiliation: §Institute of Inorganic Chemistry, Georg-August-University Göttingen, Tammanstrasse 4, D-37077 Göttingen, Germany.
authors.forename: Serhiy
authors.initials: S
authors.lastname: Demeshko
authors.affiliation: †Chemical Physics, Department of Chemistry, Lund University, Box 124, SE-221 00, Lund, Sweden.
authors.forename: Satish S
authors.initials: SS
authors.lastname: Bhat
authors.affiliation: †Chemical Physics, Department of Chemistry, Lund University, Box 124, SE-221 00, Lund, Sweden.
authors.forename: Sergey O
authors.initials: SO
authors.lastname: Malinkin
authors.affiliation: ⊥Department of Chemistry, University of Jyväskylä, P.O. Box-35, Jyväskylä, FI-40014, Finland.
authors.forename: Matti
authors.initials: M
authors.lastname: Haukka
authors.affiliation: ¶QBIS, Department of Chemistry, University de Girona, Campus Montilivi, E-17071 Girona, Spain.
authors.forename: Julio
authors.initials: J
authors.lastname: Lloret-Fillol
authors.affiliation: ∥Department of Chemistry, Beloit College, 700 College Street, Beloit, Wisconsin 53511, United States.
authors.forename: George C
authors.initials: GC
authors.lastname: Lisensky
authors.affiliation: §Institute of Inorganic Chemistry, Georg-August-University Göttingen, Tammanstrasse 4, D-37077 Göttingen, Germany.
authors.forename: Franc
authors.initials: F
authors.lastname: Meyer
authors.affiliation: #Institute of Problems of Chemical Physics, Chernogolovka, Moscow District, 142432, Russian Federation.
authors.forename: Albert A
authors.initials: AA
authors.lastname: Shteinman
authors.affiliation: ∇Stratingh Institute for Chemistry, Faculty of Mathematics and Natural Sciences, University of Groningen, Nijenborgh 4, 9747AG Groningen, The Netherlands.
authors.forename: Wesley R
authors.initials: WR
authors.lastname: Browne
authors.affiliation: ○Center for Advanced Scientific Computing and Modeling, University of North Texas, Denton, Texas 76203, United States.|◆Department of Chemistry, University of North Texas, Denton, Texas 76203, United States.
authors.forename: David A
authors.initials: DA
authors.lastname: Hrovat
authors.affiliation: ◆Department of Chemistry, University of North Texas, Denton, Texas 76203, United States.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Richmond
authors.affiliation: ¶QBIS, Department of Chemistry, University de Girona, Campus Montilivi, E-17071 Girona, Spain.
authors.forename: Miquel
authors.initials: M
authors.lastname: Costas
authors.affiliation: †Chemical Physics, Department of Chemistry, Lund University, Box 124, SE-221 00, Lund, Sweden.
authors.forename: Ebbe
authors.initials: E
authors.lastname: Nordlander
mesh_terms: D004563:Electrochemistry; D006859:Hydrogen / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry; D013440:Sulfides / Q000737:chemistry
chemical_list: D008024:Ligands; D009942:Organometallic Compounds; D011725:Pyridines; D013440:Sulfides; D006859:Hydrogen; D007501:Iron; C023666:pyridine; D010100:Oxygen