77 research outputs found
Molecular characterization of group A bovine rotavirus in southeastern and central-western Brazil, 2009-2010
Associate Editors Past and Present: A Warm Welcome to Professor Daniel J. Mindiola, and Heartfelt Thanks to Professor Tobin J. Marks
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Oxidative Atom-Transfer to a Trimanganese Complex To Form Mn 6 (Ī¼ 6 -E) (E = O, N) Clusters Featuring Interstitial Oxide and Nitride Functionalities
Utilizing a hexadentate ligand platform, a trinuclear manganese complex of the type (HL)Mn3(thf)3 was synthesized and characterized ([HL]6ā = [MeC(CH2N(C6H4-o-NH))3]6ā). The pale-orange, formally divalent trimanganese complex rapidly reacts with O-atom transfer reagents to afford the Ī¼6-oxo complex (HL)2Mn6(Ī¼6-O)(NCMe)4, where two trinuclear subunits bind the central O-atom and the (HL) ligands cooperatively bind both trinuclear subunits. The trimanganese complex (HL)Mn3(thf)3 rapidly consumes inorganic azide ([N3]NBu4) to afford a dianionic hexanuclear nitride complex [(HL)2Mn6(Ī¼6-N)](NBu4)2, which subsequently can be oxidized with elemental iodine to (HL)2Mn6(Ī¼6-N)(NCMe)4. EPR and alkylation of the interstitial light atom substituent were used to distinguish the nitride from the oxo complex. The oxo and oxidized nitride complexes give rise to well-defined Mn(II) and Mn(III) sites, determined by bond valence summation, while the dianionic nitride shows a more symmetric complex, giving rise to indistinguishable ion oxidation states based on crystal structure bond metrics.Chemistry and Chemical Biolog
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Oxidative Group Transfer to a Triiron Complex to Form a Nucleophilic Ī¼3-Nitride, [Fe3(Ī¼3-N)]ā
Utilizing a hexadentate ligand platform, a high-spin trinuclear iron complex of the type (tbsL)Fe3(thf) was synthesized and characterized ([tbsL]6ā = [1,3,5-C6H9(NPh-o-NSitBuMe2)3]6ā). The silyl-amide groups only permit ligation of one solvent molecule to the tri-iron core, resulting in an asymmetric core wherein each iron ion exhibits a distinct local coordination environment. The triiron complex (tbsL)Fe3(thf) rapidly consumes inorganic azide ([N3]NBu4) to afford an anionic, trinuclear nitride complex [(tbsL)Fe3(Ī¼3-N)]NBu4. The nearly C3-symmetric complex exhibits a highly pyramidalized nitride ligand that resides 1.205(3) Ć
above the mean triiron plane with short FeāN (1.871(3) Ć
) distances and FeāFe separation (2.480(1) Ć
). The nucleophilic nitride can be readily alkylated via reaction with methyl iodide to afford the neutral, trinuclear methylimide complex (tbsL)Fe3(Ī¼3-NCH3). Alkylation of the nitride maintains the approximate C3-symmetry in the imide complex, where the imide ligand resides 1.265(9) Ć
above the mean triiron plane featuring lengthened FeāNimide bond distances (1.892(3) Ć
) with nearly equal FeāFe separation (2.483(1) Ć
).Chemistry and Chemical Biolog
Isolation of Iron(II) Aqua and Hydroxyl Complexes Featuring a Tripodal H-bond Donor and Acceptor Ligand
A tripodal
ligand platform, trisĀ(5-cycloiminopyrrol-2-ylmethyl)Āamine (H<sub>3</sub>[NĀ(pi<sup>Cy</sup>)<sub>3</sub>]), that features a hydrogen bond-accepting
secondary coordination sphere when bound anionically to an iron center
is reported. Neutral coordination to iron affords ligand tautomerization,
resulting in a hydrogen bond-donating secondary coordination sphere,
and formation of the trisĀ(5-cyclohexyl-amineazafulvene-2-methyl)Āamine,
H<sub>3</sub>[NĀ(afa<sup>Cy</sup>)<sub>3</sub>], scaffold. Both binding
motifs result in formation of stable, high-spin ironĀ(II) complexes
featuring ancillary water, triflate, or hydroxo ligands. Structural
analysis reveals that these complexes exhibit distorted trigonal-bipyramidal
geometries with coordination of the apical nitrogen to iron as well
as three equatorial amine or imine nitrogens, depending on the axial
ancillary ligand. Formation of the aqua complex KĀ[(NĀ(pi<sup>Cy</sup>)<sub>3</sub>)ĀFeĀ(OH<sub>2</sub>)] (<b>3</b>) illustrated
the propensity of the ligand to be hydrogen bond-accepting, whereas
the iron triflate species [NĀ(afa<sup>Cy</sup>)<sub>3</sub>ĀFe]Ā(OTf)<sub>2</sub> (<b>4</b>) features a hydrogen bond-donating secondary
coordination sphere. The ability of each of the three arms of the
ligand to tautomerize independently was observed during the formation
of the ironāhydroxyl species [NĀ(afa<sup>Cy</sup>)<sub>2</sub>Ā(pi<sup>Cy</sup>)]ĀFeOH (<b>5</b>) and characterized by
X-ray crystallography and IR spectroscopy. The combined data for the
iron complexes established that each arm of the tripodal ligand can
tautomerize independently and is likely dependent on the electronic
needs of the iron center when binding various substrates
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