Studies in Coordination Chemistry. IX.1 Investigation of the Stereochemistry of Some Complex Compounds of Cobalt(II) with N-Substituted Salicylaldimines

Sacconi, L.; Ciampolini, Mario; Maggio, Francesco; Cavasino, F. Paolo

doi:10.1021/ja00876a005

Cited by 113 publications

(32 citation statements)

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“…While octahedral complexes also show bands in tlhis same region (4T1g (F)-t4T2, (F) (950-1550 nm) and 4T1g(F) -4T1,(P) (450-650 nm), the molar extinction coefficients of the 4T1g (F) -+4T2g (F) transition typically range from 5 to 40 while those of the 4T1,(F) -4TI,(P) transition range from 15 to 60, well below those reported for 2 [29,40]. In comparison, the binuclear Fe"+ compound 5, appears featureless in the visible region owing to a strong tailing absorbance at 312 nm ( E~ = 30000) [9].…”

Section: Physical Characterizationmentioning

confidence: 75%

Binuclear Non-heme Iron Catalysts

Caradonna¹

2004

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This project involved the investigation of the ability of non-heme iron metalloenzyme reactivity model complexes to catalyze the oxidation of alkane and arene molecules. The objectives were to synthesize a series of non-heme mononuclear and dinuclear iron complexes, characterize their electronic structure and reactivity properties, characterize intermediates formed during oxygen atom transfer chemistry, and elucidate the mechanisms and specificity of the reactions. These data also were to be compared to analogous heme-based chemistry.A series of diferrous, ferrous/ferric, and diferric complexes were synthesized from simple polyamide and polycarboxylate ligands and characterized by visible absorption, EPR and IR spectroscopy and by cyclic voltametry. The diferrous compounds, which are all powerful reductants, heterolytically decompose peracids and are capable of acting as oxygen atom transfer catalysts when reacted with oxygen atom donor compounds and simple olefins, yielding both allylic oxidation and epoxidation products. Lowtemperature optical spectroscopic studies provide evidence in support of an Fe(IV)=O intermediate, rather than an 0-donor adduct, as the reactive species. An isostructural dicobalt(I1) complex gives rise only to epoxidation products. These reactivity studies provide important new information of the chemistry of dinuclear nonheme iron systems.Publications resulting from this project:1. 2.3. 4."Fe2+-catalyzed heterolytic RO-OH bond cleavage and substrate oxidation: A fhctional synthetic non-heme iron monooxygenase system", Foster TL, Caradonna ' in anhydrous 1% methanol-acetonitrile under anaerobic conditions afforded @?e22+(Hzbamb)2(N-MeIm)2] (1)25a (60% yield). Isothermal distillation techniquesls indicate that 1 has a molecular weight of 4 100, consistent with its dimeric formulation. EPR spectra of 1 show a g H % 16 signal, suggesting a ferromagnetically coupled S = 4 core as previously reported for an analogous binuclear system.I9 Cyclic voltammetry experiments show two coupled le-oxidationheduction processes; a scanrate-dependent quasi-reversible process at -310 mV ("E) and an electrochemically reversible couple at -690 mV ("E), giving K , , = 2.7 x loa. Repetitive scans showed no significant decrease in either cathodic or anodic current; ligand centered redox behavior was observed outside this region of interest. The scan-rate dependence of AEp, attributed to kinetic effects, allowed the measurement of an intrinsic rate constant, k = 2 x assuming pseudo-first-order kinetics. This rate constant, thought to reflect a structural change, is independent of [I] interfaced to a "33% series U integrator. Mass spectral analyses were performed on a HP 5971 mass-selective detector attached to a HPS890 Series 2 GC. Authentic samples were used to verify all retention times. Expected reaction products were stable to GC conditions.(21) Studies using Fa12 and FeCla were performed and analyzed by GC and GUMS techniques using identical conditions as reported for 1-3 (Table 1) with catalyst:OIF'h:sub...

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Section: Physical Characterizationmentioning

confidence: 75%

Binuclear Non-heme Iron Catalysts

Caradonna¹

2004

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“…In the electronic spectra of the ligands and their Ni(II), Cu(II) and Co(II) metal complexes, the wide range bands seem to be due to both the π→π * , n→π * and d-d transitions of C＝N and charge-transfer transition arising from π electron interactions between the metal and ligand which involves either a metal-to-ligand or ligand-to-metal electron transfer. 26,27 The electronic spectrum of Cu(II) complexes in DMSO, C 2 H 5 OH and CHCl 3 exhibited a broad band at 436-643 nm which is assigned to 2 Eg→ 2 T2g transitions, characteristic for square planar geometry. 28 The absorption bands observed for the spectrum of Ni(II) complexes within the range of 423-593 nm can be assigned to the 1 2 •2H 2 O] complexes were characterized by IR spectrum and elemental analysis, and two moles of water are coordinated to the complexes.…”

Section: Resultsmentioning

confidence: 99%

Synthesis, Spectroscopic and Electrochemical Investigations of Two vic‐Dioximes and Their Mononuclear Ni(II), Cu(II) and Co(II) Metal Complexes Containing Morpholine Group

Kılıç

Taş²,

Gümgüm

et al. 2006

Chin. J. Chem.

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“…The absorption peaks of ultraviolet region are assignable to the transitions involving ligands orbitals [21]. In the electronic spectra of the ligands and their metal complexes, a wide range of peaks seems to be due to the π → π * , n → π * , and d-d transitions of C N as well as charge-transfer transitions arising from π electron interactions between the metal and ligand, which involves either a metal-to-ligand or a ligand-to-metal electron transfer [22,23]. The peaks observed in the 210-272 nm range can be assigned to the π → π * transitions of the aromatic rings.…”

Section: Ft-ir Spectramentioning

confidence: 99%