New Ligands For Manganese Catalysed Selective Oxidation Of Sulfides To Sulfoxides With Hydrogen Peroxide

In situ prepared manganese complexes with ligands 1–5 have been used in the catalytic oxidation of sulfides to sulfoxides using hydrogen peroxide at 0°C in acetone. Using ligand 4, methyl phenyl sulfoxide is obtained in 55% yield and turnover numbers up to 250, while the formation of sulfone is almost suppressed.

Meeting Minutes

Meeting to discuss homecoming activities, December graduation, job fair and University Boulevard

End-on And Side-on Peroxo Derivatives Of Non-heme Iron Complexes With Pentadentate Ligands: Models For Putative Intermediates In Biological Iron/dioxygen Chemistry

Mononuclear iron(III) species with end-on and side-on peroxide have been proposed or identified in the catalytic cycles of the antitumor drug bleomycin and a variety of enzymes, such as cytochrome P450 and Rieske dioxygenases. Only recently have biomimetic analogues of such reactive species been generated and characterized at low temperatures. We report the synthesis and characterization of a series of iron(II) complexes with pentadentate N5 ligands that react with H2O2 to generate transient low-spin Fe III -OOH intermediates. These intermediates have low-spin iron(III) centers exhibiting hydroperoxo-to-iron(III) charge-transfer bands in the 500-600-nm region. Their resonance Raman frequencies, vO-O, near 800 cm -1 are significantly lower than those observed for high-spin counterparts. The hydroperoxo-to-iron(III) charge-transfer transition blue-shifts and the vO-O of the Fe-OOH unit decreases as the N5 ligand becomes more electron donating. Thus, increasing electron density at the low-spin Fe(III) center weakens the O-O bond, in accord with conclusions drawn from published DFT calculations. The parent [(N4Py)Fe III (eta 1 -OOH)]2+ (1a) ion in this series (N4Py ) N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine) can be converted to its conjugate base, which is demonstrated to be a high-spin iron(III) complex with a side-on peroxo ligand, [(N4Py)Fe III (eta 2 -O2)]+ (1b). A detailed analysis of 1a and 1b by EPR and Mo¨ ssbauer spectroscopy provides insights into their electronic properties. The orientation of the observed 57 Fe A-tensor of 1a can be explained with the frequently employed Griffith model provided the rhombic component of the ligand field, determined by the disposition of the hydroperoxo ligand, is 45° rotated relative to the octahedral field. EXAFS studies of 1a and 1b reveal the first metrical details of the iron-peroxo units in this family of complexes: [(N4Py)Fe III (eta 1 -OOH)]2+ has an Fe-O bond of 1.76 Å, while [(N4Py)Fe III (eta 2 -O2)]+ has two Fe-O bonds of 1.93 Å, values which are in very good agreement with results obtained from DFT calculations.

Language politics and practices in the Baltic states

This monograph provides an overview of the language situation in the three Baltic countries: Estonia, Latvia and Lithuania. It examines the recent change in language regimes that the Baltic States have deliberately brought about since the restitution of their independence, the nature of these changes, the opposition they have engendered and the linguistic, political and social consequences of these policies, both locally and internationally. First, an overview is provided on the historical background to contextualise and present language policy issues in the Baltic. Then attempts to overturn major aspects of Soviet language policy and to re-institute the national language are highlighted. Aspects of the current language situation covered include a special focus on bilingual and multilingual language use in the Baltic multiethnic settings. Detailed attention is also paid to language provision in the diverging educational settings, as well as to methods of assessment. This is followed by a discussion of attitudes to language use, standardisation, testing, languages and language variants. In conclusion the scholarly treatment of Baltic language policy issues is examined, concluding with an evaluation of the contribution of the Baltic States to our overall understandings of language policy and its complexities