عنوان

Oxo and peroxo ligand transfer reactions involving methylrhenium trioxide

شماره

TLpq304306825

زبان متن نوشتاري يا گفتاري و مانند آن

انگلیسی

عنوان اصلي

Oxo and peroxo ligand transfer reactions involving methylrhenium trioxide

نام عام مواد

[Thesis]

نام نخستين پديدآور

M. M. Abu-Omar

نام ساير پديدآوران

J. H. Espenson

نام ناشر، پخش کننده و غيره

Iowa State University

تاریخ نشرو بخش و غیره

1996

نام خاص و کميت اثر

151

جزئيات پايان نامه و نوع درجه آن

Ph.D.

کسي که مدرک را اعطا کرده

Iowa State University

امتياز متن

1996

متن يادداشت

Methylrhenium dioxide (MDO), prepared in aqueous solution from the reaction of methylrhenium trioxide (MTO) and hypophosphorous acid, reacts with oxo donor compounds by oxygen-atom abstraction at record-high rates. These include inorganic oxoanions (e.g. ClO{4\sp-}), organic oxo substrates (e.g. sulfoxides), and few metal oxides (e.g. VO The mechanism of oxygen-atom transfer from oxygen donors (X=O) to MDO involves nucleophilic attack of the substrate at the oxophilic rhenium forming an adduct prior to oxo transfer. The kinetic data have been related to some extent to the element-oxygen force constants. MTO reacts with hydrogen peroxide to form the catalytically active species usd\rm CH\sb3ReO\sb2(\eta\sp2\rm O\sb2),usd A, and usd\rm CH\sb3ReO(\eta\sp2\rm O\sb2)\sb2(H\sb2O),usd B. The catalytic reactions of these rhenium peroxides with a large family of phosphines have been investigated. Systematic changes in the substituents on phosphorous were made to vary the nucleophilicity and cone angle of the phosphine. The kinetic data support a mechanism that allows nucleophilic attack of the substrate at the rhenium peroxides. MTO also catalyzes the oxidation of usd\betausd-diketones by usd\rm H\sb2O\sb2usd to give cleavage products, carboxylic acids. The kinetics of the initial oxidation which features epoxidation of the enol form, the majority species, have been investigated for a group of cyclic usd\betausd-diketones. Its rate responds to substituents in the "normal" manner: electron-donating groups accelerate the reaction. In contrast, the subsequent oxidation steps controlled by O-insertion into a C-C bond involve A and B as nucleophiles rather than their "normal" electrophilic behavior. In the absence of a substrate, the MTO-usd\rm H\sb2O\sb2usd catalyst undergoes decomposition to afford methanol and perrhenate. The deactivation kinetics feature complex dependences on hydrogen peroxide and pH. The catalyst is most stable at high acid and peroxide concentrations. Methanol and perrhenate are formed from the action of HO{2\sp-} on MTO; the mechanism of deactivation involves methyl migration to a peroxo bound oxygen. The diperoxo complex, B, on the other hand, is stable towards decomposition to methanol and perrhenate; instead it evolves molecular oxygen and regenerates the starting MTO.

موضوع مستند نشده

Chemistry

موضوع مستند نشده

Pure sciences

مستند نام اشخاص تاييد نشده

J. H. Espenson

مستند نام اشخاص تاييد نشده

M. M. Abu-Omar

نام الکترونيکي

فرمت انتشار

p

نوع ماده

[Thesis]

کد کاربرگه

276903

سطح دسترسي

a

تكميل شده

Y