Chemistry of Molybdenaoxaziridines. A Study af Oxo(N-phenylhydroxylamido-O,N ) (pyridine-2,6-dicarboxylato) (hexamethy1phosphortriamide)molybdenum(VI) and Its Catalytic Properties

Eval Rud Møller, Karl Anker Jørgensen

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The chemistry of molybdenaoxaziridines is investigated. Oxo(N-phenylhydroxylamido-O,N)(pyridine-2,6-
dicarboxylato) (hexamethylphosphortriamide)molybdenum(VI) complexes 3 are prepared in high yields by different procedures, either by a reaction between anilines and oxoperoxo(pyridine-2,6-dicarboxylato)(hexamethylphosphortriamide)molybdenum(VI) (4) or by an oxidative addition reaction of itrosobenzenes to oxo(pyridine-2,6-dicarboxylato)(hexamethylphosphortriamide)molybdenum(IV) (6). The kinetics of the reactions of a series of parasubstituted anilines and 4 are studied, and a Hammett plot showed a correlation between log(k/k,) and up with a p value of -2.29. A mechanism for the formation of 3 is proposed. The electronic structure of 3 is investigated using extended-Hiickel calculations. Based on the frontier orbitals of the system, a brief discussion of the chemical properties of 3 is presented. Complex 3 decomposes to mainly azoxybenzene and dioxo(pyridine-2,6-dicarboxylato)(hexamethylphosphortriamide)molybdenum(VI) (5). A variable-temperature study leads to an Arrhenius plot for this decomposition with a AG value of 16.1 kcal-mol-l. Based on the detected decomposition products and on the observed nitroso ligand exchange reaction, a mechanism for the decomposition of 3 is proposed. Treatment of 3 with hydrogen peroxide leads to a selective formation of nitrosobenzenes and 4. This reaction is further developed to a catalytic process
for the selective oxidation of various substituted anilines to the corresponding nitrosobenzenes in high yields. The influences of different solvents and of the temperature on the yields of the oxidation are also examined. Based on the kinetic experiments, mechanisms for the stoichiometric and the catalytic oxidation reactions are suggested.
TidsskriftAmerican Chemical Society. Journal
Udgave nummer25
Sider (fra-til)11814-11822
Antal sider9
StatusUdgivet - 1993
Udgivet eksterntJa