STUDIES ON THE EFFECT OF PHOTOLYSIS ON THE METAL VAPOR CHEMISTRY OF VARIOUS COMPOUNDS CONTAINING A CARBON-OXYGEN DOUBLE BOND

[摘要] In the last decade metal vapor synthesis has become an important method for producing organometallic species that have been unattainable or difficult to make by other routes. However, many important reactions lie just outside the reach of the procedure because the energy of activation for the process is too high. Matrix isolation experiments indicate that direct photolysis of a metal-organic cocondensate is an excellent method for introducing energy into a metal vapor reaction system so that new chemical processes can be accessed. A metal vapor reactor was built in which one could irradiate with U.V.-visible light the deposition surface during co-deposition of the reactants. The reactor was designed so that the reaction surface was a rotating drum placed between the furnace and the photolysis well. This design minimized the accumulation of a metal coating on the photolysis lamp but introduced a time lag between deposition and photolysis. The reactions of transition metal vapors with acetone produced both pinacol by a metal atom process and aldol condensation products formed by a metal particle catalyzed process. Photolysis of the co-deposited layers of some transition metals with acetone produced an increase in the amount of pinacol formed (from 1.0 to 6% for iron, 0.8 to 3.7% for cobalt and 0.0 to 1.1% for nickel). No such reductive coupling products were observed for the reaction of iron and nickel with cyclohexanone under photochemical conditions. Nickel was the only transition metal (of Cr, Mn, Fe and Ni) that reacted with ethyl acetate without photolysis. This reaction produced products which were apparently formed from the decomposition of oxidative insertion products of nickel and ethyl acetate: Et-O-Ni-Ac and Et-Ni-O-Ac. Chromium and manganese reacted via a photolytically induced oxidative insertion to produce acetaldehyde and other products which were derived from a similar R-O-M-Ac complex. The yield of acetaldehyde in this reaction was dependent on the R-group in the ester and the deposition ratio of the metal and organic.

[发布机构] Rice University