| Abstract
| - A potential catalytic cycle for the formation of new C−C and C−O linkages from hydrocarbonfeedstocks and readily available olefin and ketone substrates mediated by Cp‘M(NO)(L) (M = Mo, W;Cp‘ = Cp*, Cp; L = Lewis base) fragments has been investigated. The cycle is based on three steps: (1)oxidative addition of the hydrocarbon substrate to the metal center, (2) subsequent hydrometalation ofthe olefin or the ketone, and (3) final reductive elimination of the coupled product. Of the various Cp‘M(NO)(L) groups examined, the Cp*W(NO)(PPh3) fragment has been found to be the best candidate formediating these catalytic steps since it is not prone to form unreactive Cp*W(NO)(PPh3)2 as are some ofthe other fragments that readily decompose to 18e Cp‘M(NO)L2 complexes. Hence, Cp*W(NO)(PPh3)has been utilized to determine if the oxidative addition and hydrometalation steps can occur sequentiallyunder one-pot experimental conditions. However, olefins are too π-acidic and readily form stable 18eCp*W(NO)(PPh3)(η2-olefin) adducts, which prevent oxidative addition of the hydrocarbon substrate tothe tungsten center. Similarly, benzophenone, Ph2CO, and diisopropyl ketone, iPr2CO, also form 1:1η2-CO adducts with the π-basic tungsten center in the 16e fragment. Nevertheless, oxidative additionand hydrometalation do occur sequentially to form the desired aryl alkoxide complex, Cp*W(NO)(OCHiPr2)(Ph), in addition to the Cp*W(NO)(η2-OCiPr2)(PPh3) adduct, when benzene and diisopropyl ketoneare employed as the two substrates. The solid-state molecular structures of cis-Cp*W(NO)[η2-(CH2NMe)P(NMe2)2](H), Cp*W(NO)(OCHiPr2)(Ph), and Cp*W(NO)(η2-OCiPr2)(PPh3) have been establishedby single-crystal X-ray crystallographic analyses.
- Heating a C6D6 solution of cis-Cp*W(NO)[η2-(C6H4)PPh2](H) and excess diisopropyl ketone results in the formation of a final wine red solution whose spectroscopic analysis indicates the presence of two organometallic complexes and some free PPh3. Attempts to separate the two organometallic products either by chromatography or by fractional crystallization have not yet been successful. Nevertheless, the spectroscopic evidence suggests that they are the desired phenyl alkoxide complex Cp*W(NO)(OCHiPr2)(Ph) and the η2-adduct Cp*W(NO)(η2-OCiPr2)(PPh3). In order to confirm this inference, both complexes have been independently synthesized and fully characterized.
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