Abstraction of oxygen-bound leaving groups

Also non-heteroatom-substituted tungsten [440,443,444,451,452,461], molybdenum [437], and chromium carbene complexes [440] have been prepared by a-abstraction of alkoxide. 

Experimental Procedure 3.1.2. Preparation of an Iron Vinylidene Complex by Electrophilic Abstraction CarbonyUrj -cyclopentadienyOldimethylvinylidene)-(triphenylphosphine)iron tetrafluoroborate [464J 

HBF4-Et20 (0.06 mL, 0.53 mmol) is added to a solution of (Cp)(CO)(PPh3) FeC(0)CHMe2 (0.10 g, 0.21 mmol) in diethyl ether (25 mL). A yellow oil precipitates. Propwise addition of trifluoromethanesulfonic anhydride (0.10 mL) causes the oil to slowly redissolve and a peach-colored solid to precipitate. The resulting rnixture is stirred at 20 °C for 3h, and when the solid has settled the supernatant liquid is siphoned oflf with a cannula. The product is washed with diethyl ether (2 x 20 liiL) and dried under reduced pressure. 0.10 g (87%) of the title compound is obtained, mp 135-136 °C (dec.). H NMR (60 MHz, CDCI3) 6 1.66 (s, 6H), 5.36 (d, 1.2 Hz, 5H), 7.50 (m, 15H . 

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Fig. 3.12. Generation of alkylidene complexes by thermal a-abstraction of oxygen-bound leaving groups [53,463J.

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