Reduction of Metal-Stabilized α-CF3-Carbenium Ion Complexes under Mild Conditions: Synthesis, Structures, and Reactivity
✍ Scribed by Michel Gruselle; Bernard Malézieux; Román Andrés; Hani Amouri; Jacqueline Vaissermann; Gagik G. Melikyan
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 443 KB
- Volume
- 2000
- Category
- Article
- ISSN
- 1434-1948
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✦ Synopsis
Complexed α-CF 3 propargyl alcohols of the general formula [{Co(CO) 3 MoCp(CO) 2 }{µ-η 2 ,η 3 -CH 3 (CH 2 ) 4 CϵCCH(CF 3 )}][BF 4 ] (8) with NaSMe unexpectedly afforded the reduced alkyne 13), along with the alkyne-thioether diastereomers Co 2 (CO
). An Xray molecular structure of the propargyl-alcohol complex primarily by the formation of the transient radical species, which are subsequently transformed into the reduced alkyne [{Co 2 (CO) 4 dppm}{µ-η 2 ,η 2 -C 6 H 5 CϵCCH(CF 3 )(OH)}] (5) was also determined. The related carbenium ions [(M 2 L 6 ){µ-η 2 ,η 3 -complexes by hydrogen abstraction from the solvent medium. Interestingly, in the case of the complexed alcohols RCϵCCH(CF 3 )}][BF 4 ] (8-12) were obtained from the parent propargyl alcohol complexes by direct protonation with HBF 4 • [{Co 2 (CO) 5 P(C 6 H 5 ) 3 }{µ-η 2 ,η 2 -RCϵCCH(CF 3 )(OH)}] (3a,b) and (4a,b), the reduction process occurs in acidic medium in THF/ Et 2 O in diethyl ether. These carbenium ions were reduced further by Zn in CH 2 Cl 2 to give the alkyne adducts [(M 2 L 6 ){µ-CH 2 Cl 2 . An extensive study of the electronic and steric factors that influence the stability and reactivity of the carbenium ions η 2 ,η 2 -RCϵCCH 2 (CF 3 )}] (13-17), as confirmed by the X-ray molecular structure of [(Co 2 (CO) 4 dppm){µ-η 2 ,η 2 -C 6 H 5 -were performed, which allowed us to explain the behavior of the related radical species in solution during the reduction process. CϵCCH 2 (CF 3 )}] (17). Treatment of the carbenium ion complex Metal-stabilized carbon electron deficient systems of the In a preliminary communication, [9] we have shown that [b]