Safe generation of (perfluoroethyl)lithium

Dean M. Roddick
Amoco Chemical
Naperville, Ill.
Stanford University

Chemical & Engineering News (6 Oct 1997) Vol. 75, No. 40, pp. 6.

A number of years ago, we reported the use of (perfluoroethyl)lithium, generated in situ from metal-halogen exchange between C2F5Li and n-BuLi in ether at -90 C, in the synthesis of (perfluoroethyl)phosphines [Inorg. Chem., 28, 1624 (1989)]. Since then, we have found this reagent to be quite general for the alkylation of phosphorus halide compounds, but wish to report a potential hazard with this procedure.

Several times in our laboratory, we have experienced a violent decomposition of the ethereal C2F5Cl/n-BuLi solution after the addition of just a few drops of (R)nPCl3=n. In each of these cases, the metal-halogen exchange temperature was maintained below -90 C. We believe that this problem is due to a buildup of starting reagents at low temperatures, and wish to caution anyone who is using our published procedure to avoid temperatures below -90 C for this metal-halogen exchange reaction.

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