On Pentakis(pentafluoroethyl)stannate, [Sn(C F ) ] , and the Gas-Free Generation of Pentafluoroethyllithium, LiC F.

Pentafluoroethyllithium, LiC F , has been established as an efficient and versatile reagent for the transfer of the pentafluoroethyl unit to a number of electrophiles. Here, the stability of this species up to -40 °C is of advantage, particularly in comparison to its smaller congener LiCF . The usual production of LiC F , however, from gaseous HC F or IC F and strong bases requires specially designed apparatuses, which severely impeded its value as a laboratory reagent. In this contribution we communicate an alternative gas-free and highly efficient protocol for the synthesis of LiC F from the already commercialized stannate salt [PPh ][Sn(C F ) ]. The [Sn(C F ) ] anion represents not only the first example of a structurally characterized hypervalent pentaalkylstannate but also serves as a precursor for the synthesis of the homoleptic tetrakis(pentafluoroethyl)stannane, Sn(C F ) . The reaction of the latter with n-butyllithium provides an insight into the mechanism of LiC F generation.