For (pentafluoroethyl)phenylstannanes, (C F ) SnPh (n=1-3), and dimethylbis(pentafluoroethyl)stannane, (C F ) SnMe , a high yield synthesis was developed by the use of LiC F as a C F transfer reagent. The treatment of these products with gaseous hydrogen chloride or hydrogen bromide afforded (C F ) SnX (X=Cl, Br; n=1-3) in good yields. The (pentafluoroethyl)stannanes were fully characterized by H, C, F and Sn NMR, IR spectroscopy and mass spectrometry. The treatment of the (pentafluoroethyl)tin halides (C F ) SnX with 1,10-phenanthroline (phen) led to the formation of the corresponding octahedrally coordinated complexes [(C F ) SnX (phen)], the structures of which were elucidated by X-ray diffraction analyses. The bromostannane (C F ) SnBr reacted with sodium cyclopentadienide to give the (η -cyclopentadienyl)tris(pentafluoroethyl)stannane, (C F ) SnCp, for which single-crystal X-ray diffraction analysis could be performed. The coupling constants J( Sn, C) and J( Sn, F) of all new stannanes are strongly correlated and sensitive to the substitution pattern at the tin atom. For both coupling constants a negative sign could be assigned.

Syntheses of salts containing the tris(pentafluoroethyl)stannate(II) ion, [Sn(C F ) ] , were achieved through deprotonation of the corresponding stannane, HSn(C F ) , as well as by direct pentafluoroethylation of SnCl with LiC F . The electron-withdrawing substituents have substantial influence on the stability and reactivity of the anion as documented by its treatment with main group halides. Alkyl halides (R-X) underwent nucleophilic substitutions to afford RSn(C F ) , whereas Si, Ge, Sn, P halides gave rise to oxidation processes yielding hypervalent [SnX (C F ) ] salts (X=Cl, Br, I). Moreover the unsymmetrical distannane, nBu SnSn(C F ) , was disclosed as an alternative precursor for the Sn(C F ) moiety. Although neither the solid state structure nor its spectra in alkane solution reveal unexpected peculiarities, unusual dissociation of the compound in coordinating solvents into [nBu Sn(D) ] and [Sn(C F ) ] ions was observed.

In this contribution we present an account on pentafluoroethylated compounds of silicon, germanium and tin. The pronounced electron-withdrawing effect of the pentafluoroethyl group leads to a markedly increased Lewis acidity at the central atom which results in the stabilization of hypervalent complexes, anionic element(II) species as well as remarkable reactivities of element-element and element-hydrogen bonds. By addition to unsaturated C-C bonds or by reaction with organic halides as well as transition-metal complexes the molecules bearing a pentafluoroethyl-element group are readily accessible. Moreover, the utilization of pentafluoroethyl groups facilitates the formation of donor-stabilized germylenes and stannylenes. A series of such compounds serves as suitable pentafluoroethylation reagents. Conversely to the well-studied trifluoromethyl derivatives these compounds frequently exhibit a higher thermostability, which allows a more convenient handling.

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.

A versatile two-step synthesis of tris(pentafluoroethyl)stannane, HSn(C F ) , is presented. Electron-withdrawing C F groups significantly influence the polarity of the tin-hydrogen bond, which allows facile deprotonation of the compound, even in water. The utility of this electron-deficient stannane was illustrated in hydrostannylations of alkenes and alkynes, as well as in dehalogenation reactions. The remarkably high reactivity of HSn(C F ) is demonstrated in fast hydrostannylations, even in the absence of activators, whereby the regioselectivity of this process turns out to be solvent dependent. It is of great advantage that in dehalogenation reactions volatile halogenotris(pentafluoroethyl)stannanes, XSn(C F ) (X=I, Br), are formed that allow facile separation of the tin-containing byproducts from the reaction mixtures.

The treatment of phenyl-protected pentafluoroethylstannanes, Sn(C 2 F 5 ) 4-n Ph n (n = 1-3), with anhydrous HF results in the formation of the corresponding fluorostannanes which are associated in the solid state but form monomeric and dimeric fluoride complexes in solution. Due to the pronounced Lewis acidity caused by the electron-withdrawing pentafluoroethyl groups, these stannanes represent suitable precursors for the synthesis of neutral, monoanionic and dianionic hexacoor- [a] Centrum für Molekulare Materialien,

The tin-tin bond cleavage of hexaorganodistannanes by nucleophiles is a long-known reaction and widely used for stannate formation or stannyl group transfer. Herein, we detail our experiments to provide analytical evidence for the existence of the reasonably stable anionic complexes [XSn(C F ) {Sn(C F ) }] (X=Cl, Br, I, Sn(C F ) ) derived from hexakis(pentafluoroethyl)distannane. NMR investigations at low temperature lend further mechanistic insights. Thus, by detection of the imposing ion [Sn(C F ) {Sn(C F ) } ] , one can surmise that the chemistry of Sn (C F ) has more in common with the isolobal iodine than with classical distannanes.

A convergent approach for the incorporation of tetrafluoroaryl phosphonate moieties into cyclic triphosphazenes and linear phosphazene resins is described. Our high yield procedure is based on the treatment of chlorinated poly‐ and cyclotriphosphazenes with p‐HO(C6F4)P(O)(OR)2 (R = Me, Et) in the presence of potassium carbonate. Characterization of the modified cyclotriphosphazenes was accomplished by NMR and IR spectroscopy as well as by mass spectrometry. Similarly, a phosphazene resin decorated with phosphonic esters is characterized by NMR and IR spectra and GPC. Exchange of the ethyl group by a trimethylsilyl group in the novel phosphazene derivatives was effected by the reaction with trimethylsilyl bromide. The resulting silyl phosphonates were converted into the corresponding phosphonic acids by exposure to an excess of methanol. Proton conductivities of the novel phosphonic acid derivatives of poly‐ and cyclotriphosphazenes were studied by electrochemical impedance spectroscopy under anhydrous conditions.