A series of peralkylated polyaminophosphazenium cations exhibiting extraordinary base resistance under phase-transfer conditions were efficiently synthesized from readily available starting materials. Their half lives under these conditions exceed those of the most stable conventional organic cations by factors of up to 3000.

Several peralkylated polyaminophosphazenium cations were evaluated for the generation of novel anhydrous F- salts. Two of them have been characterized by X-ray analysis and are particularly soluble, even in apolar aprotic solvents like benzene or THF, one of them even at -30 degrees C. Such solutions probably represent the most basic metal-free and stable media known to date. Comparison of these fluorides with known F- sources demonstrates that they are of unprecedented reactivity and selectivity in E2 elimination reactions.

The electrophilic character of tin in the new compounds 3 is manifested in reactions with n~c l e o p h i l e s .~'~~ With pyridine and with 2,2'-bipyridyl, 3a forms the adducts 6a and 7a, ["] in which the tin atom is coordinatively saturated (cf. Table 1, ' 9Sn resonance signals at high field). As in the case of 3a, dynamic processes can also be demonstrated for 6a and 7a by 'Hand I3C-NMR spectroscopy. The structure for the intermediates 4 is based on consistent sets of NMR data (cf. Table 1 for 4b) and is confirmed by the isolation of the final product 5. The results suggest that the formation of compounds 4 and 5 from 3 and 4 respectively proceeds via an Sn-Substituted vinyl cation 8. [Z 4586 IE] German version : Angew. Chem. 103 (1 991) 1374 CAS Reeistrv numbers:[9] 3b, 3c, 3d, 3e: relevant 'Hand I3C NMR data correspond to the values for 3a. 119Sn/11B NMR (CD,CI,, 298 K): 6("9Sn)/6(1'B) = + 207.5/ -4.9 (3b); + 203.1/-4.5 (3c); + 2232-4.3 (3d); + 202.1/-4.4 (3e).[lo] R. Boese, D. Blaser, J Appl. Crysrallogr. 22 (1989) 394.[11] X-ray structure analysis of 3a at 115 K : P2,/c, a = 11.924 (2), b = 14.512(3), c = 14.299(2) A, a = y = 90". = 97.29(1)", V = 2454.4(7) A3, 2 = 4, e,.,,, = 1.274 gcm3, p = 1.05 mm-', Mo,. radiation (graphite monochromator), i . = 0.71069 A; 3414 independent reflections. 2979 observed (4 2 4c(F)); 2@(max) = 45"; absorption correction: empirical, Y scans in the 28 range, r): 3 2 35 max/min. Transmission: 0.926/0.815, R,,,,

le 1 fur 4b) und wird durch die Isolierung der Endprodukte 5 gesichert. Es liegt nahe, die Stufe eines Sn-substituierten Vinyl-Kations 8 vorzuschlagen. die bei der Bildung von 4 und 5 aus 3 bzw. 4 durchlaufen wird.

Nitromethane, a potential hazard in the synthesis of the phosphazenium ion 1, is no longer the recommended solvent. The preparation first described in this journal in 1991 has been modified for safety's sake.