A Free Silylium Ion: A Cyclotetrasilenylium Ion with Allylic Character

Abstract

cyclotetrasilenylium (3 + ), a silylium ion with an allylic cation character, was synthesized by the reaction of tetrakis(di-tertbutylmethylsilyl)disilene with [Et 3 Si(benzene)] + • TPFPBin toluene. The NMR spectral data and X-ray structure of 3 + • TPFPBshow that it is a free silylium ion with an allylic cation structure.

A heavy analogue of the smallest bridgehead alkene stabilized by a base

“…The lowest unoccupied molecular orbital (LUMO) of 1 opt is an out-of-phase combination of p*(Si1 À Si2) orbital and a p-type orbital on Si3 atom, and the LUMO þ 1 is an anti-bonding orbital between Si1 and Si3 atoms. The HOMO-1, LUMO and LUMO þ 1 orbitals resemble the frontier orbitals of those of tetrasilahomocyclopropenylium cation reported by Sekiguchi et al 22,34 These orbital features indicate that the zwitterionic resonance structure with tetrasilahomocyclopropenylium cation over the Si1-Si2-Si3 atom, and silyl anion on Si1 atoms (1 z , Fig. 3d) contributes significantly to the electronic structure of 1 opt .…”

Reductive Catenation of Phosphine Antimony Complexes

“…[4] Complexes of antimony or phosphorus acceptors have been demonstrated to undergo 2electron, [4a] 8-electron, [4b,c] 10-electron, [4d] or 18-electron [4e] redoxp rocesses to give the catena-pnictogen cations, [ 1 ] 2 + , [ 2 ] 4 + , [ 3 ] 2 + and [5] 3+ ,r espectively ( Figure 1). We now report an unprecedented 14-electron reductive catenation to form the cation [(Ph 3 P) 4 Sb 6 ] 4+ ,d enoted [4] 4+ ,w hich is the first example of framework B (k > 0) for antimony.…”

“…[13] In the 19 FNMR spectrum, asignal for the Sb À F moiety of 6(OTf) 2 at d F = À117.5 ppm is significantly shielded compared to that of free FSb(OTf) 2 (À95.3 ppm), but deshielded compared to those for derivatives of [(R 3 P) 2 SbF] 2+ (R = Me,E t, Pr,B u; range of d F = À173.4 to À187.1 ppm), [4b] likely as aresult of the relatively low basicity of PPh 3 .T he 19 FNMR resonance signal for the triflate substituents in 6(OTf) 2 (d F = À78.8 ppm) is comparable to that of [PPh 4 ][OTf] (À79.4 ppm) and we therefore conclude that the triflate anions are dissociated, giving [(Ph 3 P) 2 SbF] 2+ , denoted [6] 2+ ,inM eCN solutions of 6(OTf) 2 .…”

Heavy Analogs of Carbenium Ions: Si‐, Ge‐, Sn‐ and Pb‐Centered Cations

“…This value of 2653 ppm by far exceeded the value expected on the basis of the 29 Si-119 Sn chemical shift empirical correlation (1500-2000 ppm) and the value (ca. 99 The positive charge in the cationic portion 46 + was delocalized over the three Si atoms (Si1, Si2 and Si3), which was seen in the essentially planar geometry around them and Si1-Si2/Si2-Si3 bond lengths intermediate between those of typical single and double bonds. 15b Several other remarkable representatives of the stable cations based on the heavy group 14 elements were reported quite recently.…”