Structure and Bonding in Bissilylated Arenium Ions

Abstract

The aryl-bridged disilyl cations 8 with an 1,8-naphthalenediyl backbone were synthesized and were identified by NMR spectroscopy. In addition the [B(C 6 F 5 ) 4 ] -salt of the tolyl-bridged cation 8b was characterized by X-ray crystallography. The NMR spectroscopic and the structural data indicate the arenium ion nature of disilyl cations 8. Results of quantum mechanical computations corroborate the experimental findings, and a Bader-type topological analysis of the electron density in model cation 6 gives a refined picture of the bonding in aryl-bridged disilyl cations 6 and 8.

Silaimidazolium and silaimidazolidinium ions

“…21 Recently, GIAO/B3LYP/6-311G(2d,p) NMR calculations were successfully applied to verify computed structures of hydrogen and aryl substituted disilyl cations. 22 Characteristic 29 Si and 13 C NMR chemical shifts calculated at GIAO/B3LYP/6-311G(2d,p)//B3LYP/6-31G(d) for cations 7a, c, d, f, and 8, and silylenes 3 are summarized in Table 3. The agreement between the calculated 13 C NMR chemical shifts for the methine carbon atoms d 13 C calcd and the experimental data for the silylium ions 7a, c, d, f, and 8 is convincing; that is, the deviation Dd 13 C calcd is small [Dd 13 C calcd = d 13 C calcd -d 13 C exp = (-4.3)-(+9.4)].…”

Silylium Ions: From Elusive Reactive Intermediates to Potent Catalysts

“…Structural evidence for the arenium ion nature of the bissilyl cations was provided by the crystallographic characterization of toluenium ion 95a + with a naphthalene-1,8-diyl backbone (Chart 9, left). 214 In contrast, the structure of the bissilyl cation 96 + was discussed as that of a bissilyl cation bridged by a phenyl anion with only little charge delocalization into the ring (Chart 9, right). 215 Thus, the bonding situation in this cation is similar to that in dimeric [AlMe 2 Ph] 2 .…”

“…The Siegel group introduced the family of meta -terphenyl-substituted silyl cations 19 + as a new class of tunable silylium ions, ,, while the Müller laboratory developed cyclic disilyl-substituted arenium ions of type 92 + (Table ). − …”

Benzenium Ion: Aromatic as the π-Complex or Antiaromatic as the σ-Complex Being Somewhat Similar to the Cyclopentadienyl Cation

“…Scheme ). ,,− A benzenelike structure with SiR 3 substituent(s) attracting the positive charge of the structure on the way to the corresponding π-complex 11 is reported. ,,− Structures and spatial magnetic properties of 9 and 10 are identical to those of 5 with the same structural peculiarities (see the Supporting Information).…”

“…The solution 13 C NMR spectra of the hexamethyl analogue of 8 (X = −NO) , exhibit single aromatic and methyl signals; fast dynamic chemical exchange as along the ring proton flip in benzenium cation − or the alternative π-complexation can be concluded. The solid-state structure of the hexamethyl analogue proves π-complexation. ,− The same is true for 8 (cf. Figure and Table ): the nitroso substituent + NO is proved to be positioned above the benzene ring plane; the contact to C(1) is still existing [ d C(1)···N(O) = 2.8 Å], but the distance to the center of the benzene moiety is already smaller [ d N(O)···center = 2.6 Å]; and the bond length of the C(1)–H proton in 8 proves normal: on the completed, intact aromatic 6π electron delocalization of the benzene moiety in 8 can be readily concluded.…”