A stable aromatic species containing silicon. Synthesis and characterization of the 1-tert-butyl-2,3,4,5-tetraphenyl-1-silacyclopentadienide anion

Hong, Jang Hwan; Boudjouk, Philip

doi:10.1021/ja00066a090

Cited by 107 publications

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“…7 The significant shift (downfield in 29 Si and upfield in 13 C NMR) with respect to the neutral precursor disilane was attributed to cyclic delocalization. 7 Unfortunately, for this particular silolide, no X-ray structure could be obtained, 7 thus it remains unclear whether or not the NMR observations are indeed related to planarization.…”

Section: Dmentioning

confidence: 99%

“…1 Si and upfield in 13 C NMR) with respect to the neutral precursor disilane was attributed to cyclic delocalization. 7 Unfortunately, for this particular silolide, no X-ray structure could be obtained, The situation is further complicated by the fact that for 1-Me-tetraphenylsilolide the dimerization of the anion was reported, yielding tricyclic systems with a central 1,3-disilacyclobutane ring. …”

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confidence: 99%

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Planar lithium silolide: aromaticity, with significant contribution of non-classical resonance structures

et al. 2017

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The first planar lithium silolide characterized by X-ray crystallography is reported. The structural data, NMR and DFT results reveal high aromatic character, with the unusual dominance of non-classical resonance structures.The cyclopentadienide ion is a textbook example for a planar aromatic compound alongside benzene. 1a The replacement of a carbon atom by silicon results in the silacyclopentadienyl (silolide) anion, 1b-f for which the planarity and the apparently related aromaticity are far from being trivial. the structural similarity for the isoelectronic silolide anion is also expected. Computational studies have also predicted that silolide is pyramidal; 5 however, even with the non-planar silicone a moderate aromaticity was reported for the parent compound, 5a furthermore the presence of the countercation has a flattening effect on silicon. 5 A noteworthy feature of the calculated planar silolide structure was the equalization of the C-C distances, the Cb-Cb 0 bond being slightly (by 0.008 Å) shorter than Ca-Cb. Accordingly, for the planar silolide the ''b'' resonance structure had larger (30%) weight than the classical ''a'' (17%) according to a natural resonance theory (NRT) study (Fig. 1 Si and upfield in 13 C NMR) with respect to the neutral precursor disilane was attributed to cyclic delocalization. 7 Unfortunately, for this particular silolide, no X-ray structure could be obtained, The situation is further complicated by the fact that for 1-Me-tetraphenylsilolide the dimerization of the anion was reported, yielding tricyclic systems with a central 1,3-disilacyclobutane ring. 8While no planar silolide has been reported to date, Sekiguchi's 1,2,3-trisilacyclopentadienide and 1,2-disila-3-germacyclopentadienide anions have been shown to exhibit planar X-ray structures with equalized bond lengths, and with 29 Si NMR data indicating aromaticity.9 Furthermore, nearly planar transition metal (Zr, Hf or Ru) complexed silolides were also synthetized. 10In a computational search for planar silolide anions we revealed that due to the charge stabilizing effect, p-acceptor SiH 3 groups at the a carbons enhance the planarity and aromaticity of the naked silolide ring considerably. 5d This effect was already noted on the related phosphole with SiH 3 11 and BH 2 12 substituents, and the charge stabilizing effect was also shown in the case of the silyl-substituted stannole dianion. 13Furthermore, the a-silyl groups enhanced the relative weight of the b type resonance structure. 5d Z 5 -Coordination of the Li Fig. 1 Resonance structures for planar heteroaromatic five membered rings, with different heteroelements. E can be S, PR, or SiR À (R:H, alkyl, aryl, etc.). The numbering of the ring atoms is shown on resonance structure a.

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Section: Dmentioning

confidence: 99%

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confidence: 99%

Planar lithium silolide: aromaticity, with significant contribution of non-classical resonance structures

et al. 2017

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“…[2] Over the past few decades, silole and germole anions have already been synthesized by deprotonation, dehalogenation, or transmetallation of the corresponding metaloles, and their structures have been discussed extensively by NMR, or X-ray structural analysis. [3][4][5][6] Boudjouk reported the first NMR characterization of a silole anion. [5] The negative charge was concluded to delocalize in the silole ring.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Reactions of Stannole Anions

2007

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The synthesis of stannole anions bearing various substituents on the tin atom is described. The reduction of hexaphenylstannole by the proper amount of lithium gave 1,2,3,4,5‐pentaphenylstannole anion 1. The reaction of 1 with 1,n‐dihaloalkanes (n = 1, 3, 4, 5, 6) gave the corresponding 1,n‐bis(1‐stannacyclopentadien‐1‐yl)alkanes. In contrast, the reaction of 1 with 1,2‐dihaloalkanes gave the 1,1′‐bistannole. The reactions of stannole dianion 3 with an equimolar amount of bulky alkyl, aryl, silyl, and stannyl halides gave the corresponding stannole anions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

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“…Especially their anions/dianions have been reported to be aromatic systems in experimental [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] and theoretical studies [26][27][28][29][30][31] except trimethylsilyl group substituted silole and germole anions [10,18,20] . C α , C β ,C αi , C βi atoms of 2,3,4,5-tetraphenyl substituted group 14 metallole anions/dianions are participate in π-delocalization of the negative charge on Si atom to give chemical shift changes ongoing from group 14 metalloles to their anions/dianion [9,10,12] . Lately siloles have been attracted by the unique electronic structures [32] and novel aggregation-induced emission (AIE) characteristics [33] .…”

Section: Introductionmentioning

confidence: 99%

Synthesis of 1,1-Bis(n-butyl, t-butyl)-2,3,4,5-Tetraphenyl-1-Silacyclopentadiene and NMR Study of Their 2,5-Carbodianions

Hong

2013

Journal of the Chosun Natural Science

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1,1-Bis(n-butyl)-2,3,4,5-tetraphenyl-1-silacyclopentadiene (3) and 1,1-bis(t-butyl)-2,3,4,5-tetraphenyl-1-silacyclopentadiene (4) are synthesized from the reaction of the versatile silole dianion (2) with n-butyl bromide and t-butyl bromide. Reduction of (3) and (4) with an excess of lithium to give 1,1-bis(n-butyl)-2,5-dilithio-2,3,4,5-tetraphenyl-1-silacyclopenta-3-enide (6) and 1,1-bis(t-butyl)-2,5-dilithio-2,3,4,5-tetraphenyl-1-silacyclopenta-3-enide (7). 13C-NMR study of two 2,5-carbodianions (6 and 7) shows tert-carbanion at 73.18 and 78.12 ppm respectively. Two bulky tert-butyl groups in (7) increase the inversion barrier at the tert-carbanion, line broadenings of tert-butyl groups in 1 H and 13 C-NMR spectrum are observed.

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A stable aromatic species containing silicon. Synthesis and characterization of the 1-tert-butyl-2,3,4,5-tetraphenyl-1-silacyclopentadienide anion

Cited by 107 publications

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Planar lithium silolide: aromaticity, with significant contribution of non-classical resonance structures

Planar lithium silolide: aromaticity, with significant contribution of non-classical resonance structures

Synthesis and Reactions of Stannole Anions

Synthesis of 1,1-Bis(n-butyl, t-butyl)-2,3,4,5-Tetraphenyl-1-Silacyclopentadiene and NMR Study of Their 2,5-Carbodianions

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