P3F92–: An All-Pseudo-π* 2π-Aromatic

Priyakumari, Chakkingal P.; Jemmis, Eluvathingal D.

doi:10.1021/ja408308g

“…structure of 1 is fully characterized by NMR ( 1 H, 13 C, 11 B,29 Si, and mass spectrometry (LIFDI,SI) techniques. The 1 H and 13 C NMR spectral pattern and the relative integration values of 1 are in agreement with the molecular structure. The 11 B NMR spectrum of 1 shows a singlet at d = 11.09 ppm, which falls in the aromatic region of 11 B NMR.…”

mentioning

confidence: 99%

“…The solvent is reduced to 5 mL under vacuum and green block-shaped crystals of fourmembered heterocycle (2) (1-aza-2,3-disila-4-boretidine derivative) [20] are obtained in 78 % yield at À30 8C after two days. Compound 2 is fully characterized by NMR ( 1 H, 13 C, 11 B, 29 Si, Figures S7-S10, SI) and mass spectrometry (LIFDI, Figure S11, SI) methods. The 11 B NMR spectrum of 2 exhibits a sharp singlet at d = À31.18 ppm and shifts to downfield with respect to 1 whereas the 29 Si NMR resonances are observed at d = À9.55 ppm for NSiMe 3 and d = À31.94 ppm for amidinato-Si.…”

mentioning

confidence: 99%

A Neutral Three‐Membered 2π Aromatic Disilaborirane and the Unique Conversion into a Four‐Membered BSi₂N‐Ring

Sarkar

¹

,

Chaliha

²

,

Siddiqui

³

et al. 2020

Self Cite

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We report the design, synthesis, structure, bonding, and reaction of a neutral 2p aromatic three-membered disilaborirane. The disilaborirane is synthesized by a facile one-pot reductive dehalogenation of amidinato-silylene chloride and dibromoarylborane with potassium graphite. Despite the tetravalent arrangement of atoms around silicon, the threemembered silicon-boron-silicon ring is aromatic, as evidenced by NMR spectroscopy, nucleus independent chemical shift calculations, first-principles electronic structure studies using density functional theory (DFT) and natural bond orbital (NBO) based bonding analysis. Trimethylsilylnitrene, generated in situ, inserts in the SiÀSi bond of disilaborirane to obtain a four-membered heterocycle 1-aza-2,3-disila-4-boretidine derivative. Both the heterocycles are fully characterized by X-ray crystallography. The synthesis of three-membered aromatic rings has been a fascinating topic for the chemical community during the last decades. Aromaticity and Hückel 4n + 2 rule continue its diversity with the smallest, largest, homo-, hetero-, Mçbius, all-carbon, organometallic-and so on, but most of these involve overlap of p, d and f orbitals. [1-3] A challenging question is it possible to generate a carbon-free neutral threemembered aromatic ring. The neutral three-membered aromatic compound with 2p electrons is one of the longest quests to inorganic, organic and theoretical chemists. [1, 4] Most of the reported small aromatic species are anionic or cationic. [4-11] Recent reports of the carbon-free aromatic systems all involve charged species: B 3 À (observed in gas phase), [6] Li 3 + (observed in gas phase), [7] [B 3 (CO) 3 ] + (observed in gas phase), [8] [B 3 (NCy 2) 3 ] 2À (characterized by X-ray), [9] [SiRSi 2 R' 2 (R = Si t Bu 3 , R' = SiMe t Bu 2)] + (characterized by X-ray), [10] [Ge 3 R 3 , R = Si t Bu 3 ] + (characterized by X-ray). [11] To develop carbon-free small neutral Hückel p systems with orbitals beyond p, d and f, unique design strategies must be assembled. Here, we present a novel approach where two of the three p orbitals are replaced by s* MOs to generate a neutral 2p aromatic three-membered disilaborirane. To synthesize carbon-free neutral three-membered 2p aromatic system, we replace one of the CH group of the classical cyclopropenyl cation by isoelectronic BR group and the remaining two CH groups by two amidinato-silylene groups to retain the 2p aromaticity, leading to the formation of a disilaborirane. [12] We envision that the extra electrons from the two amidinato-ligands will populate the stable delocalized p MO resulting from the 2p orbital of boron atom and the two s* MOs on silicon atoms in the neutral Si 2 B three-membered ring. 13 The two p electrons will conjugate in the field of the three nuclei of Si-B-Si. Accordingly, we design and synthesize the three-membered disilaborirane (Scheme 1). A 2:1:4 molar ratio of amidinato-silylene chloride [LSi-Cl; L = PhC(NtBu) 2 ], dibromo(2,4,6-triisopropylphenyl)borane and KC 8 is reacted in THF at À78 8C and...

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“…This prompted us to try L = F, as it is already known that F atoms can stabilize hypervalent structures and we have proposed an unusual system stabilized by F atoms, (PF 3 ) 2− 3 . 2 To our surprise, even perfluorination could not stabilize structures 2 and 3. This implies that we need to look into the details of frontier orbitals of sulfurane fragments and their isolobal relationships.…”

Section: Resultsmentioning

confidence: 75%

“…The entry of anionic oligomers of CO and PF 3 in literature showed us examples for skeletal bonding involving fragment antibonding orbitals. 2,30 In these molecules, one fragment orbital is the radial nonbonding orbital and the other is antibonding orbital. The unusual feature of structures 14-16, is that both of their fragment frontier orbitals are antibonding; no surprise that they are less stable kinetically.…”

Section: Resultsmentioning

confidence: 99%

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Computational design of Oligo-sulfuranes

Priyakumari

¹

,

Jemmis

²

2016

J Chem Sci

0

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We studied the effect of electronegativity perturbation on the isolobal behavior of tetra-coordinate hypervalent compounds of S (sulfuranes, SL 4 , L is any atom or group which can provide one electron for S-L bonding). Though formally the fragment SL 4 obtained from SL 6 is an isolobal equivalent of CH 2 , a qualitative molecular orbital study shows that only SF 2 H 2 with equatorial F atoms is a practical isolobal substitute for CH 2 and can form oligomers, (SF 2 H 2) 2 , (14), (SF 2 H 2) 3 , (15) and (SF 2 H 2) 4 , (16) analogous to ethylene, cyclopropane and cyclobutane, respectively. DFT computations at the B2PLYP/6-311++g(d,p), MP2/aug-cc-pVTZ and B3LYP/6-311++g(d,p) levels confirm these structures to be minima on the PES. The skeletal S-S bonds in these structures are formed solely by the bonding combination of anti-bonding fragment orbitals of SF 2 H 2. In contrast, per-fluorination, the usual way to stabilize hypervalent structures, is found to have an opposite effect here. Calculations at the same levels show (SF 4) 2 , (SF 4) 3 , and (SF 4) 4 not to be minima. The highly stable HOMO of SF 4 fragment and large HOMO-LUMO gap makes SF 4 a stable entity, preventing it from oligomerization. Out of the various isomers of SF n H 4−n , n = 0-4, only SF 2 H 2 with equatorial F atoms can form oligomeric sulfuranes. Substitution of F by heavier analogs of the group did not lead to any stable oligomers.

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A Neutral Three‐Membered 2π Aromatic Disilaborirane and the Unique Conversion into a Four‐Membered BSi₂N‐Ring

Sarkar

¹

,

Chaliha

²

,

Siddiqui

³

et al. 2020

Self Cite

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We report the design, synthesis, structure, bonding, and reaction of a neutral 2p aromatic three-membered disilaborirane. The disilaborirane is synthesized by a facile one-pot reductive dehalogenation of amidinato-silylene chloride and dibromoarylborane with potassium graphite. Despite the tetravalent arrangement of atoms around silicon, the threemembered silicon-boron-silicon ring is aromatic, as evidenced by NMR spectroscopy, nucleus independent chemical shift calculations, first-principles electronic structure studies using density functional theory (DFT) and natural bond orbital (NBO) based bonding analysis. Trimethylsilylnitrene, generated in situ, inserts in the SiÀSi bond of disilaborirane to obtain a four-membered heterocycle 1-aza-2,3-disila-4-boretidine derivative. Both the heterocycles are fully characterized by X-ray crystallography. The synthesis of three-membered aromatic rings has been a fascinating topic for the chemical community during the last decades. Aromaticity and Hückel 4n + 2 rule continue its diversity with the smallest, largest, homo-, hetero-, Mçbius, all-carbon, organometallic-and so on, but most of these involve overlap of p, d and f orbitals. [1-3] A challenging question is it possible to generate a carbon-free neutral threemembered aromatic ring. The neutral three-membered aromatic compound with 2p electrons is one of the longest quests to inorganic, organic and theoretical chemists. [1, 4] Most of the reported small aromatic species are anionic or cationic. [4-11] Recent reports of the carbon-free aromatic systems all involve charged species: B 3 À (observed in gas phase), [6] Li 3 + (observed in gas phase), [7] [B 3 (CO) 3 ] + (observed in gas phase), [8] [B 3 (NCy 2) 3 ] 2À (characterized by X-ray), [9] [SiRSi 2 R' 2 (R = Si t Bu 3 , R' = SiMe t Bu 2)] + (characterized by X-ray), [10] [Ge 3 R 3 , R = Si t Bu 3 ] + (characterized by X-ray). [11] To develop carbon-free small neutral Hückel p systems with orbitals beyond p, d and f, unique design strategies must be assembled. Here, we present a novel approach where two of the three p orbitals are replaced by s* MOs to generate a neutral 2p aromatic three-membered disilaborirane. To synthesize carbon-free neutral three-membered 2p aromatic system, we replace one of the CH group of the classical cyclopropenyl cation by isoelectronic BR group and the remaining two CH groups by two amidinato-silylene groups to retain the 2p aromaticity, leading to the formation of a disilaborirane. [12] We envision that the extra electrons from the two amidinato-ligands will populate the stable delocalized p MO resulting from the 2p orbital of boron atom and the two s* MOs on silicon atoms in the neutral Si 2 B three-membered ring. 13 The two p electrons will conjugate in the field of the three nuclei of Si-B-Si. Accordingly, we design and synthesize the three-membered disilaborirane (Scheme 1). A 2:1:4 molar ratio of amidinato-silylene chloride [LSi-Cl; L = PhC(NtBu) 2 ], dibromo(2,4,6-triisopropylphenyl)borane and KC 8 is reacted in THF at À78 8C and...

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P₃F₉^2–: An All-Pseudo-π* 2π-Aromatic

Cited by 14 publications

References 46 publications

A Neutral Three‐Membered 2π Aromatic Disilaborirane and the Unique Conversion into a Four‐Membered BSi₂N‐Ring

A Neutral Three‐Membered 2π Aromatic Disilaborirane and the Unique Conversion into a Four‐Membered BSi₂N‐Ring

Computational design of Oligo-sulfuranes

A Neutral Three‐Membered 2π Aromatic Disilaborirane and the Unique Conversion into a Four‐Membered BSi₂N‐Ring

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P3F92–: An All-Pseudo-π* 2π-Aromatic

Cited by 14 publications

References 46 publications

A Neutral Three‐Membered 2π Aromatic Disilaborirane and the Unique Conversion into a Four‐Membered BSi2N‐Ring

A Neutral Three‐Membered 2π Aromatic Disilaborirane and the Unique Conversion into a Four‐Membered BSi2N‐Ring

Computational design of Oligo-sulfuranes

A Neutral Three‐Membered 2π Aromatic Disilaborirane and the Unique Conversion into a Four‐Membered BSi2N‐Ring

Contact Info

Product

Resources

About

P₃F₉^2–: An All-Pseudo-π* 2π-Aromatic

A Neutral Three‐Membered 2π Aromatic Disilaborirane and the Unique Conversion into a Four‐Membered BSi₂N‐Ring

A Neutral Three‐Membered 2π Aromatic Disilaborirane and the Unique Conversion into a Four‐Membered BSi₂N‐Ring

A Neutral Three‐Membered 2π Aromatic Disilaborirane and the Unique Conversion into a Four‐Membered BSi₂N‐Ring