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Gupta D, Einholz R, Bettinger HF. Strain induced reactivity of cyclic iminoboranes: the (2 + 2) cycloaddition of a 1 H-1,3,2-diazaborepine with ethene. Chem Sci 2024; 15:666-674. [PMID: 38179531 PMCID: PMC10763563 DOI: 10.1039/d3sc04901a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2023] [Accepted: 11/19/2023] [Indexed: 01/06/2024] Open
Abstract
Iminoboranes have gathered immense attention due to their reactivity and potential applications as isoelectronic and isosteric alkynes. While cyclic alkynes are well investigated and useful reagents, cyclic iminoboranes are underexplored and their existence was inferred only via trapping experiments. We report the first direct spectroscopic evidence of a cyclic seven-membered iminoborane, 1-(tert-butyldimethylsilyl)-1H-1,3,2-diazaborepine 2, under cryogenic matrix isolation conditions. The amino-iminoborane 2 was photochemically generated in solid argon at 4 K from 2-azido-1-(tert-butyldimethylsilyl)-1,2-dihydro-1,2-azaborinine (3) and was characterized using FT-IR, UV-vis spectroscopy, and computational chemistry. The characteristic BN stretching vibration (1751 cm-1) is shifted by about 240 cm-1 compared to linear amino-iminoboranes indicating a significant weakening of the bond. The Lewis acidity value determined computationally (LAB = 9.1 ± 2.6) is similar to that of boron trichloride, and twelve orders of magnitude lower than that of 1,2-azaborinine (BN-aryne, LAB = 21.5 ± 2.6), a six-membered cyclic iminoborane. In contrast to the latter, the reduced ring strain of 2 precludes nitrogen fixation, but it unexpectedly allows facile (2 + 2) cycloaddition reaction with C2H4 under matrix isolation conditions at 30 K.
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Affiliation(s)
- Divanshu Gupta
- Institut für Organische Chemie, Universität Tübingen Auf der Morgenstelle 18 72076 Tübingen Germany
| | - Ralf Einholz
- Institut für Organische Chemie, Universität Tübingen Auf der Morgenstelle 18 72076 Tübingen Germany
| | - Holger F Bettinger
- Institut für Organische Chemie, Universität Tübingen Auf der Morgenstelle 18 72076 Tübingen Germany
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2
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Bhagat V, Bettinger HF. Computational Exploration of the Intersystem Crossing from the X̃ 3A 2 to the ã 1A 1 State in Boryl Nitrenes upon Photoexcitation. J Phys Chem A 2022; 126:7660-7666. [PMID: 36254874 DOI: 10.1021/acs.jpca.2c05491] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The boryl nitrene CatBN (Cat = catecholato) turns highly reactive toward small inert molecules upon irradiation of its triplet ground state X̃3A2 with light of wavelength λ > 550 nm. A computational study of a model boryl nitrene using complete active space self-consistent field (CASSCF) theory provides evidence for the population of the highly reactive electronic state ã1A1 upon irradiation. Potential energy scans connecting different critical points (minima, minimum energy crossing points, and conical intersections) reveal two possible pathways that could relax photoexcited boryl nitrene from the Franck-Condon region of Ã3B1 to the ã1A1 state minimum. Considering the energy barriers to relaxation from one electronic state to another and the magnitude of spin-orbit couplings, the energetically most favorable pathway involves photoexcitation to Ã3B2, followed by intersystem crossing to the open-shell singlet state (b̃1A2) and internal conversion to ã1A1. The relevant minimum energy crossing point is about 7-8 kcal mol-1 higher in energy than the Franck-Condon region.
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Affiliation(s)
- Virinder Bhagat
- Institut für Organische Chemie, Universität Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany
| | - Holger F Bettinger
- Institut für Organische Chemie, Universität Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany
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3
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Vogler D, Schöner M, Kaifer E, Himmel H. Bistriazoles Connected Through a B−B Bridge, Synthesized by Highly Selective Dipolar Cycloaddition Reactions of a Diazido‐diborane(4). Chemistry 2022; 28:e202201389. [PMID: 35703332 PMCID: PMC9544427 DOI: 10.1002/chem.202201389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Indexed: 11/11/2022]
Abstract
In this work we report the first cycloaddition reactions between a diazido diborane(4) and terminal alkynes, providing unique access to bis‐1,2,3‐triazoles connected by a B−B bridge. The catalyst‐free reactions are highly selective, yielding exclusively the thermodynamically disfavored bis‐1,4‐triazoles. The reactions are enabled by the high thermal stability of the diazido‐diborane [B(hpp)(N3)]2 (hpp=1,3,4,6,7,8‐hexahydro‐2H‐pyrimido[1,2‐α]pyrimidinate). Due to the tetra‐coordinate boron atoms in this reagent, the reactions are tolerant with respect to the introduction of Lewis‐basic groups at the alkyne. The scope and limitations of the new reactions are discussed.
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Affiliation(s)
- Daniel Vogler
- Anorganisch-Chemisches Institut Ruprecht-Karls Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Maximilian Schöner
- Anorganisch-Chemisches Institut Ruprecht-Karls Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Elisabeth Kaifer
- Anorganisch-Chemisches Institut Ruprecht-Karls Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Hans‐Jörg Himmel
- Anorganisch-Chemisches Institut Ruprecht-Karls Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Germany
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4
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Bhagat V, Schumann J, Bettinger HF. Unusual Nitrene Oxidation Product Formation by Metathesis Involving the Dioxygen O-O and Borylnitrene B-N Bonds. Chemistry 2020; 26:12654-12663. [PMID: 32902001 PMCID: PMC7590100 DOI: 10.1002/chem.202002445] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 06/11/2020] [Indexed: 01/08/2023]
Abstract
The reaction of dioxygen with nitrenes can have significant energy barriers, although both reactants are triplet diradicals and the formation of nitroso-O-oxides is spin-allowed. By means of matrix-isolation infrared spectroscopy in solid argon, nitrogen, and neon, and through high-level computational quantum chemistry, it is shown herein that a 3-nitreno-1,3,2-benzodioxaborole CatBN (Cat=catecholato) reacts with dioxygen under cryogenic conditions thermally at temperatures as low as 7 K to produce two distinct products, an anti-nitroso-O-oxide and a nitritoborane CatBONO. The computed barriers for the formation of nitroso-O-oxide isomers are very low. Whereas anti-nitroso-O-oxide is kinetically trapped, its bisected isomer has a very low barrier for metathesis, yielding the CatBO+NO radicals in a strongly exothermic reaction; these radicals can combine under matrix-isolation conditions to give nitritoborane CatBONO. The trapped isomer, anti-nitroso-O-oxide, can form the nitritoborane CatBONO only after photoexcitation, possibly involving isomerization to the bisected isomer of anti-nitroso-O-oxide.
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Affiliation(s)
- Virinder Bhagat
- Institut für Organische ChemieUniversität TübingenAuf der Morgenstelle 1872076TübingenGermany
| | - Julia Schumann
- Institut für Organische ChemieUniversität TübingenAuf der Morgenstelle 1872076TübingenGermany
| | - Holger F. Bettinger
- Institut für Organische ChemieUniversität TübingenAuf der Morgenstelle 1872076TübingenGermany
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Clough BA, Mountford P. Synthesis of Titanium Borylimido Compounds Supported by Diamide-Amine Ligands and Their Reactions with Alkynes. Organometallics 2018. [DOI: 10.1021/acs.organomet.8b00250] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Benjamin A. Clough
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - Philip Mountford
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA, United Kingdom
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Ito M, Itazaki M, Nakazawa H. Selective Double Hydroboration and Dihydroborylsilylation of Organonitriles by an Iron–indium Cooperative Catalytic System. Inorg Chem 2017; 56:13709-13714. [DOI: 10.1021/acs.inorgchem.7b01369] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Masaki Ito
- Department of Chemistry, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Masumi Itazaki
- Department of Chemistry, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Hiroshi Nakazawa
- Department of Chemistry, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka 558-8585, Japan
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Clough BA, Mellino S, Protchenko AV, Slusarczyk M, Stevenson LC, Blake MP, Xie B, Clot E, Mountford P. New Titanium Borylimido Compounds: Synthesis, Structure, and Bonding. Inorg Chem 2017; 56:10794-10814. [PMID: 28836774 DOI: 10.1021/acs.inorgchem.7b01831] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report a combined experimental and computational study of the synthesis and electronic structure of titanium borylimido compounds. Three new synthetic routes to this hitherto almost unknown class of Group 4 imide are presented. The double-deprotonation reaction of the borylamine H2NB(NAr'CH)2 (Ar' = 2,6-C6H3iPr2) with Ti(NMe2)2Cl2 gave Ti{NB(NAr'CH)2}Cl2(NHMe2)2, which was easily converted to Ti{NB(NAr'CH)2}Cl2(py)3. This compound is an entry point to other borylimides, for example, reacting with Li2N2pyrNMe to form Ti(N2pyrNMe){NB(NAr'CH)2}(py)2 and with 2 equiv of NaCp to give Cp2Ti{NB(NAr'CH)2}(py) (23). Borylamine-tert-butylimide exchange between H2NB(NAr'CH)2 and Cp*Ti(NtBu)Cl(py) under forcing conditions afforded Cp*Ti{NB(NAr'CH)2}Cl(py), which could be further substituted with guanidinate or pyrrolide-amine ligands to give Cp*Ti(hpp){NB(NAr'CH)2} (16) and Cp*Ti(NpyrNMe2){NB(NAr'CH)2} (17). The Ti-Nim distances in compounds with the NB(NAr'CH)2 ligand were comparable to those of the corresponding arylimides. Dialkyl- or diaryl-substituted borylamines do not undergo the analogous double-deprotonation or imide-amine exchange reactions. Reaction of (Cp″2Ti)2(μ2:η1,η1-N2) with N3BMes2 gave the base-free, diarylborylimide Cp″2Ti(NBMes2) (26) by an oxidative route; this compound has a relatively long Ti-Nim bond and large Cp″-Ti-Cp″ angle. Reaction of 16 with H2NtBu formed equilibrium mixtures with H2NB(NAr'CH)2 and Cp*Ti(hpp)(NtBu) (ΔrG = -1.0 kcal mol-1). In contrast, the dialkylborylimide Cp*Ti{MeC(NiPr)2}(NBC8H14) (2) reacted quantitatively with H2NtBu to give the corresponding tert-butylimide and borylamine. The electronic structures and imide-amine exchange reactions of half-sandwich and sandwich titanium borylimides have been evaluated using density functional theory (DFT), supported by quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analysis, and placed more generally in context with the well-established alkyl- and arylimides and hydrazides. The calculations find that Ti-Nim bonds for borylimides are stronger and more covalent than in their organoimido or hydrazido analogues, and are strongest for alkyl- and arylborylimides. Borylamine-tert-butylimide exchange reactions fail for H2NBR2 (R = hydrocarbyl) but not for H2NB(NAr'CH)2 because the increased strength of the new Ti-Nim bond for the former is outweighed by the increased net H-N bond strengths in the borylamine. Variation of the Ti-Nim bond length over short distances is dominated by π-interactions with any appropriate orbital on the Nim atom organic substituent. However, over the full range of imides and hydrazides studied, overall bond energies do not correlate with bond length but with the Ti-Nim σ-bond character and the orthogonal π-interaction.
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Affiliation(s)
- Benjamin A Clough
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford , Mansfield Road, Oxford OX1 3TA, U.K
| | - Simona Mellino
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford , Mansfield Road, Oxford OX1 3TA, U.K
| | - Andrey V Protchenko
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford , Mansfield Road, Oxford OX1 3TA, U.K
| | - Martin Slusarczyk
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford , Mansfield Road, Oxford OX1 3TA, U.K
| | - Laura C Stevenson
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford , Mansfield Road, Oxford OX1 3TA, U.K
| | - Matthew P Blake
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford , Mansfield Road, Oxford OX1 3TA, U.K
| | - Bowen Xie
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford , Mansfield Road, Oxford OX1 3TA, U.K
| | - Eric Clot
- Institut Charles Gerhardt Montpellier, UMR 5253, CNRS-UM-ENSCM, Université de Montpellier , cc 1501, Place Eugéne Bataillon, F-34095 Montpellier Cedex 5, France
| | - Philip Mountford
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford , Mansfield Road, Oxford OX1 3TA, U.K
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Clough BA, Mellino S, Clot E, Mountford P. New Scandium Borylimido Chemistry: Synthesis, Bonding, and Reactivity. J Am Chem Soc 2017; 139:11165-11183. [DOI: 10.1021/jacs.7b05405] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Benjamin A. Clough
- Chemistry
Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA, U.K
| | - Simona Mellino
- Chemistry
Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA, U.K
| | - Eric Clot
- Institut
Charles Gerhardt Montpellier, UMR 5253 CNRS-UM-ENSCM, Université de Montpellier, cc 1501, Place Eugène Bataillon, F-34095 Montpellier Cedex 5, France
| | - Philip Mountford
- Chemistry
Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA, U.K
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9
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Swarnakar AK, Hering-Junghans C, Ferguson MJ, McDonald R, Rivard E. Reactivity of a coordinated inorganic acetylene unit, HBNH, and the azidoborane cation [HB(N 3)] . Chem Sci 2017; 8:2337-2343. [PMID: 28451338 PMCID: PMC5365008 DOI: 10.1039/c6sc04893e] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 12/17/2016] [Indexed: 12/02/2022] Open
Abstract
A donor-acceptor complex of HBNH was prepared via thermolysis of a carbene-stabilized azidoborane. The reactivity of the fundamentally important HBNH unit (inorganic alkyne analogue) was explored in detail, including attempts to convert this species and related hydrido(azido)borane cations into molecular complexes of BN. This work provides added impetus for the development of molecular precursors that can release bulk boron nitride (a desirable insulator and thermal conductor) under mild conditions, and from solution.
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Affiliation(s)
- Anindya K Swarnakar
- Department of Chemistry , University of Alberta , 11227 Saskatchewan Drive , Edmonton , Alberta , Canada T6G 2G2 .
| | - Christian Hering-Junghans
- Department of Chemistry , University of Alberta , 11227 Saskatchewan Drive , Edmonton , Alberta , Canada T6G 2G2 .
| | - Michael J Ferguson
- Department of Chemistry , University of Alberta , 11227 Saskatchewan Drive , Edmonton , Alberta , Canada T6G 2G2 .
| | - Robert McDonald
- Department of Chemistry , University of Alberta , 11227 Saskatchewan Drive , Edmonton , Alberta , Canada T6G 2G2 .
| | - Eric Rivard
- Department of Chemistry , University of Alberta , 11227 Saskatchewan Drive , Edmonton , Alberta , Canada T6G 2G2 .
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Melen RL, Stephan DW. Cycloaddition reactions of (C6F5)2BN3 with dialkyl acetylenedicarboxylates. Dalton Trans 2015; 44:5045-8. [PMID: 25687829 DOI: 10.1039/c5dt00316d] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The 1,3-dipolar cycloaddition reactions of the electron deficient boron azide, (C6F5)2BN3 (1) with the electron-poor acetylenes RO2CC≡CCO2R (R = Me, Et) afforded the new mono- and bis-1,2,3-triazole derivatives and .
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Affiliation(s)
- Rebecca L Melen
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada M5S 3H6.
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Bettinger HF, Müller M. Pathways for the cyclotetramerization of dibenz[c,e][1,2]azaborine, a BN-phenanthryne. J PHYS ORG CHEM 2014. [DOI: 10.1002/poc.3390] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Holger F. Bettinger
- Institut für Organische Chemie; Universität Tübingen; Auf der Morgenstelle 18 72076 Tübingen Germany
| | - Matthias Müller
- Institut für Organische Chemie; Universität Tübingen; Auf der Morgenstelle 18 72076 Tübingen Germany
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12
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Bellham P, Hill MS, Kociok-Köhn G. Stoichiometric and Catalytic Reactivity of tert-Butylamine–Borane with Calcium Silylamides. Organometallics 2014. [DOI: 10.1021/om500467b] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Peter Bellham
- Department of Chemistry, University of Bath, Claverton
Down, Bath BA2 7AY, U.K
| | - Michael S. Hill
- Department of Chemistry, University of Bath, Claverton
Down, Bath BA2 7AY, U.K
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Müller M, Maichle-Mössmer C, Bettinger HF. Boryl Azides in 1,3-Dipolar Cycloadditions. J Org Chem 2014; 79:5478-83. [DOI: 10.1021/jo500549m] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Matthias Müller
- Institut für
Organische Chemie, Universität Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany
| | - Cäcilia Maichle-Mössmer
- Institut für Anorganische
Chemie, Universität Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany
| | - Holger F. Bettinger
- Institut für
Organische Chemie, Universität Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany
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