WO2024019972A1 - Procédé de synthèse de tris(ortho-carboranyle)borane - Google Patents

Procédé de synthèse de tris(ortho-carboranyle)borane Download PDF

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Publication number
WO2024019972A1
WO2024019972A1 PCT/US2023/027910 US2023027910W WO2024019972A1 WO 2024019972 A1 WO2024019972 A1 WO 2024019972A1 US 2023027910 W US2023027910 W US 2023027910W WO 2024019972 A1 WO2024019972 A1 WO 2024019972A1
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Prior art keywords
carborane
ortho
bocb3
lewis acid
borane
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PCT/US2023/027910
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English (en)
Inventor
Caleb MARTIN
Manjur Oyasim AKRAM
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Baylor University
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Publication date
Priority claimed from US18/222,191 external-priority patent/US20240018167A1/en
Application filed by Baylor University filed Critical Baylor University
Publication of WO2024019972A1 publication Critical patent/WO2024019972A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
    • C07F5/00—Compounds containing elements of Groups 3 or 13 of the Periodic Table
    • C07F5/02—Boron compounds
    • C07F5/027—Organoboranes and organoborohydrides

Definitions

  • Applicants’ invention relates to a method for synthesizing tris(ortho-carborane)borane (BoCb 3 ). Applicants’ invention further relates to the resulting compound, tris(ortho- carborane)borane, which is an isolable, halide-free, single site, Lewis superacid.
  • BCF Tris(pentafluorophenyl)borane
  • a Lewis acid is a substance, such as an H + ion, that can accept a pair of nonbonding electrons, thus a Lewis acid is an electron-pair acceptor. Because it is a strong Lewis acid, it can be a co-catalyst for CH3- and H- abstraction, where abstraction is a chemical reaction in which there is the bimolecular removal of an atom from a molecular entity.
  • CH3- requires a strong Lewis acid to be abstracted.
  • BCF can cause carbon-carbon bond formation. It can catalyze hydrogenation. It can cause a carbon ring to be opened or formed. It can cause bonds to be formed between a carbon molecule and another molecule. And it can cause silylation, which is the introduction of one or more silyl groups (Si R3) to a molecule.
  • Si R3 silylation
  • BCF is a useful Lewis acid, it is not more Lewis acidic than the Lewis superacid, SbF5.
  • Boranes are useful Lewis acids in stoichiometric and catalytic reactions by taking advantage of the vacant p-orbital.
  • BoCb 3 is an isolable, halide-free, single site, Lewis superacid.
  • the present invention involves the use of BoCb3 in promoting catalytic reactions.
  • the compound, BoCb3, is disclosed for the first time.
  • BoCb 3 is a stronger Lewis acid than other stable boranes.
  • BoCb3 is trigonal planar as all C–B–C bond angles are approximately 120o and the C-B bond lengths [1.614(8)-1.627(7) ⁇ )] are slightly higher than the typical C(o- carborane)-B single bond in boranes species [1.58 ⁇ ].
  • the downfield 11 B ⁇ 1 H ⁇ resonance at 67.2 ppm is assigned to the central boron atom and peaks ranging from 7.4 to –12.4 ppm to the cluster atoms.
  • the C–H protons are the most diagnostic in the 1 H NMR spectrum and appear as a singlet at 5.02 ppm while the corresponding carbon is observed in the 13 C ⁇ 1 H ⁇ NMR spectrum at 65.0 ppm and a broad peak at 69.3 ppm is assigned to the ortho-carbons.
  • the melting point is above 250 °C which indicates its thermal stability.
  • BoCb3 is inert to oxygen. BoCb3 reacts slowly with water to give the free carborane and HOBoCb2.
  • Tris(ortho-carboranyl)borane shows reactivity with Lewis Bases and application in Frustrated Lewis Pair Si–H bond cleavage.
  • Frustrated Lewis Pairs (“FLP”) arise from the combination of a Lewis acid and Lewis base that, due to steric demands, do not form a classical adduct.
  • An “adduct” is a chemical species AB, where each molecular entity of which is formed by direct combination of two separate molecular entities A and B in such a way that there is change in connectivity, but no loss, of atoms within the moieties A and B.
  • the reactivity of tris(ortho- carboranyl)borane with ubiquitous Lewis bases reveals only small Lewis bases bind.
  • BoCb 3 may be used for FLP chemistry using an alternative approach to fluorine loading of aryl groups to enhance Lewis acidity, ortho-carboranes as large electron withdrawing substituents.
  • Tris(ortho-carboranyl)borane (BoCb3) is accessed in one pot from three commercially available chemicals. Mono- and bis-carboranylboranes have reported higher Lewis acidity than their aryl analogues but they are not as Lewis acidic as BoCb3.
  • BoCb 3 acetonitrile (CH3CN ⁇ BoCb3), triethylphosphine oxide (Et3PO ⁇ BoCb3), and benzaldehyde (PhC(H)O ⁇ BoCb3) adducts resulted.
  • acetonitrile CH3CN ⁇ BoCb3
  • Et3PO ⁇ BoCb3 triethylphosphine oxide
  • PhC(H)O ⁇ BoCb3 benzaldehyde
  • the adduct remains intact in CDCl3 solution as confirmed by 1 H NMR spectroscopy with the three ortho C ⁇ H resonances shifted upfield (5.02 ppm to 4.7 2 ppm) along with the disappearance of the tricoordinate peak at 66.9 ppm in the 11 B NMR spectrum.
  • the corresponding ethylacetate and 2,6-(CH3)2C6H3NC adducts with B(C6F5)3 are resilient in solution.
  • the Lewis acidity of BoCb 3 is higher than B(C 6 F 5 ) 3 but only the ethylacetate adduct of BoCb3 dissociates in solution.
  • BoCb 3 is a good candidate as a Lewis acid for FLP chemistry.
  • the reactions of BoCb3 with an array of phosphines [PMe3, PPh3, PCy3, P(o-tol)3, P(p-Cl- C 6 H 4 ) 3 , P(p-F-C 6 H 4 ) 3 , and P(C 6 F 5 ) 3 ] and amine bases (NEt 3 and NPh 3 ) in C 6 D 6 do not result in any adducts forming.
  • B(C6F5)3 makes adducts with PMe3, PPh3, NEt3, PCy3, P(p-Cl-C6H4)3, and P(p- F-C 6 H 4 ) 3 but not with P(o-tol) 3 or P(C 6 F 5 ) 3 .
  • the breadth of Lewis bases for FLP generation with BoCb3 is much greater than B(C6F5)3.
  • BoCb3 is compatible with many Lewis bases to induce FLP Si–H cleavage.
  • the diminished reactivity is rationalized by the weaker Lewis basicity of NPh3. Comparing the reactivity with the same phosphines and B(C 6 F 5 ) 3 , the Ph 3 P ⁇ B(C 6 F 5 ) 3 adduct required 10 equivalents of HSiEt3 to achieve full conversion to the ion pair while (p-Cl-C6H4)3P ⁇ B(C6F5)3 and (p-F-C 6 H 4 ) 3 P ⁇ B(C 6 F 5 ) 3 resulted in only partial conversion with ten equivalents. The Cy3P ⁇ B(C6F5)3 adduct did not react with HSiEt3.
  • BoCb3 is resistant to forming adducts with a wide variety of bases but generates FLPs.
  • the quenched reactivity could be applied to Si ⁇ H bond cleavage with triarylphosphines and trialkylphosphines to generate the phosphoniumsilane and tris- (orthocarboranyl)borohydride ion pairs, [R 3 PSiEt 3 ][HBoCb 3 ].
  • triarylphosphines the bulk in P(o-tol)3 and electron withdrawing nature of P(p-F-C6H4)3 required an extra equivalent of silane.
  • P(C 6 F 5 ) 3 did not react at all. Notably, many of these do not react at all with B(C 6 F 5 ) 3 and those that react require ten equivalents of triethylsilane.
  • BoCb3 would be useful as an olefin polymerization co-catalyst or activator. BoCb 3 may also be useful as a Lewis acid catalyst for bond activation reactions to access useful chemicals from abundant feedstocks.
  • FIG. 1 illustrates the structure of BoCb 3 .
  • FIGS. 2a-2e illustrates various, conventional forms of Lewis acids.
  • FIG. 3 illustrates the synthesis of BoCb3.
  • FIG. 4 is an expanded illustration of the synthesis of BoCb3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Ref.
  • FIG. 1 illustrates the solid state structure of tris(ortho- carborane)borane (BoCb3) 10, which is the compound that is the product of the described method of synthesis.
  • the ortho-carborane 12 has a chemical formula of oC 2 B 10 H 12 .
  • the ortho-carborane structure 12 is generally a icosahedron (or 20-sided polyhedron) shaped structure, with the two (2) carbon molecules (14/16, 18/20, or 22/24) and the ten (10) boron atoms 28 at the vertices.
  • BoCb 3 10 Each molecule of BoCb 3 10 has three (3) ortho-carborane structures 12.
  • the ortho- carborane (oC2B10H12) 12 is abbreviated as oCb 12.
  • oCb 12 The ortho- carborane (oC2B10H12) 12 is abbreviated as oCb 12.
  • the three (3) ortho-carboranes 12 are designated as the oCb 3 portion in the BoCb 3 .
  • the BoCb3 10 molecule is trigonal planar in shape or geometry. Trigonal refers to a geometrical arrangement of molecules having three branches connected to a central atom.
  • Trigonal planar refers to the geometry where the three branches and the central atom are in the same general plane, as illustrated in FIG. 1.
  • the borane (B) 26 is the central atom
  • the three (3) ortho-carboranes (oCb 3 ) 12 are at the ends of the three (3) branches in the trigonal geometry.
  • One (1) of the primary carbon molecules (C(1) 14, C(2) 18, and C(3) 22) are bound to the central Boron atom 26, one in each of the three (3) ortho-carborane structures 12.
  • the other substituent carbon molecules (16, 20, 24) are located in each of the three (3) ortho-carborane structures 12, and are bound in the ortho-carborane structure 12 at a vertex adjacent to that ortho- carborane structure’s 12 primary carbon molecules (14, 18, 22), which are, in turn, bound to the central Boron atom 26.
  • the ortho (o) describes a molecule with substituents at adjacent positions in the structure, thus the ortho-carborane structures 12 have, for example, substituent carbon C(1)’ 16 adjacent or next to the primary carbon C(1) 14 on the icosahedron.
  • the primary carbon C(1) 14 is bound to the central Boron (B) atom 26, carbon C(1)’ 16, and four (4) Boron atoms 28 in the ortho-carborane structure 12.
  • the CN bond lengths range from 1.1380 to 1.1448 ⁇ , respectively.
  • the FT-IR spectra showed the CN stretching frequency of CH 3 CN ⁇ BoCb 3 (2363 cm- 1 ) is blue shifted in comparison to the (C6F5)3B ⁇ NCCH3 (2341 cm -1 ). Both metrics indicate a stronger CN bond upon coordination to BoCb 3 10 which signifies stronger coordination and a stronger Lewis acid.
  • the CO bond is 1.254 ⁇ , and has a CO stretching frequency of PhC(H)O ⁇ BoCb 3 (1584/1561 cm -1 ) is blue shifted from PhC(O)H ⁇ B(C 6 F 5 ) 3 [1602 cm -1 ] which match the other results.
  • the peak for the central boron atom (67.2 ppm) shifts to the tetracoordinate region among the cluster boron peaks.
  • BoCb3 10 The very high experimental and theoretical Lewis acidity of BoCb3 10 indicates its potential as a catalyst in C–F bond activation reactions. There are only a few catalytic activities known with the boranes to activate the B-F bonds. It is noted that silanes do not seem to react with BoCb3 10 to form HBoCb2 or other unwanted side products.
  • 1 equivalent 1- fluoroadamantane is treated with 1 equivalent HSiEt 3 in presence of 1 mol% BoCb 3 in CDCl 3 at room temperature for 10 minutes, it results in the reduction product adamantane in quantitative yield (89% isolated yield) along with FSiEt 3 as side product.
  • FIGS. 2a-2e illustrates various, conventional forms of Lewis acids.
  • a Lewis acid from the MO theory (MO theory is a theory designed to explain covalent bonding.) perspective, is a molecule that has a non-bonding lowest unoccupied molecular orbital (“LUMO”). The orbital needs to unoccupied, otherwise no electrons could be donated into it. For energy minimization arguments, electrons would be donated into the unoccupied orbital that has the lowest energy, which is the LUMO.
  • MO theory is a theory designed to explain covalent bonding.
  • the steps of the method for synthesizing a volume of BoCb3 10 comprise starting with oCbH and treating it with 1.0 equivalent of nBuLi, C 7 H 8 at a temperature range of –78 °C to 23 °C for 10 hours or more, or a range of 10 hours to 24 hours, or in a preferred embodiment for generally 16 hours.
  • the resultant is treated with 0.33 mol equivalent BX3 (where X is Cl or Br) at a temperature range of –78 °C to 23 °C , or 0 °C to 23 °C, for 4 days or more, or in a preferred embodiment for generally 7 days.
  • the final product is BoCb3.
  • BCl3 the isolated yield of BoCb 3 is generally 29%.
  • BoCb3 When more electrophilic BBr 3 is used instead of BCl 3 , the isolated yield of BoCb3 is generally 35%.
  • the carborane cluster In contrast to fluoroaryl boranes, the carborane cluster is not expected delocalize the LUMO, primarily a p-orbital on boron.
  • the icosahedral C 2 B 10 cluster is exceptionally stable and can act as a sigma withdrawing group if C-bound.
  • the three-dimensional icosahedron presents a sphere-like steric profile to protect its center.
  • FIG. 4 is an expanded illustration of the synthesis of BoCb310.
  • o-carborane (10.00 mol, 1.442 g)
  • nBuLi (10.00 mmol, 4.00 mL)
  • widget 12-1 would refer to a specific widget of a widget class 12, while the class of widgets may be referred to collectively as widgets 12 and any one of which may be referred to generically as a widget 12.
  • “removably attached,” “removably attachable,” or “removable” mean that a first object that is coupled to a second object may be decoupled from the second object, or taken away from an attached position relative to the second object, using some force or movement.
  • “Removably attached,” “removably attachable,” or “removable” further mean that if the first object is not coupled with the second object, the first object may be coupled to the second object or returned to the attached position, using some force or movement.
  • Both the decoupling and the coupling may be accomplished without damaging either the first object or the second object.
  • the terms “substantially,” “approximately,” “about,” or “generally” are used herein to modify a numeric value, range of numeric values, or list numeric values, the term modifies each of the numerals. Unless otherwise indicated, all numbers expressing quantities, units, percentages, and the like used in the present specification and associated claims are to be understood as being modified in all instances by the terms “approximately,” “about,” and “generally.” As used herein, the term “approximately” encompasses +/–5 of each numerical value.
  • the numerical value is “approximately 80,” then it can be 80 +/–5, equivalent to 75 to 85.
  • the term “about” encompasses +/–10 of each numerical value. For example, if the numerical value is “about 80,” then it can be 80 +/–10, equivalent to 70 to 90.
  • the term “generally” encompasses +/–15 of each numerical value. For example, if the numerical value is “about 80,” then it can be 80% +/–15, equivalent to 65 to 95.
  • inhibiting or “reducing” or any variation of these terms refer to any measurable decrease, or complete inhibition, of a desired result.
  • the terms “promote” or “increase” or any variation of these terms includes any measurable increase, or completion, of a desired result.
  • the term “effective,” as that term is used in the specification and/or claims, means adequate to accomplish a desired, expected, or intended result.

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Abstract

La présente invention concerne un procédé permettant de synthétiser un produit de composé borane à site unique sans halogénure tris(ortho-carboranyle)borane ou BoCb3. BoCb3 a des propriétés de superacide de Lewis. Les composés, BoCb3, sont thermiquement stables, et non réactifs vis-à-vis de l'oxygène, mais sont sensibles à l'eau. L'affinité caractéristique élevée des ions fluorure est en outre traduite vers les réactions catalytiques d'activation de liaison C-F des fluorures d'alkyle non activés vis-à-vis de la réduction et des réactions de formation de liaison C-C avec des silanes, et des réactions de type Fridel-Crafts avec des arènes. Il est prévu que l'acide de Lewis synthétisé ait le potentiel d'être utilisé comme catalyseur.
PCT/US2023/027910 2022-07-18 2023-07-17 Procédé de synthèse de tris(ortho-carboranyle)borane WO2024019972A1 (fr)

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US202263390126P 2022-07-18 2022-07-18
US63/390,126 2022-07-18
US18/222,191 US20240018167A1 (en) 2022-07-18 2023-07-14 Method for the synthesis of tris(ortho-carboranyl)borane
US18/222,191 2023-07-14

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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2793280A1 (fr) * 2011-12-12 2014-10-22 Nippon Steel & Sumikin Chemical Co., Ltd. Matériau d'élément électroluminescent organique et élément électroluminescent organique qui utilise ce dernier

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2793280A1 (fr) * 2011-12-12 2014-10-22 Nippon Steel & Sumikin Chemical Co., Ltd. Matériau d'élément électroluminescent organique et élément électroluminescent organique qui utilise ce dernier

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
GODOY JAZMIN ET AL: "Toward Chemical Propulsion: Synthesis of ROMP-Propelled Nanocars", ACS NANO, vol. 5, no. 1, 16 December 2010 (2010-12-16), US, pages 85 - 90, XP093094010, ISSN: 1936-0851, DOI: 10.1021/nn102775q *

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