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Milinkovic A, Dupé A, Belaj F, Mösch-Zanetti NC. Molybdenum(VI) Bis(imido) Complexes: From Frustrated Lewis Pairs to Weakly Coordinating Cations. Chemistry 2022; 28:e202201867. [PMID: 35775999 DOI: 10.1002/chem.202201867] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Indexed: 01/07/2023]
Abstract
Molybdenum(VI) bis(imido) complexes [Mo(NtBu)2 (LR )2 ] (R=H 1 a; R=CF3 1 b) combined with B(C6 F5 )3 (1 a/B(C6 F5 )3 , 1 b/B(C6 F5 )3 ) exhibit a frustrated Lewis pair (FLP) character that can heterolytically split H-H, Si-H and O-H bonds. Cleavage of H2 and Et3 SiH affords ion pairs [Mo(NtBu)(NHtBu)(LR )2 ][HB(C6 F5 )3 ] (R=H 2 a; R=CF3 2 b) composed of a Mo(VI) amido imido cation and a hydridoborate anion, while reaction with H2 O leads to [Mo(NtBu)(NHtBu)(LR )2 ][(HO)B(C6 F5 )3 ] (R=H 3 a; R=CF3 3 b). Ion pairs 2 a and 2 b are catalysts for the hydrosilylation of aldehydes with triethylsilane, with 2 b being more active than 2 a. Mechanistic elucidation revealed insertion of the aldehyde into the B-H bond of [HB(C6 F5 )3 ]- . We were able to isolate and fully characterize, including by single-crystal X-ray diffraction analysis, the inserted products Mo(NtBu)(NHtBu)(LR )2 ][{PhCH2 O}B(C6 F5 )3 ] (R=H 4 a; R=CF3 4 b). Catalysis occurs at [HB(C6 F5 )3 ]- while [Mo(NtBu)(NHtBu)(LR )2 ]+ (R=H or CF3 ) act as the cationic counterions. However, the striking difference in reactivity gives ample evidence that molybdenum cations behave as weakly coordinating cations (WCC).
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Affiliation(s)
- Angela Milinkovic
- Institute of Chemistry - Inorganic Chemistry, University of Graz, Schubertstraße 1, 8010, Graz
| | - Antoine Dupé
- Institute of Chemistry - Inorganic Chemistry, University of Graz, Schubertstraße 1, 8010, Graz
| | - Ferdinand Belaj
- Institute of Chemistry - Inorganic Chemistry, University of Graz, Schubertstraße 1, 8010, Graz
| | - Nadia C Mösch-Zanetti
- Institute of Chemistry - Inorganic Chemistry, University of Graz, Schubertstraße 1, 8010, Graz
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Lohrey TD, Cortes EA, Bergman RG, Arnold J. Facile Activation of Triarylboranes by Rhenium(V) Oxo Imido Complexes. Inorg Chem 2020; 59:7216-7226. [PMID: 32339452 DOI: 10.1021/acs.inorgchem.0c00658] [Citation(s) in RCA: 5] [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 the synthesis and reactivity studies of a pair of rhenium(V) oxo imido complexes. Oxidation of the rhenium(III) terminal oxo ORe(η2-DHF)(BDI) (DHF = dihydrofulvalene, BDI = N,N'-bis(2,6-diisopropylphenyl)-3,5-dimethyl-β-diketiminate) with organic azides R-N3 (R = tBu, 2,6-diisopropylphenyl) yields the title complexes. Computational studies confirm that the rhenium oxo moieties of these complexes are polarized and correspondingly nucleophilic, owing to the preferential π bonding of the imido ligand to the Re center. This asymmetry in the metal-ligand multiple bond electronic structure facilitates the ready activation of B-C bonds in triarylboranes (BPh3 and B(C6F5)3), yielding rhenium(V) aryl borinate complexes. In the case of BPh3, subsequent cyclometalation of the 1,2-addition products was found to take place upon heating, ejecting benzene to form bidentate diphenylborinate complexes.
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Affiliation(s)
- Trevor D Lohrey
- Department of Chemistry, University of California, Berkeley, California 94720, United States.,Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Emmanuel A Cortes
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Robert G Bergman
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - John Arnold
- Department of Chemistry, University of California, Berkeley, California 94720, United States.,Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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Berg DJ, Gajecki L, Hill H, Twamley B. (μ-Di- tert-butyl-silanediolato)bis-[bis-(η 5-cyclo-penta-dien-yl)methyl-zirconium]. Acta Crystallogr E Crystallogr Commun 2019; 75:1848-1852. [PMID: 31871743 PMCID: PMC6895932 DOI: 10.1107/s2056989019014762] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Accepted: 10/31/2019] [Indexed: 11/10/2022]
Abstract
The reaction of t-Bu2Si(OH)2 with two equivalents of Cp2Zr(CH3)2 produces the title t-Bu2SiO2-siloxide bridged dimer, [Zr2(CH3)2(C5H5)4(C8H18O2Si)] or [Cp2Zr(CH3)]2[μ-t-Bu2SiO2] (1), where one methyl group is retained per zirconium atom. The same product is obtained at room temperature even when equimolar ratios of the silanediol and Cp2Zr(CH3)2 are used. Attempts to thermally eliminate methane and produce a bridging methyl-ene complex resulted in decomposition. The crystal structure of 1 displays typical Zr-CH3 and Zr-O distances but the Si-O distance [1.628 (2) Å] and O-Si-O angle [110.86 (15)°] are among the largest observed in this family of compounds suggesting steric crowding between the t-Bu substituents of the silicon atom and the cyclo-penta-dienyl groups. The silicon atom lies on a crystallographic twofold axis and both Cp rings are disordered over two orientations of equal occupancy.
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Affiliation(s)
- David J. Berg
- Department of Chemistry, University of Victoria, PO Box 1700 Stn CSC, Victoria, BC V8W 2Y2, Canada
| | - Leah Gajecki
- Department of Chemistry, University of Victoria, PO Box 1700 Stn CSC, Victoria, BC V8W 2Y2, Canada
| | - Hunter Hill
- Department of Chemistry, University of Victoria, PO Box 1700 Stn CSC, Victoria, BC V8W 2Y2, Canada
| | - Brendan Twamley
- School of Chemistry, Trinity College Dublin, University of Dublin, Dublin 2, Ireland
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Zwettler N, Mösch-Zanetti NC. Interaction of Metal Oxido Compounds with B(C 6 F 5 ) 3. Chemistry 2019; 25:6064-6076. [PMID: 30707470 DOI: 10.1002/chem.201805148] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Indexed: 11/07/2022]
Abstract
Lewis acid-base pair chemistry has been placed on a new level with the discovery that adduct formation between an electron donor (Lewis base) and acceptor (Lewis acid) can be inhibited by the introduction of steric demand, thus preserving the reactivity of both Lewis centers, resulting in highly unusual chemistry. Some of these highly versatile frustrated Lewis pairs (FLP) are capable of splitting a variety of small molecules, such as dihydrogen, in a heterolytic and even catalytic manner. This is in sharp contrast to classical reactions where the inert substrate must be activated by a metal-based catalyst. Very recently, research has emerged combining the two concepts, namely the formation of FLPs in which a metal compound represents the Lewis base, allowing for novel chemistry by using the heterolytic splitting power of both together with the redox reactivity of the metal. Such reactivity is not restricted to the metal center itself being a Lewis acid or base, also ancillary ligands can be used as part of the Lewis pair, still with the benefit of the redox-active metal center nearby. This Minireview is designed to highlight the novel reactions arising from the combination of metal oxido transition-metal or rare-earth-metal compounds with the Lewis acid B(C6 F5 )3 . It covers a wide area of chemistry including small molecule activation, hydrogenation and hydrosilylation catalysis, and olefin metathesis, substantiating the broad influence of the novel concept. Future goals of this young and exciting area are briefly discussed.
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Affiliation(s)
- Niklas Zwettler
- Institute of Chemistry/Inorganic Chemistry, University of Graz, Schubertstrasse 1, 8010, Graz, Austria
| | - Nadia C Mösch-Zanetti
- Institute of Chemistry/Inorganic Chemistry, University of Graz, Schubertstrasse 1, 8010, Graz, Austria
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Thompson BL, Heiden ZM. Investigation of main group promoted carbon dioxide reduction. Tetrahedron 2019; 75:2099-2105. [PMID: 30936593 DOI: 10.1016/j.tet.2019.02.029] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The reduction of carbon dioxide (CO2) is of interest to the chemical industry, as many synthetic materials can be derived from CO2. To help determine the reagents needed for the functionalization of carbon dioxide this experimental and computational study describes the reduction of CO2 to formate and CO with hydride, electron, and proton sources in the presence of sterically bulky Lewis acids and bases. The insertion of carbon dioxide into a main group hydride, generating a main group formate, was computed to be more thermodynamically favorable for more hydridic (reducing) main group hydrides. A ten kcal/mol increase in hydricity (more reducing) of a main group hydride resulted in a 35% increase in the main group hydride's ability to insert CO2 into the main group hydride bond. The resulting main group formate exhibited a hydricity (reducing ability) about 10% less than the respective main group hydride prior to CO2 insertion. Coordination of a second identical Lewis acid to a main group formate complex further reduced the hydricity by about another 20%. The addition of electrons to the CO adduct of t Bu3P and B(C6F5)3 resulted in converting the sequestered CO2 molecule to CO. Reduction of the CO2 adduct of t Bu3P and B(C6F5)3 with both electrons and protons resulted in only proton reduction.
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Affiliation(s)
- Brena L Thompson
- Department of Chemistry, Washington State University, Pullman, WA 99164 USA
| | - Zachariah M Heiden
- Department of Chemistry, Washington State University, Pullman, WA 99164 USA
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Plommer H, Murphy JN, Dawe LN, Kerton FM. Morpholine-Stabilized Cationic Aluminum Complexes and Their Reactivity in Ring-Opening Polymerization of ε-Caprolactone. Inorg Chem 2019; 58:5253-5264. [DOI: 10.1021/acs.inorgchem.9b00347] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Hart Plommer
- Department of Chemistry, Memorial University of Newfoundland, St. John’s, NL A1B 3X7, Canada
| | - Jennifer N. Murphy
- Department of Chemistry, Memorial University of Newfoundland, St. John’s, NL A1B 3X7, Canada
| | - Louise N. Dawe
- Department of Chemistry and Biochemistry, Wilfrid Laurier University, Waterloo, ON N2L 3C5, Canada
| | - Francesca M. Kerton
- Department of Chemistry, Memorial University of Newfoundland, St. John’s, NL A1B 3X7, Canada
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Andrea KA, Kerton FM. Triarylborane-Catalyzed Formation of Cyclic Organic Carbonates and Polycarbonates. ACS Catal 2019. [DOI: 10.1021/acscatal.8b04282] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Kori A. Andrea
- Department of Chemistry, Memorial University of Newfoundland, St. John’s, NF A1B 3X7, Canada
| | - Francesca M. Kerton
- Department of Chemistry, Memorial University of Newfoundland, St. John’s, NF A1B 3X7, Canada
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Fasano V, Ingleson MJ. Expanding Water/Base Tolerant Frustrated Lewis Pair Chemistry to Alkylamines Enables Broad Scope Reductive Aminations. Chemistry 2017; 23:2217-2224. [PMID: 27977048 PMCID: PMC5396349 DOI: 10.1002/chem.201605466] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Indexed: 01/05/2023]
Abstract
Lower Lewis acidity boranes demonstrate greater tolerance to combinations of water/strong Brønsted bases than B(C6 F5 )3 , this enables Si-H bond activation by a frustrated Lewis pair (FLP) mechanism to proceed in the presence of H2 O/alkylamines. Specifically, BPh3 has improved water tolerance in the presence of alkylamines as the Brønsted acidic adduct H2 O-BPh3 does not undergo irreversible deprotonation with aliphatic amines in contrast to H2 O-B(C6 F5 )3 . Therefore BPh3 is a catalyst for the reductive amination of aldehydes and ketones with alkylamines using silanes as reductants. A range of amines inaccessible using B(C6 F5 )3 as catalyst, were accessible by reductive amination catalysed by BPh3 via an operationally simple methodology requiring no purification of BPh3 or reagents/solvent. BPh3 has a complementary reductive amination scope to B(C6 F5 )3 with the former not an effective catalyst for the reductive amination of arylamines, while the latter is not an effective catalyst for the reductive amination of alkylamines. This disparity is due to the different pKa values of the water-borane adducts and the greater susceptibility of BPh3 species towards protodeboronation. An understanding of the deactivation processes occurring using B(C6 F5 )3 and BPh3 as reductive amination catalysts led to the identification of a third triarylborane, B(3,5-Cl2 C6 H3 )3 , that has a broader substrate scope being able to catalyse the reductive amination of both aryl and alkyl amines with carbonyls.
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Affiliation(s)
- Valerio Fasano
- School of ChemistryUniversity of ManchesterManchesterM13 9PLUK
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Strašák T, Sýkora J, Lamač M, Kubišta J, Horáček M, Gyepes R, Pinkas J. Reactivity of a Titanocene Pendant Si–H Group toward Alcohols. Unexpected Formation of Siloxanes from the Reaction of Hydrosilanes and Ph3COH Catalyzed by B(C6F5)3. Organometallics 2013. [DOI: 10.1021/om400253g] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Tomáš Strašák
- Institute
of Chemical Process Fundamentals, Academy of Sciences of the Czech Republic, v.v.i., Rozvojová
135, 165 02 Prague 6, Czech Republic
| | - Jan Sýkora
- Institute
of Chemical Process Fundamentals, Academy of Sciences of the Czech Republic, v.v.i., Rozvojová
135, 165 02 Prague 6, Czech Republic
| | - Martin Lamač
- J. Heyrovský Institute
of Physical Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Dolejškova 2155/3,
182 23 Prague 8, Czech Republic
| | - Jiří Kubišta
- J. Heyrovský Institute
of Physical Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Dolejškova 2155/3,
182 23 Prague 8, Czech Republic
| | - Michal Horáček
- J. Heyrovský Institute
of Physical Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Dolejškova 2155/3,
182 23 Prague 8, Czech Republic
| | - Róbert Gyepes
- J. Heyrovský Institute
of Physical Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Dolejškova 2155/3,
182 23 Prague 8, Czech Republic
- J. Selye University, Faculty of Education, Bratislavská
cesta 3322, 945 01 Komárno, Slovak Republic
| | - Jiří Pinkas
- J. Heyrovský Institute
of Physical Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Dolejškova 2155/3,
182 23 Prague 8, Czech Republic
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