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Widmann M, Riesinger C, Szlosek R, Balázs G, Scheer M. Electrophilic Functionalization of a Hexaphosphabenzene Ligand in [(Cp*Mo) 2(μ,η 6 : 6-P 6)]. Chemistry 2024; 30:e202304183. [PMID: 38240709 DOI: 10.1002/chem.202304183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Indexed: 04/06/2024]
Abstract
The electrophilic functionalization of the triple-decker sandwich complex [{Cp*Mo}2(μ,η6:6-P6)] (A) and its mono-oxidized counterpart [{Cp*Mo}2(μ,η6:6-P6)][SbF6] (B) with reactive main-group electrophiles as well as radical scavengers is shown to be a reliable method for the selective functionalization of the hexaphosphabenzene ligand. Depending on the electrophile used, the regioselectivity of the functionalization can be adjusted. Using group 16 electrophiles, the trisubstituted compounds [{Cp*Mo}2{(μ,η3 : 3-P3)(μ,η1 : 1 : 1 : 1-1,3-(SePh)2-2-Br-P3)}][TEF] (1), [{Cp*Mo}2(μ,η3 : 3-P3)(μ,η1 : 1 : 1 : 1-1,2,3-(EPh)3-P3)][SbF6] (E=S (2), Se (3)) as well as the side product [{Cp*Mo}2(μ,η4:4-P4)(μ,η1 : 1-P(SPh)2)][SbF6] (4) are obtained. By switching to phosphenium ions as group 15 electrophiles, the ring-inserted products [{Cp*Mo}2(μ,η3 : 3 : 2 : 2-P7R2)][TEF] (R=Cy (5), iPr (6)) are isolated, showing an unprecedented P7R2 structural motif. Furthermore, the reaction with MeOTf yields the dimeric [{Cp*Mo}4(1,4-Me2-μ4,η1 : 1 : 1 : 1 : 1 : 1-P6)(μ,η3 : 3-P3)2][TEF]2 (7) as the first example of a complex featuring two interconnected cyclo-P6 middle deck ligands. Finally, by combination of the methylation step with Ph2Se2, the mixed group 14/16 complex [{Cp*Mo}2{(μ,η3 : 3-P3)(μ,η1 : 1 : 1 : 11,2-(SePh)2-3-Me-P3)}][OTf] (8) is obtained.
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Affiliation(s)
- Maximilian Widmann
- Department of Inorganic Chemistry, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Christoph Riesinger
- Department of Inorganic Chemistry, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Robert Szlosek
- Department of Inorganic Chemistry, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Gábor Balázs
- Department of Inorganic Chemistry, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Manfred Scheer
- Department of Inorganic Chemistry, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
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Szlosek R, Niefanger AS, Balázs G, Seidl M, Timoshkin AY, Scheer M. Characterization of the Ligand Properties of Donor-stabilized Pnictogenyltrielanes. Chemistry 2024; 30:e202303603. [PMID: 38131435 DOI: 10.1002/chem.202303603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 12/15/2023] [Accepted: 12/21/2023] [Indexed: 12/23/2023]
Abstract
A general synthesis and the characterization of novel alkyl-substituted NHC-stabilized pnictogenylboranes NHC ⋅ BH2 ER2 (NHC=N-heterocyclic carbene, E=P, As; R2 =Me2 , Ph2 , t BuH, Cy2 , (SiMe3 )2 ) are reported. These compounds were reacted with Ni(CO)4 to the corresponding complexes of the type [(NHC ⋅ BH2 ER2 )Ni(CO)3 ] to determine their donor strength by Tolman Electronic Parameters (TEPs) and their steric demand as ligands compared to classical phosphines, superbasic phosphines and other commonly applied donor systems. The results show that the NHC-stabilized pnictogenyltrielanes can be considered as being highly basic, while their steric influence depends strongly on the organic residues as well as the donor attached to the {BH2 } moiety. Although weaker than commonly used superbasic phosphines, the donor strength of pnictogenyltrielanes in general can be classified as of similar strength as NHCs. The steric and electronic properties can easily be modified by alkyl substitution as evident from the TEP trends.
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Affiliation(s)
- Robert Szlosek
- Institut für Anorganische Chemie, Universität Regensburg, 93053, Regensburg, Germany
| | | | - Gábor Balázs
- Institut für Anorganische Chemie, Universität Regensburg, 93053, Regensburg, Germany
| | - Michael Seidl
- Institute of General and Theoretical Chemistry, Leopold-Franzens Universität Innsbruck, Innrain 80-82, 6020, Innsbruck, Austria
| | - Alexey Y Timoshkin
- Institute of Chemistry, Saint Petersburg State University, Universitetskaya emb. 7/9, 199034, St. Petersburg, Russia
| | - Manfred Scheer
- Institut für Anorganische Chemie, Universität Regensburg, 93053, Regensburg, Germany
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Ackermann MT, Szlosek R, Riesinger C, Seidl M, Timoshkin AY, Rivard E, Scheer M. NHC-Stabilized Mixed Group 13/14/15 Element Hydrides. Chemistry 2024; 30:e202303680. [PMID: 38009601 DOI: 10.1002/chem.202303680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Revised: 11/25/2023] [Accepted: 11/27/2023] [Indexed: 11/29/2023]
Abstract
The syntheses of novel N-heterocyclic carbene (NHC) adducts of group 13, 14 and 15 element hydrides are reported. Salt metathesis reactions between NaPH2 and IDipp ⋅ GeH2 BH2 OTf (1) (IDipp=1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) led to mixtures of the two isomers IDipp ⋅ GeH2 BH2 PH2 (2 a) and IDipp ⋅ BH2 GeH2 PH2 (2 b); by altering the reaction conditions an almost exclusive formation of 2 b was achieved. Attempts to purify mixtures of 2 a and 2 b by re-crystallization from THF afforded a salt [IDipp ⋅ GeH2 BH2 ⋅ IDipp][PHGeH2 BH2 PH2 BH2 GeH2 ] (4) that contains the novel anionic cyclohexyl-like inorganic heterocycle [PHGeH2 BH2 PH2 BH2 GeH2 ]- . In addition, the borane adducts IDipp ⋅ GeH2 BH2 PH2 BH3 (3 a) and IDipp ⋅ BH2 GeH2 PH2 BH3 (3 b) as even longer chain compounds were obtained from reactions of 2 a/2 b with H3 B ⋅ SMe2 and were studied by NMR spectroscopy. Accompanying DFT computations give insight into the mechanism and energetics associated with 2 a/2 b isomerization as well as their decomposition pathways.
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Affiliation(s)
- Matthias T Ackermann
- Institute of Inorganic Chemistry, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Robert Szlosek
- Institute of Inorganic Chemistry, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Christoph Riesinger
- Institute of Inorganic Chemistry, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Michael Seidl
- Institute of General and Theoretical Chemistry, University of Innsbruck, Innrain 80-82, 6020, Innsbruck, Austria
| | - Alexey Y Timoshkin
- Institute of Chemistry, Saint Petersburg State University, Universitetskaya emb. 7/9, 199034, St Petersburg, Russia
| | - Eric Rivard
- Department of Chemistry, University of Alberta, 11227 Saskatchewan Dr, Edmonton, Alberta, T6G 2G2, Canada
| | - Manfred Scheer
- Institute of Inorganic Chemistry, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
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Szlosek R, Seidl M, Balázs G, Scheer M. A General Pathway towards NHC ⋅ GaH 2 (OTf) Adducts - The Key for the Synthesis of NHC-Stabilized Cationic 13/15 Chain Compounds of Gallium. Chemistry 2023; 29:e202301752. [PMID: 37401824 DOI: 10.1002/chem.202301752] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 07/03/2023] [Accepted: 07/04/2023] [Indexed: 07/05/2023]
Abstract
A general pathway towards NHC (NHC=N-heterocyclic carbene)-stabilized galliummonotriflates NHC ⋅ GaH2 (OTf) (NHC=IDipp, 1 a; IPr2 Me2 , 1 b; IMes, 1 c; IDipp=1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-ylidene, IPr2 Me2 =1,3-bis-(diisopropyl)-4,5-dimethyl-imidazolin-2-ylidene, IMes=1,3-bis(2,4,6-trimethylphenyl)-imidazolin-2-ylidene) is reported. Quantum chemical calculations give detailed insight into the underlying reaction pathway. The obtained NHC ⋅ GaH2 (OTf) compounds were employed in reactions with donor-stabilized pnictogenylboranes to synthesize the elusive cationic parent 13/15/13 chain compounds [IDipp ⋅ GaH2 ER2 E'H2 ⋅ D][OTf] (3 a: D=IDipp, E=P, E'=B, R=H; 3 b: D=NMe3 , E=P, E'=B, R=H, 3 c: D=NMe3 , E=P, E'=B, R=Ph, 3 d: D=IDipp, E=P, E'=Ga, R=H). Supporting computational studies highlight the electronic features of the products.
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Affiliation(s)
- Robert Szlosek
- Institut für Anorganische Chemie, Universität Regensburg, 93053, Regensburg, Germany
| | - Michael Seidl
- Institut für Anorganische Chemie, Universität Regensburg, 93053, Regensburg, Germany
| | - Gábor Balázs
- Institut für Anorganische Chemie, Universität Regensburg, 93053, Regensburg, Germany
| | - Manfred Scheer
- Institut für Anorganische Chemie, Universität Regensburg, 93053, Regensburg, Germany
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Dinauer S, Piesch M, Szlosek R, Seidl M, Balazs G, Scheer M. Transformation of the Cyclo-P5 Middle Deck in [(Cp*Fe)(Cp'''Co)(µ,η5:η4-P5)] upon Functionalization - A Comprehensive Study of Reactivity. Chemistry 2023:e202300459. [PMID: 36929020 DOI: 10.1002/chem.202300459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 03/16/2023] [Accepted: 03/16/2023] [Indexed: 03/18/2023]
Abstract
[(Cp*Fe)(Cp'''Co)(µ,η 5 :η 4 -P5)] (1) was functionalized by main group nucleophiles and subsequently electrophilically quenched or oxidized. Reacting 1 with group 14 nucleophiles revealed different organo-substituted P5R middle-decks depending on the steric and electronic effects of the used alkali metal organyls (2: R = tBu; 3: R = Me). With group 15 nucleophiles, first isolatable monosubstituted complexes with phosphanides could be obtained as P5 ligands containing exocyclic {PR2} units (4: R = Cy, H; 5: R = Ph). These monoanionic complexes 2-5 were isolated and electrophilic quenching revealed novel types of neutral functionalized polyphosphorus complexes. These complexes bear formal chains of P5R'R'' (6: R' = tBu, R' = Me) in a 1,3-disubstitution pattern or P6R'R''R''' units (7: R' = Cy, R'' = H, R''' = Me; 8: R' = Me, R'' = Ph, R''' = Me) in a 1,1,3-substitution as middle-decks stabilized by one {Cp'''Co} and one {Cp*Fe} fragment. One-electron oxidation of 2, 3 or 5 by AgBF4 gave access to paramagnetic triple-decker complexes bearing P5R middle-decks in various coordination fashions (R = tBu (10), R = PPh2 (12)). For R = Me (11) a dimerization is observed revealing a diamagnetic tetranuclear cluster containing a unique dihydrofulvalene-type P10R2 ligand.
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Affiliation(s)
| | | | | | | | | | - Manfred Scheer
- University of Regensburg, Inorganic Chemistry, Universitätsstrasse 31, D-93040, Regensburg, GERMANY
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Szlosek R, Weinhart MAK, Balázs G, Seidl M, Zimmermann L, Scheer M. NHC-Stabilised Parent Tripentelyltrielanes. Chemistry 2023; 29:e202300340. [PMID: 36809680 DOI: 10.1002/chem.202300340] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 02/21/2023] [Accepted: 02/21/2023] [Indexed: 02/23/2023]
Abstract
A missing family of the extremely air sensitive tripentelyltrielanes was discovered. Their stabilisation was achieved by using the bulky NHC IDipp (NHC=N-heterocyclic carbene, IDipp=1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-ylidene). The tripentelylgallanes and tripentelylalanes IDipp ⋅ Ga(PH2 )3 (1 a), IDipp ⋅ Ga(AsH2 )3 (1 b), IDipp ⋅ Al(PH2 )3 (2 a) and IDipp ⋅ Al(AsH2 )3 (2 b) were synthesised by salt metathesis of IDipp ⋅ ECl3 (E=Al, Ga, In) with alkali metal pnictogenides such as NaPH2 /LiPH2 ⋅ DME and KAsH2 , respectively. Moreover, the detection of the first NHC-stabilised tripentelylindiumane IDipp ⋅ In(PH2 )3 (3) was possible by multinuclear NMR spectroscopy. Initial investigations of the coordination ability of these compounds resulted in the successful isolation of the coordination compound [IDipp ⋅ Ga(PH2 )2 (μ3 -PH2 {HgC6 F4 }3 )] (4) by reaction of 1 a with (HgC6 F4 )3 . The compounds were characterised by multinuclear NMR spectroscopy as well as single crystal X-ray diffraction studies. Supporting computational studies highlight the electronic features of the products.
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Affiliation(s)
- Robert Szlosek
- Institut für Anorganische Chemie, Universität Regensburg, 93053, Regensburg, Germany
| | - Michael A K Weinhart
- Institut für Anorganische Chemie, Universität Regensburg, 93053, Regensburg, Germany
| | - Gábor Balázs
- Institut für Anorganische Chemie, Universität Regensburg, 93053, Regensburg, Germany
| | - Michael Seidl
- Institut für Anorganische Chemie, Universität Regensburg, 93053, Regensburg, Germany
| | - Lisa Zimmermann
- Institut für Anorganische Chemie, Universität Regensburg, 93053, Regensburg, Germany
| | - Manfred Scheer
- Institut für Anorganische Chemie, Universität Regensburg, 93053, Regensburg, Germany
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Riesinger C, Dielmann F, Szlosek R, Virovets AV, Scheer M. Synthesis and Reactivity of a Cyclooctatetraene-Like Polyphosphorus Ligand Complex [Cyclo-P 8 ]. Angew Chem Int Ed Engl 2023; 62:e202218828. [PMID: 36692270 DOI: 10.1002/anie.202218828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 01/23/2023] [Accepted: 01/24/2023] [Indexed: 01/25/2023]
Abstract
The thermolysis of Cp'''Ta(CO)4 with white phosphorus (P4 ) gives access to [{Cp'''Ta}2 (μ,η2 : 2 : 2 : 2 : 1 : 1 -P8 )] (A), representing the first complex containing a cyclooctatetraene-like (COT) cyclo-P8 ligand. While ring sizes of n >6 have remained elusive for cyclo-Pn structural motifs, the choice of the transition metal, co-ligand and reaction conditions allowed the isolation of A. Reactivity investigations reveal its versatile coordination behaviour as well as its redox properties. Oxidation leads to dimerization to afford [{Cp'''Ta}4 (μ4 ,η2 : 2 : 2 : 2 : 2 : 2 : 2 : 2 : 1 : 1 : 1 : 1 -P16 )][TEF]2 (4, TEF=[Al(OC{CF3 }3 )4 ]- ). Reduction, however, leads to the fission of one P-P bond in A followed by rapid dimerization to form [K@[2.2.2]cryptand]2 [{Cp'''Ta}4 (μ4 ,η2 : 2 : 2 : 2 : 2 : 2 : 2 : 2 : 1 : 1 : 1 : 1 -P16 )] (5), which features an unprecedented chain-type P16 ligand. Lastly, A serves as a P2 synthon, via ring contraction to the triple-decker complex [{Cp'''Ta}2 (μ,η6 : 6 -P6 )] (B).
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Affiliation(s)
- Christoph Riesinger
- Institute of Inorganic Chemistry, University of Regensburg, Universitätsstr. 31, 93053, Regensburg, Germany
| | - Fabian Dielmann
- Department of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Innrain 80-82, 6020, Innsbruck, Austria
| | - Robert Szlosek
- Institute of Inorganic Chemistry, University of Regensburg, Universitätsstr. 31, 93053, Regensburg, Germany
| | - Alexander V Virovets
- Institute of Inorganic Chemistry, Goethe-University Frankfurt am Main, Max-von-Laue-Straße 7, 60438, Frankfurt am Main, Germany
| | - Manfred Scheer
- Institute of Inorganic Chemistry, University of Regensburg, Universitätsstr. 31, 93053, Regensburg, Germany
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Riesinger C, Dielmann F, Szlosek R, Virovets A, Scheer M. Synthesis and Reactivity of a Cyclo‐Octatetraene‐Like Polyphosphorus Ligand Complex [Cyclo‐P8]. Angew Chem Int Ed Engl 2023. [DOI: 10.1002/ange.202218828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
| | - Fabian Dielmann
- Universität Innsbruck: Universitat Innsbruck chemistry AUSTRIA
| | | | - Alexander Virovets
- Universität Frankfurt am Main: Goethe-Universitat Frankfurt am Main chemstry GERMANY
| | - Manfred Scheer
- University of Regensburg Inorganic Chemistry Universitätsstrasse 31 D-93040 Regensburg GERMANY
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Szlosek R, Ackermann MT, Marquardt C, Seidl M, Timoshkin AY, Scheer M. Coordination of Pnictogenylboranes Towards Tl(I) Salts and a Tl- Mediated P-P Coupling. Chemistry 2023; 29:e202202911. [PMID: 36259382 PMCID: PMC10099240 DOI: 10.1002/chem.202202911] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2022] [Indexed: 11/05/2022]
Abstract
The coordination chemistry of only Lewis-base (LB)-stabilized pnictogenylboranes EH2 BH2 ⋅NMe3 (E=P, As) towards Tl(I) salts has been studied. The reaction of Tl[BArCl ] (BArCl =[B(3,5-C6 H3 Cl2 )4 ]- ) with the corresponding pnictogenylborane results in the formation of [Tl(EH2 BH2 ⋅NMe3 )][BArCl ] (1 a: E=P; 1 b: E=As). Whereas the Tl ion in 1 a/b is monocoordinated, the exchange of the weakly coordinating anion (WCA) in the Tl(I) salt leads to the formation of a trigonal pyramidal coordination mode at the Tl atom by coordination of three equivalents of EH2 BH2 ⋅ NMe3 in [Tl(EH2 BH2 ⋅ NMe3 )3 ][WCA] (2 a: E=P, WCA=TEFCl ; 2 b: E=As, WCA=TEF) (TEF=[Al{OC(CF3 )3 }4 ]- , TEFCl =[Al{(OC(CF3 )2 (CCl3 )}4 ]- ). Furthermore, by using two equivalents of PH2 BH2 ⋅NMe3 , a Tl(I)-mediated P-P coupling takes place in CH2 Cl2 as solvent resulting in [Me3 N⋅BH2 PH2 PHBH2 ⋅NMe3 ][WCA] (WCA=TEF, 3 a; BArCl , 3 b; TEFCl , 3 c). In contrast, for the arsenic derivatives 1 b and 2 b, no coupling reaction is observed. The underlying chemical processes are elucidated by quantum chemical computations.
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Affiliation(s)
- Robert Szlosek
- Institut für Anorganische Chemie, Universität Regensburg, 93053, Regensburg, Germany
| | - Matthias T Ackermann
- Institut für Anorganische Chemie, Universität Regensburg, 93053, Regensburg, Germany
| | - Christian Marquardt
- Institut für Anorganische Chemie, Universität Regensburg, 93053, Regensburg, Germany
| | - Michael Seidl
- Institut für Anorganische Chemie, Universität Regensburg, 93053, Regensburg, Germany
| | - Alexey Y Timoshkin
- Institute of Chemistry, Saint Petersburg State University, Universitetskaya emb., Sankt-Peterburg, 7/9, 199304 St. Petersburg, Russia
| | - Manfred Scheer
- Institut für Anorganische Chemie, Universität Regensburg, 93053, Regensburg, Germany
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Margeson MJ, Seeberger F, Kelly JA, Leitl J, Coburger P, Szlosek R, Müller C, Wolf R. Expedient Hydrofunctionalisation of Carbonyls and Imines Initiated by Phosphacyclohexadienyl Anions. ChemCatChem 2021. [DOI: 10.1002/cctc.202100651] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Matthew J. Margeson
- Institute of Inorganic Chemistry University of Regensburg 93040 Regensburg Germany
| | - Felix Seeberger
- Institute of Inorganic Chemistry University of Regensburg 93040 Regensburg Germany
| | - John A. Kelly
- Institute of Inorganic Chemistry University of Regensburg 93040 Regensburg Germany
| | - Julia Leitl
- Institute of Inorganic Chemistry University of Regensburg 93040 Regensburg Germany
| | - Peter Coburger
- Institute of Inorganic Chemistry University of Regensburg 93040 Regensburg Germany
| | - Robert Szlosek
- Institute of Inorganic Chemistry University of Regensburg 93040 Regensburg Germany
| | - Christian Müller
- Freie Universität Berlin Institut für Chemie und Biochemie Fabeckstr. 34/36 14195 Berlin Germany
| | - Robert Wolf
- Institute of Inorganic Chemistry University of Regensburg 93040 Regensburg Germany
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