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A General Concept for the Electronic and Steric Modification of 1-Metallacyclobuta-2,3-dienes: A Case Study of Group 4 Metallocene Complexes. Chemistry 2024:e202400708. [PMID: 38529695 DOI: 10.1002/chem.202400708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2024] [Revised: 03/22/2024] [Accepted: 03/25/2024] [Indexed: 03/27/2024]
Abstract
The synthesis of group 4 metal 1-metallacyclobuta-2,3-dienes as organometallic analogues of elusive 1,2-cyclobutadiene has so far been limited to SiMe3 substituted examples. We present the synthesis of two Ph substituted dilithiated ligand precursors for the preparation of four new 1-metallacyclobuta-2,3-dienes [rac-(ebthi)M] (M=Ti, Zr; ebthi=1,2-ethylene-1,10-bis(η5-tetrahydroindenyl)). The organolithium compounds [Li2(RC3Ph)] (1 b: R=Ph, 1 c: R=SiMe3) as well as the metallacycles of the general formula [rac-(ebthi)M(R1C3R2)] (2 b: M=Ti, R1=R2=Ph, 2 c: M=Ti, R1=Ph, R2=SiMe3; 3 b: M=Zr, R1=R2=Ph; 3 c: M=Zr, R1=Ph, R2=SiMe3) were fully characterised. Single crystal X-ray diffraction and quantum chemical bond analysis of the Ti and Zr complexes reveal ligand influence on the biradicaloid character of the titanocene complexes. X-band EPR spectroscopy of structurally similar Ti complexes [rac-(ebthi)Ti(Me3SiC3SiMe3)] (2 a), 2 b, and 2 c was carried out to evaluate the accessibility of an EPR active triplet state. Cyclic voltammetry shows that introduction of Ph groups renders the complexes easier to reduce. 13C CPMAS NMR analysis provides insights into the cause of the low field shift of the resonances of metal-bonded carbon atoms and provides evidence of the absence of the β-C-Ti interaction.
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2
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Atroposelective Ir-Catalyzed C-H Borylation of Phthalazine Heterobiaryls. J Org Chem 2023; 88:14222-14226. [PMID: 37751525 PMCID: PMC10563123 DOI: 10.1021/acs.joc.3c01534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Indexed: 09/28/2023]
Abstract
The atroposelective iridium-catalyzed borylation of menthyloxy-substituted phthalazine heterobiaryls with diborons is reported. Utilizing [Ir(OMe)(COD)]2/2-aminopyridine as a rarely used efficient catalyst system, the heterobiaryls were selectively borylated in the 2-position of the carbocycle, exclusively yielding only one of the atropisomers, depending on the substitution of the phthalazine with (+)-menthyl or (-)-menthyl moieties. Exemplary further functionalization of a borylated atropisomer demonstrated that nickel-catalyzed Suzuki-Miyaura cross-coupling with an aryl halide was able to provide stereoretention to a certain degree (up to 75% de).
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3
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Bis(N-Heterocyclic Carbene) Manganese(I) Complexes: Efficient and Simple Hydrogenation Catalysts. Angew Chem Int Ed Engl 2023; 62:e202307987. [PMID: 37395302 DOI: 10.1002/anie.202307987] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 06/29/2023] [Accepted: 06/30/2023] [Indexed: 07/04/2023]
Abstract
The use of bis(NHC) manganese(I) complexes 3 as catalysts for the hydrogenation of esters was investigated. For that purpose, a series of complexes has been synthesized via an improved two step procedure utilizing bis(NHC)-BEt3 adducts. By applying complexes 3 with KHBEt3 as additive, various aromatic and aliphatic esters were hydrogenated successfully at mild temperatures and low catalyst loadings, highlighting the efficiency of the novel catalytic system. The versatility of the developed catalytic system was further demonstrated by the hydrogenation of other substrate classes like ketones, nitriles, N-heteroarenes and alkenes. Mechanistic experiments and DFT calculations indicate an inner sphere mechanism with the loss of one CO ligand and reveal the role of BEt3 as cocatalyst.
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4
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Unusual selectivity in the ring-opening of γ-valerolactone oxide by amines. Chem Commun (Camb) 2023. [PMID: 37337749 DOI: 10.1039/d3cc01957h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/21/2023]
Abstract
Primary and secondary amines selectively react with the lactone moiety of γ-valerolactone oxide (GVLO). Several primary amines afforded the resulting epoxyamides with an intact epoxy group. In some cases addition of two equivalents of amine resulted in additional epoxide opening to give α,γ-dihydroxy-β-amino-amides. The selective lactone-opening in GVLO was further corroborated by DFT-studies.
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5
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Interplay between Catalyst Complexes and Dormant States: In Situ Spectroscopic Investigations on a Catalyst System for Alkene Hydroformylation. ACS Catal 2023. [DOI: 10.1021/acscatal.2c06320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2023]
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6
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{μ-2,2'-(Ethane-1,2-di-yl)bis-[4,6-bis-(tri-methyl-sil-yl)-1,3-di-hydro-cyclo-penta-[ c]pyrrol-5-one]}bis-[tri-carbonyl-iron(0)]. IUCRDATA 2023; 8:x230346. [PMID: 37151201 PMCID: PMC10162033 DOI: 10.1107/s2414314623003462] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Accepted: 04/17/2023] [Indexed: 05/09/2023] Open
Abstract
The binuclear title compound, [Fe2(C28H48N2O2Si4)(CO)6], consists of two central iron(0) atoms, each of them surrounded by a cyclo-penta-dienone moiety and three carbonyl ligands in a three-legged piano-stool shape. Furthermore, the bis-(cyclo-penta-dienone) ligand acts as a bridge between the two metal atoms.
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Carbonyl-bis-{6,6'-[(3,3'-di- tert-butyl-5,5'-dimeth-oxy-1,1'-biphenyl-2,2'-di-yl)bis(oxy)]bis-(dibenzo[ d, f][1,3,2]-dioxaphosphepine)}hydridorhodium(I) toluene- d 8 2.25-solvate. IUCRDATA 2023; 8:x230083. [PMID: 36911081 PMCID: PMC9993892 DOI: 10.1107/s2414314623000834] [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: 11/23/2022] [Accepted: 01/30/2023] [Indexed: 02/16/2023] Open
Abstract
The crystal-structure determination of the title compound, [RhH(C46H44O8P2)2(CO)]·2.25C7D8, is reported. The bis-phosphite ligand, C46H44O8P2, is well known as Biphephos. One specific characteristic of this hydrido rhodium(I) monocarbonyl complex is that one bis-phosphite ligand is coordinated in the expected bidentate mode and the other is coordinated in a monodentate mode. Thus, one phosphite moiety remains non-coordinating. All three coordinating phospho-rus atoms occupy the equatorial positions in the trigonal-bipyramidal environment around the rhodium atom. The crystals of the hydrido rhodium(I) monocarbonyl complex contains deuterated solvent mol-ecules (toluene-d 8). Most of them are included in the model, but the contributions of about 0.84 toluene per unit cell were removed from the diffraction data, using the SQUEEZE procedure in PLATON [Spek (2015 ▸). Acta Cryst. C71, 9-18].
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Efficient Hydrogenation of N-Heterocycles Catalyzed by NNP-Manganese(I) Pincer Complexes at Ambient Temperature. Chemistry 2023; 29:e202202774. [PMID: 36193859 PMCID: PMC10100126 DOI: 10.1002/chem.202202774] [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: 09/06/2022] [Indexed: 11/06/2022]
Abstract
Manganese-catalyzed hydrogenation reactions have aroused widespread interest in recent years. Among the catalytic systems described, especially PNP- and NNP-Mn pincer catalysts have been reported for the hydrogenation of aldehydes, ketones, nitriles, aldimines and esters. Furthermore, NNP-Mn pincer compounds are efficient catalysts for the hydrogenolysis of less reactive amides, ureas, carbonates, and carbamates. Herein, the synthesis and application of specific imidazolylaminophosphine ligands and the corresponding Mn pincer complexes are described. These new catalysts have been characterized and studied by a combination of experimental and theoretical investigations, and their catalytic activities have been tested in several hydrogenation reactions with good to excellent performance. Especially, the reduction of N-heterocycles can be performed under very mild conditions.
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An Improved Cobalt-catalysed Alkoxycarbonylation of Olefins using Secondary Phosphine Oxide Promotors. Catal Sci Technol 2023. [DOI: 10.1039/d3cy00066d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/12/2023]
Abstract
In general, cobalt-catalysed carbonylations of olefins require high carbon monoxide (CO) pressure and high temperature to proceed efficiently. In contrast, the presence of secondary phosphine oxide (SPO) promotors, allow the...
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10
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Synthesis of Bifunctional Phosphonium Salts Bearing Perfluorinated Side Chains and Their Application in the Synthesis of Cyclic Carbonates from Epoxides and CO2. ASIAN J ORG CHEM 2022. [DOI: 10.1002/ajoc.202200156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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11
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Revisiting Reduction of CO 2 to Oxalate with First-Row Transition Metals: Irreproducibility, Ambiguous Analysis, and Conflicting Reactivity. JACS AU 2022; 2:731-744. [PMID: 35373201 PMCID: PMC8970009 DOI: 10.1021/jacsau.2c00005] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Indexed: 06/14/2023]
Abstract
Construction of higher C≥2 compounds from CO2 constitutes an attractive transformation inspired by nature's strategy to build carbohydrates. However, controlled C-C bond formation from carbon dioxide using environmentally benign reductants remains a major challenge. In this respect, reductive dimerization of CO2 to oxalate represents an important model reaction enabling investigations on the mechanism of this simplest CO2 coupling reaction. Herein, we present common pitfalls encountered in CO2 reduction, especially its reductive coupling, based on established protocols for the conversion of CO2 into oxalate. Moreover, we provide an example to systematically assess these reactions. Based on our work, we highlight the importance of utilizing suitable orthogonal analytical methods and raise awareness of oxidative reactions that can likewise result in the formation of oxalate without incorporation of CO2. These results allow for the determination of key parameters, which can be used for tailoring of prospective catalytic systems and will promote the advancement of the entire field.
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Abstract
![]()
Low-valent molybdenum
PNP pincer complexes were studied as catalysts
for the semihydrogenation of alkynes. For that purpose, tBu-substituted PNP complexes PNPtBuMo(CO)2 (6a) and PNPtBuMo(CO)3 (6c) and the NNP complex NNPiPrMo(CO)2(PPh3) ((rac)-7) were synthesized and characterized. By utilizing
the cyclohexyl-substituted complex PNPCyMo(CO)2(CH3CN) (5a), several diphenylacetylene
derivatives are transformed to the corresponding (Z)-alkenes with good to very good diastereoselectivities (up to 91:9).
Mechanistic experiments indicate an outer-sphere mechanism including
metal–ligand cooperativity.
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13
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Front Cover Picture: Use of Iridium‐Catalyzed Transfer Vinylation for the Synthesis of Bio‐Based (bis)‐Vinyl Ethers (Adv. Synth. Catal. 7/2022). Adv Synth Catal 2022. [DOI: 10.1002/adsc.202200201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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14
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Use of Iridium‐Catalyzed Transfer Vinylation for the Synthesis of Bio‐Based (bis)‐Vinyl Ethers. Adv Synth Catal 2022. [DOI: 10.1002/adsc.202101348] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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15
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A Selective and General Cobalt‐Catalyzed Hydroaminomethylation of Olefins to Amines. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202112597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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16
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Mono- and dinuclear zirconocene( iv) amide complexes for the catalytic dehydropolymerisation of phenylsilane. RSC Adv 2022; 12:26277-26283. [PMID: 36275119 PMCID: PMC9477068 DOI: 10.1039/d2ra04955d] [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: 08/08/2022] [Accepted: 09/08/2022] [Indexed: 11/21/2022] Open
Abstract
Mono- and dinuclear zirconocene amide complexes were tested as catalysts for the dehydropolymerisation of phenylsilane. The dinuclear complex is surprisingly stable, producing mixtures of polysilanes and cyclic oligomers.
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Betti base derived P-stereogenic phosphine-diamidophosphite ligands with a single atom spacer and their application in asymmetric catalysis. Catal Sci Technol 2022. [DOI: 10.1039/d1cy02017j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Small bite-angle P-chirogenic PNP ligands have been synthesized stereo-selectively and employed in Rh-catalyzed asymmetric hydrogenation and Pd-catalyzed asymmetric allylic substitution resulting in moderate to excellent enantioselectivities.
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18
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( In situ) spectroscopic studies on state-of-the-art Pd( ii) catalysts in solution for the alkoxycarbonylation of alkenes. Catal Sci Technol 2022. [DOI: 10.1039/d0cy02248a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
(In situ) liquid-phase spectroscopic investigations on state-of-the-art Pd catalysts modified with pyridyl-substituted diphosphine ligands for alkene alkoxycarbonylations have been performed for characterizing resting state complexes in solution.
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19
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Manganese N,N,N-Pincer Complex-catalyzed Epoxidation of Unactivated Aliphatic Olefins. Catal Sci Technol 2022. [DOI: 10.1039/d2cy01472f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A practical in situ generated manganese(II) catalyst system with the commercially available bis(2-picolyl) amine ligand enables epoxidation of terminal aliphatic olefins in good yields with tert-butyl hydroperoxide as oxidant. Crystallization...
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20
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Synthesis of α-Keto Aldehydes via Selective Cu(I)-catalyzed Oxidation of α-Hydroxy Ketones. Chem Commun (Camb) 2022; 58:4639-4642. [DOI: 10.1039/d2cc00773h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
An efficient approach to synthesize α-keto aldehydes was established through selective oxidation of α-hydroxy ketones catalyzed by Cu(I) using oxygen as oxidant. A wide array of α-keto aldehydes was prepared...
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21
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Iron‐Catalyzed Epoxidation of Linear α‐Olefins with Hydrogen Peroxide. ChemCatChem 2021. [DOI: 10.1002/cctc.202101668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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22
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1,3-Thiazole-4-carbonitrile. IUCRDATA 2021; 6:x211332. [DOI: 10.1107/s2414314621013328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Accepted: 12/15/2021] [Indexed: 05/31/2023] Open
Abstract
The title compound, C4H2N2S, is a 1,3-thiazole substituted in the 4-position by a nitrile group. In the crystal, C—H...N hydrogen bonds and aromatic π–π stacking interactions are observed.
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1-Zirconacyclobuta-2,3-dienes: synthesis of organometallic analogs of elusive 1,2-cyclobutadiene, unprecedented intramolecular C-H activation, and reactivity studies. Chem Sci 2021; 12:16074-16084. [PMID: 35024129 PMCID: PMC8672727 DOI: 10.1039/d1sc06052j] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 11/22/2021] [Indexed: 01/25/2023] Open
Abstract
The structure, bonding, and reactivity of small, highly unsaturated ring systems is of fundamental interest for inorganic and organic chemistry. Four-membered metallacyclobuta-2,3-dienes, also referred to as metallacycloallenes, are among the most exotic examples for ring systems as these represent organometallic analogs of 1,2-cyclobutadiene, the smallest cyclic allene. Herein, the synthesis of the first examples of 1-zirconacyclobuta-2,3-dienes of the type [Cp'2Zr(Me3SiC3SiMe3)] (Cp'2 = rac-(ebthi), (ebthi = 1,2-ethylene-1,1'-bis(η5-tetrahydroindenyl)) (2a); rac-Me2Si(thi)2, thi = (η5-tetrahydroindenyl), (2b)) is presented. Both complexes undergo selective thermal C-H activation at the 7-position of the ansa-cyclopentadienyl ligand to produce a new type of "tucked-in" zirconocene system, 3a and 3b, that possesses a η3-propargyl/allenyl ligand. Both types of complexes react with carbonyl compounds, producing enynes in the case of 2a and 2b, as well as η1-allenyl complexes for 3a and 3b. Computational analysis of the structure and bonding of 2a and 3a reveals significant differences to a previously described related Ti complex. All complexes were fully characterised, including X-ray crystallography and experimental results were supported by DFT analysis.
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A Selective and General Cobalt-Catalyzed Hydroaminomethylation of Olefins to Amines. Angew Chem Int Ed Engl 2021; 61:e202112597. [PMID: 34738697 PMCID: PMC9299624 DOI: 10.1002/anie.202112597] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Indexed: 11/10/2022]
Abstract
A new cobalt catalyst is presented for the domino hydroformylation-reductive amination reaction of olefins. The optimal Co-tert-BuPy-Xantphos catalyst shows good to excellent linear-to-branched (n/iso) regioselectivity for the reactions of aliphatic alkenes with aromatic amines under mild conditions. This system is far more selective than traditional cobalt(I) catalysts and even better than most known rhodium catalysts.
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1-[(Methylsulfonyl)oxy]pyridin-1-ium methanesulfonate. IUCRDATA 2021; 6:x211026. [PMID: 36340987 PMCID: PMC9462295 DOI: 10.1107/s2414314621010269] [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: 09/13/2021] [Accepted: 10/04/2021] [Indexed: 11/20/2022] Open
Abstract
The title compound is a pyridinium salt that consists of a sulfonated pyridine N-oxide cation and a methanesulfonate anion. The title molecular salt, C6H8NO3S+·CH3O3S−, consists of a cationic sulfonated pyridine N-oxide moiety and a methanesulfonate anion. An N—O bond length of 1.4004 (15) Å is observed in the cation. In the crystal, weak C—H⋯O interactions link the components into a three-dimensional network.![]()
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HCOOH disproportionation to MeOH promoted by molybdenum PNP complexes. Chem Sci 2021; 12:13101-13119. [PMID: 34745541 PMCID: PMC8513996 DOI: 10.1039/d1sc04181a] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 08/31/2021] [Indexed: 12/15/2022] Open
Abstract
Molybdenum(0) complexes with aliphatic aminophosphine pincer ligands have been prepared which are competent for the disproportionation of formic acid, thus representing the first example so far reported of non-noble metal species to catalytically promote such transformation. In general, formic acid disproportionation allows for an alternative access to methyl formate and methanol from renewable resources. MeOH selectivity up to 30% with a TON of 57 could be achieved while operating at atmospheric pressure. Selectivity (37%) and catalyst performance (TON = 69) could be further enhanced when the reaction was performed under hydrogen pressure (60 bars). A plausible mechanism based on experimental evidence is proposed. Mo(0) complexes with aliphatic PNP-pincer ligands enable the first example of non-noble metal catalyzed formic acid disproportionation leading to methanol with a selectivity of up to 37% and a turnover number up to 69.![]()
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Palladium-Catalyzed Cascade Carbonylation to α,β-Unsaturated Piperidones via Selective Cleavage of Carbon-Carbon Triple Bonds. Angew Chem Int Ed Engl 2021; 60:22393-22400. [PMID: 34382728 PMCID: PMC8519052 DOI: 10.1002/anie.202108120] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 07/29/2021] [Indexed: 12/23/2022]
Abstract
A direct and selective synthesis of α,β-unsaturated piperidones by a new palladium-catalyzed cascade carbonylation is described. In the presented protocol, easily available propargylic alcohols react with aliphatic amines to provide a broad variety of interesting heterocycles. Key to the success of this transformation is a remarkable catalytic cleavage of the present carbon-carbon triple bond by using a specific catalyst with 2-diphenylphosphinopyridine as ligand and appropriate reaction conditions. Mechanistic studies and control experiments revealed branched unsaturated acid 11 as crucial intermediate.
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Palladium‐Catalyzed Cascade Carbonylation to α,β‐Unsaturated Piperidones via Selective Cleavage of Carbon–Carbon Triple Bonds. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202108120] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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Palladium-Catalyzed Domino Aminocarbonylation of Alkynols: Direct and Selective Synthesis of Itaconimides. JACS AU 2021; 1:1257-1265. [PMID: 34467363 PMCID: PMC8397365 DOI: 10.1021/jacsau.1c00221] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Indexed: 06/13/2023]
Abstract
The first direct and selective synthesis of substituted itaconimdes by palladium-catalyzed aminocarbonylation of alkynols is reported. Key to the success of this transformation is the use of a novel catalyst system involving ligand L11 and appropriate reaction conditions. In the protocol here presented, easily available propargylic alcohols react with N-nucleophiles including aryl- and alkylamines as well as aryl hydrazines to provide a broad variety of interesting heterocycles with high catalyst activity and excellent selectivity. The synthetic utility of the protocol is demonstrated in the synthesis of natural product 11 with aminocarbonylation as the key step. Mechanistic studies and control experiments reveal the crucial role of the hydroxyl group in the substrate for the control of selectivity.
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3,3-Difluoroallyl ammonium salts: highly versatile, stable and selective gem-difluoroallylation reagents. Nat Commun 2021; 12:3257. [PMID: 34059673 PMCID: PMC8167079 DOI: 10.1038/s41467-021-23504-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Accepted: 04/30/2021] [Indexed: 02/04/2023] Open
Abstract
The selective synthesis of fluorinated organic molecules continues to be of major importance for the development of bioactive compounds (agrochemicals and pharmaceuticals) as well as unique materials. Among the established synthetic toolbox for incorporation of fluorine-containing units, efficient and general reagents for introducing -CF2- groups have been largely neglected. Here, we present the synthesis of 3,3-difluoropropen-1-yl ammonium salts (DFPAs) as stable, and scalable gem-difluoromethylation reagents, which allow for the direct reaction with a wide range of fascinating nucleophiles. DFPAs smoothly react with N-, O-, S-, Se-, and C-nucleophiles under mild conditions without necessity of metal catalysts with exclusive regioselectivity. In this way, the presented reagents also permit the straightforward preparation of many analogues of existing pharmaceuticals.
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Stereoselective Synthesis of a cis-Cedrane-8,9-diol as a Key Intermediate for an Amber Odorant. Org Process Res Dev 2021. [DOI: 10.1021/acs.oprd.0c00423] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Catalytic, Kinetic, and Mechanistic Insights into the Fixation of CO 2 with Epoxides Catalyzed by Phenol-Functionalized Phosphonium Salts. CHEMSUSCHEM 2021; 14:363-372. [PMID: 33068328 PMCID: PMC7839512 DOI: 10.1002/cssc.202002267] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 10/15/2020] [Indexed: 06/11/2023]
Abstract
A series of hydroxy-functionalized phosphonium salts were studied as bifunctional catalysts for the conversion of CO2 with epoxides under mild and solvent-free conditions. The reaction in the presence of a phenol-based phosphonium iodide proceeded via a first order rection kinetic with respect to the substrate. Notably, in contrast to the aliphatic analogue, the phenol-based catalyst showed no product inhibition. The temperature dependence of the reaction rate was investigated, and the activation energy for the model reaction was determined from an Arrhenius-plot (Ea =39.6 kJ mol-1 ). The substrate scope was also evaluated. Under the optimized reaction conditions, 20 terminal epoxides were converted at room temperature to the corresponding cyclic carbonates, which were isolated in yields up to 99 %. The reaction is easily scalable and was performed on a scale up to 50 g substrate. Moreover, this method was applied in the synthesis of the antitussive agent dropropizine starting from epichlorohydrin and phenylpiperazine. Furthermore, DFT calculations were performed to rationalize the mechanism and the high efficiency of the phenol-based phosphonium iodide catalyst. The calculation confirmed the activation of the epoxide via hydrogen bonding for the iodide salt, which facilitates the ring-opening step. Notably, the effective Gibbs energy barrier regarding this step is 97 kJ mol-1 for the bromide and 72 kJ mol-1 for the iodide salt, which explains the difference in activity.
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Correction: HCOOH disproportionation to MeOH promoted by molybdenum PNP complexes. Chem Sci 2021; 12:15772-15774. [PMID: 35003611 PMCID: PMC8654050 DOI: 10.1039/d1sc90239c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 11/09/2021] [Indexed: 11/21/2022] Open
Abstract
Correction for ‘HCOOH disproportionation to MeOH promoted by molybdenum PNP complexes’ by Elisabetta Alberico et al., Chem. Sci., 2021, 12, 13101–13119, DOI: 10.1039/D1SC04181A.
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Mechanistic insights into dehydrocoupling of amine boranes using dinuclear zirconocene complexes. Catal Sci Technol 2021. [DOI: 10.1039/d1cy00531f] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Catalytic dehydrocoupling of H3B·NMe2H using Cp2Zr(Cl)(μ-Me3SiC3SiMe3)Zr(Cl)Cp2 (1)/MeLi was studied. Spectroscopic monitoring and stoichiometric experiments show the formation and interconversion of several catalytically active Zr species.
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Efficient methylation of anilines with methanol catalysed by cyclometalated ruthenium complexes. Catal Sci Technol 2021. [DOI: 10.1039/d0cy02210a] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Cyclometalated ruthenium allow the effective and selective N-methylation of anilines under mild conditions.
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Bis(benzo[ h]quinolin-10-olato-κ 2
N, O)bromidomanganese(III). IUCRDATA 2020; 5:x201570. [PMID: 36337335 PMCID: PMC9462173 DOI: 10.1107/s2414314620015709] [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: 11/14/2020] [Accepted: 11/30/2020] [Indexed: 11/13/2022] Open
Abstract
The manganese(III) atom of the title compound is coordinated by one bromide and two benzo[h]quinolin-10-olate ligands and exhibits a distorted square-pyramidal coordination environment. The title compound, [MnBr(C13H8NO)2], consists of a manganese(III) atom, which is coordinated by one bromido and two benzo[h]quinolin-10-olato ligands. The MnIII complex exhibits a distorted square-pyramidal coordination geometry with the Br ligand in the apical position. Neighbouring complexes are held together by π–π interactions and weak C—H⋯Br hydrogen bonds.![]()
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Ligand-Controlled Palladium-Catalyzed Carbonylation of Alkynols: Highly Selective Synthesis of α-Methylene-β-Lactones. Angew Chem Int Ed Engl 2020; 59:21585-21590. [PMID: 32573055 PMCID: PMC7756850 DOI: 10.1002/anie.202006550] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 06/12/2020] [Indexed: 12/20/2022]
Abstract
The first general and regioselective Pd-catalyzed cyclocarbonylation to give α-methylene-β-lactones is reported. Key to the success for this process is the use of a specific sterically demanding phosphine ligand based on N-arylated imidazole (L11) in the presence of Pd(MeCN)2 Cl2 as pre-catalyst. A variety of easily available alkynols provide under additive-free conditions the corresponding α-methylene-β-lactones in moderate to good yields with excellent regio- and diastereoselectivity. The applicability of this novel methodology is showcased by the direct carbonylation of biologically active molecules including natural products.
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The role of allyl ammonium salts in palladium-catalyzed cascade reactions towards the synthesis of spiro-fused heterocycles. Nat Commun 2020; 11:5383. [PMID: 33097719 PMCID: PMC7584656 DOI: 10.1038/s41467-020-19110-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 09/22/2020] [Indexed: 12/16/2022] Open
Abstract
There is a continuous need for designing new and improved synthetic methods aiming at minimizing reaction steps while increasing molecular complexity. In this respect, catalytic, one-pot cascade methodologies constitute an ideal tool for the construction of complex molecules with high chemo-, regio-, and stereoselectivity. Herein, we describe two general and efficient cascade procedures for the synthesis of spiro-fused heterocylces. This transformation combines selective nucleophilic substitution (SN2′), palladium-catalyzed Heck and C–H activation reactions in a cascade manner. The use of allylic ammonium salts and specific Pd catalysts are key to the success of the transformations. The synthetic utility of these methodologies is showcased by the preparation of 48 spiro-fused dihydrobenzofuranes and indolines including a variety of fluorinated derivatives. Synthetic methods aiming at minimizing reaction steps while increasing molecular complexity are highly sought after by organic chemists. Here, the authors report two cascade procedures combining nucleophilic substitution, palladium-catalyzed Heck and C–H activation reactions for the synthesis of spiro-fused heterocycles.
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Cascade Synthesis of Pyrroles from Nitroarenes with Benign Reductants Using a Heterogeneous Cobalt Catalyst. Angew Chem Int Ed Engl 2020; 59:18679-18685. [PMID: 32779271 PMCID: PMC7589247 DOI: 10.1002/anie.202007613] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Indexed: 01/02/2023]
Abstract
A bifunctional 3d-metal catalyst for the cascade synthesis of diverse pyrroles from nitroarenes is presented. The optimal catalytic system Co/NGr-C@SiO2 -L is obtained by pyrolysis of a cobalt-impregnated composite followed by subsequent selective leaching. In the presence of this material, (transfer) hydrogenation of easily available nitroarenes and subsequent Paal-Knorr/Clauson-Kass condensation provides >40 pyrroles in good to high yields using dihydrogen, formic acid, or a CO/H2 O mixture (WGSR conditions) as reductant. In addition to the favorable step economy, this straightforward domino process does not require any solvents or external co-catalysts. The general synthetic utility of this methodology was demonstrated on a variety of functionalized substrates including the preparation of biologically active and pharmaceutically relevant compounds, for example, (+)-Isamoltane.
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Cover Feature: Synthesis of Molybdenum Pincer Complexes and Their Application in the Catalytic Hydrogenation of Nitriles (ChemCatChem 18/2020). ChemCatChem 2020. [DOI: 10.1002/cctc.202001354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Ligand‐Controlled Palladium‐Catalyzed Carbonylation of Alkynols: Highly Selective Synthesis of α‐Methylene‐β‐Lactones. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202006550] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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P-Chirogenic Diphosphazanes with Axially Chiral Substituents and Their Use in Rh-Catalyzed Asymmetric Hydrogenation. J Org Chem 2020; 85:14537-14544. [DOI: 10.1021/acs.joc.0c01108] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Cascade Synthesis of Pyrroles from Nitroarenes with Benign Reductants Using a Heterogeneous Cobalt Catalyst. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202007613] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Site-Selective Suzuki–Miyaura Reaction of 6,8-Dichloro-1,2,4-triazolo[4,3-a]pyridines. Synlett 2020. [DOI: 10.1055/s-0040-1707138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Triazolopyridines have found various applications as pharmaceuticals, agrochemicals, or optical materials. Consequently, the introduction of various functionalities at specific sites of this heterocyclic framework is of great importance. In this regard, we report the development of a site-selective Suzuki–Miyaura reactions leading to substituted triazolopyridines at positions 6 and 8. Under optimized conditions, the respective products have been obtained with high selectivity and yield.
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Efficient Palladium-Catalyzed Synthesis of 2-Aryl Propionic Acids. Molecules 2020; 25:molecules25153421. [PMID: 32731527 PMCID: PMC7435766 DOI: 10.3390/molecules25153421] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 07/23/2020] [Accepted: 07/24/2020] [Indexed: 12/05/2022] Open
Abstract
A flexible two-step, one-pot procedure was developed to synthesize 2-aryl propionic acids including the anti-inflammatory drugs naproxen and flurbiprofen. Optimal results were obtained in the presence of the novel ligand neoisopinocampheyldiphenylphosphine (NISPCPP) (9) which enabled the efficient sequential palladium-catalyzed Heck coupling of aryl bromides with ethylene and hydroxycarbonylation of the resulting styrenes to 2-aryl propionic acids. This cascade transformation leads with high regioselectivity to the desired products in good yields and avoids the need for additional purification steps.
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Synthesis of Molybdenum Pincer Complexes and Their Application in the Catalytic Hydrogenation of Nitriles. ChemCatChem 2020. [DOI: 10.1002/cctc.202000736] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Abstract
The molecular structure of the title compound, (BenzMIm)Br (BenzMIm=1-benzyl-3-methylimidazolium), consists of separated bromide anions and 1-benzyl-3-methylimidazolium cations connected via short C—H⋯Br contacts. The title compound, (BenzMIm)Br (BenzMIm=1-benzyl-3-methylimidazolium), C11H13N2+·Br−, was obtained as single crystals directly from a pure and liquid sample of the compound over several weeks. The molecular structure of (BenzMIm)Br consists of separated bromide anions and 1-benzyl-3-methylimidazolium cations connected via short C—H⋯Br contacts. The compound exhibits a relatively low melting point (m.p. = 72°C) and is a supercooled, highly viscous transparent liquid at ambient conditions. The title compound crystallizes with two unique ion pairs in the asymmetric unit of the orthorhombic unit cell.![]()
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Dehydropolymerisation of Methylamine Borane and an N-Substituted Primary Amine Borane Using a PNP Fe Catalyst. Chemistry 2020; 26:7889-7899. [PMID: 32118328 PMCID: PMC7383739 DOI: 10.1002/chem.202000809] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Indexed: 01/30/2023]
Abstract
Dehydropolymerisation of methylamine borane (H3 B⋅NMeH2 ) using the well-known iron amido complex [(PNP)Fe(H)(CO)] (PNP=N(CH2 CH2 PiPr2 )2 ) (1) gives poly(aminoborane)s by a chain-growth mechanism. In toluene, rapid dehydrogenation of H3 B⋅NMeH2 following first-order behaviour as a limiting case of a more general underlying Michaelis-Menten kinetics is observed, forming aminoborane H2 B=NMeH, which selectively couples to give high-molecular-weight poly(aminoborane)s (H2 BNMeH)n and only traces of borazine (HBNMe)3 by depolymerisation after full conversion. Based on a series of comparative experiments using structurally related Fe catalysts and dimethylamine borane (H3 B⋅NMe2 H) polymer formation is proposed to occur by nucleophilic chain growth as reported earlier computationally and experimentally. A silyl functionalised primary borane H3 B⋅N(CH2 SiMe3 )H2 was studied in homo- and co-dehydropolymerisation reactions to give the first examples for Si containing poly(aminoborane)s.
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