Enhanced product selectivity promoted by remote metal coordination in acceptor-free alcohol dehydrogenation catalysis

Valencia, Marta; Müller‐Bunz, Helge; Gossage, Robert A.; Albrecht, Martin

doi:10.1039/c6cc00267f

Cited by 55 publications

(40 citation statements)

References 50 publications

(3 reference statements)

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“…The activity of related triazolylidene iridium complexesa sc atalyst precursors for the oxidation of oxygen-containing protic substrates, such as H 2 Oo ra lcohols, [20,21] prompted us to investigate the ability of complexes 1 and 2 to catalyze the related dehydrogenation of amines. In particular,w ea imed at probing the bifunctionalc haracter of the triazolylidene iridium system 1 due to the presence of ab asic pyridyl group as compared to the inert phenyl substituent in complex 2.…”

Section: Catalytic Experiments With Protic Substratesmentioning

confidence: 99%

“…[16,21,25] Under these conditions, both complexes 1 and 2 were active catalysts and converted primary amines into am ixture of secondary imines, secondary amines,a nd tertiary amines in different proportions. [16,21,25] Under these conditions, both complexes 1 and 2 were active catalysts and converted primary amines into am ixture of secondary imines, secondary amines,a nd tertiary amines in different proportions.…”

Section: Catalytic Experiments With Protic Substratesmentioning

confidence: 99%

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Triazolylidene‐Iridium Complexes with a Pendant Pyridyl Group for Cooperative Metal–Ligand Induced Catalytic Dehydrogenation of Amines

Valencia

Pereira

Müller‐Bunz

et al. 2017

Chemistry A European J

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Two iridium(III) complexes containing a C,N-bidentate pyridyl-triazolylidene ligand were prepared that are structurally very similar but differ in their pendant substituent. Whereas complex 1 contains a non-coordinating pyridyl unit, complex 2 has a phenyl group on the triazolylidene substituent. The presence of the basic pyridyl unit has distinct effects on the catalytic activity of the complex in the oxidative dehydrogenation of benzylic amines, inducing generally higher rates, higher selectivity towards formation of imines versus secondary amines, and notable quantities of tertiary amines when compared to the phenyl-functionalized analogue. The role of the pyridyl functionality has been elucidated from a set of stoichiometric experiments, which demonstrate hydrogen bonding between the pendant pyridyl unit and the amine protons of the substrate. Such N ⋅⋅⋅H-N interactions are demonstrated by X-ray diffraction analysis, H NMR, and IR spectroscopy, and suggest a pathway of substrate bond-activation that involves concerted substrate binding through the Lewis acidic iridium center and the Lewis basic pyridyl site appended to the triazolylidene ligand, in agreement with ligand-metal cooperative substrate activation.

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Section: Catalytic Experiments With Protic Substratesmentioning

confidence: 99%

Section: Catalytic Experiments With Protic Substratesmentioning

confidence: 99%

Triazolylidene‐Iridium Complexes with a Pendant Pyridyl Group for Cooperative Metal–Ligand Induced Catalytic Dehydrogenation of Amines

Valencia

Pereira

Müller‐Bunz

et al. 2017

Chemistry A European J

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“…The formation of the triazole-pyridine moiety enables the use of such ac omposite as ab identate ligand for the complexation of various metallic centers. [79][80][81] The use of the dimer [IrCp*Cl 2 ] 2 (Cp* = 1,2,3,4,5-pentamethylcyclopentadiene)a sp recursor leads to supported iridium complexes 10-G 3 .T his composite was characterizedb yX PS and inductively coupled plasma atomic emission spectroscopy (ICP-AES). It is noteworthy that, for the sake of dendrimer economy, 0.2 equivalents of PAMAM were employed for the synthesis of 4-G 3 instead of 2equivalents as described above.A lthough the amount of introduced dendrimer is ten times less, we observe an itrogen content of 7.03 at %, which is only 27 %l ower and really appreciable ( Table 3).…”

Section: Resultsmentioning

confidence: 99%

Synthesis and Catalytic Applications of Multi‐Walled Carbon Nanotube–Polyamidoamine Dendrimer Hybrids

Desmecht

Steenhaut

Pennetreau

et al. 2018

Chemistry A European J

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Polyamidoamine (PAMAM) dendrimers were covalently immobilized on multi-walled carbon nanotubes (MWNT) by two "grafting to" strategies. We demonstrate the existence of non-covalent interactions between the two components but outline the superiority of our two grafting approaches, namely xanthate and click chemistry. MWNT surfaces were functionalized with activated ester and propargylic moieties prior to their reaction with PAMAM or azido-PAMAM dendrimers, respectively. The grafting of PAMAM generations 0 to 3 was evaluated with X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). The versatility of our hybrids was demonstrated by post-functionalization sequences involving copper alkyne-azide cycloaddition (CuAAC). We synthesized homogeneous supported iridium complexes at the extremities of the dendrimers. In addition, our materials were used as templates for the encapsulation of Pd nanoparticles (NPs), validating our nanocomposites for catalytic applications. The palladium-based catalyst was active for carbonylative coupling over five consecutive runs without loss of activity.

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“…Azidomethylpyridine 3 g was efficiently clicked to yield a bidentate click ligand supported on MWNTs 4 g (1.73 at % N; Table , entry 6). Such click ligands are known to coordinate different metals, and we illustrated this by immobilizing 0.27 at % of iridium (Table , entry 7) on 4 g to give 6 (Scheme ) . Work is ongoing for the use of 6 in homogeneous supported catalysis.…”

Section: Methodsmentioning

confidence: 99%

Versatile Two‐Step Functionalization of Nanocarbons: Grafting of Propargylic Groups and Click Post‐Functionalization

2017

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Chemical functionalization of nanocarbons is essential for further applications in various fields. We developed a facile, inexpensive, and gram‐scale one‐pot route towards alkynyl‐functionalized nanocarbons. Nucleophilic addition/propargylic capture places alkyne moieties at the surface of carbon nanotubes (CNTs) and graphene. Thermogravimetric analysis coupled with mass spectrometry and Raman analysis confirmed the efficiency of this process. Conductivity measurements demonstrated the maintenance of the CNT electrical properties. The attached alkynyl moieties were reacted with various azide derivatives through the click‐Huisgen [3+2] cycloaddition and characterized with XPS. The efficient addition of those derivatives enables the application of our finding in various fields. This route is a reliable and convenient alternative to the known diazonium functionalization and oxidation‐esterification reactions to graft alkyne groups.

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Enhanced product selectivity promoted by remote metal coordination in acceptor-free alcohol dehydrogenation catalysis

Cited by 55 publications

References 50 publications

Triazolylidene‐Iridium Complexes with a Pendant Pyridyl Group for Cooperative Metal–Ligand Induced Catalytic Dehydrogenation of Amines

Triazolylidene‐Iridium Complexes with a Pendant Pyridyl Group for Cooperative Metal–Ligand Induced Catalytic Dehydrogenation of Amines

Synthesis and Catalytic Applications of Multi‐Walled Carbon Nanotube–Polyamidoamine Dendrimer Hybrids

Versatile Two‐Step Functionalization of Nanocarbons: Grafting of Propargylic Groups and Click Post‐Functionalization

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