Bis(di-tert-butylphosphino)ethan-nickel(0)-Komplexe / Bis(di-tert-butylphosphino)ethane-nickel(0) Complexes

Pörschke, Klaus‐Richard; Pluta, Christian; Proft, Bernd; Lutz, Frank

doi:10.1515/znb-1993-0511

Cited by 53 publications

(66 citation statements)

References 3 publications

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“…The ligands IMes, SIPr, and dtbpe as well as the complexes (IPr)Cu-(OAc), (IPr)Cu(Me), (IPr)Cu(Et), and (IPr)Cu(OTf) were prepared according to literature procedures. 30,47,[52][53][54] (SIPr)Cu(OAc) (1) 0.059 g, 0.50 mmol), and toluene (15 mL), and the resulting solution was stirred for 2 h at room temperature. The solution was filtered through Celite, approximately half of the solvent was removed in vacuo, and hexanes were added to form a white precipitate.…”

Section: Methodsmentioning

confidence: 99%

Single-Electron Oxidation of Monomeric Copper(I) Alkyl Complexes: Evidence for Reductive Elimination through Bimolecular Formation of Alkanes

et al. 2006

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Monomeric Cu(I) alkyl complexes (NHC)Cu(R) (NHC ) N-heterocyclic carbene; R ) Me or Et) and (dtbpe)Cu(Me) (dtbpe ) 1,2-bis(di-tert-butylphosphino)ethane) have been prepared, isolated, and characterized. Single-electron oxidation of the Cu(I) alkyl complexes upon reaction with AgOTf to form putative Cu(II) intermediates of the type [(L)Cu(R)] + (L ) NHC or dtbpe, R ) Me or Et) results in the rapid production of (L)Cu(X) (X ) OTf) and R 2 . Experimental studies suggest that the reductive elimination of R 2 from Cu(II) occurs through a nonradical bimolecular mechanism. Computational studies of the Cu-C methyl yield bond dissociation enthalpies of [(SIPr)Cu-CH 3 ] n+ (80 kcal/mol for n ) 0 {Cu(I)} and 38 kcal/mol for n ) 1 {Cu(II)}).

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Section: Methodsmentioning

confidence: 99%

Single-Electron Oxidation of Monomeric Copper(I) Alkyl Complexes: Evidence for Reductive Elimination through Bimolecular Formation of Alkanes

et al. 2006

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“…[31] Complexes 4 and 5, also used in some additional hydration experiments, were prepared analogously, starting H} NMR spectra of all complexes, before their use. The chelating bisphosphine ligands, dippe [32] and dtbpe [33] were synthesized from 1,2-bis(dichlorophosphino)ethane (Strem) and the corresponding Grignard or lithium alkyls (Aldrich), and dcype was purchased from Strem. Neutral alumina used for the preparation of complexes 3 -5, was heated to 200 8C under vacuum for two days and stored in the glovebox.…”

Section: Experimental Section General Considerationsmentioning

confidence: 99%

Catalytic Hydration of Benzonitrile and Acetonitrile using Nickel(0)

2006

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Abstract:The homogeneous catalytic hydration of benzo-and acetonitrile under thermal conditions was achieved using nickel(0) compounds of the type [(dippe)Ni(h 2 -NCR)] with R ¼ phenyl or methyl (compounds 1 and 2, respectively), as the specific starting intermediates. Alternatively, the complexes may be prepared in situ by direct reaction of the precursor [(dippe)NiH] 2 (3) with the respective nitrile. Hydration appears to occur homogeneously, as tested by mercury drop experiments, producing benzamide and acetamide, respectively. Addition of Bu 4 NI did not lead to catalysis inhibition, suggesting the prevalence of Ni (0) intermediates during catalysis. Hydration using analogous complexes of 3, such as [(dtbpe)NiH] 2 (4) and [(dcype)NiH] 2 (5) was also addressed.

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“…The second coordinated COD is then replaced by CO to form 17 by bubbling carbon monoxide into the reaction mixture. [10,54] This route can be pursued under very mild conditions in organic solvents, and is therefore also suitable for phosphines containing an ethoxysilane group that might lead to side reactions [17] or crosslinking [16] otherwise. For phosphines with OH instead of SiOEt groups, such as 3 and 4, route 2 can be applied.…”

Section: Synthesis Of the Nickel Catalystsmentioning

confidence: 99%

New Silica‐Immobilized Nickel Catalysts for Cyclotrimerizations of Acetylenes

Reinhard¹,

Šoba²,

Röminger³

et al. 2003

Adv Synth Catal

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New dicarbonylnickel catalysts with a variety of mono-and bidentate phosphine ligands, such as Ph 2 P(CH 2 ) x PPh(CH 2 ) y Si(OEt) 3 (x 2, 3; y 2, 3), have been synthesized and fully characterized, three of them by X-ray analyses. All the catalysts have been immobilized on silica by reaction of the ethoxysilane or hydroxy groups of the phosphine linkers with the surface silanol groups. The clean immobilization was proved by 31 P solid-state NMR. It has been demonstrated that the C À O À Si bridge, in contrast to the strong Si À O À Si bond, is easily cleaved by organic solvents and water. With respect to the cyclotrimerization of phenylacetylene the optimal reaction conditions for all molecular and immobilized catalysts have been determined. Cyclooctane was the best solvent, and the optimal reaction temperature was 100 8C for reactions in homogeneous phase, and 155 8C for surface-bound catalysts. The bite angles and spacer lengths of the chelating ligands did not play a major role for the performance of the homogeneous or immobilized catalysts. The latter could be recycled for 12 times, with final substrate conversions still typically between 30 and 40%, and turnover numbers (TON) around 1500. With an excess of substrate in one run a TON of 4810 was obtained for an immobilized carbonylnickel complex with a dppp-type chelate phosphine (x 3, y 2). Reduction of the surface coverage generally resulted in catalysts with longer lifetimes, for example, reduction to one fourth gave a record TON of 7616 for this catalyst. The selectivities of the catalysts all followed one trend. The main products were the cyclotrimers 1,2,4-and 1,3,5-triphenylbenzene, besides dimers, linear trimers and tetramers as side-products. The fraction of the latter decreased at higher temperatures with homogeneous catalysts, and vanished entirely after a few cycles with the immobilized catalysts. On recycling, the initial ratio of unsymmetrical to symmetrical cyclotrimers of typically 5 : 1 gradually changed to about 1 : 1 for all catalysts.

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Bis(di-tert-butylphosphino)ethan-nickel(0)-Komplexe / Bis(di-tert-butylphosphino)ethane-nickel(0) Complexes

Cited by 53 publications

References 3 publications

Single-Electron Oxidation of Monomeric Copper(I) Alkyl Complexes: Evidence for Reductive Elimination through Bimolecular Formation of Alkanes

Single-Electron Oxidation of Monomeric Copper(I) Alkyl Complexes: Evidence for Reductive Elimination through Bimolecular Formation of Alkanes

Catalytic Hydration of Benzonitrile and Acetonitrile using Nickel(0)

New Silica‐Immobilized Nickel Catalysts for Cyclotrimerizations of Acetylenes

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