Electronic effects in the nickel-catalysed hydrocyanation of styrene applying chelating phosphorus ligands with large bite angles ‡

Goertz, Wolfgang; Keim, Wilhelm; Vogt, Dieter; Englert, Ulli; Boele, Mdk; Veen, van der La; Kamer, P.C.J.; Leeuwen, van

doi:10.1039/a802269k

Cited by 95 publications

(132 citation statements)

References 27 publications

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“…There seems to be a small difference between the xanthene and the phenoxathiin backbone, comparing the results obtained with ligands 2 and 3. A possible explanation for this apparent difference in activity could be a slight distortion or flipping motion of the phenoxathiin backbone in the catalyst complex, as found by Goertz et al 44 The activities obtained with these rhodium diphosphonite systems are higher than for the related diphosphine ligands (generally termed Xantphos),) 19c,43 and while the regioselectivies are generally lower than with the corresponding diphosphines and diphosphites, they outperform the previously reported diphosphonite ligands. 22 Industrial feedstocks such as Raffinate II from cracking facilities 4,45 constitute a mixture of unsaturated C 4 compounds.…”

Section: Resultsmentioning

confidence: 75%

Rhodium Complexes of Sterically Demanding Diphosphonites: Coordination Chemistry and Catalysis

et al. 2004

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The coordination chemistry of various sterically constrained diphosphonites 1-6 with rhodium are reported. The stoichiometric reaction of ligand 5 with [Rh(µ-Cl(CO) 2 ] 2 gives rise to the sole formation of trans-[RhCl(CO)(5)] (7), as shown by NMR and IR spectroscopy and X-ray crystallography. The molecular structure reveals a weak interaction between the metal center and the oxygen from the xanthene backbone. This complex serves as a structural model for the first intermediate in the catalytic cycle of rhodium hydroformylation, [Rh(H)-(CO)(PkP)]. A detailed study on the solution structure of the catalyst resting state under catalytic conditions is performed by high-pressure NMR and FT-IR spectroscopy. The spectroscopic data show that under hydroformylation conditions the bidentate ligands form well-defined complexes with the structure [Rh(H)(CO) 2 (PkP)]. All ligands show preference for a bis-equatorial (ee) coordination mode in the trigonal-bipyramidal Rh complexes. These novel sterically constrained diphosphonite ligands are applied in the rhodium hydroformylation of 1-octene and 2-butene, and good activities and regioselectivities are obtained.

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Section: Resultsmentioning

confidence: 75%

Rhodium Complexes of Sterically Demanding Diphosphonites: Coordination Chemistry and Catalysis

et al. 2004

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“…[31] Isomerization reactions of unsaturated substrates with Ni(0) complexes based on monodentate phosphites as well as bidentate phosphines have been extensively investigated. [32,33] This reaction is normally facilitated by the use of Lewis acids such as ZnCl 2 , BPh 3 or AlCl 3 . The isomerization leads to a mixture of 3PN : 2M3BN in the thermodynamic ratio of 93 : 7.…”

Section: Full Papersmentioning

confidence: 99%

“…On the other hand, this undesired side-reaction can be suppressed using sterically demanding ligands. [3] With this in mind, we decided to explore the synthesis of new bulky diphosphonites based on rigid xanthene-derived backbones.…”

Section: Introductionmentioning

confidence: 99%

Sterically Demanding Diphosphonite Ligands –Synthesis and Application in Nickel‐Catalyzed Isomerization of 2‐Methyl‐3‐Butenenitrile

et al. 2004

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Dedicated to Professor Joachim Bargon (Universit‰t Bonn) on the occasion of his 65 th birthday.Abstract: The synthesis of a novel class of sterically demanding diphosphonites 1 ± 8, based on rigid backbones, is described. The starting materials are all commercially available and the methodology allows for a modular approach. All ligands have been fully characterized, including an X-ray crystal structure for compound 1, 4,5-bis{di[(2-tert-butyl)phenyl]phosphonito}-9,9-dimethylxanthene. The coordination of these diphosphonite ligands towards Ni(II) and Ni(0) precursors is investigated, both by NMR spectroscopy as well as X-ray crystallography and compared with the behaviour of diphosphine ligands such as Xantphos. The molecular structure for complex 9, trans-[NiBr 2 (1)] is described in detail. The nickel-catalyzed isomerization of 2-methyl-3-butenenitrile to 3-pentenenitrile is studied, a relevant step in the industrially important hydrocyanation of butadiene (the DuPont adiponitrile process). Good activities and selectivities to the desired 3-pentenenitrile are obtained in this reversible C À C bond activation reaction.

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“…[7] It was shown earlier that chelating p-acceptor ligands with a high binding affinity to Ni(0) can lead to very stable nickel bis-chelate complexes, decreasing the catalytic activity. [9] All studies show that finding a suitable ligand system is rather tedious and fine tuning is necessary in order to obtain both high conversion and high enantioselectivity. Thus, we investigated a modular ligand suitable for modification on several positions.…”

Section: Introductionmentioning

confidence: 99%

Binaphthol‐Based Diphosphite Ligands in Asymmetric Nickel‐Catalyzed Hydrocyanation of Styrene and 1,3‐Cyclohexadiene: Influence of Steric Properties

et al. 2007

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A series of chiral (R)-binaphthol-based diphosphite ligands with different substituents was prepared and applied in the asymmetric nickel-catalyzed hydrocyanation of styrene and 1,3-cyclohexadiene to investigate the influence of their steric properties. The optimum steric properties for the hydrocyanation reaction lie within a narrow window. With the optimized ligand, hydrocyanation of styrene gave full conversion (Subs/Ni = 100) with 49 % ee, the TON was determined to be 600. Hydrocyanation of 1,3-cyclohexadiene gave 50 % conversion (Subs/Ni = 500) with an excellent ee of 86 %. This demonstrates that high ees are not only accessible for vinylarenes but also for conjugated dienes in the asymmetric nickelcatalyzed hydrocyanation.

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Electronic effects in the nickel-catalysed hydrocyanation of styrene applying chelating phosphorus ligands with large bite angles ‡

Cited by 95 publications

References 27 publications

Rhodium Complexes of Sterically Demanding Diphosphonites: Coordination Chemistry and Catalysis

Rhodium Complexes of Sterically Demanding Diphosphonites: Coordination Chemistry and Catalysis

Sterically Demanding Diphosphonite Ligands –Synthesis and Application in Nickel‐Catalyzed Isomerization of 2‐Methyl‐3‐Butenenitrile

Binaphthol‐Based Diphosphite Ligands in Asymmetric Nickel‐Catalyzed Hydrocyanation of Styrene and 1,3‐Cyclohexadiene: Influence of Steric Properties

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