A Neutral Three-Coordinate Alkylrhodium(I) Complex: Stabilization of a 14-Electron Species by γ-C−H Agostic Interactions with a Saturated Hydrocarbon Group

Urtel, Heiko; Meier, Ch.; Eisenträger, Frank; Röminger, Frank; Joschek, Jens P.; Hofmann, Peter

doi:10.1002/1521-3773(20010216)40:4<781::aid-anie7810>3.0.co;2-t

Cited by 95 publications

(54 citation statements)

References 41 publications

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“…In effect, there are many X‐ray structures that show agostic CH bonds involved in agostic interaction to the empty coordination site of otherwise T‐shaped d 8 complexes 26. This evidence goes back to the pioneering study of the structure of [Rh(PPh 3 ) 3 ](ClO 4 ) (the proposed 14‐electron species in Wilkinson's catalyst) in which the ortho CH of one of the phenyl groups is involved in agostic bonding b) (see above),27 and continues through many reports until the very recent [RhNp( κ 2 ‐dtbpm)] (Np=neopentyl; dtbpm=Bu t PCH 2 P t Bu), where again an agostic interaction occupies the fourth coordination position (c) 28. These agostic ligands are very weakly bonded and can easily be displaced.…”

Section: Resultsmentioning

confidence: 53%

14-Electron T-Shaped [PdRXL] Complexes: Evidence or Illusion? Mechanistic Consequences for the Stille Reaction and Related Processes

2002

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Mit zwei Methoden wurden kürzlich anorganische, doppelhelicale Materialien hergestellt: Silicium‐Mikroröhren (siehe Bild) aus einer NaSi‐Schmelze, die unter hohem Druck durch eine Öffnung gepresst wird, und Kohlenstoff‐Nanoröhren aus Plättchen geschichteter Hydroxide mit Hydrotalcitstruktur, die beidseitig mit aktiven Katalysatorpartikeln versehen sind. Damit ist nun der Weg frei für die Erforschung von Anwendungen derartig strukturierter Materialien.

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Section: Resultsmentioning

confidence: 53%

14-Electron T-Shaped [PdRXL] Complexes: Evidence or Illusion? Mechanistic Consequences for the Stille Reaction and Related Processes

2002

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“…From the molecular structural standpoint agostic interactions are classified in α, β or γ etc. according to relative location of the C–H bond to the metal center, the latter much less observed and predominantly of 2 nd and 3 rd row transition metals and structurally identified …”

Section: Introductionmentioning

confidence: 99%

Spontaneous Bicyclometalation of a Single Cobalt(I) Complex Stabilized by a δ‐C–H Agostic Interaction

2018

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CoCH3(PMe3)4 is known for a long time for its potential to activate less reactive C–H Bonds under extremely mild conditions by methane elimination. A spontaneous second C–H bond activation at the same center of cobalt complex is not expected. In contrast to previous investigations with certain aryl‐iminophosphane chelating ligands, in this work two consecutive metalation steps at the same complex center lead to a rare example of a cobalt metallabicycle. In the first step a C–H activation results in a five‐membered chelate ring, whereas the second ring is formed by an incomplete C–H activation which stops at a stable, rarely observed δ‐C–H agostic interaction. The results are supported by NMR spectroscopy, X ray structure analysis and density functional theory (DFT) calculations. Knowledge of such agostic interactions are essential in order to understand catalytic reaction paths and studies of such molecular structures of their ring sizes, bite angles and electronic properties have shown that these ligands allow sensitive control within the metal coordination sphere.

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“…18 Just as an interaction of the metal center with a -hydrogen seems to precede -hydrogen elimination, an interaction of the rhodium with the -aryl group of the alkoxide 2a seems to precede the -aryl elimination event. 19 Simple lengthening of the C-C bond and shortening of the Rh-C bond to the ipso carbon in 2a and its analogs would generate the initial arylrhodium ketone complex that would react with phosphine to displace the ketone and form the final arylrhodium product.In summary, we have prepared a series of isolated rhodium(I) tertiary phenylmethoxide complexes that undergo mild -phenyl eliminations. The bisphosphine complexes undergo elimination directly from the isolated species, and the trisphosphine complexes undergo elimination after dissociation of a phosphine.…”

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confidence: 99%

Direct Observation of β-Aryl Eliminations from Rh(I) Alkoxides

2006

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beta-Aryl eliminations from a series of rhodium(I) alkoxides to form rhodium aryl complexes and free ketones are reported. Tertiary phenylmethoxide complexes [Rh(PEt3)n(OCPhRR')] (n = 2, 3) were prepared via alcoholysis of {Rh(PEt3)2[N(SiMe3)2} by the corresponding alcohols HOCPhRR' in the presence and absence of added PEt3. Heating of these complexes in the presence of added PEt3 generated the rhodium phenyl complex, (PEt3)3RhPh, and the corresponding ketones in good to high yields. Kinetic results are most consistent with irreversible beta-phenyl elimination from a bisphosphine-ligated rhodium alkoxide complex. Such bisphosphine complexes result from ligand dissociation from the trisphosphine complexes and have been isolated in some cases. The bisphosphine complexes are stabilized by Rh-Cphenyl interactions, as evidenced by an X-ray structure, and this structure with a metal-aryl interaction likely illustrates the pathway for C-C bond cleavage.

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A Neutral Three-Coordinate Alkylrhodium(I) Complex: Stabilization of a 14-Electron Species by γ-C−H Agostic Interactions with a Saturated Hydrocarbon Group

Cited by 95 publications

References 41 publications

14-Electron T-Shaped [PdRXL] Complexes: Evidence or Illusion? Mechanistic Consequences for the Stille Reaction and Related Processes

14-Electron T-Shaped [PdRXL] Complexes: Evidence or Illusion? Mechanistic Consequences for the Stille Reaction and Related Processes

Spontaneous Bicyclometalation of a Single Cobalt(I) Complex Stabilized by a δ‐C–H Agostic Interaction

Direct Observation of β-Aryl Eliminations from Rh(I) Alkoxides

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