Abstract
Oxidative addition of aryl bromides to 12-electron [Rh(PiBu 3)2]-[BArF4] (ArF = 3,5-(CF3)2C6H3) forms a variety of products. With p-tolyl bromides, RhIII dimeric complexes result [Rh(PiBu3)2(o/p-MeC6H4)(µ-Br)] 2-[BArF4]2. Similarly, reaction with p-ClC6H4Br gives [Rh(PiBu3) 2(p-ClC6H4)(µ-Br)]2[BAr F4]2. In contrast, the use of o-BrC 6H4Me leads to a product in which toluene has been eliminated and an isobutyl phosphine has undergone C-H activation: [Rh(PiBu 2-(CH2CHCH3CH2)}(PiBu 3)(µ-Br)]2-[BArF4]2. Trapping experiments with ortho-biomo anisole or ortho-bromo thioanisole indicate that a possible intermediate for this process is a low-coordinate RhIII complex that then undergoes C-H activation. The anisole and thioanisole complexes have been isolated and their structures show OMe or SMe interactions with the metal centre alongside supporting agostic interactions, [Rn(PiBu3)2(C6H4OMe)Br]-[BA F4] (the solid-state structure of the 5-methyl substituted analogue is reported) and [Rh(PiBu3)2(C6H 4SMe)-Br][BArF4]. The anisole-derived complex proceeds to give [Rh-{PiBu2(CH2CHCH3CH 2)}(PiBu3)(µ-Br)]2[BArF4]2, whereas the thioanisole complex is unreactive. The isolation of [Rh(PiBu3)2(C6H4OMe)Br] [BArF4] and its onward reactivity to give the products of C-H activation and aryl elimination suggest that it is implicated on the pathway of a s-bond metathesis reaction, a hypothesis strengthened by DFT calculations. Calculations also suggest that C-H bond cleavage through phosphine-assisted deprotonation of a non-agostic bond is also competitive, although the subsequent protonation of the aryl ligand is too high in energy to account for product formation. C-H activation through oxidative addition is also ruled out on the basis of these calculations. These new complexes have been characterised by solution NMR/ESIMS techniques and in the solid-state by X-ray crystallography. © 2010 Wiley-VCH. Verlag GmbH & Co. KGaA, Weinheim.
| Original language | English |
|---|---|
| Pages (from-to) | 8376-8389 |
| Number of pages | 14 |
| Journal | Chemistry - A European Journal |
| Volume | 16 |
| Issue number | 28 |
| DOIs | |
| Publication status | Published - 26 Jul 2010 |
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Keywords
- Agostic interactions
- C-H activation
- Density functional calculations
- Transition metals
- X-ray diffraction
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Reactivity of the latent 12-electron fragment [Rh(PiBu3) 2]+with aryl bromides : Aryl-br and phosphine ligand C-H activation. / Townsend, Nell S.; Chaplin, Adrian B.; Abu Naser, M; Thompson, Amber L.; Rees, Nicholas H.; Macgregor, Stuart A.; Weller, Andrew S.
In: Chemistry - A European Journal, Vol. 16, No. 28, 26.07.2010, p. 8376-8389.Research output: Contribution to journal › Article
TY - JOUR
T1 - Reactivity of the latent 12-electron fragment [Rh(PiBu3) 2]+with aryl bromides
T2 - Aryl-br and phosphine ligand C-H activation
AU - Townsend, Nell S.
AU - Chaplin, Adrian B.
AU - Abu Naser, M
AU - Thompson, Amber L.
AU - Rees, Nicholas H.
AU - Macgregor, Stuart A.
AU - Weller, Andrew S.
PY - 2010/7/26
Y1 - 2010/7/26
N2 - Oxidative addition of aryl bromides to 12-electron [Rh(PiBu 3)2]-[BArF4] (ArF = 3,5-(CF3)2C6H3) forms a variety of products. With p-tolyl bromides, RhIII dimeric complexes result [Rh(PiBu3)2(o/p-MeC6H4)(µ-Br)] 2-[BArF4]2. Similarly, reaction with p-ClC6H4Br gives [Rh(PiBu3) 2(p-ClC6H4)(µ-Br)]2[BAr F4]2. In contrast, the use of o-BrC 6H4Me leads to a product in which toluene has been eliminated and an isobutyl phosphine has undergone C-H activation: [Rh(PiBu 2-(CH2CHCH3CH2)}(PiBu 3)(µ-Br)]2-[BArF4]2. Trapping experiments with ortho-biomo anisole or ortho-bromo thioanisole indicate that a possible intermediate for this process is a low-coordinate RhIII complex that then undergoes C-H activation. The anisole and thioanisole complexes have been isolated and their structures show OMe or SMe interactions with the metal centre alongside supporting agostic interactions, [Rn(PiBu3)2(C6H4OMe)Br]-[BA F4] (the solid-state structure of the 5-methyl substituted analogue is reported) and [Rh(PiBu3)2(C6H 4SMe)-Br][BArF4]. The anisole-derived complex proceeds to give [Rh-{PiBu2(CH2CHCH3CH 2)}(PiBu3)(µ-Br)]2[BArF4]2, whereas the thioanisole complex is unreactive. The isolation of [Rh(PiBu3)2(C6H4OMe)Br] [BArF4] and its onward reactivity to give the products of C-H activation and aryl elimination suggest that it is implicated on the pathway of a s-bond metathesis reaction, a hypothesis strengthened by DFT calculations. Calculations also suggest that C-H bond cleavage through phosphine-assisted deprotonation of a non-agostic bond is also competitive, although the subsequent protonation of the aryl ligand is too high in energy to account for product formation. C-H activation through oxidative addition is also ruled out on the basis of these calculations. These new complexes have been characterised by solution NMR/ESIMS techniques and in the solid-state by X-ray crystallography. © 2010 Wiley-VCH. Verlag GmbH & Co. KGaA, Weinheim.
AB - Oxidative addition of aryl bromides to 12-electron [Rh(PiBu 3)2]-[BArF4] (ArF = 3,5-(CF3)2C6H3) forms a variety of products. With p-tolyl bromides, RhIII dimeric complexes result [Rh(PiBu3)2(o/p-MeC6H4)(µ-Br)] 2-[BArF4]2. Similarly, reaction with p-ClC6H4Br gives [Rh(PiBu3) 2(p-ClC6H4)(µ-Br)]2[BAr F4]2. In contrast, the use of o-BrC 6H4Me leads to a product in which toluene has been eliminated and an isobutyl phosphine has undergone C-H activation: [Rh(PiBu 2-(CH2CHCH3CH2)}(PiBu 3)(µ-Br)]2-[BArF4]2. Trapping experiments with ortho-biomo anisole or ortho-bromo thioanisole indicate that a possible intermediate for this process is a low-coordinate RhIII complex that then undergoes C-H activation. The anisole and thioanisole complexes have been isolated and their structures show OMe or SMe interactions with the metal centre alongside supporting agostic interactions, [Rn(PiBu3)2(C6H4OMe)Br]-[BA F4] (the solid-state structure of the 5-methyl substituted analogue is reported) and [Rh(PiBu3)2(C6H 4SMe)-Br][BArF4]. The anisole-derived complex proceeds to give [Rh-{PiBu2(CH2CHCH3CH 2)}(PiBu3)(µ-Br)]2[BArF4]2, whereas the thioanisole complex is unreactive. The isolation of [Rh(PiBu3)2(C6H4OMe)Br] [BArF4] and its onward reactivity to give the products of C-H activation and aryl elimination suggest that it is implicated on the pathway of a s-bond metathesis reaction, a hypothesis strengthened by DFT calculations. Calculations also suggest that C-H bond cleavage through phosphine-assisted deprotonation of a non-agostic bond is also competitive, although the subsequent protonation of the aryl ligand is too high in energy to account for product formation. C-H activation through oxidative addition is also ruled out on the basis of these calculations. These new complexes have been characterised by solution NMR/ESIMS techniques and in the solid-state by X-ray crystallography. © 2010 Wiley-VCH. Verlag GmbH & Co. KGaA, Weinheim.
KW - Agostic interactions
KW - C-H activation
KW - Density functional calculations
KW - Transition metals
KW - X-ray diffraction
UR - http://www.scopus.com/inward/record.url?scp=77954846478&partnerID=8YFLogxK
U2 - 10.1002/chem.201000554
DO - 10.1002/chem.201000554
M3 - Article
VL - 16
SP - 8376
EP - 8389
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
SN - 0947-6539
IS - 28
ER -