Abstract
In continuation of our studies on bond activation and catalysis by pincer complexes, based on metal-ligand cooperation, we present here a rare example of amine N-H activation by Rh(I) complexes. The novel dearomatized pincer complexes [(PNN*)RhL′] (PNN = 2-(CH 2-P tBu 2)-6-(CH 2-NEt 2)C 5H 3N, PNN* = deprotonated PNN, L′ = N 2 (5), C 2H 4 (6)) and [( iPrPNP)RhL′] ( iPrPNP = 2,6-(CH 2-P iPr 2) 2C 5H 3N, iPrPNP* = deprotonated iPrPNP, L′ = C 2H 4 (7), cyclooctene (9)) were prepared and fully characterized by NMR and X-ray analysis. Complexes 5-7 and 9 undergo facile N-H activation of anilines involving aromatization of the pincer ligand without a change in the formal oxidation state of the metal center to form stable anilide complexes [(PNN)Rh(NHAr)] and [( iPrPNP)Rh(NHAr)] (Ar = C 6H 5, o-Br-C 6H 4, m-Cl-p-Cl-C 6H 3, p-NO 2-C 6H 4). Anilines possessing electron-withdrawing groups accelerate the N-H activation and yield more stable anilide complexes. The pincer and the ancillary ligands also affect the activation rate, which supports an associative mechanism. Spin saturation transfer experiments show chemical exchange between the pyridylic arm of the pincer ligand and the NH- protons of anilines prior to and after the N-H activation. The reverse N-H formation by metal-ligand cooperation from the anilide complexes was observed to give free anilines and dearomatized Rh(I) complexes upon addition of CO or PEt 3. Deprotonation of complexes [(PNL)Rh(p-NO 2-NH 2C 6H 4)] (13, P = P tBu 2, L = NEt 2; 15, P = L = P iPr 2) yields the dearomatized anionic complexes [(PNL)Rh(p-NO 2-NH 2C 6H 4)]. An associative mechanism, involving N-H activation of an apically coordinated aniline in a pentacoordinated Rh(I) complex, is suggested.
| Original language | English |
|---|---|
| Pages (from-to) | 4083-4101 |
| Number of pages | 19 |
| Journal | Organometallics |
| Volume | 31 |
| Issue number | 11 |
| DOIs | |
| Publication status | Published - Jun 11 2012 |
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ASJC Scopus subject areas
- Organic Chemistry
- Physical and Theoretical Chemistry
- Inorganic Chemistry
Cite this
N-H activation by Rh(I) via metal-ligand cooperation. / Feller, Moran; Diskin-Posner, Yael; Shimon, Linda J W; Ben-Ari, Eyal; Milstein, David.
In: Organometallics, Vol. 31, No. 11, 11.06.2012, p. 4083-4101.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - N-H activation by Rh(I) via metal-ligand cooperation
AU - Feller, Moran
AU - Diskin-Posner, Yael
AU - Shimon, Linda J W
AU - Ben-Ari, Eyal
AU - Milstein, David
PY - 2012/6/11
Y1 - 2012/6/11
N2 - In continuation of our studies on bond activation and catalysis by pincer complexes, based on metal-ligand cooperation, we present here a rare example of amine N-H activation by Rh(I) complexes. The novel dearomatized pincer complexes [(PNN*)RhL′] (PNN = 2-(CH 2-P tBu 2)-6-(CH 2-NEt 2)C 5H 3N, PNN* = deprotonated PNN, L′ = N 2 (5), C 2H 4 (6)) and [( iPrPNP)RhL′] ( iPrPNP = 2,6-(CH 2-P iPr 2) 2C 5H 3N, iPrPNP* = deprotonated iPrPNP, L′ = C 2H 4 (7), cyclooctene (9)) were prepared and fully characterized by NMR and X-ray analysis. Complexes 5-7 and 9 undergo facile N-H activation of anilines involving aromatization of the pincer ligand without a change in the formal oxidation state of the metal center to form stable anilide complexes [(PNN)Rh(NHAr)] and [( iPrPNP)Rh(NHAr)] (Ar = C 6H 5, o-Br-C 6H 4, m-Cl-p-Cl-C 6H 3, p-NO 2-C 6H 4). Anilines possessing electron-withdrawing groups accelerate the N-H activation and yield more stable anilide complexes. The pincer and the ancillary ligands also affect the activation rate, which supports an associative mechanism. Spin saturation transfer experiments show chemical exchange between the pyridylic arm of the pincer ligand and the NH- protons of anilines prior to and after the N-H activation. The reverse N-H formation by metal-ligand cooperation from the anilide complexes was observed to give free anilines and dearomatized Rh(I) complexes upon addition of CO or PEt 3. Deprotonation of complexes [(PNL)Rh(p-NO 2-NH 2C 6H 4)] (13, P = P tBu 2, L = NEt 2; 15, P = L = P iPr 2) yields the dearomatized anionic complexes [(PNL)Rh(p-NO 2-NH 2C 6H 4)]. An associative mechanism, involving N-H activation of an apically coordinated aniline in a pentacoordinated Rh(I) complex, is suggested.
AB - In continuation of our studies on bond activation and catalysis by pincer complexes, based on metal-ligand cooperation, we present here a rare example of amine N-H activation by Rh(I) complexes. The novel dearomatized pincer complexes [(PNN*)RhL′] (PNN = 2-(CH 2-P tBu 2)-6-(CH 2-NEt 2)C 5H 3N, PNN* = deprotonated PNN, L′ = N 2 (5), C 2H 4 (6)) and [( iPrPNP)RhL′] ( iPrPNP = 2,6-(CH 2-P iPr 2) 2C 5H 3N, iPrPNP* = deprotonated iPrPNP, L′ = C 2H 4 (7), cyclooctene (9)) were prepared and fully characterized by NMR and X-ray analysis. Complexes 5-7 and 9 undergo facile N-H activation of anilines involving aromatization of the pincer ligand without a change in the formal oxidation state of the metal center to form stable anilide complexes [(PNN)Rh(NHAr)] and [( iPrPNP)Rh(NHAr)] (Ar = C 6H 5, o-Br-C 6H 4, m-Cl-p-Cl-C 6H 3, p-NO 2-C 6H 4). Anilines possessing electron-withdrawing groups accelerate the N-H activation and yield more stable anilide complexes. The pincer and the ancillary ligands also affect the activation rate, which supports an associative mechanism. Spin saturation transfer experiments show chemical exchange between the pyridylic arm of the pincer ligand and the NH- protons of anilines prior to and after the N-H activation. The reverse N-H formation by metal-ligand cooperation from the anilide complexes was observed to give free anilines and dearomatized Rh(I) complexes upon addition of CO or PEt 3. Deprotonation of complexes [(PNL)Rh(p-NO 2-NH 2C 6H 4)] (13, P = P tBu 2, L = NEt 2; 15, P = L = P iPr 2) yields the dearomatized anionic complexes [(PNL)Rh(p-NO 2-NH 2C 6H 4)]. An associative mechanism, involving N-H activation of an apically coordinated aniline in a pentacoordinated Rh(I) complex, is suggested.
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U2 - 10.1021/om300248r
DO - 10.1021/om300248r
M3 - Article
AN - SCOPUS:84862137636
VL - 31
SP - 4083
EP - 4101
JO - Organometallics
JF - Organometallics
SN - 0276-7333
IS - 11
ER -