Abstract
The dearomatized complex cis-[Re(PNPtBu*)(CO)2] (4) undergoes cooperative activation of Cî - N triple bonds of nitriles via [1,3]-addition. Reversible C-C and Re-N bond formation in 4 was investigated in a combined experimental and computational study. The reversible formation of the ketimido complexes (5-7) was observed. When nitriles bearing an alpha methylene group are used, reversible formation of the enamido complexes (8 and 9) takes place. The reversibility of the activation of the nitriles in the resulting ketimido compounds was demonstrated by the displacement of p-CF 3-benzonitrile from cis-[Re(PNPtBu-N=CPh pCF3)(CO)2] (6) upon addition of an excess of benzonitrile and by the temperature-dependent [1,3]-addition of pivalonitrile to complex 4. The reversible binding of the nitrile in the enamido compound cis-[Re(PNP tBu-HNC=CHPh)(CO)2] (9) was demonstrated via the displacement of benzyl cyanide from 9 by CO. Computational studies suggest a stepwise activation of the nitriles by 4, with remarkably low activation barriers, involving precoordination of the nitrile group to the Re(I) center. The enamido complex 9 reacts via β-carbon methylation to give the primary imino complex cis-[Re(PNPtBu-HN=CC(Me)Ph)(CO)2]OTf 11. Upon deprotonation of 11 and subsequent addition of benzyl cyanide, complex 9 is regenerated and the monomethylation product 2-phenylpropanenitrile is released. Complexes 4 and 9 were found to catalyze the Michael addition of benzyl cyanide derivatives to α,β-unsaturated esters and carbonyls.
| Original language | English |
|---|---|
| Pages (from-to) | 17004-17018 |
| Number of pages | 15 |
| Journal | Journal of the American Chemical Society |
| Volume | 135 |
| Issue number | 45 |
| DOIs | |
| Publication status | Published - Nov 13 2013 |
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ASJC Scopus subject areas
- Chemistry(all)
- Catalysis
- Biochemistry
- Colloid and Surface Chemistry
Cite this
Activation of nitriles by metal ligand cooperation. reversible formation of ketimido- and enamido-rhenium PNP pincer complexes and relevance to catalytic design. / Vogt, Matthias; Nerush, Alexander; Iron, Mark A.; Leitus, Gregory; Diskin-Posner, Yael; Shimon, Linda J W; Ben-David, Yehoshoa; Milstein, David.
In: Journal of the American Chemical Society, Vol. 135, No. 45, 13.11.2013, p. 17004-17018.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Activation of nitriles by metal ligand cooperation. reversible formation of ketimido- and enamido-rhenium PNP pincer complexes and relevance to catalytic design
AU - Vogt, Matthias
AU - Nerush, Alexander
AU - Iron, Mark A.
AU - Leitus, Gregory
AU - Diskin-Posner, Yael
AU - Shimon, Linda J W
AU - Ben-David, Yehoshoa
AU - Milstein, David
PY - 2013/11/13
Y1 - 2013/11/13
N2 - The dearomatized complex cis-[Re(PNPtBu*)(CO)2] (4) undergoes cooperative activation of Cî - N triple bonds of nitriles via [1,3]-addition. Reversible C-C and Re-N bond formation in 4 was investigated in a combined experimental and computational study. The reversible formation of the ketimido complexes (5-7) was observed. When nitriles bearing an alpha methylene group are used, reversible formation of the enamido complexes (8 and 9) takes place. The reversibility of the activation of the nitriles in the resulting ketimido compounds was demonstrated by the displacement of p-CF 3-benzonitrile from cis-[Re(PNPtBu-N=CPh pCF3)(CO)2] (6) upon addition of an excess of benzonitrile and by the temperature-dependent [1,3]-addition of pivalonitrile to complex 4. The reversible binding of the nitrile in the enamido compound cis-[Re(PNP tBu-HNC=CHPh)(CO)2] (9) was demonstrated via the displacement of benzyl cyanide from 9 by CO. Computational studies suggest a stepwise activation of the nitriles by 4, with remarkably low activation barriers, involving precoordination of the nitrile group to the Re(I) center. The enamido complex 9 reacts via β-carbon methylation to give the primary imino complex cis-[Re(PNPtBu-HN=CC(Me)Ph)(CO)2]OTf 11. Upon deprotonation of 11 and subsequent addition of benzyl cyanide, complex 9 is regenerated and the monomethylation product 2-phenylpropanenitrile is released. Complexes 4 and 9 were found to catalyze the Michael addition of benzyl cyanide derivatives to α,β-unsaturated esters and carbonyls.
AB - The dearomatized complex cis-[Re(PNPtBu*)(CO)2] (4) undergoes cooperative activation of Cî - N triple bonds of nitriles via [1,3]-addition. Reversible C-C and Re-N bond formation in 4 was investigated in a combined experimental and computational study. The reversible formation of the ketimido complexes (5-7) was observed. When nitriles bearing an alpha methylene group are used, reversible formation of the enamido complexes (8 and 9) takes place. The reversibility of the activation of the nitriles in the resulting ketimido compounds was demonstrated by the displacement of p-CF 3-benzonitrile from cis-[Re(PNPtBu-N=CPh pCF3)(CO)2] (6) upon addition of an excess of benzonitrile and by the temperature-dependent [1,3]-addition of pivalonitrile to complex 4. The reversible binding of the nitrile in the enamido compound cis-[Re(PNP tBu-HNC=CHPh)(CO)2] (9) was demonstrated via the displacement of benzyl cyanide from 9 by CO. Computational studies suggest a stepwise activation of the nitriles by 4, with remarkably low activation barriers, involving precoordination of the nitrile group to the Re(I) center. The enamido complex 9 reacts via β-carbon methylation to give the primary imino complex cis-[Re(PNPtBu-HN=CC(Me)Ph)(CO)2]OTf 11. Upon deprotonation of 11 and subsequent addition of benzyl cyanide, complex 9 is regenerated and the monomethylation product 2-phenylpropanenitrile is released. Complexes 4 and 9 were found to catalyze the Michael addition of benzyl cyanide derivatives to α,β-unsaturated esters and carbonyls.
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U2 - 10.1021/ja4071859
DO - 10.1021/ja4071859
M3 - Article
VL - 135
SP - 17004
EP - 17018
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 45
ER -