Abstract
The unsaturated PCP-type complexes Rh(L){2,6-(CH2PtBu2)2C 6H3}X (L = Et, nPr; X = Cl, I) complexes convert upon heating to the corresponding Rh(III)-hydride complexes Rh(H)-{2,6-(CH2PtBu2)2C 6H3}X (X = Cl, I) and ethylene or propylene, products indicative of a β-H elimination process. The iPr analogue is observed upon reaction of Rh(η1-N2){2,6-(CH2Pt-Bu 2)2C6H3} with iPrI at -10°C and decomposes readily at room temperature to give Rh-(H){2,6-(CH2PtBu2)2C 6H3}I and propylene. Analogous alkyl complexes - lacking β-hydrogens - are stable under the applied reaction conditions. The mechanism of this process has been studied by NMR, using 13C and deuterium labeling of the alkyl ligand (L = Et-d5, 13CH2-CH3). 13C labeling shows that the β-H elimination is irreversible. A deuterium isotope effect of kEt/kEt-d5 = 1.4 and a rate order of Et <nPr ≪ iPr were observed. The overall process follows first-order kinetics in the Rh(III)-alkyl complexes. The activation parameters for the thermolysis of Rh(Et)(2,6-(CH2PtBu2)2C 6H3)I in toluene were determined: ΔH‡ = 21.2 kcal/mol, ΔS‡ = -21.1 eu, and ΔG‡298K = 27.5 kcal/mol.
| Original language | English |
|---|---|
| Pages (from-to) | 2413-2419 |
| Number of pages | 7 |
| Journal | Organometallics |
| Volume | 18 |
| Issue number | 13 |
| Publication status | Published - Jun 21 1999 |
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ASJC Scopus subject areas
- Inorganic Chemistry
- Organic Chemistry
Cite this
Directly observed β-H elimination of unsaturated PCP-based rhodium(III)-alkyl complexes. / van der Boom, Milko; Higgitt, Catherine L.; Milstein, David.
In: Organometallics, Vol. 18, No. 13, 21.06.1999, p. 2413-2419.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Directly observed β-H elimination of unsaturated PCP-based rhodium(III)-alkyl complexes
AU - van der Boom, Milko
AU - Higgitt, Catherine L.
AU - Milstein, David
PY - 1999/6/21
Y1 - 1999/6/21
N2 - The unsaturated PCP-type complexes Rh(L){2,6-(CH2PtBu2)2C 6H3}X (L = Et, nPr; X = Cl, I) complexes convert upon heating to the corresponding Rh(III)-hydride complexes Rh(H)-{2,6-(CH2PtBu2)2C 6H3}X (X = Cl, I) and ethylene or propylene, products indicative of a β-H elimination process. The iPr analogue is observed upon reaction of Rh(η1-N2){2,6-(CH2Pt-Bu 2)2C6H3} with iPrI at -10°C and decomposes readily at room temperature to give Rh-(H){2,6-(CH2PtBu2)2C 6H3}I and propylene. Analogous alkyl complexes - lacking β-hydrogens - are stable under the applied reaction conditions. The mechanism of this process has been studied by NMR, using 13C and deuterium labeling of the alkyl ligand (L = Et-d5, 13CH2-CH3). 13C labeling shows that the β-H elimination is irreversible. A deuterium isotope effect of kEt/kEt-d5 = 1.4 and a rate order of Et <nPr ≪ iPr were observed. The overall process follows first-order kinetics in the Rh(III)-alkyl complexes. The activation parameters for the thermolysis of Rh(Et)(2,6-(CH2PtBu2)2C 6H3)I in toluene were determined: ΔH‡ = 21.2 kcal/mol, ΔS‡ = -21.1 eu, and ΔG‡298K = 27.5 kcal/mol.
AB - The unsaturated PCP-type complexes Rh(L){2,6-(CH2PtBu2)2C 6H3}X (L = Et, nPr; X = Cl, I) complexes convert upon heating to the corresponding Rh(III)-hydride complexes Rh(H)-{2,6-(CH2PtBu2)2C 6H3}X (X = Cl, I) and ethylene or propylene, products indicative of a β-H elimination process. The iPr analogue is observed upon reaction of Rh(η1-N2){2,6-(CH2Pt-Bu 2)2C6H3} with iPrI at -10°C and decomposes readily at room temperature to give Rh-(H){2,6-(CH2PtBu2)2C 6H3}I and propylene. Analogous alkyl complexes - lacking β-hydrogens - are stable under the applied reaction conditions. The mechanism of this process has been studied by NMR, using 13C and deuterium labeling of the alkyl ligand (L = Et-d5, 13CH2-CH3). 13C labeling shows that the β-H elimination is irreversible. A deuterium isotope effect of kEt/kEt-d5 = 1.4 and a rate order of Et <nPr ≪ iPr were observed. The overall process follows first-order kinetics in the Rh(III)-alkyl complexes. The activation parameters for the thermolysis of Rh(Et)(2,6-(CH2PtBu2)2C 6H3)I in toluene were determined: ΔH‡ = 21.2 kcal/mol, ΔS‡ = -21.1 eu, and ΔG‡298K = 27.5 kcal/mol.
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M3 - Article
VL - 18
SP - 2413
EP - 2419
JO - Organometallics
JF - Organometallics
SN - 0276-7333
IS - 13
ER -