Abstract
Decomposition of trans-HIr(OCH3)(C6H5)(PMe3)3 (2) formed by oxidative addition of methanol to Ir(C6H5)(PMe3)3 (1) was studied in detail. Thermolysis of this complex yields trans-H2Ir(C6H5)(PMe3)3 (2) and formaldehyde. Complex 2 is less stable than its two dihydrido isomers, showing that it is the kinetic product of this reaction. The elimination process follows first order kinetics and exhibits a kinetic isotope effect of kH/kD=3.2±0.2, the observed activation parameters are ΔH‡ obs=8.3±1.0 kcal mol-1; ΔS‡ obs=-34±3.5 e.u. and ΔG‡ obs (298 K)=18.4±2.0 kcal mol-1. Catalysis by methanol was observed. The process does not involve a vacant coordination site cis to the coordinated methoxide, as shown by labeling experiments and by the lack of exchange with P(CD3)3. Thus, in this case the β-hydride elimination process does not follow the usual pathway. A mechanism, in which following methoxide dissociation, C-H cleavage of free methanol takes place, is suggested.
| Original language | English |
|---|---|
| Pages (from-to) | 479-484 |
| Number of pages | 6 |
| Journal | Journal of Organometallic Chemistry |
| Volume | 593-594 |
| Publication status | Published - Jan 15 2000 |
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Keywords
- Alkoxide
- Elimination
- Hydride
- Iridium
- Mechanism
- O-H activation
ASJC Scopus subject areas
- Biochemistry
- Inorganic Chemistry
- Organic Chemistry
- Physical and Theoretical Chemistry
- Materials Chemistry
Cite this
Hydride elimination from an iridium(III) alkoxide complex : A case in which a vacant cis coordination site is not required. / Blum, Ofer; Milstein, David.
In: Journal of Organometallic Chemistry, Vol. 593-594, 15.01.2000, p. 479-484.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Hydride elimination from an iridium(III) alkoxide complex
T2 - A case in which a vacant cis coordination site is not required
AU - Blum, Ofer
AU - Milstein, David
PY - 2000/1/15
Y1 - 2000/1/15
N2 - Decomposition of trans-HIr(OCH3)(C6H5)(PMe3)3 (2) formed by oxidative addition of methanol to Ir(C6H5)(PMe3)3 (1) was studied in detail. Thermolysis of this complex yields trans-H2Ir(C6H5)(PMe3)3 (2) and formaldehyde. Complex 2 is less stable than its two dihydrido isomers, showing that it is the kinetic product of this reaction. The elimination process follows first order kinetics and exhibits a kinetic isotope effect of kH/kD=3.2±0.2, the observed activation parameters are ΔH‡ obs=8.3±1.0 kcal mol-1; ΔS‡ obs=-34±3.5 e.u. and ΔG‡ obs (298 K)=18.4±2.0 kcal mol-1. Catalysis by methanol was observed. The process does not involve a vacant coordination site cis to the coordinated methoxide, as shown by labeling experiments and by the lack of exchange with P(CD3)3. Thus, in this case the β-hydride elimination process does not follow the usual pathway. A mechanism, in which following methoxide dissociation, C-H cleavage of free methanol takes place, is suggested.
AB - Decomposition of trans-HIr(OCH3)(C6H5)(PMe3)3 (2) formed by oxidative addition of methanol to Ir(C6H5)(PMe3)3 (1) was studied in detail. Thermolysis of this complex yields trans-H2Ir(C6H5)(PMe3)3 (2) and formaldehyde. Complex 2 is less stable than its two dihydrido isomers, showing that it is the kinetic product of this reaction. The elimination process follows first order kinetics and exhibits a kinetic isotope effect of kH/kD=3.2±0.2, the observed activation parameters are ΔH‡ obs=8.3±1.0 kcal mol-1; ΔS‡ obs=-34±3.5 e.u. and ΔG‡ obs (298 K)=18.4±2.0 kcal mol-1. Catalysis by methanol was observed. The process does not involve a vacant coordination site cis to the coordinated methoxide, as shown by labeling experiments and by the lack of exchange with P(CD3)3. Thus, in this case the β-hydride elimination process does not follow the usual pathway. A mechanism, in which following methoxide dissociation, C-H cleavage of free methanol takes place, is suggested.
KW - Alkoxide
KW - Elimination
KW - Hydride
KW - Iridium
KW - Mechanism
KW - O-H activation
UR - http://www.scopus.com/inward/record.url?scp=0034649996&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0034649996&partnerID=8YFLogxK
M3 - Article
VL - 593-594
SP - 479
EP - 484
JO - Journal of Organometallic Chemistry
JF - Journal of Organometallic Chemistry
SN - 0022-328X
ER -