Abstract
Reactions of the metal hydride complexes Cp*(CO)2MH (M = Fe, Ru, Os) with Ph3C+BF4 - in CH2C12 were studied. Hydride transfer from Cp*(CO)2FeH to Ph3C+BF4 - gives Cp*(CO)2FeFBF3. Hydride transfer from the ruthenium hydride Cp*(CO)2RuH to Ph3C+ BF4 - produces the bridging hydride complex {[Cp*(CO)2Ru]2(μ-H)}+BF4 -, indicating that Cp*(CO)2RuH exhibits significant nucleophilicity in addition to hydridic reactivity of the Ru-H bond. The osmium hydride Cp*(CO)2OsH reacts with Ph3C+BF4 - in CH2C12 to give a mixture of Cp*(CO)2OsFBF3 and [Cp*(CO)2Os(ClCH2Cl)]+BF4 -. The kinetics of these hydride transfer reactions were monitored by stopped-flow methods, leading to the second-order rate law -d[Ph3C+ BF4 - ]/dt = k[Ph3C+BF4 -] [MH]. The temperature dependence of the rate constants was determined for the iron hydride, the osmium hydride, and the osmium deuteride Cp*(CO)2OsD. Activation parameters for hydride transfer from Cp*(CO)2FeH are ΔH‡ = 2.6 ± 0.1 kcal mol-1 and ΔS‡ = -22.1 ± 0.4 cal K-1 mol-1; for Cp*(CO)2OsH the activation parameters are ΔH‡ = 4.9 ± 0.1 kcal mol-1 and ΔS‡ = -16.8 ± 0.5 cal K-1 mol-1. A kinetic isotope effect (kH/kD = 1.6 at 0 °C) was found for the reaction of Cp*(CO)2OsD. The order of kinetic hydricity is HRu > HFe > HOs. Second-order rate constants (extrapolated to 25 °C from data collected at lower temperatures) are k = 3.2 ± 105 M-1 s-1 for Cp*(CO)2OsH and k = 1.1 × 106 M-1 s-1 for Cp*(CO)2FeH; for Cp*(CO)2RuH, k > 5 × 106 M-1 s -1 is estimated at 25 °C. Rate constants were also determined for hydride transfer to Ph2(p-MeOC6H4)C+ at 25 °C: k = 1.5 × 105 M-1 s-1 for Cp*(CO)2RuH, k = 4.1 × 104 M-1 s-1 for Cp*(CO)2FeH, and k = 3.2 × 103 M-1 s-1 for Cp*(CO)2OsH.
| Original language | English |
|---|---|
| Pages (from-to) | 2325-2331 |
| Number of pages | 7 |
| Journal | Organometallics |
| Volume | 21 |
| Issue number | 11 |
| DOIs | |
| Publication status | Published - May 27 2002 |
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ASJC Scopus subject areas
- Inorganic Chemistry
- Organic Chemistry
Cite this
Hydride transfer from (η5-C5Me5)(CO)2MH (M = Fe, Ru, Os) to trityl cation : Different products from different metals and the kinetics of hydride transfer. / Cheng, Tan Yun; Bullock, R. Morris.
In: Organometallics, Vol. 21, No. 11, 27.05.2002, p. 2325-2331.Research output: Contribution to journal › Article
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TY - JOUR
T1 - Hydride transfer from (η5-C5Me5)(CO)2MH (M = Fe, Ru, Os) to trityl cation
T2 - Different products from different metals and the kinetics of hydride transfer
AU - Cheng, Tan Yun
AU - Bullock, R. Morris
PY - 2002/5/27
Y1 - 2002/5/27
N2 - Reactions of the metal hydride complexes Cp*(CO)2MH (M = Fe, Ru, Os) with Ph3C+BF4 - in CH2C12 were studied. Hydride transfer from Cp*(CO)2FeH to Ph3C+BF4 - gives Cp*(CO)2FeFBF3. Hydride transfer from the ruthenium hydride Cp*(CO)2RuH to Ph3C+ BF4 - produces the bridging hydride complex {[Cp*(CO)2Ru]2(μ-H)}+BF4 -, indicating that Cp*(CO)2RuH exhibits significant nucleophilicity in addition to hydridic reactivity of the Ru-H bond. The osmium hydride Cp*(CO)2OsH reacts with Ph3C+BF4 - in CH2C12 to give a mixture of Cp*(CO)2OsFBF3 and [Cp*(CO)2Os(ClCH2Cl)]+BF4 -. The kinetics of these hydride transfer reactions were monitored by stopped-flow methods, leading to the second-order rate law -d[Ph3C+ BF4 - ]/dt = k[Ph3C+BF4 -] [MH]. The temperature dependence of the rate constants was determined for the iron hydride, the osmium hydride, and the osmium deuteride Cp*(CO)2OsD. Activation parameters for hydride transfer from Cp*(CO)2FeH are ΔH‡ = 2.6 ± 0.1 kcal mol-1 and ΔS‡ = -22.1 ± 0.4 cal K-1 mol-1; for Cp*(CO)2OsH the activation parameters are ΔH‡ = 4.9 ± 0.1 kcal mol-1 and ΔS‡ = -16.8 ± 0.5 cal K-1 mol-1. A kinetic isotope effect (kH/kD = 1.6 at 0 °C) was found for the reaction of Cp*(CO)2OsD. The order of kinetic hydricity is HRu > HFe > HOs. Second-order rate constants (extrapolated to 25 °C from data collected at lower temperatures) are k = 3.2 ± 105 M-1 s-1 for Cp*(CO)2OsH and k = 1.1 × 106 M-1 s-1 for Cp*(CO)2FeH; for Cp*(CO)2RuH, k > 5 × 106 M-1 s -1 is estimated at 25 °C. Rate constants were also determined for hydride transfer to Ph2(p-MeOC6H4)C+ at 25 °C: k = 1.5 × 105 M-1 s-1 for Cp*(CO)2RuH, k = 4.1 × 104 M-1 s-1 for Cp*(CO)2FeH, and k = 3.2 × 103 M-1 s-1 for Cp*(CO)2OsH.
AB - Reactions of the metal hydride complexes Cp*(CO)2MH (M = Fe, Ru, Os) with Ph3C+BF4 - in CH2C12 were studied. Hydride transfer from Cp*(CO)2FeH to Ph3C+BF4 - gives Cp*(CO)2FeFBF3. Hydride transfer from the ruthenium hydride Cp*(CO)2RuH to Ph3C+ BF4 - produces the bridging hydride complex {[Cp*(CO)2Ru]2(μ-H)}+BF4 -, indicating that Cp*(CO)2RuH exhibits significant nucleophilicity in addition to hydridic reactivity of the Ru-H bond. The osmium hydride Cp*(CO)2OsH reacts with Ph3C+BF4 - in CH2C12 to give a mixture of Cp*(CO)2OsFBF3 and [Cp*(CO)2Os(ClCH2Cl)]+BF4 -. The kinetics of these hydride transfer reactions were monitored by stopped-flow methods, leading to the second-order rate law -d[Ph3C+ BF4 - ]/dt = k[Ph3C+BF4 -] [MH]. The temperature dependence of the rate constants was determined for the iron hydride, the osmium hydride, and the osmium deuteride Cp*(CO)2OsD. Activation parameters for hydride transfer from Cp*(CO)2FeH are ΔH‡ = 2.6 ± 0.1 kcal mol-1 and ΔS‡ = -22.1 ± 0.4 cal K-1 mol-1; for Cp*(CO)2OsH the activation parameters are ΔH‡ = 4.9 ± 0.1 kcal mol-1 and ΔS‡ = -16.8 ± 0.5 cal K-1 mol-1. A kinetic isotope effect (kH/kD = 1.6 at 0 °C) was found for the reaction of Cp*(CO)2OsD. The order of kinetic hydricity is HRu > HFe > HOs. Second-order rate constants (extrapolated to 25 °C from data collected at lower temperatures) are k = 3.2 ± 105 M-1 s-1 for Cp*(CO)2OsH and k = 1.1 × 106 M-1 s-1 for Cp*(CO)2FeH; for Cp*(CO)2RuH, k > 5 × 106 M-1 s -1 is estimated at 25 °C. Rate constants were also determined for hydride transfer to Ph2(p-MeOC6H4)C+ at 25 °C: k = 1.5 × 105 M-1 s-1 for Cp*(CO)2RuH, k = 4.1 × 104 M-1 s-1 for Cp*(CO)2FeH, and k = 3.2 × 103 M-1 s-1 for Cp*(CO)2OsH.
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U2 - 10.1021/om020012o
DO - 10.1021/om020012o
M3 - Article
VL - 21
SP - 2325
EP - 2331
JO - Organometallics
JF - Organometallics
SN - 0276-7333
IS - 11
ER -