Kinetic and thermodynamic studies of reaction of •Cr(CO)3C5Me5, HCr(CO)3C5Me5, and PhSCr(CO)3C5Me5 with •NO. Reductive elimination of thermodynamically unstable molecules HNO and RSNO driven by formation of the strong CR-NO bond

Kenneth B. Capps, Andreas Bauer, Kengkaj Sukcharoenphon, Carl Hoff

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Abstract

Reaction of H-Cr(CO)3C5Me5 with •NO at 1-2 atm pressure in toluene solution yields Cr(NO)(CO)2C5Me5 as the sole metal-containing product in addition to N2O and HNO2 as the principle nitrogen-containing products. N2O and HNO2 are attributed to decomposition of the initial product HNO. Kinetic studies yield the rate law d[P]/dt = -k2nd order[HCr(CO)3C5Me5][•NO]; k2nd order = 0.14 M-1 s-1 at 10 °C, with ΔH = 11.7 ± 1.5 kcal/mol and ΔS = -16.3 ± 3.5 cal/(mol deg). The rate of reaction is not inhibited by CO. The kinetic isotope effect for. reaction of D-Cr(CO)3C5Me5 is kH/kD = 1.7. These observations are consistent with a first step involving direct H (D) atom transfer from the metal hydride to •NO, forming HNO. Also supporting this mechanism is the ∼150 times slower reaction of H-Mo(CO)3C5Me5 and failure to observe reaction for H-W(CO)3C5Me5 in keeping with metal-hydrogen bond strengths Cr < Mo < W. Reaction of PhS-Cr(CO)3C5Me5 with NO at 1-2 atm pressure in toluene solution also forms Cr(NO)(CO)2C5Me5 as the sole metal-containing product. The initial product is the unstable nitrosothiol PhS-NO. Kinetic studies yield the rate law d[P]/df = -k1st order [PhS-Cr(CO)3C5Me5]; k1st order = 3.1 ± 0.3 × 10-3 s-1 at 10 °C, with ΔH = 21.6 ± 1.2 kcal/mol, ΔS = + 3.9 ± 1.5 cal/(mol deg). The rate of reaction is independent of both NO and CO pressure. The transition state in the first-order process is proposed to involve migration of bound thiolate to coordinated CO, forming Cr(CO)2 (n2-C(=O)SPh)C5Me5. The enthalpy of reaction of •Cr(CO)3C5Me5 and NO yielding Cr(NO)(CO)2C5Me5 and CO has been measured by solution calorimetry: Δ° = -33.2 ± 1.8 kcal/mol. The Cr-NO bond strength is estimated as ∼70 kcal/mol and provides the net thermodynamic driving force for the proposed elimination of the unstable molecules HNO and PhSNO.

Original languageEnglish
Pages (from-to)6206-6211
Number of pages6
JournalInorganic Chemistry
Volume38
Issue number26
StatePublished - Dec 1 1999

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Carbon Monoxide
elimination
Thermodynamics
thermodynamics
Molecules
Kinetics
kinetics
molecules
products
toluene
Metals
metals
metal hydrides
Toluene
isotope effect
heat measurement
enthalpy
hydrogen bonds
decomposition
nitrogen

ASJC Scopus subject areas

  • Inorganic Chemistry

Cite this

@article{52f484b9c8ab4ced8dd260448e8e5114,
title = "Kinetic and thermodynamic studies of reaction of •Cr(CO)3C5Me5, HCr(CO)3C5Me5, and PhSCr(CO)3C5Me5 with •NO. Reductive elimination of thermodynamically unstable molecules HNO and RSNO driven by formation of the strong CR-NO bond",
abstract = "Reaction of H-Cr(CO)3C5Me5 with •NO at 1-2 atm pressure in toluene solution yields Cr(NO)(CO)2C5Me5 as the sole metal-containing product in addition to N2O and HNO2 as the principle nitrogen-containing products. N2O and HNO2 are attributed to decomposition of the initial product HNO. Kinetic studies yield the rate law d[P]/dt = -k2nd order[HCr(CO)3C5Me5][•NO]; k2nd order = 0.14 M-1 s-1 at 10 °C, with ΔH≠ = 11.7 ± 1.5 kcal/mol and ΔS≠ = -16.3 ± 3.5 cal/(mol deg). The rate of reaction is not inhibited by CO. The kinetic isotope effect for. reaction of D-Cr(CO)3C5Me5 is kH/kD = 1.7. These observations are consistent with a first step involving direct H (D) atom transfer from the metal hydride to •NO, forming HNO. Also supporting this mechanism is the ∼150 times slower reaction of H-Mo(CO)3C5Me5 and failure to observe reaction for H-W(CO)3C5Me5 in keeping with metal-hydrogen bond strengths Cr < Mo < W. Reaction of PhS-Cr(CO)3C5Me5 with NO at 1-2 atm pressure in toluene solution also forms Cr(NO)(CO)2C5Me5 as the sole metal-containing product. The initial product is the unstable nitrosothiol PhS-NO. Kinetic studies yield the rate law d[P]/df = -k1st order [PhS-Cr(CO)3C5Me5]; k1st order = 3.1 ± 0.3 × 10-3 s-1 at 10 °C, with ΔH≠ = 21.6 ± 1.2 kcal/mol, ΔS≠ = + 3.9 ± 1.5 cal/(mol deg). The rate of reaction is independent of both NO and CO pressure. The transition state in the first-order process is proposed to involve migration of bound thiolate to coordinated CO, forming Cr(CO)2 (n2-C(=O)SPh)C5Me5. The enthalpy of reaction of •Cr(CO)3C5Me5 and NO yielding Cr(NO)(CO)2C5Me5 and CO has been measured by solution calorimetry: Δ° = -33.2 ± 1.8 kcal/mol. The Cr-NO bond strength is estimated as ∼70 kcal/mol and provides the net thermodynamic driving force for the proposed elimination of the unstable molecules HNO and PhSNO.",
author = "Capps, {Kenneth B.} and Andreas Bauer and Kengkaj Sukcharoenphon and Carl Hoff",
year = "1999",
month = "12",
day = "1",
language = "English",
volume = "38",
pages = "6206--6211",
journal = "Inorganic Chemistry",
issn = "0020-1669",
publisher = "American Chemical Society",
number = "26",

}

TY - JOUR

T1 - Kinetic and thermodynamic studies of reaction of •Cr(CO)3C5Me5, HCr(CO)3C5Me5, and PhSCr(CO)3C5Me5 with •NO. Reductive elimination of thermodynamically unstable molecules HNO and RSNO driven by formation of the strong CR-NO bond

AU - Capps, Kenneth B.

AU - Bauer, Andreas

AU - Sukcharoenphon, Kengkaj

AU - Hoff, Carl

PY - 1999/12/1

Y1 - 1999/12/1

N2 - Reaction of H-Cr(CO)3C5Me5 with •NO at 1-2 atm pressure in toluene solution yields Cr(NO)(CO)2C5Me5 as the sole metal-containing product in addition to N2O and HNO2 as the principle nitrogen-containing products. N2O and HNO2 are attributed to decomposition of the initial product HNO. Kinetic studies yield the rate law d[P]/dt = -k2nd order[HCr(CO)3C5Me5][•NO]; k2nd order = 0.14 M-1 s-1 at 10 °C, with ΔH≠ = 11.7 ± 1.5 kcal/mol and ΔS≠ = -16.3 ± 3.5 cal/(mol deg). The rate of reaction is not inhibited by CO. The kinetic isotope effect for. reaction of D-Cr(CO)3C5Me5 is kH/kD = 1.7. These observations are consistent with a first step involving direct H (D) atom transfer from the metal hydride to •NO, forming HNO. Also supporting this mechanism is the ∼150 times slower reaction of H-Mo(CO)3C5Me5 and failure to observe reaction for H-W(CO)3C5Me5 in keeping with metal-hydrogen bond strengths Cr < Mo < W. Reaction of PhS-Cr(CO)3C5Me5 with NO at 1-2 atm pressure in toluene solution also forms Cr(NO)(CO)2C5Me5 as the sole metal-containing product. The initial product is the unstable nitrosothiol PhS-NO. Kinetic studies yield the rate law d[P]/df = -k1st order [PhS-Cr(CO)3C5Me5]; k1st order = 3.1 ± 0.3 × 10-3 s-1 at 10 °C, with ΔH≠ = 21.6 ± 1.2 kcal/mol, ΔS≠ = + 3.9 ± 1.5 cal/(mol deg). The rate of reaction is independent of both NO and CO pressure. The transition state in the first-order process is proposed to involve migration of bound thiolate to coordinated CO, forming Cr(CO)2 (n2-C(=O)SPh)C5Me5. The enthalpy of reaction of •Cr(CO)3C5Me5 and NO yielding Cr(NO)(CO)2C5Me5 and CO has been measured by solution calorimetry: Δ° = -33.2 ± 1.8 kcal/mol. The Cr-NO bond strength is estimated as ∼70 kcal/mol and provides the net thermodynamic driving force for the proposed elimination of the unstable molecules HNO and PhSNO.

AB - Reaction of H-Cr(CO)3C5Me5 with •NO at 1-2 atm pressure in toluene solution yields Cr(NO)(CO)2C5Me5 as the sole metal-containing product in addition to N2O and HNO2 as the principle nitrogen-containing products. N2O and HNO2 are attributed to decomposition of the initial product HNO. Kinetic studies yield the rate law d[P]/dt = -k2nd order[HCr(CO)3C5Me5][•NO]; k2nd order = 0.14 M-1 s-1 at 10 °C, with ΔH≠ = 11.7 ± 1.5 kcal/mol and ΔS≠ = -16.3 ± 3.5 cal/(mol deg). The rate of reaction is not inhibited by CO. The kinetic isotope effect for. reaction of D-Cr(CO)3C5Me5 is kH/kD = 1.7. These observations are consistent with a first step involving direct H (D) atom transfer from the metal hydride to •NO, forming HNO. Also supporting this mechanism is the ∼150 times slower reaction of H-Mo(CO)3C5Me5 and failure to observe reaction for H-W(CO)3C5Me5 in keeping with metal-hydrogen bond strengths Cr < Mo < W. Reaction of PhS-Cr(CO)3C5Me5 with NO at 1-2 atm pressure in toluene solution also forms Cr(NO)(CO)2C5Me5 as the sole metal-containing product. The initial product is the unstable nitrosothiol PhS-NO. Kinetic studies yield the rate law d[P]/df = -k1st order [PhS-Cr(CO)3C5Me5]; k1st order = 3.1 ± 0.3 × 10-3 s-1 at 10 °C, with ΔH≠ = 21.6 ± 1.2 kcal/mol, ΔS≠ = + 3.9 ± 1.5 cal/(mol deg). The rate of reaction is independent of both NO and CO pressure. The transition state in the first-order process is proposed to involve migration of bound thiolate to coordinated CO, forming Cr(CO)2 (n2-C(=O)SPh)C5Me5. The enthalpy of reaction of •Cr(CO)3C5Me5 and NO yielding Cr(NO)(CO)2C5Me5 and CO has been measured by solution calorimetry: Δ° = -33.2 ± 1.8 kcal/mol. The Cr-NO bond strength is estimated as ∼70 kcal/mol and provides the net thermodynamic driving force for the proposed elimination of the unstable molecules HNO and PhSNO.

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M3 - Article

VL - 38

SP - 6206

EP - 6211

JO - Inorganic Chemistry

JF - Inorganic Chemistry

SN - 0020-1669

IS - 26

ER -