Kinetic and thermodynamic studies of the reactivity of (trimethylsilyl) diazomethane with HMo(CO)3(C5R5) (R = H, Me). Estimation of the Mo-N2CH2SiMe3 bond strength and experimental determination of the enthalpy of formation of (trimethylsilyl)diazomethane

George C. Fortman, Derek Isrow, James E. McDonough, Paul Von Ragué Schleyer, Henry F. Schaefer, Brian Scott, Gregory J. Kubas, Tamás Kégl, Ferenc Ungváry, Carl D. Hoff

Research output: Contribution to journalArticle

Abstract

The rates of reaction of N2CHSiMe3 with HMo(CO) 3Cp (Cp = η5-C5H5) in heptane obey the rate law -d[HMo(CO)3Cp]/dt = k[HMo(CO)3Cp][N 2CHSiMe3] (k = 0.035 ± 0.01 M-1 s -1 at 0 °C; Δ H= 11.7 ± 2.0 kcal/mol and ΔS = -22.0 ± 3.0 cal/(mol K)). Isotopic scrambling between DMo(CO)3Cp and N2CHSiMe 3 occurs at a rate faster than the overall reaction. Reversible 1,2-addition to form the tightly bound intermediate [Me3SiCH 2Nβ=Nαδ+]][ δ-M(CO)3Cp] is proposed as the first step of the reaction. Spectroscopic and computational data support this formulation. The contact ion pairs can undergo heterolytic cleavage to ions or homolytic cleavage to radicals, and the solvent influence on kobs (THF > toluene > heptane) is interpreted in terms of this model. The enthalpy of this reaction has been measured by solution calorimetry at 272 K in THF: ΔH = -11.6 ± 1.2 kcal/mol. These data, together with computed organic reaction energies allow estimation of the bond strength between the three-electron donors · N2CHSiMe3 and · Mo(CO) 2Cp to be 25 ± 5 kcal/mol stronger than the two-electron Mo-CO bond. Coordination of N2CHSiMe3 to the complexes M(PR3)2(CO)3 (M = Mo, W; R = Cy, iPr; Cy = cyclohexyl; iPr = isopropyl) alters the course of reaction with HMo(CO)3Cp. The stoichiometric reaction of Me3SiCH= N=NMo(PiPr3)2(CO)3 with 2 equiv of HMo(CO)3Cp produces SiMe4, Mo(N2)(P iPr3)2(CO)3, and [Mo(CO) 3Cp]2. In the presence of excess N2CHSiMe 3 this reaction is catalytic and has been used to experimentally measure the heat of hydrogenation of N2CHSiMe3 to N 2 and SiMe4 by 2 equiv of HMo(CO)3Cp. The derived enthalpy of formation of N2CHSiMe3 (5.8 ± 3.0 kcal/mol) is in reasonable agreement with high-level theoretical calculations. X-ray crystal structure data are reported for W(CO) 2(N2CH2SiMe3)Cp: triclinic, space group P1̄, a = 6.3928(7) Å, b = 10.6551(12) Å, c = 10.8766(12) Å, α = 100.632(2)°, β= 96.254(2)°, V = 721.32 Å3, Z = 2.

Original languageEnglish
Pages (from-to)4873-4884
Number of pages12
JournalOrganometallics
Volume27
Issue number19
DOIs
StatePublished - Oct 13 2008

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Diazomethane
Carbon Monoxide
Enthalpy
reactivity
enthalpy
Thermodynamics
thermodynamics
Kinetics
kinetics
heptanes
cleavage
Heptanes
hydrogenation
toluene
ions
electrons
heat measurement
Ions
formulations
heat

ASJC Scopus subject areas

  • Organic Chemistry
  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

Cite this

Kinetic and thermodynamic studies of the reactivity of (trimethylsilyl) diazomethane with HMo(CO)3(C5R5) (R = H, Me). Estimation of the Mo-N2CH2SiMe3 bond strength and experimental determination of the enthalpy of formation of (trimethylsilyl)diazomethane. / Fortman, George C.; Isrow, Derek; McDonough, James E.; Von Ragué Schleyer, Paul; Schaefer, Henry F.; Scott, Brian; Kubas, Gregory J.; Kégl, Tamás; Ungváry, Ferenc; Hoff, Carl D.

In: Organometallics, Vol. 27, No. 19, 13.10.2008, p. 4873-4884.

Research output: Contribution to journalArticle

Fortman, George C. ; Isrow, Derek ; McDonough, James E. ; Von Ragué Schleyer, Paul ; Schaefer, Henry F. ; Scott, Brian ; Kubas, Gregory J. ; Kégl, Tamás ; Ungváry, Ferenc ; Hoff, Carl D. / Kinetic and thermodynamic studies of the reactivity of (trimethylsilyl) diazomethane with HMo(CO)3(C5R5) (R = H, Me). Estimation of the Mo-N2CH2SiMe3 bond strength and experimental determination of the enthalpy of formation of (trimethylsilyl)diazomethane. In: Organometallics. 2008 ; Vol. 27, No. 19. pp. 4873-4884.
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title = "Kinetic and thermodynamic studies of the reactivity of (trimethylsilyl) diazomethane with HMo(CO)3(C5R5) (R = H, Me). Estimation of the Mo-N2CH2SiMe3 bond strength and experimental determination of the enthalpy of formation of (trimethylsilyl)diazomethane",
abstract = "The rates of reaction of N2CHSiMe3 with HMo(CO) 3Cp (Cp = η5-C5H5) in heptane obey the rate law -d[HMo(CO)3Cp]/dt = k[HMo(CO)3Cp][N 2CHSiMe3] (k = 0.035 ± 0.01 M-1 s -1 at 0 °C; Δ H‡= 11.7 ± 2.0 kcal/mol and ΔS‡ = -22.0 ± 3.0 cal/(mol K)). Isotopic scrambling between DMo(CO)3Cp and N2CHSiMe 3 occurs at a rate faster than the overall reaction. Reversible 1,2-addition to form the tightly bound intermediate [Me3SiCH 2Nβ=Nαδ+]][ δ-M(CO)3Cp] is proposed as the first step of the reaction. Spectroscopic and computational data support this formulation. The contact ion pairs can undergo heterolytic cleavage to ions or homolytic cleavage to radicals, and the solvent influence on kobs (THF > toluene > heptane) is interpreted in terms of this model. The enthalpy of this reaction has been measured by solution calorimetry at 272 K in THF: ΔH = -11.6 ± 1.2 kcal/mol. These data, together with computed organic reaction energies allow estimation of the bond strength between the three-electron donors · N2CHSiMe3 and · Mo(CO) 2Cp to be 25 ± 5 kcal/mol stronger than the two-electron Mo-CO bond. Coordination of N2CHSiMe3 to the complexes M(PR3)2(CO)3 (M = Mo, W; R = Cy, iPr; Cy = cyclohexyl; iPr = isopropyl) alters the course of reaction with HMo(CO)3Cp. The stoichiometric reaction of Me3SiCH= N=NMo(PiPr3)2(CO)3 with 2 equiv of HMo(CO)3Cp produces SiMe4, Mo(N2)(P iPr3)2(CO)3, and [Mo(CO) 3Cp]2. In the presence of excess N2CHSiMe 3 this reaction is catalytic and has been used to experimentally measure the heat of hydrogenation of N2CHSiMe3 to N 2 and SiMe4 by 2 equiv of HMo(CO)3Cp. The derived enthalpy of formation of N2CHSiMe3 (5.8 ± 3.0 kcal/mol) is in reasonable agreement with high-level theoretical calculations. X-ray crystal structure data are reported for W(CO) 2(N2CH2SiMe3)Cp: triclinic, space group P1̄, a = 6.3928(7) {\AA}, b = 10.6551(12) {\AA}, c = 10.8766(12) {\AA}, α = 100.632(2)°, β= 96.254(2)°, V = 721.32 {\AA}3, Z = 2.",
author = "Fortman, {George C.} and Derek Isrow and McDonough, {James E.} and {Von Ragu{\'e} Schleyer}, Paul and Schaefer, {Henry F.} and Brian Scott and Kubas, {Gregory J.} and Tam{\'a}s K{\'e}gl and Ferenc Ungv{\'a}ry and Hoff, {Carl D.}",
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TY - JOUR

T1 - Kinetic and thermodynamic studies of the reactivity of (trimethylsilyl) diazomethane with HMo(CO)3(C5R5) (R = H, Me). Estimation of the Mo-N2CH2SiMe3 bond strength and experimental determination of the enthalpy of formation of (trimethylsilyl)diazomethane

AU - Fortman, George C.

AU - Isrow, Derek

AU - McDonough, James E.

AU - Von Ragué Schleyer, Paul

AU - Schaefer, Henry F.

AU - Scott, Brian

AU - Kubas, Gregory J.

AU - Kégl, Tamás

AU - Ungváry, Ferenc

AU - Hoff, Carl D.

PY - 2008/10/13

Y1 - 2008/10/13

N2 - The rates of reaction of N2CHSiMe3 with HMo(CO) 3Cp (Cp = η5-C5H5) in heptane obey the rate law -d[HMo(CO)3Cp]/dt = k[HMo(CO)3Cp][N 2CHSiMe3] (k = 0.035 ± 0.01 M-1 s -1 at 0 °C; Δ H‡= 11.7 ± 2.0 kcal/mol and ΔS‡ = -22.0 ± 3.0 cal/(mol K)). Isotopic scrambling between DMo(CO)3Cp and N2CHSiMe 3 occurs at a rate faster than the overall reaction. Reversible 1,2-addition to form the tightly bound intermediate [Me3SiCH 2Nβ=Nαδ+]][ δ-M(CO)3Cp] is proposed as the first step of the reaction. Spectroscopic and computational data support this formulation. The contact ion pairs can undergo heterolytic cleavage to ions or homolytic cleavage to radicals, and the solvent influence on kobs (THF > toluene > heptane) is interpreted in terms of this model. The enthalpy of this reaction has been measured by solution calorimetry at 272 K in THF: ΔH = -11.6 ± 1.2 kcal/mol. These data, together with computed organic reaction energies allow estimation of the bond strength between the three-electron donors · N2CHSiMe3 and · Mo(CO) 2Cp to be 25 ± 5 kcal/mol stronger than the two-electron Mo-CO bond. Coordination of N2CHSiMe3 to the complexes M(PR3)2(CO)3 (M = Mo, W; R = Cy, iPr; Cy = cyclohexyl; iPr = isopropyl) alters the course of reaction with HMo(CO)3Cp. The stoichiometric reaction of Me3SiCH= N=NMo(PiPr3)2(CO)3 with 2 equiv of HMo(CO)3Cp produces SiMe4, Mo(N2)(P iPr3)2(CO)3, and [Mo(CO) 3Cp]2. In the presence of excess N2CHSiMe 3 this reaction is catalytic and has been used to experimentally measure the heat of hydrogenation of N2CHSiMe3 to N 2 and SiMe4 by 2 equiv of HMo(CO)3Cp. The derived enthalpy of formation of N2CHSiMe3 (5.8 ± 3.0 kcal/mol) is in reasonable agreement with high-level theoretical calculations. X-ray crystal structure data are reported for W(CO) 2(N2CH2SiMe3)Cp: triclinic, space group P1̄, a = 6.3928(7) Å, b = 10.6551(12) Å, c = 10.8766(12) Å, α = 100.632(2)°, β= 96.254(2)°, V = 721.32 Å3, Z = 2.

AB - The rates of reaction of N2CHSiMe3 with HMo(CO) 3Cp (Cp = η5-C5H5) in heptane obey the rate law -d[HMo(CO)3Cp]/dt = k[HMo(CO)3Cp][N 2CHSiMe3] (k = 0.035 ± 0.01 M-1 s -1 at 0 °C; Δ H‡= 11.7 ± 2.0 kcal/mol and ΔS‡ = -22.0 ± 3.0 cal/(mol K)). Isotopic scrambling between DMo(CO)3Cp and N2CHSiMe 3 occurs at a rate faster than the overall reaction. Reversible 1,2-addition to form the tightly bound intermediate [Me3SiCH 2Nβ=Nαδ+]][ δ-M(CO)3Cp] is proposed as the first step of the reaction. Spectroscopic and computational data support this formulation. The contact ion pairs can undergo heterolytic cleavage to ions or homolytic cleavage to radicals, and the solvent influence on kobs (THF > toluene > heptane) is interpreted in terms of this model. The enthalpy of this reaction has been measured by solution calorimetry at 272 K in THF: ΔH = -11.6 ± 1.2 kcal/mol. These data, together with computed organic reaction energies allow estimation of the bond strength between the three-electron donors · N2CHSiMe3 and · Mo(CO) 2Cp to be 25 ± 5 kcal/mol stronger than the two-electron Mo-CO bond. Coordination of N2CHSiMe3 to the complexes M(PR3)2(CO)3 (M = Mo, W; R = Cy, iPr; Cy = cyclohexyl; iPr = isopropyl) alters the course of reaction with HMo(CO)3Cp. The stoichiometric reaction of Me3SiCH= N=NMo(PiPr3)2(CO)3 with 2 equiv of HMo(CO)3Cp produces SiMe4, Mo(N2)(P iPr3)2(CO)3, and [Mo(CO) 3Cp]2. In the presence of excess N2CHSiMe 3 this reaction is catalytic and has been used to experimentally measure the heat of hydrogenation of N2CHSiMe3 to N 2 and SiMe4 by 2 equiv of HMo(CO)3Cp. The derived enthalpy of formation of N2CHSiMe3 (5.8 ± 3.0 kcal/mol) is in reasonable agreement with high-level theoretical calculations. X-ray crystal structure data are reported for W(CO) 2(N2CH2SiMe3)Cp: triclinic, space group P1̄, a = 6.3928(7) Å, b = 10.6551(12) Å, c = 10.8766(12) Å, α = 100.632(2)°, β= 96.254(2)°, V = 721.32 Å3, Z = 2.

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