Organo-f-element thermochemistry. Thorium vs. Uranium and ancillary ligand effects on metal-ligand bond disruption enthalpies in bis(pentamethylcyclopentadienyl)actinide bis(hydrocarbyls) and bis(pentamethylcyclopentadienyl)alkoxyactinide hydrides and hydrocarbyls

Joseph W. Bruno, H. A. Stecher, Tobin J Marks, David C. Sonnenberger, Tobin J. Marks

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Abstract

Thorium- and uranium-ligand bond disruption enthalpies (D(M-R)) have been determined for a series of complexes of the type Cp′2M(R)X, where M = Th or U, Cp′ = η5-(CH3)5C5, R = alkyl, aryl, or hydride, and X = alkyl, chloride, or alkoxide. The thermodynamic data were obtained by anaerobic, batch-titration, solution calorimetry from the enthalpies of solution of the organo-f-element complexes in toluene and from the subsequent enthalpies of alcoholysis with tert-butyl alcohol or methanol. Average (of Cp′2U(R)-R and Cp′2U(OR′)-R) values for the nonstepwise alcoholysis of the Cp′2UR2 series; (gas phase, solution phase, in kcal/mol, quantity in parentheses = 2σ) are as follows: 67.8 (3.5), 71.8 (3.3) (R = CH3), 61.8 (2.7). 58.3 (2.1) (R = benzyl), and 73.3 (3.3), 73.3 (3.1) (R = CH2Si(CH3)3). For the Cp′2U(Cl)R series, D(U-R) = 70.1 (1.7) 74.6 (1.6) (R = CH3), 66.1 (2.8), 63.0 (2.7) (R = benzyl), 86.7 (2.6), 85.5 (2.6) (R = phenyl), and 90.5 (2.3), 89.2 (2.2) for Cp′2Th(C6H5)Cl. Data for hydride/alkyl pairs include Cp′2U(R)-OR′ (R′ = Si[C(CH3)3](CH3)2)where D(U-R) = 76.4 (1.1), 82.4 (7) (R = H) and 72.4 (1.4), 76.0 (1.2) (R = CH3) as well as Cp′2Th(R)-OR′ (R′ = CH[C(CH3)3]2) where D(Th-R = 87.8 (1.5), 93.3 (1.2) (R = H) and 81.5 (3.1), 81.2 (3.1) (R = n-C4H9). For Cp′2Th(H){O-2,6-[C(CH3)3]C 6H3}, D(Th-H) = 84.9 (1.2), 92.1 (1.0). For corresponding Th/U pairs, D(Th-R) - D(U-R) ≈ 10 kcal/mol. Alkoxide ancillary ligands appear to strengthen the M-R bond by several kcal/mol and to depress D(M-H)gas - D(M-R)gas to ≲;5 kcal/mol. Chloride coligands have a smaller effect on D(M-R). These results show that ancillary ligands should significantly affect the thermodynamics of important M-H/M-C transposition processes such as β-H elimination.

Original languageEnglish
Pages (from-to)7275-7280
Number of pages6
JournalJournal of the American Chemical Society
Volume108
Issue number23
Publication statusPublished - 1986

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Actinoid Series Elements
Thorium
Thermochemistry
Uranium
Actinides
Chemical bonds
Hydrides
Enthalpy
Gases
Metals
Ligands
Thermodynamics
Chlorides
tert-Butyl Alcohol
Calorimetry
Toluene
Titration
Methanol
Alcohols

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

@article{26cf8a8e1e58440bb034749ea171ba95,
title = "Organo-f-element thermochemistry. Thorium vs. Uranium and ancillary ligand effects on metal-ligand bond disruption enthalpies in bis(pentamethylcyclopentadienyl)actinide bis(hydrocarbyls) and bis(pentamethylcyclopentadienyl)alkoxyactinide hydrides and hydrocarbyls",
abstract = "Thorium- and uranium-ligand bond disruption enthalpies (D(M-R)) have been determined for a series of complexes of the type Cp′2M(R)X, where M = Th or U, Cp′ = η5-(CH3)5C5, R = alkyl, aryl, or hydride, and X = alkyl, chloride, or alkoxide. The thermodynamic data were obtained by anaerobic, batch-titration, solution calorimetry from the enthalpies of solution of the organo-f-element complexes in toluene and from the subsequent enthalpies of alcoholysis with tert-butyl alcohol or methanol. Average (of Cp′2U(R)-R and Cp′2U(OR′)-R) values for the nonstepwise alcoholysis of the Cp′2UR2 series; (gas phase, solution phase, in kcal/mol, quantity in parentheses = 2σ) are as follows: 67.8 (3.5), 71.8 (3.3) (R = CH3), 61.8 (2.7). 58.3 (2.1) (R = benzyl), and 73.3 (3.3), 73.3 (3.1) (R = CH2Si(CH3)3). For the Cp′2U(Cl)R series, D(U-R) = 70.1 (1.7) 74.6 (1.6) (R = CH3), 66.1 (2.8), 63.0 (2.7) (R = benzyl), 86.7 (2.6), 85.5 (2.6) (R = phenyl), and 90.5 (2.3), 89.2 (2.2) for Cp′2Th(C6H5)Cl. Data for hydride/alkyl pairs include Cp′2U(R)-OR′ (R′ = Si[C(CH3)3](CH3)2)where D(U-R) = 76.4 (1.1), 82.4 (7) (R = H) and 72.4 (1.4), 76.0 (1.2) (R = CH3) as well as Cp′2Th(R)-OR′ (R′ = CH[C(CH3)3]2) where D(Th-R = 87.8 (1.5), 93.3 (1.2) (R = H) and 81.5 (3.1), 81.2 (3.1) (R = n-C4H9). For Cp′2Th(H){O-2,6-[C(CH3)3]C 6H3}, D(Th-H) = 84.9 (1.2), 92.1 (1.0). For corresponding Th/U pairs, D(Th-R) - D(U-R) ≈ 10 kcal/mol. Alkoxide ancillary ligands appear to strengthen the M-R bond by several kcal/mol and to depress D(M-H)gas - D(M-R)gas to ≲;5 kcal/mol. Chloride coligands have a smaller effect on D(M-R). These results show that ancillary ligands should significantly affect the thermodynamics of important M-H/M-C transposition processes such as β-H elimination.",
author = "Bruno, {Joseph W.} and Stecher, {H. A.} and Marks, {Tobin J} and Sonnenberger, {David C.} and Marks, {Tobin J.}",
year = "1986",
language = "English",
volume = "108",
pages = "7275--7280",
journal = "Journal of the American Chemical Society",
issn = "0002-7863",
publisher = "American Chemical Society",
number = "23",

}

TY - JOUR

T1 - Organo-f-element thermochemistry. Thorium vs. Uranium and ancillary ligand effects on metal-ligand bond disruption enthalpies in bis(pentamethylcyclopentadienyl)actinide bis(hydrocarbyls) and bis(pentamethylcyclopentadienyl)alkoxyactinide hydrides and hydrocarbyls

AU - Bruno, Joseph W.

AU - Stecher, H. A.

AU - Marks, Tobin J

AU - Sonnenberger, David C.

AU - Marks, Tobin J.

PY - 1986

Y1 - 1986

N2 - Thorium- and uranium-ligand bond disruption enthalpies (D(M-R)) have been determined for a series of complexes of the type Cp′2M(R)X, where M = Th or U, Cp′ = η5-(CH3)5C5, R = alkyl, aryl, or hydride, and X = alkyl, chloride, or alkoxide. The thermodynamic data were obtained by anaerobic, batch-titration, solution calorimetry from the enthalpies of solution of the organo-f-element complexes in toluene and from the subsequent enthalpies of alcoholysis with tert-butyl alcohol or methanol. Average (of Cp′2U(R)-R and Cp′2U(OR′)-R) values for the nonstepwise alcoholysis of the Cp′2UR2 series; (gas phase, solution phase, in kcal/mol, quantity in parentheses = 2σ) are as follows: 67.8 (3.5), 71.8 (3.3) (R = CH3), 61.8 (2.7). 58.3 (2.1) (R = benzyl), and 73.3 (3.3), 73.3 (3.1) (R = CH2Si(CH3)3). For the Cp′2U(Cl)R series, D(U-R) = 70.1 (1.7) 74.6 (1.6) (R = CH3), 66.1 (2.8), 63.0 (2.7) (R = benzyl), 86.7 (2.6), 85.5 (2.6) (R = phenyl), and 90.5 (2.3), 89.2 (2.2) for Cp′2Th(C6H5)Cl. Data for hydride/alkyl pairs include Cp′2U(R)-OR′ (R′ = Si[C(CH3)3](CH3)2)where D(U-R) = 76.4 (1.1), 82.4 (7) (R = H) and 72.4 (1.4), 76.0 (1.2) (R = CH3) as well as Cp′2Th(R)-OR′ (R′ = CH[C(CH3)3]2) where D(Th-R = 87.8 (1.5), 93.3 (1.2) (R = H) and 81.5 (3.1), 81.2 (3.1) (R = n-C4H9). For Cp′2Th(H){O-2,6-[C(CH3)3]C 6H3}, D(Th-H) = 84.9 (1.2), 92.1 (1.0). For corresponding Th/U pairs, D(Th-R) - D(U-R) ≈ 10 kcal/mol. Alkoxide ancillary ligands appear to strengthen the M-R bond by several kcal/mol and to depress D(M-H)gas - D(M-R)gas to ≲;5 kcal/mol. Chloride coligands have a smaller effect on D(M-R). These results show that ancillary ligands should significantly affect the thermodynamics of important M-H/M-C transposition processes such as β-H elimination.

AB - Thorium- and uranium-ligand bond disruption enthalpies (D(M-R)) have been determined for a series of complexes of the type Cp′2M(R)X, where M = Th or U, Cp′ = η5-(CH3)5C5, R = alkyl, aryl, or hydride, and X = alkyl, chloride, or alkoxide. The thermodynamic data were obtained by anaerobic, batch-titration, solution calorimetry from the enthalpies of solution of the organo-f-element complexes in toluene and from the subsequent enthalpies of alcoholysis with tert-butyl alcohol or methanol. Average (of Cp′2U(R)-R and Cp′2U(OR′)-R) values for the nonstepwise alcoholysis of the Cp′2UR2 series; (gas phase, solution phase, in kcal/mol, quantity in parentheses = 2σ) are as follows: 67.8 (3.5), 71.8 (3.3) (R = CH3), 61.8 (2.7). 58.3 (2.1) (R = benzyl), and 73.3 (3.3), 73.3 (3.1) (R = CH2Si(CH3)3). For the Cp′2U(Cl)R series, D(U-R) = 70.1 (1.7) 74.6 (1.6) (R = CH3), 66.1 (2.8), 63.0 (2.7) (R = benzyl), 86.7 (2.6), 85.5 (2.6) (R = phenyl), and 90.5 (2.3), 89.2 (2.2) for Cp′2Th(C6H5)Cl. Data for hydride/alkyl pairs include Cp′2U(R)-OR′ (R′ = Si[C(CH3)3](CH3)2)where D(U-R) = 76.4 (1.1), 82.4 (7) (R = H) and 72.4 (1.4), 76.0 (1.2) (R = CH3) as well as Cp′2Th(R)-OR′ (R′ = CH[C(CH3)3]2) where D(Th-R = 87.8 (1.5), 93.3 (1.2) (R = H) and 81.5 (3.1), 81.2 (3.1) (R = n-C4H9). For Cp′2Th(H){O-2,6-[C(CH3)3]C 6H3}, D(Th-H) = 84.9 (1.2), 92.1 (1.0). For corresponding Th/U pairs, D(Th-R) - D(U-R) ≈ 10 kcal/mol. Alkoxide ancillary ligands appear to strengthen the M-R bond by several kcal/mol and to depress D(M-H)gas - D(M-R)gas to ≲;5 kcal/mol. Chloride coligands have a smaller effect on D(M-R). These results show that ancillary ligands should significantly affect the thermodynamics of important M-H/M-C transposition processes such as β-H elimination.

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