Direct solution calorimetric measurements of enthalpies of proton and electron transfer reactions for transition metal complexes. Thermochemical study of metal-hydride and metal-metal bond energies

Gabor Kiss, Steven P. Nolan, Carl Hoff

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Abstract

Enthalpies of reaction with sodium amalgam, sodium benzophenone ketyl, and metal carbonyl anions of organometallic complexes in THF solution have been measured. Relative to reduction with Na metal, the following enthalpies of reduction (kcal mol-1) are reported: benzophenone = -38.5, Cr(CO)2(PEt3)C5H5 = -54.3, Cr(CO)2(PPh3)C5H5 = -59.8, 1/2[Mo(CO)3C5Me5]2 = -59.9, 1/2[W(CO)3C5H5]2 = -61.7, 1/2[Mo(CO)3C5H5]2 = -63.5, Cr(CO)2(P(OMe)3)C5H5 = -64.4, 1/2[C5H5(CO)3Mo-Cr(CO)3C5H5] = -66.1, 1/2[Cr(CO)3C5H5]2 = -68.2, Cr(CO)3C5Me5 = -72.3, Cr(CO)3C5H5 = -75.6, 1/2Co2(CO)8 = -77.9. The value for the enthalpy of reduction of benzophenone is 14.5 kcal mol-1 more exothermic than recent literature data. The enthalpies of electron transfer and proton transfer between NaCr(CO)2C5H5 and other chromium radicals and hydrides have been measured and span about 20 kcal mol-1. These measurements are used in thermochemical cycles to calculate enthalpies of H atom transfer. The role of substituents in determining enthalpies of reaction relevant to electrochemical and pKa measurement enthalpies of reaction is discussed. The heat of hydrogenation of Mn2(CO)10 has been determined using calorimetrically determined enthalpies of H atom transfer. The heat of hydrogenation, +4 kcal mol-1 in THF, allows estimation of the MnH bond strength = 68 kcal mol-1.

Original languageEnglish
Pages (from-to)285-292
Number of pages8
JournalInorganica Chimica Acta
Volume227
Issue number2
DOIs
StatePublished - Dec 15 1994

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metal hydrides
Coordination Complexes
Carbon Monoxide
Metal complexes
Hydrides
Transition metals
Protons
Enthalpy
electron transfer
enthalpy
Metals
transition metals
Electrons
protons
metals
energy
Hydrogenation
hydrogenation
Sodium
sodium

Keywords

  • Calorimetry
  • Electron transfer reactions
  • Enthalpy
  • Metal hydrides
  • Metal-metal bond energies
  • Proton transfer reactions

ASJC Scopus subject areas

  • Biochemistry
  • Inorganic Chemistry
  • Physical and Theoretical Chemistry
  • Materials Chemistry

Cite this

@article{85bca355a61f4fea9cf00017faa5b774,
title = "Direct solution calorimetric measurements of enthalpies of proton and electron transfer reactions for transition metal complexes. Thermochemical study of metal-hydride and metal-metal bond energies",
abstract = "Enthalpies of reaction with sodium amalgam, sodium benzophenone ketyl, and metal carbonyl anions of organometallic complexes in THF solution have been measured. Relative to reduction with Na metal, the following enthalpies of reduction (kcal mol-1) are reported: benzophenone = -38.5, Cr(CO)2(PEt3)C5H5 = -54.3, Cr(CO)2(PPh3)C5H5 = -59.8, 1/2[Mo(CO)3C5Me5]2 = -59.9, 1/2[W(CO)3C5H5]2 = -61.7, 1/2[Mo(CO)3C5H5]2 = -63.5, Cr(CO)2(P(OMe)3)C5H5 = -64.4, 1/2[C5H5(CO)3Mo-Cr(CO)3C5H5] = -66.1, 1/2[Cr(CO)3C5H5]2 = -68.2, Cr(CO)3C5Me5 = -72.3, Cr(CO)3C5H5 = -75.6, 1/2Co2(CO)8 = -77.9. The value for the enthalpy of reduction of benzophenone is 14.5 kcal mol-1 more exothermic than recent literature data. The enthalpies of electron transfer and proton transfer between NaCr(CO)2C5H5 and other chromium radicals and hydrides have been measured and span about 20 kcal mol-1. These measurements are used in thermochemical cycles to calculate enthalpies of H atom transfer. The role of substituents in determining enthalpies of reaction relevant to electrochemical and pKa measurement enthalpies of reaction is discussed. The heat of hydrogenation of Mn2(CO)10 has been determined using calorimetrically determined enthalpies of H atom transfer. The heat of hydrogenation, +4 kcal mol-1 in THF, allows estimation of the MnH bond strength = 68 kcal mol-1.",
keywords = "Calorimetry, Electron transfer reactions, Enthalpy, Metal hydrides, Metal-metal bond energies, Proton transfer reactions",
author = "Gabor Kiss and Nolan, {Steven P.} and Carl Hoff",
year = "1994",
month = "12",
day = "15",
doi = "10.1016/0020-1693(94)04218-7",
language = "English",
volume = "227",
pages = "285--292",
journal = "Inorganica Chimica Acta",
issn = "0020-1693",
publisher = "Elsevier BV",
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TY - JOUR

T1 - Direct solution calorimetric measurements of enthalpies of proton and electron transfer reactions for transition metal complexes. Thermochemical study of metal-hydride and metal-metal bond energies

AU - Kiss, Gabor

AU - Nolan, Steven P.

AU - Hoff, Carl

PY - 1994/12/15

Y1 - 1994/12/15

N2 - Enthalpies of reaction with sodium amalgam, sodium benzophenone ketyl, and metal carbonyl anions of organometallic complexes in THF solution have been measured. Relative to reduction with Na metal, the following enthalpies of reduction (kcal mol-1) are reported: benzophenone = -38.5, Cr(CO)2(PEt3)C5H5 = -54.3, Cr(CO)2(PPh3)C5H5 = -59.8, 1/2[Mo(CO)3C5Me5]2 = -59.9, 1/2[W(CO)3C5H5]2 = -61.7, 1/2[Mo(CO)3C5H5]2 = -63.5, Cr(CO)2(P(OMe)3)C5H5 = -64.4, 1/2[C5H5(CO)3Mo-Cr(CO)3C5H5] = -66.1, 1/2[Cr(CO)3C5H5]2 = -68.2, Cr(CO)3C5Me5 = -72.3, Cr(CO)3C5H5 = -75.6, 1/2Co2(CO)8 = -77.9. The value for the enthalpy of reduction of benzophenone is 14.5 kcal mol-1 more exothermic than recent literature data. The enthalpies of electron transfer and proton transfer between NaCr(CO)2C5H5 and other chromium radicals and hydrides have been measured and span about 20 kcal mol-1. These measurements are used in thermochemical cycles to calculate enthalpies of H atom transfer. The role of substituents in determining enthalpies of reaction relevant to electrochemical and pKa measurement enthalpies of reaction is discussed. The heat of hydrogenation of Mn2(CO)10 has been determined using calorimetrically determined enthalpies of H atom transfer. The heat of hydrogenation, +4 kcal mol-1 in THF, allows estimation of the MnH bond strength = 68 kcal mol-1.

AB - Enthalpies of reaction with sodium amalgam, sodium benzophenone ketyl, and metal carbonyl anions of organometallic complexes in THF solution have been measured. Relative to reduction with Na metal, the following enthalpies of reduction (kcal mol-1) are reported: benzophenone = -38.5, Cr(CO)2(PEt3)C5H5 = -54.3, Cr(CO)2(PPh3)C5H5 = -59.8, 1/2[Mo(CO)3C5Me5]2 = -59.9, 1/2[W(CO)3C5H5]2 = -61.7, 1/2[Mo(CO)3C5H5]2 = -63.5, Cr(CO)2(P(OMe)3)C5H5 = -64.4, 1/2[C5H5(CO)3Mo-Cr(CO)3C5H5] = -66.1, 1/2[Cr(CO)3C5H5]2 = -68.2, Cr(CO)3C5Me5 = -72.3, Cr(CO)3C5H5 = -75.6, 1/2Co2(CO)8 = -77.9. The value for the enthalpy of reduction of benzophenone is 14.5 kcal mol-1 more exothermic than recent literature data. The enthalpies of electron transfer and proton transfer between NaCr(CO)2C5H5 and other chromium radicals and hydrides have been measured and span about 20 kcal mol-1. These measurements are used in thermochemical cycles to calculate enthalpies of H atom transfer. The role of substituents in determining enthalpies of reaction relevant to electrochemical and pKa measurement enthalpies of reaction is discussed. The heat of hydrogenation of Mn2(CO)10 has been determined using calorimetrically determined enthalpies of H atom transfer. The heat of hydrogenation, +4 kcal mol-1 in THF, allows estimation of the MnH bond strength = 68 kcal mol-1.

KW - Calorimetry

KW - Electron transfer reactions

KW - Enthalpy

KW - Metal hydrides

KW - Metal-metal bond energies

KW - Proton transfer reactions

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U2 - 10.1016/0020-1693(94)04218-7

DO - 10.1016/0020-1693(94)04218-7

M3 - Article

AN - SCOPUS:0006345267

VL - 227

SP - 285

EP - 292

JO - Inorganica Chimica Acta

JF - Inorganica Chimica Acta

SN - 0020-1693

IS - 2

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