On the origin of selective nitrous oxide N-N bond cleavage by three-coordinate molybdenum(III) complexes

J. P F Cherry, A. R. Johnson, L. M. Baraldo, Y. C. Tsai, C. C. Cummins, S. V. Kryatov, E. V. Rybak-Akimova, K. B. Capps, Carl Hoff, C. M. Haar, S. P. Nolan

Research output: Contribution to journalArticle

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Abstract

Reaction of Mo(N[R]Ar)3 (R = tBu or C(CD3)2CH3) with N2O gives rise exclusively to a 1:1 mixture of nitride NMo(N[R]Ar)3 and nitrosyl ONMo(N[R]Ar)3, rather than the known oxo complex OMo(N[R]Ar)3 and dinitrogen. Solution calorimetry measurements were used to determine the heat of reaction of Mo(N[R]Ar)3 with N2O and, independently, the heat of reaction of Mo(N[R]Ar)3 with NO. Derived from the latter measurements is an estimate (155.3 ± 3.3 kcal·mol-1) of the molybdenum-nitrogen bond dissociation enthalpy for the terminal nitrido complex, NMo(N[R]Ar)3. Comparison of the new calorimetry data with those obtained previously for oxo transfer to Mo(N[R]Ar)3 shows that the nitrous oxide N-N bond cleavage reaction is under kinetic control. Stopped-flow kinetic measurements revealed the reaction to be first order in both Mo(N[R]Ar)3 and N2O, consistent with a mechanism featuring post-rate-determining dinuclear N-N bond scission, but also consistent with cleavage of the N-N bond at a single metal center in a mechanism requiring the intermediacy of nitric oxide. The new 2-adamantyl-substituted molybdenum complex Mo(N[2-Ad]Ar)3 was synthesized and found also to split N2O, resulting in a 1:1 mixture of nitrosyl and nitride products; the reaction exhibited first-order kinetics and was found to be ca. 6 times slower than that for the tert-butylsubstituted derivative. Discussed in conjunction with studies of the 2-adamantyl derivative Mo(N[2-Ad]Ar)3 is the role of ligand-imposed steric constraints on small-molecule, e.g. N2 and N2O, activation reactivity. Bradley's chromium complex Cr(NiPr2)3 was found to be competitive with Mo(N[R]Ar)3 for NO binding, while on its own exhibiting no reaction with N2O. Competition experiments permitted determination of ratios of second-order rate constants for NO binding by the two molybdenum complexes and the chromium complex. Analysis of the product mixtures resulting from carrying out the N2O cleavage reactions with Cr(Nipr2)3 present as an in situ NO scavenger rules out as dominant any mechanism involving the intermediacy of NO. Simplest and consistent with all the available data is a post-rate-determining bimetallic N-N scission process. Kinetic funneling of the reaction as indicated is taken to be governed by the properties of nitrous oxide as a ligand, coupled with the azophilic nature of three-coordinate molybdenum(III) complexes.

Original languageEnglish
Pages (from-to)7271-7286
Number of pages16
JournalJournal of the American Chemical Society
Volume123
Issue number30
DOIs
StatePublished - Oct 1 2001

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Molybdenum
Nitrous Oxide
Calorimetry
Kinetics
Oxides
Chromium
Nitrides
Hot Temperature
Ligands
Derivatives
Nitric oxide
Enthalpy
Rate constants
Nitric Oxide
Nitrogen
Metals
Chemical activation
Molecules
Experiments

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Cherry, J. P. F., Johnson, A. R., Baraldo, L. M., Tsai, Y. C., Cummins, C. C., Kryatov, S. V., ... Nolan, S. P. (2001). On the origin of selective nitrous oxide N-N bond cleavage by three-coordinate molybdenum(III) complexes. Journal of the American Chemical Society, 123(30), 7271-7286. https://doi.org/10.1021/ja0031063

On the origin of selective nitrous oxide N-N bond cleavage by three-coordinate molybdenum(III) complexes. / Cherry, J. P F; Johnson, A. R.; Baraldo, L. M.; Tsai, Y. C.; Cummins, C. C.; Kryatov, S. V.; Rybak-Akimova, E. V.; Capps, K. B.; Hoff, Carl; Haar, C. M.; Nolan, S. P.

In: Journal of the American Chemical Society, Vol. 123, No. 30, 01.10.2001, p. 7271-7286.

Research output: Contribution to journalArticle

Cherry, JPF, Johnson, AR, Baraldo, LM, Tsai, YC, Cummins, CC, Kryatov, SV, Rybak-Akimova, EV, Capps, KB, Hoff, C, Haar, CM & Nolan, SP 2001, 'On the origin of selective nitrous oxide N-N bond cleavage by three-coordinate molybdenum(III) complexes', Journal of the American Chemical Society, vol. 123, no. 30, pp. 7271-7286. https://doi.org/10.1021/ja0031063
Cherry, J. P F ; Johnson, A. R. ; Baraldo, L. M. ; Tsai, Y. C. ; Cummins, C. C. ; Kryatov, S. V. ; Rybak-Akimova, E. V. ; Capps, K. B. ; Hoff, Carl ; Haar, C. M. ; Nolan, S. P. / On the origin of selective nitrous oxide N-N bond cleavage by three-coordinate molybdenum(III) complexes. In: Journal of the American Chemical Society. 2001 ; Vol. 123, No. 30. pp. 7271-7286.
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abstract = "Reaction of Mo(N[R]Ar)3 (R = tBu or C(CD3)2CH3) with N2O gives rise exclusively to a 1:1 mixture of nitride NMo(N[R]Ar)3 and nitrosyl ONMo(N[R]Ar)3, rather than the known oxo complex OMo(N[R]Ar)3 and dinitrogen. Solution calorimetry measurements were used to determine the heat of reaction of Mo(N[R]Ar)3 with N2O and, independently, the heat of reaction of Mo(N[R]Ar)3 with NO. Derived from the latter measurements is an estimate (155.3 ± 3.3 kcal·mol-1) of the molybdenum-nitrogen bond dissociation enthalpy for the terminal nitrido complex, NMo(N[R]Ar)3. Comparison of the new calorimetry data with those obtained previously for oxo transfer to Mo(N[R]Ar)3 shows that the nitrous oxide N-N bond cleavage reaction is under kinetic control. Stopped-flow kinetic measurements revealed the reaction to be first order in both Mo(N[R]Ar)3 and N2O, consistent with a mechanism featuring post-rate-determining dinuclear N-N bond scission, but also consistent with cleavage of the N-N bond at a single metal center in a mechanism requiring the intermediacy of nitric oxide. The new 2-adamantyl-substituted molybdenum complex Mo(N[2-Ad]Ar)3 was synthesized and found also to split N2O, resulting in a 1:1 mixture of nitrosyl and nitride products; the reaction exhibited first-order kinetics and was found to be ca. 6 times slower than that for the tert-butylsubstituted derivative. Discussed in conjunction with studies of the 2-adamantyl derivative Mo(N[2-Ad]Ar)3 is the role of ligand-imposed steric constraints on small-molecule, e.g. N2 and N2O, activation reactivity. Bradley's chromium complex Cr(NiPr2)3 was found to be competitive with Mo(N[R]Ar)3 for NO binding, while on its own exhibiting no reaction with N2O. Competition experiments permitted determination of ratios of second-order rate constants for NO binding by the two molybdenum complexes and the chromium complex. Analysis of the product mixtures resulting from carrying out the N2O cleavage reactions with Cr(Nipr2)3 present as an in situ NO scavenger rules out as dominant any mechanism involving the intermediacy of NO. Simplest and consistent with all the available data is a post-rate-determining bimetallic N-N scission process. Kinetic funneling of the reaction as indicated is taken to be governed by the properties of nitrous oxide as a ligand, coupled with the azophilic nature of three-coordinate molybdenum(III) complexes.",
author = "Cherry, {J. P F} and Johnson, {A. R.} and Baraldo, {L. M.} and Tsai, {Y. C.} and Cummins, {C. C.} and Kryatov, {S. V.} and Rybak-Akimova, {E. V.} and Capps, {K. B.} and Carl Hoff and Haar, {C. M.} and Nolan, {S. P.}",
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T1 - On the origin of selective nitrous oxide N-N bond cleavage by three-coordinate molybdenum(III) complexes

AU - Cherry, J. P F

AU - Johnson, A. R.

AU - Baraldo, L. M.

AU - Tsai, Y. C.

AU - Cummins, C. C.

AU - Kryatov, S. V.

AU - Rybak-Akimova, E. V.

AU - Capps, K. B.

AU - Hoff, Carl

AU - Haar, C. M.

AU - Nolan, S. P.

PY - 2001/10/1

Y1 - 2001/10/1

N2 - Reaction of Mo(N[R]Ar)3 (R = tBu or C(CD3)2CH3) with N2O gives rise exclusively to a 1:1 mixture of nitride NMo(N[R]Ar)3 and nitrosyl ONMo(N[R]Ar)3, rather than the known oxo complex OMo(N[R]Ar)3 and dinitrogen. Solution calorimetry measurements were used to determine the heat of reaction of Mo(N[R]Ar)3 with N2O and, independently, the heat of reaction of Mo(N[R]Ar)3 with NO. Derived from the latter measurements is an estimate (155.3 ± 3.3 kcal·mol-1) of the molybdenum-nitrogen bond dissociation enthalpy for the terminal nitrido complex, NMo(N[R]Ar)3. Comparison of the new calorimetry data with those obtained previously for oxo transfer to Mo(N[R]Ar)3 shows that the nitrous oxide N-N bond cleavage reaction is under kinetic control. Stopped-flow kinetic measurements revealed the reaction to be first order in both Mo(N[R]Ar)3 and N2O, consistent with a mechanism featuring post-rate-determining dinuclear N-N bond scission, but also consistent with cleavage of the N-N bond at a single metal center in a mechanism requiring the intermediacy of nitric oxide. The new 2-adamantyl-substituted molybdenum complex Mo(N[2-Ad]Ar)3 was synthesized and found also to split N2O, resulting in a 1:1 mixture of nitrosyl and nitride products; the reaction exhibited first-order kinetics and was found to be ca. 6 times slower than that for the tert-butylsubstituted derivative. Discussed in conjunction with studies of the 2-adamantyl derivative Mo(N[2-Ad]Ar)3 is the role of ligand-imposed steric constraints on small-molecule, e.g. N2 and N2O, activation reactivity. Bradley's chromium complex Cr(NiPr2)3 was found to be competitive with Mo(N[R]Ar)3 for NO binding, while on its own exhibiting no reaction with N2O. Competition experiments permitted determination of ratios of second-order rate constants for NO binding by the two molybdenum complexes and the chromium complex. Analysis of the product mixtures resulting from carrying out the N2O cleavage reactions with Cr(Nipr2)3 present as an in situ NO scavenger rules out as dominant any mechanism involving the intermediacy of NO. Simplest and consistent with all the available data is a post-rate-determining bimetallic N-N scission process. Kinetic funneling of the reaction as indicated is taken to be governed by the properties of nitrous oxide as a ligand, coupled with the azophilic nature of three-coordinate molybdenum(III) complexes.

AB - Reaction of Mo(N[R]Ar)3 (R = tBu or C(CD3)2CH3) with N2O gives rise exclusively to a 1:1 mixture of nitride NMo(N[R]Ar)3 and nitrosyl ONMo(N[R]Ar)3, rather than the known oxo complex OMo(N[R]Ar)3 and dinitrogen. Solution calorimetry measurements were used to determine the heat of reaction of Mo(N[R]Ar)3 with N2O and, independently, the heat of reaction of Mo(N[R]Ar)3 with NO. Derived from the latter measurements is an estimate (155.3 ± 3.3 kcal·mol-1) of the molybdenum-nitrogen bond dissociation enthalpy for the terminal nitrido complex, NMo(N[R]Ar)3. Comparison of the new calorimetry data with those obtained previously for oxo transfer to Mo(N[R]Ar)3 shows that the nitrous oxide N-N bond cleavage reaction is under kinetic control. Stopped-flow kinetic measurements revealed the reaction to be first order in both Mo(N[R]Ar)3 and N2O, consistent with a mechanism featuring post-rate-determining dinuclear N-N bond scission, but also consistent with cleavage of the N-N bond at a single metal center in a mechanism requiring the intermediacy of nitric oxide. The new 2-adamantyl-substituted molybdenum complex Mo(N[2-Ad]Ar)3 was synthesized and found also to split N2O, resulting in a 1:1 mixture of nitrosyl and nitride products; the reaction exhibited first-order kinetics and was found to be ca. 6 times slower than that for the tert-butylsubstituted derivative. Discussed in conjunction with studies of the 2-adamantyl derivative Mo(N[2-Ad]Ar)3 is the role of ligand-imposed steric constraints on small-molecule, e.g. N2 and N2O, activation reactivity. Bradley's chromium complex Cr(NiPr2)3 was found to be competitive with Mo(N[R]Ar)3 for NO binding, while on its own exhibiting no reaction with N2O. Competition experiments permitted determination of ratios of second-order rate constants for NO binding by the two molybdenum complexes and the chromium complex. Analysis of the product mixtures resulting from carrying out the N2O cleavage reactions with Cr(Nipr2)3 present as an in situ NO scavenger rules out as dominant any mechanism involving the intermediacy of NO. Simplest and consistent with all the available data is a post-rate-determining bimetallic N-N scission process. Kinetic funneling of the reaction as indicated is taken to be governed by the properties of nitrous oxide as a ligand, coupled with the azophilic nature of three-coordinate molybdenum(III) complexes.

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