N 2 hydrogenation promoted by a side-on bound hafnocene dinitrogen complex

Wesley H. Bernskoetter; Andrea V. Olmos; Emil Lobkovsky; Paul J. Chirik

doi:10.1021/om0509037

N ₂ hydrogenation promoted by a side-on bound hafnocene dinitrogen complex

Wesley H. Bernskoetter, Andrea V. Olmos, Emil Lobkovsky, Paul J. Chirik

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73 Scopus citations

Abstract

Reduction of the hafnocene diiodide (η ⁵-C ₅Me ₄H) ₂HfI ₂ with excess sodium amalgam under 1 atm of dinitrogen yielded the hafnocene dinitrogen complex [(η ⁵- C ₅Me ₄H) ₂Hf] ₂(μ ₂, η ²:η ²-N ₂). X-ray diffraction has established a strongly activated, side-on bound, bridging N ₂ ligand with an N-N bond length of 1.423(11) Å. Exposure of the dinitrogen compound to 1 atm of dihydrogen at 23°C resulted in rapid hydrogenation of the N ₂ ligand, affording the hydrido hafnocene diazenido complex [(η ⁵-C ₅Me ₄H) ₂-HfH] ₂(μ ₂,η ²:η ²-N ₂H ₂). Confirmation of N ₂ hydrogenation has been provided by NMR and IR spectroscopic studies and X-ray diffraction. Pseudo-first-order observed rate constants for H ₂ addition have been measured by monitoring the disappearance of a principally LMCT band centered at 886 nm [(η ⁵-C ₅Me ₄H) ₂Hf] ₂-(μ ₂,η ²:η ²-N ₂) as a function of time. The hafnocene complex hydrogenates dinitrogen approximately 4 times faster than the corresponding zirconocene compound. Divergent chemistry from zirconium is observed upon thermolysis of [(η ⁵-C ₅Me ₄H) ₂HfH] ₂(μ ₂,η ²:η ²-N ₂H ₂), which results in cyclopentadienyl methyl group cyclometalation rather than N-N bond scission.

Original language	English (US)
Pages (from-to)	1021-1027
Number of pages	7
Journal	Organometallics
Volume	25
Issue number	4
DOIs	https://doi.org/10.1021/om0509037
State	Published - Feb 13 2006
Externally published	Yes

All Science Journal Classification (ASJC) codes

Physical and Theoretical Chemistry
Organic Chemistry
Inorganic Chemistry

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10.1021/om0509037

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@article{90cc520ff9ae4ca8b9085fd4bf085a95,

title = "N 2 hydrogenation promoted by a side-on bound hafnocene dinitrogen complex",

abstract = "Reduction of the hafnocene diiodide (η 5-C 5Me 4H) 2HfI 2 with excess sodium amalgam under 1 atm of dinitrogen yielded the hafnocene dinitrogen complex [(η 5- C 5Me 4H) 2Hf] 2(μ 2, η 2:η 2-N 2). X-ray diffraction has established a strongly activated, side-on bound, bridging N 2 ligand with an N-N bond length of 1.423(11) {\AA}. Exposure of the dinitrogen compound to 1 atm of dihydrogen at 23°C resulted in rapid hydrogenation of the N 2 ligand, affording the hydrido hafnocene diazenido complex [(η 5-C 5Me 4H) 2-HfH] 2(μ 2,η 2:η 2-N 2H 2). Confirmation of N 2 hydrogenation has been provided by NMR and IR spectroscopic studies and X-ray diffraction. Pseudo-first-order observed rate constants for H 2 addition have been measured by monitoring the disappearance of a principally LMCT band centered at 886 nm [(η 5-C 5Me 4H) 2Hf] 2-(μ 2,η 2:η 2-N 2) as a function of time. The hafnocene complex hydrogenates dinitrogen approximately 4 times faster than the corresponding zirconocene compound. Divergent chemistry from zirconium is observed upon thermolysis of [(η 5-C 5Me 4H) 2HfH] 2(μ 2,η 2:η 2-N 2H 2), which results in cyclopentadienyl methyl group cyclometalation rather than N-N bond scission.",

author = "Bernskoetter, {Wesley H.} and Olmos, {Andrea V.} and Emil Lobkovsky and Chirik, {Paul J.}",

year = "2006",

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doi = "10.1021/om0509037",

language = "English (US)",

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journal = "Organometallics",

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T1 - N 2 hydrogenation promoted by a side-on bound hafnocene dinitrogen complex

AU - Bernskoetter, Wesley H.

AU - Olmos, Andrea V.

AU - Lobkovsky, Emil

AU - Chirik, Paul J.

PY - 2006/2/13

Y1 - 2006/2/13

N2 - Reduction of the hafnocene diiodide (η 5-C 5Me 4H) 2HfI 2 with excess sodium amalgam under 1 atm of dinitrogen yielded the hafnocene dinitrogen complex [(η 5- C 5Me 4H) 2Hf] 2(μ 2, η 2:η 2-N 2). X-ray diffraction has established a strongly activated, side-on bound, bridging N 2 ligand with an N-N bond length of 1.423(11) Å. Exposure of the dinitrogen compound to 1 atm of dihydrogen at 23°C resulted in rapid hydrogenation of the N 2 ligand, affording the hydrido hafnocene diazenido complex [(η 5-C 5Me 4H) 2-HfH] 2(μ 2,η 2:η 2-N 2H 2). Confirmation of N 2 hydrogenation has been provided by NMR and IR spectroscopic studies and X-ray diffraction. Pseudo-first-order observed rate constants for H 2 addition have been measured by monitoring the disappearance of a principally LMCT band centered at 886 nm [(η 5-C 5Me 4H) 2Hf] 2-(μ 2,η 2:η 2-N 2) as a function of time. The hafnocene complex hydrogenates dinitrogen approximately 4 times faster than the corresponding zirconocene compound. Divergent chemistry from zirconium is observed upon thermolysis of [(η 5-C 5Me 4H) 2HfH] 2(μ 2,η 2:η 2-N 2H 2), which results in cyclopentadienyl methyl group cyclometalation rather than N-N bond scission.

AB - Reduction of the hafnocene diiodide (η 5-C 5Me 4H) 2HfI 2 with excess sodium amalgam under 1 atm of dinitrogen yielded the hafnocene dinitrogen complex [(η 5- C 5Me 4H) 2Hf] 2(μ 2, η 2:η 2-N 2). X-ray diffraction has established a strongly activated, side-on bound, bridging N 2 ligand with an N-N bond length of 1.423(11) Å. Exposure of the dinitrogen compound to 1 atm of dihydrogen at 23°C resulted in rapid hydrogenation of the N 2 ligand, affording the hydrido hafnocene diazenido complex [(η 5-C 5Me 4H) 2-HfH] 2(μ 2,η 2:η 2-N 2H 2). Confirmation of N 2 hydrogenation has been provided by NMR and IR spectroscopic studies and X-ray diffraction. Pseudo-first-order observed rate constants for H 2 addition have been measured by monitoring the disappearance of a principally LMCT band centered at 886 nm [(η 5-C 5Me 4H) 2Hf] 2-(μ 2,η 2:η 2-N 2) as a function of time. The hafnocene complex hydrogenates dinitrogen approximately 4 times faster than the corresponding zirconocene compound. Divergent chemistry from zirconium is observed upon thermolysis of [(η 5-C 5Me 4H) 2HfH] 2(μ 2,η 2:η 2-N 2H 2), which results in cyclopentadienyl methyl group cyclometalation rather than N-N bond scission.

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JO - Organometallics

JF - Organometallics

IS - 4

ER -

N ₂ hydrogenation promoted by a side-on bound hafnocene dinitrogen complex

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