Homogeneous hydrogenation of norbornadiene with parahydrogen and phosphonic ester phosphine rhodium complexes studied by in situ nmr spectroscopy

doi:10.1016/0040-4020(95)00687-4

Tetrahedron

Volume 51, Issue 41, 9 October 1995, Pages 11199-11206

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Abstract

1) Homogeneous hydrogenation of norbornadiene with enriched parahydrogen (p-H₂) and phosphonic ester phosphine rhodium complexes is detected using in situ NMR spectroscopy The obtained polarization spectra remain unchanged during the catalysis in thf-d₈ as a solvent but change with time when the hydrogenation is executed in acetone-d₆. 2) The observed phenomenon is attributed to a change of the phase correlation of the transferred parahydrogen nuclei via nuclear singlet-triplet (S/T₀) mixing during the reaction. 3) Simultaneously, ³¹P NMR spectra change indicating a change in the nature of the original rhodium complex when the hydrogenation is carried out in acetone-d₆.

References and notes (14)

ChinnM.S. et al.
J. Am. Chem. Soc.
(1992)
WoelkK. et al.
Z. Phys. Chem.
(1993)
BowersC.R. et al.
Phys. Rev. Lett.
(1986)
BargonJ. et al.
Z. Phys. Chem.
(1993)
FreibergJ. et al.
J. prakt. Chem.
(1993)
EisenschmidT.C. et al.
J. Am. Chem. Soc.
(1987)
BowersC.R. et al.
J. Am. Chem. Soc.
(1987)
KirssR.U. et al.
J. Am. Chem. Soc.
(1988)

There are more references available in the full text version of this article.

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Citation Excerpt :
The action of these catalysts in the hydrogenation of an allene species, 1-methoxypropa-1,2-diene, was also investigated, in which the magnitudes of the enhanced resonances were used as a probe for regioselectivity in the reaction [66]. Further rhodium-catalysed hydrogenation reactions with parahydrogen were also reported by this group [67,68]. Eisenberg and co-workers used the parahydrogen effect as a mechanistic probe in the study of the hydrogenation of phenylacetylene to styrene by Ru(BINAP)(OAc)2 [4].
Mechanism of the hydrogenation of 2,5-norbornadiene catalyzed by [Rh(NBD)(PPh<inf>3</inf>)<inf>2</inf>]BF<inf>4</inf> in dichloromethane: A kinetic and spectroscopic investigation
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A kinetic investigation of the selective hydrogenation of 2,5-norbornadiene to norbornene catalyzed by [Rh(NBD)(PPh₃)₂]BF₄ (1) has been carried out in dichloromethane at room temperature. The reaction is independent of the substrate concentration, while it is first order in catalyst and hydrogen pressure. Furthermore, the addition of triphenylphosphine inhibits the reduction. Moreover, it has been observed that under hydrogen atmosphere and at low temperature, complex 1 is in equilibrium with the dihydrido cis–trans-[RhH₂(NBD)(PPh₃)₂]BF₄, and that the addition of one equivalent of [Rh(NBD){P(p-Tol)₃}₂]BF₄ to a chloroform-d₁ solution of 1 affords [Rh(NBD)(PPh₃){P(p-Tol)₃}]BF₄ in 54% yield. On the basis of these observations and other spectroscopic results, we propose that the hydrogenation of 2,5-norbornadiene to norbornene catalyzed by 1 proceeds by the five-coordinate dihydrido [RhH₂(NBD)(PPh₃)]⁺, which is formed by oxidative addition of molecular hydrogen to both 1 and a tricoordinate species [Rh(NBD)(PPh₃)]⁺, depending on the concentration of free phosphine in the catalytic solution.
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Homogeneous hydrogenation of norbornadiene with parahydrogen and phosphonic ester phosphine rhodium complexes studied by in situ nmr spectroscopy

Abstract

J. Am. Chem. Soc.

Z. Phys. Chem.

Phys. Rev. Lett.

Z. Phys. Chem.

J. prakt. Chem.

J. Am. Chem. Soc.

J. Am. Chem. Soc.

J. Am. Chem. Soc.