Transformation of a norbornadiene unit to ethylenylcyclopentene requiring cooperation between boron and rhodium centers
Transformation of a norbornadiene unit to ethylenylcyclopentene requiring cooperation between boron and rhodium centers
The synthesis of the lithium salt of a bis-substituted borohydride anion containing a phenyl substituent and a 2-mercaptopyridyl unit (mp) is reported herein. This salt has been used as a pro-ligand for the synthesis of rhodium(I) complex, [Rh{κ
3-H,H,S-H
2B(Ph)(mp)}(NBD)] (1) (where NBD = 2,5-norbornadiene). The new boron-based ligand coordinates to the rhodium center via the thione donor and the two B-H bonds of the BPhH
2 unit, with a dihydroborate motif. Reaction of complex 1 with two equivalents of triphenylphosphine leads to an unprecedented rearrangement and transfer of the former norbornadiene ligand to the boron center. The transformation occurs via an initial hydride migration from boron to rhodium center followed by a hydroboration of one of the double bonds. Finally, a ring-opening process occurs involving both boron and rhodium centers leading to an unusual boron-bound ethylenylcyclopentene unit. The product of this reaction was confirmed as [Rh{η
1-S,η
2-B,C-B(Ph)(CHCH
2(C
5H
7)(mp)}(PPh
3)
2] (2). The net result of these transformations is the incorporation of the two hydrogen atoms from the secondary borohydride ligand [BPhH
2(mp)]
- into the former norbornadiene unit. The end point positions of these hydrogen atoms were confirmed by deuterium labeling experiments. Complex 2 was further reacted with carbon monoxide to generate [Rh{η
1-S,η
2-B,C-B(Ph)(CHCH
2(C
5H
7)(mp)}(CO)(PPh
3)] (3) via ligand substitution. The new ligand and the three complexes, 1, 2, and 3, have been characterized by spectroscopic techniques as well as by X-ray crystallography. Detailed characterization of 2 and 3 revealed an unusual η
2-B,C coordination mode within these complexes. Further studies have demonstrated that complexes 2 and 3 react with hydrogen gas (or dimethylamine borane as a source of H
2) to generate the hydrogen addition products involving the unprecedented activation of the Rh-η
2-B,C motif. Complexes 2 and 3 were further found to be active catalysts for the hydrogenation of olefins and the dehydrogenation of dimethylamine borane.
1976-1988
Iannetelli, Angelo
3f6fd91d-6ac8-433e-9e46-1c0831be4ed7
Da Costa, Rosenildo Correa
ce76806a-0dba-4086-99c2-626e9b932c80
Guwy, Alan J.
a78123af-3953-4791-84d3-ade657813e94
Tizzard, Graham J.
8474c0fa-40df-43a6-a662-7f3c4722dbf2
Coles, Simon J.
3116f58b-c30c-48cf-bdd5-397d1c1fecf8
Owen, Gareth R.
fd633ee9-dcaa-438c-9b3b-82e9d091a1c6
26 May 2020
Iannetelli, Angelo
3f6fd91d-6ac8-433e-9e46-1c0831be4ed7
Da Costa, Rosenildo Correa
ce76806a-0dba-4086-99c2-626e9b932c80
Guwy, Alan J.
a78123af-3953-4791-84d3-ade657813e94
Tizzard, Graham J.
8474c0fa-40df-43a6-a662-7f3c4722dbf2
Coles, Simon J.
3116f58b-c30c-48cf-bdd5-397d1c1fecf8
Owen, Gareth R.
fd633ee9-dcaa-438c-9b3b-82e9d091a1c6
Iannetelli, Angelo, Da Costa, Rosenildo Correa, Guwy, Alan J., Tizzard, Graham J., Coles, Simon J. and Owen, Gareth R.
(2020)
Transformation of a norbornadiene unit to ethylenylcyclopentene requiring cooperation between boron and rhodium centers.
Organometallics, 39 (10), .
(doi:10.1021/acs.organomet.0c00155).
Abstract
The synthesis of the lithium salt of a bis-substituted borohydride anion containing a phenyl substituent and a 2-mercaptopyridyl unit (mp) is reported herein. This salt has been used as a pro-ligand for the synthesis of rhodium(I) complex, [Rh{κ
3-H,H,S-H
2B(Ph)(mp)}(NBD)] (1) (where NBD = 2,5-norbornadiene). The new boron-based ligand coordinates to the rhodium center via the thione donor and the two B-H bonds of the BPhH
2 unit, with a dihydroborate motif. Reaction of complex 1 with two equivalents of triphenylphosphine leads to an unprecedented rearrangement and transfer of the former norbornadiene ligand to the boron center. The transformation occurs via an initial hydride migration from boron to rhodium center followed by a hydroboration of one of the double bonds. Finally, a ring-opening process occurs involving both boron and rhodium centers leading to an unusual boron-bound ethylenylcyclopentene unit. The product of this reaction was confirmed as [Rh{η
1-S,η
2-B,C-B(Ph)(CHCH
2(C
5H
7)(mp)}(PPh
3)
2] (2). The net result of these transformations is the incorporation of the two hydrogen atoms from the secondary borohydride ligand [BPhH
2(mp)]
- into the former norbornadiene unit. The end point positions of these hydrogen atoms were confirmed by deuterium labeling experiments. Complex 2 was further reacted with carbon monoxide to generate [Rh{η
1-S,η
2-B,C-B(Ph)(CHCH
2(C
5H
7)(mp)}(CO)(PPh
3)] (3) via ligand substitution. The new ligand and the three complexes, 1, 2, and 3, have been characterized by spectroscopic techniques as well as by X-ray crystallography. Detailed characterization of 2 and 3 revealed an unusual η
2-B,C coordination mode within these complexes. Further studies have demonstrated that complexes 2 and 3 react with hydrogen gas (or dimethylamine borane as a source of H
2) to generate the hydrogen addition products involving the unprecedented activation of the Rh-η
2-B,C motif. Complexes 2 and 3 were further found to be active catalysts for the hydrogenation of olefins and the dehydrogenation of dimethylamine borane.
Text
Manuscript NBD Activation CH2Cype_FINAL_Author Submitted Version
- Accepted Manuscript
More information
Accepted/In Press date: 24 April 2020
Published date: 26 May 2020
Additional Information:
Publisher Copyright:
© 2020 American Chemical Society.
Identifiers
Local EPrints ID: 440687
URI: http://eprints.soton.ac.uk/id/eprint/440687
ISSN: 0276-7333
PURE UUID: 2ad0dac9-c175-457c-a509-5aef9be6ff61
Catalogue record
Date deposited: 13 May 2020 16:35
Last modified: 17 Mar 2024 05:32
Export record
Altmetrics
Contributors
Author:
Angelo Iannetelli
Author:
Rosenildo Correa Da Costa
Author:
Alan J. Guwy
Author:
Gareth R. Owen
Download statistics
Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.
View more statistics