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Modification of rhenium carbonyls with thienyl nucleophiles
Thesis (PhD)--University of Pretoria, 2011.
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University of Pretoria
2013
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| access_status_str | Open Access |
| author2 | Lotz, Simon |
| author_browse | Lotz, Simon |
| author_facet | Lotz, Simon |
| collection | Thesis |
| dc_rights_str_mv | © 2009 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
| description | Thesis (PhD)--University of Pretoria, 2011. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/28475 |
| institution | University of Pretoria (South Africa) |
| last_indexed | 2026-06-10T12:39:58.654Z |
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| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2013 |
| publishDateRange | 2013 |
| publishDateSort | 2013 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/28475 Modification of rhenium carbonyls with thienyl nucleophiles Lotz, Simon andrew.j.olivier@gmail.com Olivier, Andrew John Rhenium carbonyls Dirhenium acylate UCTD Thesis (PhD)--University of Pretoria, 2011. In the reaction between [Re(CO)5Br] and 2–lithiumthienyl, X–ligand substitution was expected. Li+{C4H3S}¯did not substitute Br¯, but an intermediate negatively charged complex was obtained (non–mobile on silica gel) and it was found that the thienyl had bonded to a carbonyl ligand, producing a dirhenium acylate complex. Such complexes are the precursors to neutral Fischer carbene complexes. After alkylation with Et3OBF4, [Re2 (CO) 9C(OEt)C4H3S] (1) was obtained, instead of a monorhenium monocarbene complex. Greater yields of 1 could be obtained, from reactions with [Re2(CO) 10] instead of [Re(CO) 5Br]. [Re2 (CO) 10] reacted with 5–lithium–2,2'–bithienyl and 2–lithium–3,6– dimethylthieno[3,2–b]thienyl and was then alkylated with Et3OBF4. The reactions proceeded smoothly and [Re2 (CO) 9C(OEt)C8H5S2] (2) and [Re2 (CO) 9C(OEt)C8H7S2] (3) were obtained. The substrates thiophene, 2,2'–bithiophene and 3,6–dimethylthieno[3,2–b]thiophene, can all be doubly lithiated under appropriate reaction conditions. These lithiated species were reacted with two equivalents of [Re2 (CO) 10]. In the case of bithiophene this produced, in good yield, the tetrametal biscarbene complex [Re2 (CO) 9C(OEt)C8H4S2C(OEt)Re2 (CO) 9] (8). In the thiophene and dimethylthieno[3,2–b]thiophene cases [Re2 (CO) 9C(OEt)C4H2SC(OEt)Re2 (CO) 9] (7) and [Re2 (CO) 9C(OEt)C8H6S2C(OEt)Re2 (CO) 9] (9) could be isolated in meagre quantities. This was ascribed to poor double lithiation (also steric hindrance in the case of 7). The carbene ligands reacted with water on the silica gel during column chromatography or in a control experiment with degassed water to produce aldehydes by reductive elimination from the metal. Protonation of the acylrhenate afforded rhenium hydrides which is also a potential precursor to aldehyde formation. This is believed to be a facile process for especially complex 9, isolated in very small quantity. Complexes 7–9 produced monocarbene aldehyde complexes [Re2(CO) 9C(OEt)C4H2SC(O)H] (12), [Re2 (CO) 9C(OEt)C8H4S2C(O)H] (13) and [Re2 (CO) 9C(OEt)C8H6S2C(O)H] (14), as well as dialdehyde compounds. Complexes 2 and 3 also produced aldehyde compounds. The formation of aldehydes from ethoxycarbene complexes is believed to involve hydroxycarbene intermediate species. Experiments were performed on [Re2 (CO) 10] and [Re(CO) 5Br]. They were reacted with 2–lithiumthienyl and then protonated. In the case of [Re2(CO) 10], hydride signals were observed on the 1H NMR spectrum, as well as aldehyde signals. In the case of [Re(CO) 5Br] there was strong NMR evidence indicating the formation of a hydroxycarbene complex. Complexes 1, 2, and 3 were reacted with Br2 (l). The metal–metal bonds were cleaved by the bromine to produce monorhenium carbene complexes [Re(CO) 4{C(OEt)C4H3S}Br] (4), [Re(CO) 4{C(OEt)C8H5S2}Br] (5), and [Re(CO) 4{C(OEt)C8H7S2}Br] 6) and [Re(CO) 5Br]. Complex 8 reacted with bromine to produce a monocleaved complex [Re2 (CO) 9C(OEt)C8H4S2C(OEt)Re(CO) 4Br] (11) and a biscleaved complex [Re(CO) 4Br{C(OEt)C8H4S2C(OEt)}Re2 (CO) 4Br] (10). Unique complexes [Re(CO) 4{C(OH)C4H3S}{μ–H}Re(CO) 4{C(O)C4H3S}] (15) and [Re(CO) 4{C(OH)C8H5S2}{μ–H}Re(CO) 4{C(O) C8H5S2}] (16) were obtained by starting with [Re(CO) 5Br] or [Re2 (CO) 10] and reacting them with 2–lithiumthienyl and 5–lithium–2,2'– bithienyl. These complexes were isolated from the column as very polar compounds after eluation of the aldehyde complexes. The dirhenium complex was obtained with a carbonyl– modified ligand (hydroxycarbene/acyl) on each of the metals. The complexes consist of two fragments held together by a hydrogen atom that bridges the two rhenium atoms (hydrido) and one that bridges the oxygen atoms of the carbene/acyl ligands (protonic). Chemistry unrestricted 2013-09-07T13:36:13Z 2010-10-06 2013-09-07T13:36:13Z 2010-04-16 2011-06-06 2010-10-06 Thesis Olivier, AJ 2009, Modification of Rhenium carbonyls with thienyl nucleophiles , PhD thesis, University of Pretoria, Pretoria, viewed yymmdd < http://hdl.handle.net/2263/28475 > D10/687/ag http://hdl.handle.net/2263/28475 http://upetd.up.ac.za/thesis/available/etd-10062010-182746/ © 2009 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. application/pdf application/pdf application/pdf application/pdf application/pdf application/pdf application/pdf application/pdf application/pdf University of Pretoria |
| spellingShingle | Rhenium carbonyls Dirhenium acylate UCTD Modification of rhenium carbonyls with thienyl nucleophiles |
| title | Modification of rhenium carbonyls with thienyl nucleophiles |
| title_full | Modification of rhenium carbonyls with thienyl nucleophiles |
| title_fullStr | Modification of rhenium carbonyls with thienyl nucleophiles |
| title_full_unstemmed | Modification of rhenium carbonyls with thienyl nucleophiles |
| title_short | Modification of rhenium carbonyls with thienyl nucleophiles |
| title_sort | modification of rhenium carbonyls with thienyl nucleophiles |
| topic | Rhenium carbonyls Dirhenium acylate UCTD |
| url | http://hdl.handle.net/2263/28475 http://upetd.up.ac.za/thesis/available/etd-10062010-182746/ |