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- Moberg, Viktor, et al.
(författare)
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Chiral and achiral phosphine derivatives of alkylidyne tricobalt carbonyl clusters as catalyst precursors for (asymmetric) inter- and intramolecular Pauson-Khand reactions.
- 2008
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9234 .- 1477-9226. ; :18, s. 2442-2453
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Tidskriftsartikel (refereegranskat)abstract
- Phosphine derivatives of alkylidyne tricobalt carbonyl clusters have been tested as catalysts/catalyst precursors in intermolecular and (asymmetric) intramolecular Pauson-Khand reactions. A number of new phosphine derivatives of the tricobalt alkylidyne clusters [Co(3)(mu(3)-CR)(CO)(9)] (R = H, CO(2)Et) were prepared and characterised. The clusters [Co(3)(mu(3)-CR)(CO)(9-x)(PR'(3))(x)] (PR'(3) = achiral or chiral monodentate phosphine, x = 1-3) and [Co(3)(mu(3)-CR)(CO)(7)(P-P)] (P-P = chiral diphosphine; 1,1'- and 1,2-structural isomers) were assayed as catalysts for intermolecular and (asymmetric) intramolecular Pauson-Khand reactions. The phosphine-substituted tricobalt clusters proved to be viable catalysts/catalyst precursors that gave moderate to very good product yields (up to approximately 90%), but the enantiomeric excesses were too low for the clusters to be of practical use in the asymmetric reactions.
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| 2. |
- Mottalib, Abdul, et al.
(författare)
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Chiral diphosphine derivatives of alkylidyne tricobalt carbonyl clusters - A comparative study of different cobalt carbonyl (pre)catalysts for (asymmetric) intermolecular Pauson-Khand reactions
- 2016
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Ingår i: Polyhedron. - : Elsevier BV. - 0277-5387. ; 103, s. 275-282
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Tidskriftsartikel (refereegranskat)abstract
- Reaction of the tricobalt carbyne cluster [Co-3(mu(3)-CH)(CO)(9)] with chiral diphosphines of the Josiphos and Walphos families affords the new clusters [Co-3(mu(3)-CH)(CO)(7)(P-P*)] in good yield (P-P* = J004 (1), J005 (2), J007 (3), W001 (4), W003 (5)). The new alkylidyne tricobalt clusters, and the previously known [Co-3(mu(3)-CH)(CO)(7)(mu-J003)], have been tested as catalysts/catalyst precursors for intermolecular Pauson-Khand cyclization, using norbornene and phenylacetylene as substrate. The diphosphine-substituted tricobalt carbonyl clusters proved to be viable catalysts/catalyst precursors that gave products in moderate to good yields, but the enantiomeric excesses were low. When the chiral diphosphine ligands were used as promoters/auxiliary ligands for the same Pauson-Khand reaction, using either [Co-2(CO)(8)] or [Co-4(CO)(12)] as catalyst precursors, both the overall yields and the selectivities with respect to cyclopentenone formation were significantly improved. The best results were obtained for ligands J007 and W001, with [Co-4(CO)12] as pre-catalyst, where yields of 96%, and virtually 100% selectivity were obtained. However, the enantioselectivity of product formation was low or non-existent. The crystal structure of [Co-3(mu(3)-CH)(CO)(7)(mu-J004)] is described. [J003 = [(R)-1-{(S)-2-(dicyclohexylphosphino)-ferrocenyl} ethyldicyclohexylphosphine], J004 = [(R)-1-{(S)-2-(dicyclohexylphosphino)-ferrocenyl} ethyldiphenylphosphine], J005 = [(R)-1-{(S)-2-(diphenylphosphino)ferrocenyl}ethyl-di-3,5-xylylphosphine], J007 = [(R)-1-{(S)-2-di-(4-methoxy-3,5-dimethylphenyl)phosphino)ferrocenyl) ethyldicyclohexylphosphine], W001 = [(R)-1-{(R)-2-(2'-diphenyl phosphinophenyl)ferrocenyl} ethyldi(bis-3,5-trifluoromethylphenyl) phosphine], W003 [(R)-1-{(R)-2-(2'-diphenylphosphino-phenyl)ferrocenyl}ethyldi(3,5-xylyl)phosphine]. (C) 2015 Elsevier Ltd. All rights reserved.
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| 3. |
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| 4. |
- Uddin, Md. Nazim, et al.
(författare)
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Carbon-Phosphorus Bond Activation of Tri(2-thienyl)phosphine at Dirhenium and Dimanganese Centers
- 2009
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Ingår i: Organometallics. - : American Chemical Society (ACS). - 1520-6041 .- 0276-7333. ; 28:5, s. 1514-1523
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Tidskriftsartikel (refereegranskat)abstract
- Reaction of [Re-2(CO)(9)(NCMe)] with tri(2-thienyl)phosphine (PTh3) in refluxing cyclohexane affords three substituted dirhenium complexes: [Re-2(CO)(9)(PTh3)] (1), [Re-2(CO)(8)(NCMe)(PTh3)] (2), and [Re-2(CO)(8)(PTh3)(2)] (3). Complex 2 was also obtained from the room-temperature reaction of [Re-2(CO)(8)(NCMe)(2)] with PTh3 and is an unusual example in which the acetonitrile and phosphine ligands are coordinated to the same rhenium atom. Thermolysis of 1 and 3 in refluxing xylene affords [Re-2(CO)(8)(mu-PTh2)(mu-eta(1):kappa(1)-C4H3S)] (4) and [Re-2(CO)(7)(PTh3)(mu-PTh2)(mu-H)] (5), respectively, both resulting from carbon-phosphorus bond cleavage of a coordinated PTh3 ligand. Reaction of [Re-2(CO)10] and PTh3 in refluxing xylene gives a complex mixture of products. These products include 3-5, two further binuclear products, [Re-2(CO)(7)(PTh3)(mu-PTh2)(mu-eta(1):kappa(1)-C4H3S)] (6) and [Re-2(CO)(7)(mu-kappa(1):kappa(2)-Th2PC4H2SPTh)(mu-eta(1):kappa(1)-C4H3S )] (7), and the mononuclear hydrides [ReH(CO)(4)(PTh3)] (8) and trans-[ReH(CO)(3)(PTh3)(2)] (9). Binuclear 6 is structurally similar to 4 and can be obtained from reaction of the latter with 1 equiv of PTh3. Formation of 7 involves a series of rearrangements resulting in the formation of a unique new diphosphine ligand, Th2PC4H2SPTh. Reaction of [Mn-2(CO)(10)] with PTh3 in refluxing toluene affords the phosphine-substituted product [Mn-2(CO)(9)(PTh3)] (10) and two carbon-phosphorus bond cleavage products, [Mn-2)(CO)(6)(mu-PTh2)(mu-eta(1):eta(5)-C4H3S)] (11) and [Mn-2(CO)(5)(PTh3)(mu-PTh2)(mu-PTh2)(mu-eta(1):eta(5)-C4H3S)] (12). Both 11 and 12 contain a bridging thienyl ligand that is bonded to one manganese atom in a eta(5)-fashion. The molecular structures of eight of these new complexes were established by single-crystal X-ray diffraction studies, allowing a detailed analysis of the disposition of the coordinated ligands.
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