Addition of organolithium nucleophiles to the diiron allenyl complex [Fe2(CO)6(μ-PPh2){μ-η1: η2 α,β-(H)Cα=Cβ =CγH2}]:Synthesis and characterization of organodiiron-coordinated β,γ-unsaturated ketones
The binuclear allenyl complex [Fe2(CO)6(μ-PPh2){μ-η 1:η2α,β-(H)C α=Cβ=CγH2}] (1) has been prepared, and its reactivity with organolithium nucleophiles is described. Prop-2-yne bromide reacts with [Fe2(CO)7(μ-PPh2)]-Na +, via an SN2 mechanism, to give [Fe2(CO)6(μ-PPh2){μ-η1: η2α,β-(H)Cα=C β=CγH2}], t...
| Main Authors: | , , , , , |
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| Format: | Journal article |
| Language: | English |
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1997
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| _version_ | 1797051853645545472 |
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| author | Doherty, S Elsegood, M Clegg, W Rees, N Scanlan, T Waugh, M |
| author_facet | Doherty, S Elsegood, M Clegg, W Rees, N Scanlan, T Waugh, M |
| author_sort | Doherty, S |
| collection | OXFORD |
| description | The binuclear allenyl complex [Fe2(CO)6(μ-PPh2){μ-η 1:η2α,β-(H)C α=Cβ=CγH2}] (1) has been prepared, and its reactivity with organolithium nucleophiles is described. Prop-2-yne bromide reacts with [Fe2(CO)7(μ-PPh2)]-Na +, via an SN2 mechanism, to give [Fe2(CO)6(μ-PPh2){μ-η1: η2α,β-(H)Cα=C β=CγH2}], the first example of a phosphido-bridged allenyl complex. The molecular structure of [Fe2(CO)6(μ-PPh2){μ-η 1:η2-(H)Cα=Cβ=C γH2}]: (1) was determined by single-crystal X-ray diffraction and shows that the allenyl ligand is coordinated through Cα-Cβ. Variable-temperature 1H and 13C NMR studies reveal a high-energy exchange process that equilibrates the diastereotopic allenyl protons, presumably via a zwitterionic intermediate, as well as two independent trigonal rotations that act to exchange the carbonyl ligands on each unique Fe(CO)3 group. Complex 1 reacts with organolithium reagents (RLi; R = Me, nBu, Ph, C4H3S), via allenyl-carbonyl-nucleophile coupling, to afford the binuclear β,γ-unsaturated ketones [Fe2(CO)5{P(OMe)3}(μ-PPh 2)(μ-η1:η2-{RC(O)CH 2}C=CH2)] (R = Me, 3a; nBu, 3b; Ph, 3c; C4H3S, 3d), and a single-crystal X-ray structure determination of 3a was undertaken to confirm the connectivity of the hydrocarbyl ligand. The most likely mechanism for the formation of 3a-d involves nucleophilic attack of R- at CO to give an acylate intermediate followed by migration of RCO to Cα of the allenyl and protonation of the resulting enolate to give the unstable alkenyl complexes [Fe2(CO)5(μ-PPh2)(μ-η 1(C):η1-(C):η2(C)-{RC(O)CH 2}C=CH2)] (R = Me, 2a; Bu, 2b; Ph, 2c; C4H3S, 2d). Finally, substitution of the metal-coordinated ester carbonyl in 2a-d with trimethylphosphite affords 3a-d as stable crystalline products. |
| first_indexed | 2024-03-06T18:25:18Z |
| format | Journal article |
| id | oxford-uuid:07bc8b37-cadf-4cc2-95be-d1ab3989a6cd |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-06T18:25:18Z |
| publishDate | 1997 |
| record_format | dspace |
| spelling | oxford-uuid:07bc8b37-cadf-4cc2-95be-d1ab3989a6cd2022-03-26T09:09:11ZAddition of organolithium nucleophiles to the diiron allenyl complex [Fe2(CO)6(μ-PPh2){μ-η1: η2 α,β-(H)Cα=Cβ =CγH2}]:Synthesis and characterization of organodiiron-coordinated β,γ-unsaturated ketonesJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:07bc8b37-cadf-4cc2-95be-d1ab3989a6cdEnglishSymplectic Elements at Oxford1997Doherty, SElsegood, MClegg, WRees, NScanlan, TWaugh, MThe binuclear allenyl complex [Fe2(CO)6(μ-PPh2){μ-η 1:η2α,β-(H)C α=Cβ=CγH2}] (1) has been prepared, and its reactivity with organolithium nucleophiles is described. Prop-2-yne bromide reacts with [Fe2(CO)7(μ-PPh2)]-Na +, via an SN2 mechanism, to give [Fe2(CO)6(μ-PPh2){μ-η1: η2α,β-(H)Cα=C β=CγH2}], the first example of a phosphido-bridged allenyl complex. The molecular structure of [Fe2(CO)6(μ-PPh2){μ-η 1:η2-(H)Cα=Cβ=C γH2}]: (1) was determined by single-crystal X-ray diffraction and shows that the allenyl ligand is coordinated through Cα-Cβ. Variable-temperature 1H and 13C NMR studies reveal a high-energy exchange process that equilibrates the diastereotopic allenyl protons, presumably via a zwitterionic intermediate, as well as two independent trigonal rotations that act to exchange the carbonyl ligands on each unique Fe(CO)3 group. Complex 1 reacts with organolithium reagents (RLi; R = Me, nBu, Ph, C4H3S), via allenyl-carbonyl-nucleophile coupling, to afford the binuclear β,γ-unsaturated ketones [Fe2(CO)5{P(OMe)3}(μ-PPh 2)(μ-η1:η2-{RC(O)CH 2}C=CH2)] (R = Me, 3a; nBu, 3b; Ph, 3c; C4H3S, 3d), and a single-crystal X-ray structure determination of 3a was undertaken to confirm the connectivity of the hydrocarbyl ligand. The most likely mechanism for the formation of 3a-d involves nucleophilic attack of R- at CO to give an acylate intermediate followed by migration of RCO to Cα of the allenyl and protonation of the resulting enolate to give the unstable alkenyl complexes [Fe2(CO)5(μ-PPh2)(μ-η 1(C):η1-(C):η2(C)-{RC(O)CH 2}C=CH2)] (R = Me, 2a; Bu, 2b; Ph, 2c; C4H3S, 2d). Finally, substitution of the metal-coordinated ester carbonyl in 2a-d with trimethylphosphite affords 3a-d as stable crystalline products. |
| spellingShingle | Doherty, S Elsegood, M Clegg, W Rees, N Scanlan, T Waugh, M Addition of organolithium nucleophiles to the diiron allenyl complex [Fe2(CO)6(μ-PPh2){μ-η1: η2 α,β-(H)Cα=Cβ =CγH2}]:Synthesis and characterization of organodiiron-coordinated β,γ-unsaturated ketones |
| title | Addition of organolithium nucleophiles to the diiron allenyl complex [Fe2(CO)6(μ-PPh2){μ-η1: η2
α,β-(H)Cα=Cβ =CγH2}]:Synthesis and characterization of organodiiron-coordinated β,γ-unsaturated ketones |
| title_full | Addition of organolithium nucleophiles to the diiron allenyl complex [Fe2(CO)6(μ-PPh2){μ-η1: η2
α,β-(H)Cα=Cβ =CγH2}]:Synthesis and characterization of organodiiron-coordinated β,γ-unsaturated ketones |
| title_fullStr | Addition of organolithium nucleophiles to the diiron allenyl complex [Fe2(CO)6(μ-PPh2){μ-η1: η2
α,β-(H)Cα=Cβ =CγH2}]:Synthesis and characterization of organodiiron-coordinated β,γ-unsaturated ketones |
| title_full_unstemmed | Addition of organolithium nucleophiles to the diiron allenyl complex [Fe2(CO)6(μ-PPh2){μ-η1: η2
α,β-(H)Cα=Cβ =CγH2}]:Synthesis and characterization of organodiiron-coordinated β,γ-unsaturated ketones |
| title_short | Addition of organolithium nucleophiles to the diiron allenyl complex [Fe2(CO)6(μ-PPh2){μ-η1: η2
α,β-(H)Cα=Cβ =CγH2}]:Synthesis and characterization of organodiiron-coordinated β,γ-unsaturated ketones |
| title_sort | addition of organolithium nucleophiles to the diiron allenyl complex fe2 co 6 μ pph2 μ η1 η2 α β h cα cβ cγh2 synthesis and characterization of organodiiron coordinated β γ unsaturated ketones |
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