Chowdhury, MAH;
Haque, MR;
Ghosh, S;
Mobin, SM;
Tocher, DA;
Hogarth, G;
Richmond, MG;
... Roesky, HW; + view all
(2017)
Reversible C-H bond activation at a triosmium centre: A comparative study of the reactivity of unsaturated triosmium clusters Os3(CO)8(μ-dppm)(μ-H)2 and Os3(CO)8(μ-dppf)(μ-H)2 with activated alkynes.
Journal of Organometallic Chemistry
, 836-83
pp. 68-80.
10.1016/j.jorganchem.2017.02.041.
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Abstract
Heating a benzene solution of the unsaturated cluster Os3(CO)8(μ-dppm)(μ-H)2 (1) [dppm = bis(diphenylphosphino)methane] with MeO2CCtriple bond; length of mdashCCO2Me (DMAD) or EtO2CCtriple bond; length of mdashCCO2Et (DEAD) at 80 °C furnished the dinuclear compounds Os2(CO)4(μ-dppm)(μ-η2;η1;к1-RO2CCCHCO2R)(μ-H) (3a, R = Me, 3b, R = Et) and the saturated trinuclear complexes Os3(CO)7(μ-dppm)(μ3-η2;η1;η1-RO2CCCCO2R)(μ-H)2 (4a, R = Me, 4b, R = Et). In contrast, similar reactions using unsaturated Os3(CO)8(μ-dppf)(μ-H)2 (2) [dppf = bis(diphenylphosphino)ferrocene] afforded only the trinuclear complexes Os3(CO)8(μ-dppf)(μ-η2;η1-RO2CCHCCO2R)(μ-H) (5a, R = Me; 5b, R = Et) and Os3(CO)7(μ-dppf)(μ3-η2;η1;η1-RO2CCCCO2R)(μ-H)2 (6a, R = Me; 6b, R = Et). Control experiments confirm that 5a and 5b decarbonylate at 80 °C to give 6a and 6b, respectively. Both 5a and 5b exist as a pair of isomers in solution, as demonstrated by 1H NMR and 31P{1H} NMR spectroscopy. DFT calculations on cluster 5a (as the dppf-Me4 derivative) indicate that the isomeric mixture derives from a torsional motion that promotes the conformational flipping of the cyclopentadienyl groups of the dppf-Me4 ligand relative to the metallic plane. VT NMR measurements on clusters 6a and 6b indicate that while the hydride ligand associated with the dppf-bridged Os-Os bond is nonfluxional at room temperature, the second hydride rapidly oscillates between the two non-dppf-bridged Os-Os edges. DFT examination of this hydride fluxionality confirms a “windshield wiper” motion for the labile hydride that gives rise to a time-average coupling of this hydride to both phosphorus centers of the dppf ligand. Thermolysis of 6a and 6b in refluxing toluene yielded Os3(CO)7(μ-dppf)(μ-η2;η1;к1-CCHCO2R) (7a, R=Me; 7b, R=Et). The vinylidene moieties in 7a and 7b derive from the carbon-carbon bond cleavage of coordinated alkyne ligands, and these two products exhibit high thermal stability in refluxing toluene.
| Type: | Article |
|---|---|
| Title: | Reversible C-H bond activation at a triosmium centre: A comparative study of the reactivity of unsaturated triosmium clusters Os3(CO)8(μ-dppm)(μ-H)2 and Os3(CO)8(μ-dppf)(μ-H)2 with activated alkynes |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1016/j.jorganchem.2017.02.041 |
| Publisher version: | http://dx.doi.org/10.1016/j.jorganchem.2017.02.041 |
| Language: | English |
| Additional information: | Unsaturated osmium clusters; Diphosphines; Reversible C-H bond activation; Activated alkynes; C-C bond scission; DFT |
| Keywords: | Science & Technology, Physical Sciences, Chemistry, Inorganic & Nuclear, Chemistry, Organic, Chemistry, Unsaturated osmium clusters, Diphosphines, Reversible C-H bond activation, Activated alkynes, C-C bond scission, DFT, X-RAY STRUCTURES, OSMIUM CARBONYL HYDRIDES, SET MODEL CHEMISTRY, CRYSTAL-STRUCTURE, SUBSTITUTED ACETYLENES, TRIRUTHENIUM CLUSTERS, HOMOGENEOUS CATALYSIS, OLEFIN ISOMERIZATION, DIPHOSPHINE LIGANDS, TOTAL ENERGIES |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry |
| URI: | https://discovery.ucl.ac.uk/id/eprint/1547608 |
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