Synthesis and reactivity studies of the diphosphine ligand 2-(ferrocenylidene)-4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (fbpcd): Bridge-to-chelate ligand isomerization kinetics in Os3(CO)10(fbpcd) and X-ray diffraction structure of the ortho-metalated cluster HOs3(CO)9[μ-PhP(C6H4)CC(PPh2)C(O)CCH(C5H4FeCp)C(O)]

Watson, William H.; Poola, Bhaskar; Richmond, Michael G.

doi:10.1016/j.poly.2007.03.057

Cited by 15 publications

(9 citation statements)

References 29 publications

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“…The bridging of the Os(1) and Os(2) atoms by the dppbz ligand in 2 is thermodynamically less favorable than the chelation in isomer 3 . This factor also serves as the driving force for the facile isomerizations, observed in related, diphosphine-bridged isomers of Os 3 (CO) 10 (P-P) . Three significantly adverse perturbations result from the stretching of the dppbz ligand across the Os(1)−Os(2) vector in 2 , and they in turn account for the ground-state destabilization in 2 relative to 3 .…”

Section: Resultsmentioning

confidence: 99%

“…This transformation verifies that 3 is the thermodynamically most stable of the isomeric Os 3 (CO) 10 (dppbz) clusters. The addition of CO suppresses the formation of the hydride cluster 4 , but CO addition has been shown not to affect the equilibrium for the bridged-to-chelated ligand isomerization in other decacarbonyl clusters Os 3 (CO) 10 (P-P) …”

Section: Resultsmentioning

confidence: 99%

“…Our interest in the coordinative flexibility of diphosphine ligands in polynuclear clusters , led us to measure the kinetics for the conversion 2 → 3 . The isomerization reactions were conveniently monitored by UV−vis spectroscopy, under CO, over the temperature range 318−343 K; the first-order rate constants given in Table were obtained.…”

Section: Resultsmentioning

confidence: 99%

“…One of us (M.G.R.) has held a long-term interest in the synthesis and mechanistic study of Ru 3 , Os 3 , and tetrahedrane clusters, containing rigid diphosphine ligands. ,− Several of these reports have addressed the dynamic isomerization of the ancillary diphosphine ligand about the cluster core, as illustrated for the cluster compound Os 3 (CO) 10 (dppen) (where dppen = (Z)-1,2-bis(diphenylphosphino)ethylene) in eq . This particular reaction is reversible, and the thermodynamically favored isomer contains a chelating dppen ligand with a K eq value of 6.9 over the temperature range 358−373 K .…”

Section: Introductionmentioning

confidence: 99%

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Experimental and Computational Studies of the Isomerization Reactions of Bidentate Phosphine Ligands in Triosmium Clusters: Kinetics of the Rearrangements from Bridged to Chelated Isomers and X-ray Structures of the Clusters Os₃(CO)₁₀(dppbz), 1,1-Os₃(CO)₁₀(dppbzF₄), HOs₃(CO)₉[μ-1,2-PhP(C₆H₄-η¹)C₆H₄PPh₂], and HOs₃(CO)₉[μ-1,2-PhP(C₆H
Zhang
¹
,
Kandala²,
Yang³
et al. 2011
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The diphosphine ligand 1,2-bis(diphenylphosphino)benzene (dppbz) reacts with the activated cluster 1,2-Os 3 (CO) 10 (MeCN) 2 (1) at room temperature to furnish a mixture of the triosmium clusters 1,2-Os 3 (CO) 10 (dppbz) (2) and 1,1-Os 3 (CO) 10 (dppbz) (3), along with a trace amount of the hydride cluster HOs 3 (CO) 9 [μ-1,2-PhP(C 6 H 4-η 1)C 6 H 4 PPh 2 ] (4). The dppbz-bridged cluster 2 forms as the kinetically controlled product and irreversibly transforms to the corresponding chelated isomer 3 at ambient temperature. The disposition of the dppbz ligand in 2 and 3 has been established by X-ray crystallography and 31 P NMR spectroscopy, and the kinetics for the conversion 2 f 3 have been followed by UV-vis spectroscopy in toluene over the temperature range 318-343 K. The calculated activation parameters (ΔH q = 21.6(3) kcal/mol; ΔS q =-11(1) eu) and lack of CO inhibition support an intramolecular isomerization mechanism that involves the simultaneous migration of phosphine and CO groups about the cluster polyhedron. The reaction between 1 and the fluorinated diphosphine ligand 1,2-bis(diphenylphosphino)tetrafluorobenzene (dppbzF 4) was examined under similar reaction conditions and was found to afford the chelated cluster 1,1-Os 3 (CO) 10 (dppbzF 4) (6) as the sole observable product. The absence of the expected bridged isomer 1,2-Os 3 (CO) 10 (dppbzF 4) (5) suggests that the dppbzF 4 ligand destabilizes 5, thus accounting for the rapid isomerization of 5 to 6. Near-UV irradiation of clusters 3 and 6 leads to CO loss and ortho metalation of an ancillary aryl group. The resulting hydride clusters 4 and HOs 3 (CO) 9 [μ-1,2-PhP(C 6 H 4-η 1)C 6 F 4 PPh 2 ] (7) have been isolated and fully characterized by spectroscopic and X-ray diffraction analyses. Both 4 and 7 react with added CO under mild conditions to regenerate 3 and 6, respectively, in quantitative yield. The rearrangements of bridged to chelated diphosphine complexes in this genre of decacarbonyl clusters have been investigated by DFT calculations. The computational results support a concerted process, involving the scrambling of equatorial CO and phosphine groups via a classical merry-go-round exchange scheme. The barriers computed for this mechanism agree well with those that have been measured, and steric compression within the bridged diphosphine groups of the reactants has been calculated to reduce the barrier heights for the rearrangement.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Experimental and Computational Studies of the Isomerization Reactions of Bidentate Phosphine Ligands in Triosmium Clusters: Kinetics of the Rearrangements from Bridged to Chelated Isomers and X-ray Structures of the Clusters Os₃(CO)₁₀(dppbz), 1,1-Os₃(CO)₁₀(dppbzF₄), HOs₃(CO)₉[μ-1,2-PhP(C₆H₄-η¹)C₆H₄PPh₂], and HOs₃(CO)₉[μ-1,2-PhP(C₆H
Zhang
¹
,
Kandala²,
Yang³
et al. 2011
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“…The isomerization of diphosphine ligands about triosmium clusters has been shown to occur through a concerted scrambling of equatorial CO and phosphine ligands via a merry-go-round process. ,, In these examples, where the diphosphine ligands possess an unsaturated backbone, the single-step exchange process is kinetically favored over alternative, multistep sequences involving pairwise ligand exchanges across a single Os–Os vector. In order to rule out a possible merry-go-round manifold in the conversion of 1,2-( P eq , S eq )-Os 3 (CO) 10 (Ph 2 PCH 2 CH 2 SMe) to 1,1-( P eq , S ax )-Os 3 (CO) 10 (Ph 2 PCH 2 CH 2 SMe), the energetics associated with the migration of the phosphine ligand to the MeS-substituted osmium center in species A2 were computationally modeled.…”

Section: Resultsmentioning

confidence: 99%

DFT Investigation of the Mechanism of Phosphine-Thioether Isomerization in the Triosmium Cluster Os₃(CO)₁₀(Ph₂PCH₂CH₂SMe): Migratory Preference for the Formation of an Edge-Bridged Thioether versus a Phosphine Moiety

Hrovat¹,

Nordlander

Richmond³

2012

Organometallics

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The rearrangement of the phosphine-thioether ligand in 1,2-(P eq,S eq)-Os3(CO)10(Ph2PCH2CH2SMe) to 1,1-(P eq,S ax)-Os3(CO)10(Ph2PCH2CH2SMe) was investigated by electronic structure calculations. The chelated isomer lies 2.5 kcal/mol lower in energy than its bridged counterpart, and the barrier computed for the mechanism is in agreement with the results from our earlier experimental study. Phosphine-thioether isomerization occurs via three distinct steps that involve the migration of the CO and SMe groups in a plane that is perpendicular to the trimetallic core. One of the intermediates on the reaction surface corresponds to the 50e cluster Os3(CO)9(μ-CO)(μ-Ph2PCH2CH2SMe), whose edge-bridging thioether moiety functions as a 4e donor ligand. Alternative mechanisms involving ligand dissociation/association and merry-go-round sequences are energetically prohibitive.

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