Synthesis and structure of two tetranuclear osmium carbonyl isotopomers: a crystallographic isotope effect

Canal, John P.; Jennings, Michael C.; Yap, Glenn P. A.; Pomeroy, Roland K.

doi:10.1039/b711872d

Cited by 3 publications

(2 citation statements)

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“…There is a plethora of NMR reports on CO scrambling about triangular faces in polynuclear clusters . Indeed, our calculations find TS-ee (Figure ), the triply bridged transition structure for the one-step conversion of B-ee to C-ee in eq , to be 4.3 kcal/mol lower in enthalpy than TS-ea , the highest energy transition structure for the three-step conversion of B-ee to C-ee via the mechanism in eqs − .…”

Section: Resultsmentioning

confidence: 71%

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
Organometallics
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6
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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: 71%

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
Organometallics
21
2
6
0
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“…[17][18][19][20][21] Mixed valence Os(0/II) compounds tend to have bridges in the À2.8 to À0.44 ppm range. 24,25 Square planar Pd(II) and Pt(II) complexes have m 2 -OH bridges that range from À3 to 2 ppm. [26][27][28][29][30][31][32][33][34] Sn has the largest range producing signals anywhere from 1.63 to 7.33 ppm.…”

Section: H-nmr Spectra Of Hydroxo/aquo Bridged Coordination Compoundsmentioning

confidence: 99%

Solution structural characterization of an array of nanoscale aqueous inorganic Ga13−xInx (0 ≤ x ≤ 6) clusters by ¹H-NMR and QM computations

et al. 2015

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The problems of detecting hydrides in metal carbonyl clusters by 1H NMR: the case study of [H4−nNi22(C2)4(CO)28(CdBr)2]n− (n = 2–4)

et al. 2009

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The new tetra-acetylide carbonyl clusters [H(4-n)Ni(22)(C(2))(4)(CO)(28)(CdBr)(2)](n-) (n = 2-4) have been prepared by reacting [Ni(10)C(2)(CO)(15)](2-) with a large excess of CdBr(2).xH(2)O and the molecular structure of the di-anion [H(2)Ni(22)(C(2))(4)(CO)(28)(CdBr)(2)](2-) has been fully elucidated by means of X-ray crystallography. The corresponding [HNi(22)(C(2))(4)(CO)(28)(CdBr)(2)](3-) and [Ni(22)(C(2))(4)(CO)(28)(CdBr)(2)](4-) conjugated bases are quantitatively obtained upon dissolution of [H(2)Ni(22)(C(2))(4)(CO)(28)(CdBr)(2)](2-) salts in more basic solvents such as acetonitrile and DMSO, respectively. The hydride nature of both [H(2)Ni(22)(C(2))(4)(CO)(28)(CdBr)(2)](2-) and [HNi(22)(C(2))(4)(CO)(28)(CdBr)(2)](3-) has been directly proved by (1)H NMR spectroscopy. Their resonances are very broad under all experimental conditions and their chemical shift greatly depends on solvent as well as temperature. Observation of the hydride resonances in [H(4-n)Ni(22)(C(2))(4)(CO)(28)(CdBr)(2)](n-) (n = 2, 3) makes these clusters a case study of the phenomena behind the loss of any NMR signal in higher-nuclearity metal carbonyl cluster anions (MCCA). In the attempt to obtain a better insight on this experimental spectroscopic behaviour, solutions of [NMe(4)](3)[HNi(22)(C(2))(4)(CO)(28)(CdBr)(2)] have been investigated by dynamic light scattering (DLS) at various concentrations. The DLS experiments point out the presence in solution of a distribution of particles with nominal hydrodynamic diameters enormously greater than those of the free cluster ions resulting, probably, from aggregation in solution. This could formally justify the observed NMR behaviour, even if the present observations are preliminary and their quantitative assessment requires further systematic studies on MCCA aggregation in solution.

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Synthesis and structure of two tetranuclear osmium carbonyl isotopomers: a crystallographic isotope effect

Cited by 3 publications

References 53 publications

Solution structural characterization of an array of nanoscale aqueous inorganic Ga13−xInx (0 ≤ x ≤ 6) clusters by ¹H-NMR and QM computations

The problems of detecting hydrides in metal carbonyl clusters by 1H NMR: the case study of [H4−nNi22(C2)4(CO)28(CdBr)2]n− (n = 2–4)

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Synthesis and structure of two tetranuclear osmium carbonyl isotopomers: a crystallographic isotope effect

Cited by 3 publications

References 53 publications

Solution structural characterization of an array of nanoscale aqueous inorganic Ga13−xInx (0 ≤ x ≤ 6) clusters by 1H-NMR and QM computations

The problems of detecting hydrides in metal carbonyl clusters by 1H NMR: the case study of [H4−nNi22(C2)4(CO)28(CdBr)2]n− (n = 2–4)

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Solution structural characterization of an array of nanoscale aqueous inorganic Ga13−xInx (0 ≤ x ≤ 6) clusters by ¹H-NMR and QM computations