Structure and dynamics of a dihydrogen/hydride ansa molybdenocene complex.
In contrast to [Cp(2)MoH(3)](+), which is a thermally stable trihydride complex, the ansa-bridged analogue [(eta-C(5)H(4))(2)CMe(2)MoH(H(2))](+) (1) is a thermally labile dihydrogen/hydride complex. Partial deuteration of the hydride ligands allows observation of J(H)(-)(D) = 11.9 Hz in 1-d(1) and 9...
| Asıl Yazarlar: | , , , , , |
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| Materyal Türü: | Journal article |
| Dil: | English |
| Baskı/Yayın Bilgisi: |
2004
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| _version_ | 1826264158074568704 |
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| author | Pons, V Conway, S Green, M Green, J Herbert, B Heinekey, D |
| author_facet | Pons, V Conway, S Green, M Green, J Herbert, B Heinekey, D |
| author_sort | Pons, V |
| collection | OXFORD |
| description | In contrast to [Cp(2)MoH(3)](+), which is a thermally stable trihydride complex, the ansa-bridged analogue [(eta-C(5)H(4))(2)CMe(2)MoH(H(2))](+) (1) is a thermally labile dihydrogen/hydride complex. Partial deuteration of the hydride ligands allows observation of J(H)(-)(D) = 11.9 Hz in 1-d(1) and 9.9 Hz in 1-d(2) (245 K), indicative of a dihydrogen/hydride structure. There is a slight preference for deuterium to concentrate in the dihydrogen ligand. A rapid dynamic process interchanges the hydride and dihydrogen moieties in complex 1. Low temperature (1)H NMR spectra of 1 give a single hydride resonance, which broadens at very low temperature due to rapid dipole-dipole relaxation (T(1) = 23 ms (750 MHz, 175 K) for the hydride resonance in 1). Low temperature (1)H NMR spectra of 1-d(2) allow the observation of decoalescence at 180 K into two resonances. The bound dihydrogen ligand exhibits hindered rotation with DeltaG(150) = 7.4 kcal/mol, but H atom exchange is still rapid at all accessible temperatures (down to 130 K). Density functional calculations confirm the dihydrogen/hydride structure as the ground state for the molecule and give estimates for the energy of two hydrogen exchange processes in good agreement with experiment. The presence of the C ansa bridge is shown to decrease the ability of the metallocene fragment to donate to the hydrogens, thus stabilizing the (eta(2)-H(2)) unit and modulating the barrier to H(2) rotation. |
| first_indexed | 2024-03-06T20:03:15Z |
| format | Journal article |
| id | oxford-uuid:280d3e16-342b-4330-8fc9-fa43945dfc79 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-06T20:03:15Z |
| publishDate | 2004 |
| record_format | dspace |
| spelling | oxford-uuid:280d3e16-342b-4330-8fc9-fa43945dfc792022-03-26T12:10:32ZStructure and dynamics of a dihydrogen/hydride ansa molybdenocene complex.Journal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:280d3e16-342b-4330-8fc9-fa43945dfc79EnglishSymplectic Elements at Oxford2004Pons, VConway, SGreen, MGreen, JHerbert, BHeinekey, DIn contrast to [Cp(2)MoH(3)](+), which is a thermally stable trihydride complex, the ansa-bridged analogue [(eta-C(5)H(4))(2)CMe(2)MoH(H(2))](+) (1) is a thermally labile dihydrogen/hydride complex. Partial deuteration of the hydride ligands allows observation of J(H)(-)(D) = 11.9 Hz in 1-d(1) and 9.9 Hz in 1-d(2) (245 K), indicative of a dihydrogen/hydride structure. There is a slight preference for deuterium to concentrate in the dihydrogen ligand. A rapid dynamic process interchanges the hydride and dihydrogen moieties in complex 1. Low temperature (1)H NMR spectra of 1 give a single hydride resonance, which broadens at very low temperature due to rapid dipole-dipole relaxation (T(1) = 23 ms (750 MHz, 175 K) for the hydride resonance in 1). Low temperature (1)H NMR spectra of 1-d(2) allow the observation of decoalescence at 180 K into two resonances. The bound dihydrogen ligand exhibits hindered rotation with DeltaG(150) = 7.4 kcal/mol, but H atom exchange is still rapid at all accessible temperatures (down to 130 K). Density functional calculations confirm the dihydrogen/hydride structure as the ground state for the molecule and give estimates for the energy of two hydrogen exchange processes in good agreement with experiment. The presence of the C ansa bridge is shown to decrease the ability of the metallocene fragment to donate to the hydrogens, thus stabilizing the (eta(2)-H(2)) unit and modulating the barrier to H(2) rotation. |
| spellingShingle | Pons, V Conway, S Green, M Green, J Herbert, B Heinekey, D Structure and dynamics of a dihydrogen/hydride ansa molybdenocene complex. |
| title | Structure and dynamics of a dihydrogen/hydride ansa molybdenocene complex. |
| title_full | Structure and dynamics of a dihydrogen/hydride ansa molybdenocene complex. |
| title_fullStr | Structure and dynamics of a dihydrogen/hydride ansa molybdenocene complex. |
| title_full_unstemmed | Structure and dynamics of a dihydrogen/hydride ansa molybdenocene complex. |
| title_short | Structure and dynamics of a dihydrogen/hydride ansa molybdenocene complex. |
| title_sort | structure and dynamics of a dihydrogen hydride ansa molybdenocene complex |
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