Structure and dynamics of a dihydrogen/hydride ansa molybdenocene complex
In contrast to [Cp2MoH3](+), which is a thermally stable trihydride complex, the ansa-bridged analogue [(eta-C5H4)(2)-CMe2MoH(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...
| Main Authors: | , , , , , |
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| Format: | Journal article |
| Language: | English |
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American Chemical Society
2004
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| _version_ | 1797095587519135744 |
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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 [Cp2MoH3](+), which is a thermally stable trihydride complex, the ansa-bridged analogue [(eta-C5H4)(2)-CMe2MoH(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 H-1 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 H-1 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)(double dagger) = 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 | 2024-03-07T04:29:59Z |
| format | Journal article |
| id | oxford-uuid:cdf78fee-df1c-4bf3-99cc-933cc7598c0d |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T04:29:59Z |
| publishDate | 2004 |
| publisher | American Chemical Society |
| record_format | dspace |
| spelling | oxford-uuid:cdf78fee-df1c-4bf3-99cc-933cc7598c0d2022-03-27T07:32:28ZStructure and dynamics of a dihydrogen/hydride ansa molybdenocene complexJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:cdf78fee-df1c-4bf3-99cc-933cc7598c0dChemistry & allied sciencesInorganic chemistryOrganometallic ChemistryEnglishOxford University Research Archive - ValetAmerican Chemical Society2004Pons, VConway, SGreen, MGreen, JHerbert, BHeinekey, DIn contrast to [Cp2MoH3](+), which is a thermally stable trihydride complex, the ansa-bridged analogue [(eta-C5H4)(2)-CMe2MoH(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 H-1 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 H-1 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)(double dagger) = 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 | Chemistry & allied sciences Inorganic chemistry Organometallic Chemistry 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 |
| topic | Chemistry & allied sciences Inorganic chemistry Organometallic Chemistry |
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