University of Illinois Urbana-Champaign

New Chemistry of Transition Metal Alkyls and Hydrides: Bonding and Reactivity

Jefferis, Jesse M.

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Description

Title
New Chemistry of Transition Metal Alkyls and Hydrides: Bonding and Reactivity
Author(s)
Jefferis, Jesse M.
Issue Date
2000
Doctoral Committee Chair(s)
Girolami, Gregory S.
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Inorganic
Language
eng
Abstract
Protonation of the osmium(II) hydrides (C5Me5)Os(PR 3)2H with tetrafluoroboric acid affords the corresponding osmium(IV) dihydride complexes of stoichiometry [(C5Me5)Os(PR 3)2H2+], where PR3 = PMe3, PEt3, PPh3, 1/2 dmpe, 1/2 dmpm, 1/2 dppm, or 1/2 dpdtm (where dmpe = 1,2-bis(dimethylphosphino)ethane, dmpm = bis(dimethylphosphino)methane, dppm = bis(diphenylphosphino)methane, and dpdtm = (diphenylphosphino)(di-p-tolylphosphino)methane. In the cisoid compounds [(C5Me5)Os(dmpm)H2 +] and [(C5Me5)Os(dppm)H2 +], the two hydride ligands undergo chemical exchange on the NMR time scale with activation free energies of 17.5 and 16.9 kcal mol-1 , respectively. Protonation of all the (C5Me5)Os(PR 3)2H complexes at low temperature affords the cisoid isomers, which must be the kinetic products. For the compounds [(C5Me 5)Os(PMe3)2H2+] and [(C5Me5)Os(PPh3)2H2 +], the cisoid isomers convert to the transoid isomers by two pathways, one unimolecular and one bimolecular; the latter involves intermolecular hydride exchange between the dihydride cations and the neutral monohydride.
Graduation Semester
2000
Type of Resource
text
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