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

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemistry

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Jefferis, Jesse M.

Contributors dc:contributor

• Girolami, Gregory S.

• Chemistry, Inorganic

Language dc:language

eng

Identifier

(MiAaPQ)AAI9990027

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/84483