Oxyligands in triosmium carbonyl cluster compounds

Frauenhoff, Greg Robert

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https://hdl.handle.net/2142/22589 Copy

Description

Title

Oxyligands in triosmium carbonyl cluster compounds

Author(s)

Frauenhoff, Greg Robert

Issue Date

1989

Doctoral Committee Chair(s)

Klemperer, Walter G.

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

• Tridentate triply bridging phosphonate and arsonate clusters of the general formula ($\mu$-H)$\sb2$Os$\sb3$(CO)$\sb9$($\mu\sb3$, $\eta\sp3$-O$\sb3$ER) (E = P, R = Ph (1), Me; E = As, R = Ph) were prepared. The reaction scheme involved (1) generation of a solution containing a labile cluster species by reaction of H$\sb3$Os$\sb3$(CO)$\sb9$CH with neat trifluoromethanesulfonic (triflic) acid, (2) addition of a large excess of the appropriate free acid, and (3) water quench. A diffraction study of 1 showed the capping PhPO$\sb3$ ligand in a triply bridging tridentate coordination mode. Compound 1 is fluxional, and hydride migration was established as the low barrier dynamic process. Solid/solution structure equivalence for this class of clusters was demonstrated.
• The bis triflate cluster H$\sb2$Os$\sb3$(CO)$\sb9$(O$\sb3$SCF$\sb3$) was isolated (76% yield) from the triflic acid/H$\sb3$Os$\sb3$(CO)$\sb9$CH solution. It reacts with neat carboxylic acids to give clusters of the general formula ($\mu$-H)$\sb2$Os$\sb3$(CO)$\sb9$($\mu$, $\eta\sp2$-O$\sb2$CR)($\eta\sp1$-O$\sb2$CR) (R = H, CF$\sb3$) and ($\mu$-H)$\sb2$Os$\sb3$(CO)$\sb9$($\mu$, $\eta\sp2$-O$\sb2$CR) ($\eta\sp1$-O$\sb3$SCF$\sb3$) (R = H, CH$\sb3$, CF$\sb3$). A diffraction study of ($\mu$-H)$\sb2$Os$\sb3$(CO)$\sb9$($\mu,\ \eta\sp2$-O$\sb2$CCH$\sb3$)($\eta\sp1$-O$\sb3$SCF$\sb3$) showed the oxyligands in the trans axial configuration. This compound was found to be unreactive towards a variety of potential ligands (e.g. THF, NCCF$\sb3$, CO). It did react with halides and thiosulfate to give HOs$\sb3$(CO)$\sb{10}$X derivatives and H$\sb2$Os$\sb3$(CO)$\sb9$($\mu\sb3$-S) respectively. Reaction of H$\sb2$Os$\sb3$(CO)$\sb9$(O$\sb3$SCF$\sb3)\sb2$ with acetonitrile gave (($\mu$-H)$\sb2$Os$\sb3$(CO)$\sb9$(NCCH$\sb3)\sb3$) (O$\sb3$SCF$\sb3$) $\sb2$. This cluster exists as isomers at low temperature ($-30\sp\circ$C). These isomers interconvert by hydride migration.
• Os$\sb3$(CO)$\sb{12}$ chemisorbed to silica has been examined by magic-angle-spinning $\sp{13}$C NMR, and the structure of the chemisorbed species identified as ($\mu$-H)Os$\sb3$(CO)$\sb9$($\mu$-OSi=) by comparison with model compounds. Molecular models, such as ($\mu$-H)Os$\sb3$(CO)$\sb{11}(\eta\sp1$-O$\sb2$CCF$\sb3$), for possible intermediates in the chemisorption reaction were prepared.

Type of Resource

text

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Copyright 1989 Frauenhoff, Greg Robert

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