Files in this item



application/pdf8916246.pdf (7MB)Restricted to U of Illinois
(no description provided)PDF


Title:Oxyligands in triosmium carbonyl cluster compounds
Author(s):Frauenhoff, Greg Robert
Doctoral Committee Chair(s):Klemperer, Walter G.
Department / Program:Chemistry
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Chemistry, Inorganic
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.
Issue Date:1989
Rights Information:Copyright 1989 Frauenhoff, Greg Robert
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI8916246
OCLC Identifier:(UMI)AAI8916246

This item appears in the following Collection(s)

Item Statistics