Part I. Synthesis and thermolysis of cyclopentadienyl and pentamethylcyclopentadienyl molybdenum dioxo alkoxides. Part II. Structural characterization of polysilicate intermediates formed during sol-gel polymerization

Part I. The molybdenum(VI) dioxo alkoxides ($\eta\sp5$-$C\sb5$H$\sb5$)MoO$\sb2$(OR) (R=CH$\sb2$CH$\sb3$, CH(CH$\sb3)\sb2$) and ($\eta\sp5$-C$\sb5$(CH$\sb3)\sb5$) MoO$\sb2$(OR) (R=CH$\sb3$, CH$\sb2$CH$\sb3$, CH(CH$\sb3)\sb2$) have been prepared and characterized. Single crystal X-ray diffraction studies showed that CpMoO$\sb2$(OCH$\sb2$CH$\sb3$) and Cp$\sp{*}$MoO$\sb2$(OCH$\sb2$CH$\sb3$) adopt the expected piano stool geometry. Oxygen-17 NMR chemical shifts of the terminal oxygens showed that Cp$\sp{*}$ is a better electron donor to the metal center than Cp. Oxygen-17 NMR also showed that for a series of compounds, CpMoO$\sb2$(OR) (R=Me, Et, i-Pr and t-Bu), electron donation increased in the order methoxide $<$ ethoxide $<$ 2-propoxide $<$ t-butoxide. Thermolysis of CpMoO$\sb2$ (OCH$\sb2$(CH$\sb3)\sb2$)) at 55$\sp\circ$C in CD$\sb3$CN produced, after a ten minute induction period in which no organic products were observed, equal amounts of acetone and 2-propanol. Thermolysis of CpMoO$\sb2$(OCH$\sb2$CH$\sb3$) produced ethanol and very small amounts of acetaldehyde. Acetaldehyde was found to react readily with CpMoO$\sb2$(OCH$\sb2$CH$\sb3$) to produce acetal and (CpMoO$\sb2)\sb2$O. Thermolysis of Cp$\sp{*}$MoO$\sb2$(OCH$\sb2$CH$\sb3$) at 80$\sp\circ$C in CD$\sb3$CN resulted in the formation of half an equivalent of ethanol, half an equivalent of tetramethylfulvene and 1/4 equivalent of (Cp$\sp{*}$Mo$\sb2$O$\sb4$(OCH$\sb2$CH$\sb3$)) $\sb2$. Single crystal X-ray structural analysis revealed that the latter complex was comprised of two Mo$\sb2$O$\sb4$ units linked by bridging alkoxide ligands and capped on each end by an $\eta\sp5$-C$\sb5$Me$\sb5$ ligand. The thermal behavior of the title compounds stands in contrast to the thermal decomposition of ((P$\sb3$O$\sb9$)MoO$\sb2$(OCH$\sb2$CH$\sb3$)) $\sp{2-}$, a model compound for alkoxides on a MoO$\sb3$ surface, which at 180$\sp\circ$C in CD$\sb3$CN produced, with no induction period, half an equivalent of acetaldehyde and half an equivalent of ethanol (Wang, R. C. Ph.D. Thesis, University of Illinois, 1988).

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

2011

Author dc:creator

• Rosenberg, Frank Stewart

Contributors dc:contributor

• Klemperer, Walter G.

• Chemistry, Analytical
• Chemistry, Inorganic
• Engineering, Chemical

Statement dc:rights

• Copyright 1990 Rosenberg, Frank Stewart

Language dc:language

eng

Identifier

AAI9026307
(UMI)AAI9026307

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/18981