The making and breaking of carbon-carbon and carbon-hydrogen bonds at Group 5 metal centers

Bryan David Steffey, Purdue University

Abstract

Compounds of the type Ta(OAr)$\sb{\rm 5-x}$(Ph)$\sb{\rm x}$ (OAr = 2,6-dimethyl, 2,6-diisopropyl phenoxide) were synthesized to study their structure and thermal stability. The isocyanide insertion chemistry of Ta(OAr)$\sb2$Ph$\sb3$ was studied. Migratory produced compounds of the type $\eta\sp2$-iminoacyl (Ta(OAr)$\sb2$(Ph)($\eta\sp2$-xyNCPh)$\sb2$) and mixed $\eta\sp2$-iminoacyl-$\eta\sp2$-imine (Ta(OAr)($\eta\sp2$-Bu$\sp{\rm t}$NCPh)($\eta\sp2$-Bu$\sp{\rm t}$NCPh$\sb2$)) were synthesized. Thermolysis of the mixed $\eta\sp2$-iminoacyl-$\eta\sp2$-imine compounds yielded an imido vinylic tantalum complex, Ta(OAr)$\sb2$(NBu$\sp{\rm t}$)(NCPhCPh$\sb2$). The reduction chemistry of tantalum and niobium aryloxide chlorides were studied. It was found that when the compounds, Ta(OAr-2,6Bu$\sp{\rm t}\sb2$)$\sb2$Cl$\sb3$, Ta(OAr-2,6Ph$\sb2$)$\sb3$Cl$\sb3$, and Nb(OAr-2,6Ph$\sb2$)$\sb3$Cl$\sb2$ were reduced with two equivalents of sodium the cyclometallated products, Ta(OC$\sb6$H$\sb3$CMe$\sb2$CH$\sb2$)$\sb2$Cl, Ta(O$\sim$C)$\sb2$(OAr-2,6PH$\sb2$), and Nb(O$\sim$C)(OAr-2,6Ph$\sb2$) were formed. The compound, Nb(OAr-2,6Ph$\sb2$)$\sb3$Cl$\sb2$, when reduced in the presence of H$\sb2$ was capable of hydrogenating one of the side phenyl rings of the 2,6-diphenylphenoxide ligand forming Nb(OAr-2,6Ph$\sb2$)$\sb2$(OAr-2,Ph-6-$\eta\sp4$-C$\sb6$H$\sb7$). Hydrogenation of this compound followed by hydrolysis would yield 2-cyclohexyl-6-phenylphenol and 2,6-dicyclohexylphenol.

Degree

Ph.D.

Advisors

Rothwell, Purdue University.

Subject Area

Chemistry

COinS