Hydrogenation of arenes by heterogeneous group 5 metal species

Robert D Profilet, Purdue University

Abstract

The Group 5 metal alkylidyne bridged compounds (($\rm Me\sb3SiCH\sb2)\sb2M$-($\mu$-$\rm CSiMe\sb3)\rbrack\sb2$ (M = Nb, Ta) supported on silica will catalyze the exhaustive hydrogenation of a variety of aromatic substrates including benzene, toluene, the three isomers of xylene, and naphthalene. The process is non-stereoselective for the hydrogenation of naphthalene to decahydronaphthalene and for the hydrogenation of xylenes to dimethylcyclohexanes producing a mixture of cis and trans isomers. Hydrogenation of the alkylidyne bridged dimer ((cb)$\sb2\rm Ta(\mu$-$\rm CSiMe\sb3)\sb2Ta(cb)\sb2$) (cbH = 9H-carbazole) in the presence of PMe$\sb2$Ph leads to the green hexahydride compound ((cb)(PMe$\sb2$Ph)$\sb2$(H)Ta($\mu$-$\rm H)\sb2\rbrack \sb2$ which contains a Ta-Ta distance of 2.5359(4) A and a Ta-N(carbazole)distance of 2.184(4) A. Reaction of ((cb)$\sb2\rm M(\mu$-$\rm CSiMe\sb3)\sb2M(cb)\sb2$) (M = Nb, Ta) with alkynes at 110$\sp\circ$ over a period of 3 days produced novel cyclic compounds which can be considered 1,3-dimetallabenzenes. Structural and spectroscopic studies show the central six-membered ring to puckered in the solid state but undergo flipping via a planar form in solution. The addition of aniline to ($\rm Ti(OC\sb6H\sb3Ph\sb2$-$\rm 2,6)\sb2Ph\sb2$) in hydrocarbon solvents leads to the formation of ($\rm Ti(OC\sb6H\sb3Ph\sb2$-$\rm 2,6)(NHPh)\sb2$). The aryl amido complexes ($\rm (ArO)\sb2Zr(NHC\sb6H\sb5)\sb2$) and) M(NHAr)$\sb4$) (M = Zr, Hf) (Ar = 2,6-diisopropylphenyl) were prepared by reaction of ($\rm (ArO)\sb2M(CH\sb3)\sb2$) and ($\rm M(CH\sb2C\sb6H\sb5)\sb4$) with the corresponding arylamines. The aryl amido compounds can be readily converted into five coordinate terminal imido derivatives by pyridine induced elimination of aryl amine. The room temperature addition of 3 equivalents of diphenylamine ($\rm Ph\sb2NH)$ to ($\rm M(CH\sb2C\sb6H\sb5)\sb4$) (M = Zr, Hf) in hydrocarbon solvents leads to formation of the ($\rm (Ph\sb2N)\sb3M(CH\sb2C\sb6H\sb5)$). Reaction of this complex with either xylyl- or terbutyl-isocyanide leads to the formation of iminoacyl complexes containing ancillary amido ligation.

Degree

Ph.D.

Advisors

Rothwell, Purdue University.

Subject Area

Chemistry|Organic chemistry

COinS