Catalytic and stoichiometric reactivity of group 4 metal compounds supported by achiral and chiral aryloxide ligation

Matthew Grant Thorn, Purdue University

Abstract

Treatment of [TiCl4] with two equivalents of [ArOH] (ArO = substituted aromatic ring) leads to the formation of titanium dichlorides [(ArO)2TiCl2]. These dichlorides will undergo one electron reduction (Na/Hg) to afford Ti-Ti dimers [(ArO)2TiCl]2 and two electron reduction (Na/Hg or BunLi) in the presence of olefins to afford titanacyclopentanes that, in some cases, will catalytically dimerize styrene and cyclize 1,7-octadiene. These titanacyclopentanes will also react in a stoichiometric fashion with phophines, imines, ketones, and organic isocyanides to produce new titanacycles including ones that contain heteroatoms. Alternatively [(ArO)2TiCl2] can be alkylated to give [(ArO)2TiR2] (R = Me, CH2Ph). These dialkyl compounds will react with [B(C6F5)3] to form cationic species [(ArO)2TiR]+[RB(C 6F5)3]– which in some cases are active catalysts for the polymerization of α-olefins. Treatment of [(ArO)2TiR2] (ArO = 2,6-diphenylphenoxide; R = Me) with organic isocyanides leads to the formation of a bis(η2-iminoacyl) compound that undergoes intramolecular coupling to give the titanium enediamide [(ArO)2Ti(Ar′NC{Me}=C{Me}NAr′ )] (Ar′ = 2,6-dimethylphenyl). Treatment of [CpTiCl 3] with one equivalent of chiral or non-chiral [ArOH] leads to the formation of dichlorides [Cp(ArO)TiCl2] that can be reduced by one electron (Na/Hg) affording [Cp(ArO)TiCl]2 dimers or alkylated with two equivalents of MeLi to afford [Cp(ArO)TiMe2]. The reaction dynamics of the polymerization catalyst [Cp(ArO)TiMe]+[MeB(C6F 5)3]– (ArO = dl-2-(1-naphthyl)-4,6-di- tert-butylphenoxide), formed from the reaction of [Cp(ArO)TiMe 2] with [B(C6F5)3], show that exchange of diastereotopic methyl groups occurs on the NMR time scale. Treatment of [CpZr(CH2Ph)3] with one equivalent of [ArOH] leads to the formation of the dibenzyl species [Cp(ArO)Zr(CH2Ph)2] that will react with one or two equivalents or ButNC affording mono and bis(η2-iminoacyl) compounds respectively.

Degree

Ph.D.

Advisors

Rothwell, Purdue University.

Subject Area

Chemistry

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