Synthesis, structure, and resolution of Group 4 metals containing 2-indenylphenoxide ligation

Luke Edward Turner, Purdue University

Abstract

The reaction of dilithiated 2-bromo-4,6,-di-tert-butylphenol with 1-indanone produces, on dehydration, 2-(inden-3-yl)-4,6-di-tert -butylphenol. Addition of one equivalent of the ortho-indenylphenol to Group 4 tetrakis(dialkylamides) results in elimination of two equivalents of amine to produce constrained geometry metal complexes, [M(OC6H 2{η5-Ind}-2-But2-4,6)(NR 2)2]. The coordination of the π-carbacyclic fragment to Group 4 metal centers gives rise to two enantiomeric outcomes, p- R and p-S, owing to the planar chirality of the indenyl ring. Reaction of racemic [Ti(OC6H2{η 5-Ind}-2-But2-4,6)(NR2) 2] with (S)-3,3′-bis(trimethylsilyl)-1,1 ′-binaphthyl-2,2′-diol produces a binaphthoxide complex as two diastereomers, (p-S, aS) and (p-R, a S), where “a” refers to the axial binaphthylchirality. The (p-S, aS) isomer comprises 90% of the product mixture, indicating isomerization of the complex to a predominate p-S indenyl ring geometry. Introduction of a methyl group at the C2 position of the indenyl ring results in restricted rotation about the indenyl-phenol axis, producing (aS) and (aR) atropisomers. Chelation of the rotationally rigid ligand to Group 4 metals produces (p-S)/(p-R) racemates that can be resolved with (S)-3,3′-bis(trimethylsilyl)-1,1 ′-binaphthyl-2,2′-diol. Contrary to the resolution of [Ti(OC6H2{η5-Ind}-2-Bu t2-4,6)(NR2)2], no isomerization is observed as the (p-S, aS) and (p- R, aS) diastereomers are equally populated. The chelation of two 2-indenyl phenol ligands to Group 4 metals results in a metallospirane with three diastereomeric possibities. The distribution of these isomers is dependent on the ligand substitution as well as the metal center. Reaction of 2-indenylphenol ligands with [CpTiCl3] results in chelation of the phenoxide fragment, while the indenyl ring “dangles” in (aR) and (aS) fixed geometries.

Degree

Ph.D.

Advisors

Rothwell, Purdue University.

Subject Area

Chemistry

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