Semester

Fall

Date of Graduation

1998

Document Type

Thesis

Degree Type

MS

College

Eberly College of Arts and Sciences

Department

Chemistry

Abstract

Upon thermolysis in aromatic solvents, diarylzirconacenes and diaryltitanocenes form benzyne intermediates. Formation of the benzyne intermediate presumably occurs via H-atom abstraction of an ortho-H of an aryl ligand by the adjacent sigma-bonded aryl ligand to give the benzyne intermediate. The diphenylzirconocene benzyne intermediate can be stabilized by the addition of PMe3 to afford the PMe3 adduct which has been isolated and structurally characterized. This benzyne intermediate couples with a variety of unsaturated organic fragments including nitriles, alkenes, and acetylenes to form metallacyclic species and has found applications in organic synthesis. This benzyne also couples with tungsten hexacarbonyl to afford a Fischer-type metalloxycarbene complex.;Procedures for making the diphenyl precursors [(C5R4 )SiMe2(N-t-Bu)]M(C6H5)2 (R=H, Me; M = Ti, Zr) were developed. Separate coupling reactions involving two of the diphenyl precursors [(C5H4)SiMe2(N-t-Bu)]Ti(C 6H5)2 and [(C5Me4)SiMe 2(N-t-Bu)]Zr(C6H5)2, with diphenylacetylene affords [(C5H4)SiMe2(N-t-Bu)]Ti[(C6 H4)C(Ph)=C(Ph)] and [(C5Me4)SiMe 2(N-t-Bu)]Zr[(C6H4)C(Ph)=C(Ph)], respectively. These compounds have been characterized by 1H and 13 C NMR along with 2D COSY and HETCOR NMR measurements. The structure of [(C5H4)SiMe2(N-t-Bu)]Ti[(C6H 4)C(Ph) = C(Ph)] was also verified through X-ray structural analysis.;Comparison of the molecular structure to that of CpTi(C4)Ph) 4) reveals the two inequivalant bonds are considerably shorter than the two Ti-C bonds of CpTi(C4)Ph)4) in the literature. This difference can be attributed to the presence of the bifunctional ansa-monocyclopentadienyl ligand resulting in an increased electrophilicity of the d 0 Ti(IV) metal center.

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