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Date of Award

6-23-2014

Document Type

Thesis and Dissertation-ISU Access Only

Degree Name

Master of Science (MS)

Department

Department of Chemistry

First Advisor

Lisa F. Szczepura

Abstract

The field of cluster chemistry is relatively young when compared to studies on single metal coordination complexes. The fundamental studies on the hexanuclear cluster core will provide a better understanding of the differences from single metal center. Research described in this thesis focuses on developing synthetic methodologies towards the preparation of hexanuclear clusters containing novel types of N-donor terminal ligands and subsequently studying the reactivity of these systems.

Previous studies in the Szczepura group have shown that nitrile groups can be activated by the [Re6Se8]2+ cluster to react with inorganic azides to form tetrazolate rings. The initial goal of the reaction was to substitute the nitrile with azide, however, cycloaddition was observed. This unexpected result emphasizes the need for further studies involving the synthesis and reactivity of various nitrile ligands. Two complexes containing a nitrile group coordinated to a hexarhenium cluster, [Re6Se8(PEt3)5(p-nitrobenzonitrile)](SbF6)2∙acetone and [Re6Se8(PEt3)5(NCC(CH3)3)](SbF6)2∙NCC(CH3)3, were studied by X-ray diffraction. These structures are reported here.

The formation of tetrazolate rings on the [Re6Se8]2+ cluster core sparks interest that other cycloaddition reactions may be feasible. Two new hexarhenium clusters, [Re6Se8(PEt3)5(NC(CH3)O(CH2)2)](BPh4)2 and [Re6Se8(PEt3)5(NC(CH3)O(CH2)3)](BPh4)2, containing oxazoline and oxazine ligands were isolated in high yield and purity. Initial isolation of these cluster complexes by a former student in the Szczepura group resulted in impure materials due to reaction with halide counter ions. However, metathesis with the tetraphenylborate ion enabled us to improve the purity and yield of these products.

The oxazoline and oxazine ligands are neutral and can be removed via irradiation with a Hg/Xe lamp. Details of the ring removal studies via irradiation, along with preliminary studies involving the potential catalytic reactivity of these hexarhenium clusters will be discussed.

Comments

Imported from ProQuest Ren_ilstu_0092N_10313.pdf

Page Count

87

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