New synthetic and structural chemistry supported by [Re6(u3-Se)8]2+ clusters

Abstract

Transition metal clusters are a unique class of chemical substances. Not only do they have well-defined molecular structures, they also exhibit interesting and potentially useful properties that are inherent to metal-metal bonded species. They may be viewed as atom-like building blocks with adjustable properties. Detailed in this dissertation are the efforts to develop synthetic methodologies necessary to bring a cluster system out of the limited sphere of fundamental cluster chemistry and into general synthetic applicability. Specifically, the design and synthesis, structural characterization, and synthetic applications of the cluster complexes of the [Re₆(μ₃-Se)₈]²⁺ core will be discussed. Chapter 1 provides necessary background information of the [Re₆(μ₃-Se)₈]²⁺ core-containing cluster system, the rationales of cluster-supported synthetic and structural chemistry, and the impetus for these endeavors. Chapter 2 details the synthetic applications of stereospecific complexes of the [Re₆(μ₃-Se)₈]²⁺ clusters for the assembly of nanoscopic multicluster arrays using molecular and supramolecular approaches. The synthesis and structural characterization of a triangle-shaped tricluster array and a tetracluster assembly composed of two hydrogen-bonded diclusters are described. Chapters 3 and 4 describe the synthesis of the [Re₆(μ₃-Se)₈]²⁺ core-containing cluster complexes with the water-soluble 1,3,5-triaza-7-phosphaadamantane (PTA) ligand and the chemistry of these cluster-complex ligands for the coordination of a variety of secondary metal ions. In Chapter 5, the supramolecular chemistry of the cluster-PTA complexes with Ag(I) is detailed. The coordination of Ag(I) to a cluster complex with two PTA ligands disposed trans- to each other produces a 2-dimensional, porous solid with nano-sized hydrophobic pores that are potentially useful for storage of hydrocarbons and for occlusion of certain substrates for activation and possible catalysis. Chapter 6 summarizes the efforts to synthesize cluster-polymer hybrid materials by using an initiating cluster complex for the controlled radical polymerization. The synthesis, spectroscopic and structural characterizations of a novel cluster complex with an initiating ligand are described. Preliminary results of its application for the controlled polymerization of methyl methacrylate are detailed. Chapter 7 draws a set of conclusions based on the results presented in Chapters 2-6 and elaborates on some future directions aimed at moving one step forward the cluster-supported synthetic and materials chemistry.