Highly Symmetrical Metal Alkoxides and Amines

无机化学、生物无机化学和金属有机化学计划中的这个项目关注的是对金属上的一些基团施加空间约束改变金属与其他基团相互作用时的性质的方式。这项工作的目标是利用空间约束来微调金属的化学和光谱性质，从而在金属催化中提供更好的控制和选择性。金属醇盐和酰胺将利用配体骨架来合成，当它们与金属结合时，配体骨架限制了给体原子的位置。例如，配体可能具有三脚架的形状，给体原子位于腿的末端，或者它可能是四齿的，给体原子的位置就像它们位于桌子的四条腿的末端一样。这些配合物中的金属原子周围存在着高度的局域对称性，与非环配体的配合物相比，导致配体与金属之间的pi键减少。由此产生的金属上负电荷的减少有望增加受约束配体的施主原子以外的其他配体的金属-配体成键，并增强双核LMML物种中的M-M多键，其中L是受约束的多齿配体。这些影响的大小将通过光谱学(异核核磁共振和IR)、结构(通过X射线结晶学)和化学(通过研究配合物经历配位球膨胀、小分子插入、烷烃置换和团簇形成反应的趋势)来研究。

This project in the Inorganic, Bioinorganic and Organometallic Chemistry Program is concerned with the way in which imposing steric constraint on some of the groups bound to a metal changes the properties of the metal in its interactions with other groups. The goal of the work is to use steric constraints to fine-tune the chemical and spectroscopic properties of the metal, and, for example, thereby to provide better control and selectivity in metal-based catalysis. Metal alkoxides and amides will be synthesized utilizing ligand frameworks which constrain the positions of the donor atoms as they bind to the metal. For example, the ligand may have the shape of a tripod, with the donor atoms at the ends of the legs, or it may be quadridentate with the donor atoms positioned as though they were at the ends of the four legs of a table. High local symmetry will exist around the metal atom in these complexes, resulting in a reduction of ligand-to-metal pi bonding compared to complexes of acyclic ligands. The resultant reduction in negative charge on the metal is expected to increase the metal-ligand bonding of ligands other than the donor atoms of the constrained ligand, and also to augment M-M multiple bonding in the dinuclear LMML species, where L is the constrained multidentate ligand. The magnitude of these effects will be studied spectroscopically (heteronuclear NMR and IR), structurally (via X-ray crystallography) and chemically (by studying the tendencies of complexes to undergo coordination sphere expansion, small molecule insertions, alkane metatheses and cluster-forming reactions).