Trimethylsilylated allyl complexes of groups I – V: formation, structure, and catalytic reactions

Abstract

Trimethylsilylated allyl ligands allow for the synthesis of thermally stable allyl complexes with metals throughout the periodic table. In this work, bulky allyl ligands were used in the synthesis of complexes with early transition and lanthanide metals. Structural variations in these complexes and their use as initiators in the polymerization of methyl methacrylate were explored. The synthesis and structures of late lanthanide allyl complexes and the effect of varying the reaction precursors is explored in Chapter I. This chapter also highlights similarities and differences between the lanthanide chemistry of cyclopentadienyl and bulky allyl ligands. In the course of this work, novel dimethysilylene and allylidene and diholmium complexes were isolated, and their structures are described. Chapter II describes the synthesis of diallylytterbium complexes and their subsequent treatment with terpyridyl ligands. These adducts exhibit internal charge transfer from the diamagnetic Yb(II) f14 metal center to the lowest unoccupied molecular orbital (LUMO) on the N-heterocylic ligand. Varying the substituents on the allyl ligands influences the electronics of these complexes, an effect that was characterized with various spectroscopic methods. In Chapter III, the use of allyl metal complexes as catalysts for the polymerization of methyl methacrylate was investigated. In general, Group I and II allyl complexes exhibited higher activity than that of lanthanide species. Heightened catalytic activity was observed in mixed metal lanthanate complexes, presumably due to the presence of a Group I metal (Li or K) in the composition of the catalyst. Chapter IV explores the use of density functional theory calculations to predict 89Y NMR chemical shifts. The shift for a wide variety of organoyttrium complexes was cal-culated and compared with literature values. This method was used to identify the structure of Y[1,3-(SiMe3)2C3H3]3, which was synthesized despite a mismatch in stoichiometry of the starting materials. A unique divanadium complex with three bridging trimethylsilylated allyl ligands and one terminal chloride atom was synthesized, and its structure is described in Chapter V. Computational studies of the importance of the trimethylsilyl groups were performed and are also described.