| This dissertation discusses two independent projects. In the first project, reported in Chapter II, the synthesis and characterization of platinum-silicon four-membered rings of two different structural types are presented. The second project, discussed in Chapter III, focuses on the synthesis and characterization of a series of six-coordinate silicon-phosphine adducts. The summary of each project separately is as follows.; The reaction of Pt(PR3)3 (R = Et or Pr) and Si(Hex)H 3 (Hex = n-hexyl) gives [Pt(PR3)2SiH(n-Hex)] 2 (R = Et, 2.1a; R = Pr, 2.1b) and [(R 3P)Pt(μ-Si(μ-H)(Hex)(Pt(PR3)2)H)]2 (R = Et, 2.2a; R = Pr, 2.2b) The ratio of 2.1a to 2.2a is highly dependent on the reaction conditions whereas 2.1b is always the major product in the PPr3 substituted case. Evidence, which suggests that 2.1a and 2.1b are precursors to 2.2a and 2.2b, respectively, is presented. X-ray crystallography of the rings 2.1b and 2.2a shows they contain short Si-Si and Pt-Pt contacts, respectively. The 29Si NMR chemical shifts for the two types of rings differ by over 250 ppm. A 2D-NMR study of these rings has provided detailed coupling information, including information on the agostic Pt-H-Si hydride in 2.2a.; The systematic study of the reactions of SiCl4 with the monodentate phosphines PMe3, PEt3, PPr3, and the bidentate phosphine Et2PCH2CH2PEt2 (depe) to form hexacoordinate silicon adducts SiCl4(PR3) 2 is presented. In addition, the redistribution of HSiCl3 in the presence of a tertiary organophosphine to produce the same hexacoordinate silicon adducts and several redistribution products is established. Multinuclear NMR spectroscopy of all the adducts and X-ray crystallography of the PMe 3 and the PEt3 derivatives helped establish the structures. They are octahedral with the phosphine ligands in SiCl4(PMe 3)2, SiCl4(PEt3)2, and SiCl 4(PPr3)2 trans to one another. In contrast, due to structural constraints of the chelating phosphine, in SiCl4(depe) the ligands are cis. Only SiCl 4(PMe3)2 does not dissociate in solution at room temperature; consequently, variable-temperature NMR spectroscopy was used to obtain the spectra for SiCl4(PEt3)2, SiCl 4(PPr3)2, and SiCl4(depe). As expected for an octahedral compound, the chemical shifts for the adducts are upfield. Unexpected, however, was the unusually large one bond Si-P coupling constants for SiCl4(PMe3)2, SiCl4(PEt 3)2 and SiCl4(PPr3)2. |
