Platinum-silicon four membered rings and phosphine adducts of silicon tetrachloride.

摘要

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.