This thesis reports on unsaturated silicon compounds, as well as excursions from these into germanium chemistry, single molecule electronics, and silyl protective group chemistry. Both experimental and computational investigations were performed. Potassium germenolates were synthesized through reactions of tris(timethylsilyl) substituted acyl- and carbamylgermanes with potassium tert-butoxide. The potassium germenolates calculated by density functional theory have pyramidal structures at the Ge atoms, similar to the Si in the corresponding potassium silenolates, indicating negative charge on germanium rather than on oxygen. Germenolates also display germyl anion-like reactivity instead of germene-like reactivity as they are alkylated at Ge and initiate anionic polymerization of dienes rather than form [4+2] cycloadducts. The NMR chemical shifts reveal more negative charge at Ge in germenolates than at Si in analogous silenolates. Computations indicate that silabenzenes and silapyridines are reachable via [1,3]-silyl shifts from cyclic conjugated acylsilanes. Differently sized substituents were considered to prevent dimerizations, and 1-triisopropylsilyl-2-triisopropylsiloxy-6-tert-butylsilabenzene is a good synthetic target. Computations also show that silaphenolates are species with negative charge primarily localized at oxygen atom. Their planar structures, bond lengths, and NICS values reveal significant influence of aromaticity. Electrostatic repulsion should increase their stability, however, steric bulk is also important. Furthermore, it was found computationally that [1,3]-silyl shift from an acylsilane to a silene can function as a molecular switch reaction. Conductance calculations support this proposition.   Finally, tris(trimethylsilyl)silylmethaneamide (hypersilylamide) together with catalytic amounts of triflic acid were found to be efficient for protection of a range of alkyl and aryl alcohols and thiols in good to excellent yields. The protocol can be used to protect the less hindered OH group of a diol and has a broad functional group tolerance. A catalytic cycle is proposed. Hypersilyl protected alcohols and thiols are deprotected efficiently under photolytic conditions.

<p>This thesis describes synthesis and reactivity studies of 2-amino-2-siloxysilenes and 2-silenolates, species that are strongly influenced by reversed Si=C bond polarization, i.e. an Si^δ-=C^δ+ polarization as compared to the natural Si^δ+=C^δ- polarization. Because of the reversed polarization, the 2-amino-2-siloxysilenes are zwitterions and the 2-silenolates are predominantly described by the resonance structure with the negative charge at Si. </p><p>Transient zwitterionic 2-amino-2-siloxysilenes are formed thermolytically from carbamylpolysilanes (<i>tris</i>(trimethylsilyl)silylamides) and trapped with 1,3-dienes in nearly quantitative yields. These silenes have structure and reactivity characteristics that differ from earlier studied Si=C bonded compounds. They are thermodynamically stable toward dimerization and react with 1,3-dienes to give exclusively [4+2] cycloadducts. Their reactions with 1,3-dienes proceed in accordance with inverse electron demand (IED) Diels-Alder reactions which is explained by the electron-rich nature of these silenes. The 2-amino-2-siloxysilenes are also less reactive toward alcohols than earlier silenes. Hence, alcohols do not react with 2-amino-2-siloxysilenes but with the silene precursor, the carbamylpolysilanes, leading to alkoxysilanes in high yields. The latter reaction represents a novel base-free synthetic protocol for protection of primary and secondary alcohols with the fluoride resistant but photolabile <i>tris</i>(trimethylsilyl)silyl group.</p><p>Another class of formally Si=C bonded compounds, metal 2-silenolates, has been formed in high yields using a novel facile method. Reaction of acyl- and carbamylpolysilanes with potassium <i>tert</i>-butoxide in tetrahydrofurane gives potassium 2-silenolates. The potassium 2-silenolates are stable at room temperature, in contrast to earlier lithium 2-silenolates that degrade rapidly at ambient temperature. The first crystallisable complex of a 2-silenolate was formed and characterized by X-ray crystallography. This 2-silenolate has a pyramidal central Si (ΣSi = 317.8°), and an Si-C single rather than Si=C double bond (r(SiC) = 1.926 Å). The potassium 2-silenolates give exclusively Si alkylated products with alkyl halides and only [4+2] cycloadducts with 1,3-dienes.</p>

This thesis describes synthesis and reactivity studies of 2-amino-2-siloxysilenes and 2-silenolates, species that are strongly influenced by reversed Si=C bond polarization, i.e. an Siδ-=Cδ+ polarization as compared to the natural Siδ+=Cδ- polarization. Because of the reversed polarization, the 2-amino-2-siloxysilenes are zwitterions and the 2-silenolates are predominantly described by the resonance structure with the negative charge at Si. Transient zwitterionic 2-amino-2-siloxysilenes are formed thermolytically from carbamylpolysilanes (tris(trimethylsilyl)silylamides) and trapped with 1,3-dienes in nearly quantitative yields. These silenes have structure and reactivity characteristics that differ from earlier studied Si=C bonded compounds. They are thermodynamically stable toward dimerization and react with 1,3-dienes to give exclusively [4+2] cycloadducts. Their reactions with 1,3-dienes proceed in accordance with inverse electron demand (IED) Diels-Alder reactions which is explained by the electron-rich nature of these silenes. The 2-amino-2-siloxysilenes are also less reactive toward alcohols than earlier silenes. Hence, alcohols do not react with 2-amino-2-siloxysilenes but with the silene precursor, the carbamylpolysilanes, leading to alkoxysilanes in high yields. The latter reaction represents a novel base-free synthetic protocol for protection of primary and secondary alcohols with the fluoride resistant but photolabile tris(trimethylsilyl)silyl group. Another class of formally Si=C bonded compounds, metal 2-silenolates, has been formed in high yields using a novel facile method. Reaction of acyl- and carbamylpolysilanes with potassium tert-butoxide in tetrahydrofurane gives potassium 2-silenolates. The potassium 2-silenolates are stable at room temperature, in contrast to earlier lithium 2-silenolates that degrade rapidly at ambient temperature. The first crystallisable complex of a 2-silenolate was formed and characterized by X-ray crystallography. This 2-silenolate has a pyramidal central Si (ΣSi = 317.8°), and an Si-C single rather than Si=C double bond (r(SiC) = 1.926 Å). The potassium 2-silenolates give exclusively Si alkylated products with alkyl halides and only [4+2] cycloadducts with 1,3-dienes.