Synthesis, structure, and reactivity of novel higher-coordinate silicon(II) and silicon(IV) complexes

Die vorliegende Arbeit stellt einen Beitrag zur Chemie des höherkoordinierten Siliciums dar. Im Vordergrund standen die Synthese und Charakterisierung neuer neutraler penta- und hexakoordinierter Silicium(IV)-Komplexe sowie die Synthese, Charakterisierung und Untersuchung der Reaktivität eines neuartigen Donor-stabilisierten Silylens.This thesis is a contribution to the chemistry of higher-coordinate silicon. The main focus of this work was the synthesis and characterization of novel neutral five- and six-coordinate silicon(IV) complexes as well as the synthesis, characterization, and reactivity of a novel donor-stabilized silylene

Bis[<i>N</i>,<i>N</i>′‑diisopropylbenzamidinato(−)]silicon(II): Cycloaddition Reactions with Organic 1,3-Dienes and 1,2-Diketones

Reaction of the donor-stabilized silylene <b>1</b> (which is three-coordinate in the solid state and four-coordinate in solution) with organic 1,3-dienes (2,3-dimethyl-1,3-butadiene, 1,3-butadiene, (<i>E</i>,<i>E</i>)-1,4-diphenyl-1,3-butadiene, 2,3-dibenzyl-1,3-butadiene, 1,3-cyclohexadiene, or cyclo­octatetraene) and 1,2-diketones (3,5-di-<i>tert</i>-butyl-1,2-benzoquinone or 1,2-diphenyl­ethane-1,2-dione) leads to the formation of the respective cycloaddition products <b>2</b>–<b>9</b>. Compounds <b>2</b>–<b>9</b> were characterized by crystal structure analyses (<b>7</b> was studied as the hemi solvate <b>7</b>·​0.5<i>n</i>-C₆H₁₄) and NMR spectroscopic studies in the solid state and in solution. As the amidinato ligands can switch between a monodentate and bidentate coordination mode, for some of the cycloaddition products studied, the silicon coordination number in the solid state and in solution is different. For example, compound <b>4</b> is four- (<b>4a</b>) and six-coordinate (<b>4b</b>) in the solid state (isolated as a 1:1 cocrystallizate of <b>4a</b> and <b>4b</b>) and five-coordinate in solution. As demonstrated for the methanolysis of <b>2</b> (formation of <b>10</b>; proof of principle), compounds <b>2</b>–<b>7</b> with their reactive Si–N bonds are starting materials for the synthesis of promising mono- and bicyclic organosilicon compounds

Five-Coordinate Silicon(II) Compounds with Si–M Bonds (M = Cr, Mo, W, Fe): Bis[<i>N</i>,<i>N</i>′‑diisopropylbenzamidinato(−)]silicon(II) as a Ligand in Transition-Metal Complexes

Reaction of the donor-stabilized silylene <b>1</b> with [Cr­(CO)₆], [Mo­(CO)₆], [W­(CO)₆], or [Fe­(CO)₅] leads to the formation of the transition-metal silylene complexes <b>2</b>–<b>5</b>, which contain five-coordinate silicon­(II) moieties with Si–M bonds (M = Cr, Mo, W, Fe). These compounds were characterized by NMR spectroscopic studies in the solid state and in solution and by crystal structure analyses. These experimental investigations were complemented by computational studies to gain insight into the bonding situation of <b>2</b>–<b>5</b>. The nature of the Si–M bonds is best described as a single bond