Controlled Synthesis and Molecular Structures of Methoxy‐, Amino‐, and Chloro‐Functionalized Disiloxane Building Blocks

Abstract

Functionalized disiloxane units with defined structures are interesting molecular models for investigating the reactivity and chemoselectivity in transformations that are of interest in synthesis, surface chemistry, and materials science. (Mes)PhSi(OMe)2 (1) (Mes = mesityl) and (Mes)PhSiCl2 (5) were chosen as starting compounds for the controlled synthesis of methoxy‐, amino‐, and chloro‐functionalized unsymmetric disiloxanes. Two synthesis routes towards (Mes)PhSi(OMe)(OSiPh3) (3) were followed, one via the aminomethoxysilane (Mes)PhSi(OMe)(NC4H8) (2) and the other via the chlorodisiloxane (Mes)PhSiCl(OSiPh3) (6). The amino‐substituted disiloxane (Mes)PhSi(NC4H8)(OSiPh3) (4) was obtained from the chloro derivative 6 with N‐pyrrolidinyllithium, but the same reaction starting from compound 3 was not successful. All provided disiloxanes were structurally characterized by X‐ray crystallography.

Functional Group Variation in tert‐Butyldiphenylsilanes (TBDPS): Syntheses, Reactivities, and Effects on the Intermolecular Interaction Pattern in the Molecular Crystalline State

“…[15] This reluctance of reactivity has recently also been observed for mesityl-substituted methoxysiloxanes. [7] In the case of a secondary carbon atom connected to silicon, a high reactivity can still be found for methoxytriorganosilanes, as the easy substitution reaction on a 2-(methoxydiphenylsilyl)pyrrolidine derivative with phenyllithium shows. [4c] Similar to the methoxysilane (4), heating a solution of the aminosilane ( 5) and phenyllithium at reflux in toluene for 15 hours showed no conversion to tertbutyltriphenylsilane (3) (Scheme 1).…”

“…Since the pyrrolidinyl group now serves with additional CÀ H bonds, the missing CÀ H•••heteroatom hydrogen bonds in aminosilane 5 are apparently compensated by an increased number of isotropic H•••H interactions (82.8 %), the closest being found between H18B and H8 (2.318 Å) and between H18B and H17B (2.443 Å) (Figure 3, right). The NÀ Si bond length [1.7266( 17) Å] in 5 is a little longer than in pyrrolidinyl-substituted molecules with an NSiN [27] or NSiO [7,28] pattern. The planarization around the nitrogen atom [sum of angles: 356.9( 5)°] is also somewhat less pronounced in 5, which might be due to the missing interplay of lone electron pairs of two silicon-heteroatom bonds.…”

“…[6] We recently reported on the synthesis of monofunctionalized disiloxane building blocks and their reactivity and chemoselectivity in further transformations. [7] Driven by this previous study [7] and by our interest in structure-forming principles in molecular crystals, [8] we herein focus on silanes exhibiting a bulky and rigid tert-butyldiphenyl-silyl (TBDPS) backbone (tBuPh 2 SiÀ R, R = Cl, Ph, OMe, NC 4 H 8 ). The TBDPS moiety is a widely used effective and bulky protecting group, as has already been impressively demonstrated in many organic syntheses, [9] and became an integral part of new catalyst designs.…”

“…This can also provide useful information for understanding structure‐reactivity relationships and for building more complex functional molecular crystalline frameworks [6] . We recently reported on the synthesis of monofunctionalized disiloxane building blocks and their reactivity and chemoselectivity in further transformations [7] …”

Crystal Structure and Hirshfeld Surface Analysis of Trimethoxy(1‐naphthyl)silane – Intermolecular Interactions in a One‐Component Single‐Crystalline Trimethoxysilane

“…Not only a successive substitution of methoxy by aryl groups would shift this balance of stabilizing interactions, but also a change of the anisotropy of the aryl substituent. These findings can explain why, for example, phenyl‐, [10] mesityl‐, [32] cyclohexyl‐, [13b] tert ‐butyltrimethoxy‐silane, [10] and aminomethyl‐functionalized trimethoxysilanes [10,33] are liquids at room temperature, and why diphenyl‐, [10] 1‐naphthylphenyl‐, [11a] and mesitylphenyldimethoxysilane [7d] also show no tendency to crystallize at room temperature. On the other hand, methoxytriphenylsilane [34] forms single‐crystals at room temperature, which is associated with an increasing importance of directional C−H⋅⋅⋅π interactions and totally in line with the results described herein.…”