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

Hidden silylium-type reactivity of a siloxane-based phosphonium-hydroborate ion pair

A new class of siloxane-based cations with hidden silylium-type reactivity is provided, which, in combination with an arylborate counteranion, initiates a highly selective para-C(sp²)-F defunctionalization of a perfluorinated aryl group. The hydrodefluorinated aryl borane is obtained as a crystalline solid via continuous sublimation during the reaction. The heterocyclic six-membered cation could be obtained single-crystalline after dehydrogenative anion exchange. DFT calculations give insight into the bonding within the siloxane-based cation and the mechanism of the ion pair reaction.

Molecular Scissors for Tailor-Made Modification of Siloxane Scaffolds

The controlled design of functional oligosiloxanes is an important topic in current research. A consecutive Si−O−Si bond cleavage/formation using siloxanes that are substituted with 1,2‐diaminobenzene derivatives acting as molecular scissors is presented. The method allows to cut at certain positions of a siloxane scaffold forming a cyclic diaminosilane or ‐siloxane intermediate and then to introduce new functional siloxy units. The procedure could be extended to a direct one‐step cleavage of chlorooligosiloxanes. Both siloxane formation and cleavage proceed with good to excellent yields, high regioselectivity, and great variability of the siloxy units. Control of the selectivity is achieved by the choice of the amino substituent. Insight into the mechanism was provided by low temperature NMR studies and the isolation of a lithiated intermediate.

The crystal structure of adamantylmethoxydiphenylsilane, C23H28OSi

C23H28OSi, monoclinic, P21/c (no. 14), a = 14.2882(11) Å, b = 17.8169(10) Å, c = 7.6201(6) Å, β = 103.780(8)°, V = 1884.0(2) Å3, Z = 4, R gt (F) = 0.0538, wR ref (F 2) = 0.1241, T = 173(2) K.