Heavier Carbonyl Olefination: The Sila-Wittig Reaction

The Wittig reaction is one of the most versatile tools in the repertoire of organic chemists. Thus, a broad variety of carbonyl compounds can be converted to tailor-made alkenes with phosphorus ylides under mild conditions. However, no comparable reaction has been reported for silanones, the silicon congeners of ketones. Here, we demonstrate for the first time the successful application of the Wittig olefination to iminosilyl­silanone 1. The selective formation of a series of silenes (R2SiCR2) via the sila-Wittig reaction revealed an unprecedented approach to otherwise elusive compounds. In addition, the highly reactive and zwitterionic nature of 1 was also susceptible to nucleophilic attacks and cycloaddition reactions by and with the phosphorus ylides. Our results therefore make another important contribution to discovering the differences and similarities between carbon and silicon

Heavier Carbonyl Olefination: The Sila-Wittig Reaction

The Wittig reaction is one of the most versatile tools in the repertoire of organic chemists. Thus, a broad variety of carbonyl compounds can be converted to tailor-made alkenes with phosphorus ylides under mild conditions. However, no comparable reaction has been reported for silanones, the silicon congeners of ketones. Here, we demonstrate for the first time the successful application of the Wittig olefination to iminosilyl­silanone 1. The selective formation of a series of silenes (R2SiCR2) via the sila-Wittig reaction revealed an unprecedented approach to otherwise elusive compounds. In addition, the highly reactive and zwitterionic nature of 1 was also susceptible to nucleophilic attacks and cycloaddition reactions by and with the phosphorus ylides. Our results therefore make another important contribution to discovering the differences and similarities between carbon and silicon

2‑Methoxyethylamino-bis(phenolate)yttrium Catalysts for the Synthesis of Highly Isotactic Poly(2-vinylpyridine) by Rare-Earth Metal-Mediated Group Transfer Polymerization

Highly isotactic poly­(2-vinylpyridine) (P2VP) was synthesized by the group transfer polymerization of the prochiral 2-vinylpyridine (2VP) with 2-methoxyethylamino­bis­(phenolate)yttrium complexes. Isotacticities of up to <i>P</i>_<i>m</i> = 0.92, narrow molecular weight distributions, and high molecular weights were achieved by steric modifications of the variable bisphenolate ligand structure. The resulting polymer samples were characterized by thermoanalysis (DSC, TGA), GPC, and ¹³C NMR. The origin of the isotactic microstructure was attributed to an enantiomorphic site control mechanism based on ¹³C NMR mechanistic studies and allowed new insights into ¹³C pentad assignments

Disilene–Silylene Interconversion: A Synthetically Accessible Acyclic Bis(silyl)silylene

Silylenes have recently shown fascinating reactivity patterns, which are normally observed almost exclusively for transition-metal complexes. In particular, very reactive representatives are considered to be promising candidates, which may become powerful and economical alternatives for catalytic applications in the future. Here, we present the isolation of an equilibrium mixture consisting of a tetrasilyldisilene and its isomeric bis­(silyl)­silylene, the first isolable silylene of this type. Preliminary investigations demonstrate the extreme inherent reactivity via facile small-molecule activation even under very mild conditions. Thus, the oxidative addition of challenging targets such as H2 and NH3 was achieved. In addition, by synthesizing donor-stabilized bis­(silyl)­silylenes we gained further insights into the disilene–silylene rearrangement by 1,2-silyl migrations. Thorough theoretical calculations support the observed experimental results

Disilene–Silylene Interconversion: A Synthetically Accessible Acyclic Bis(silyl)silylene

Silylenes have recently shown fascinating reactivity patterns, which are normally observed almost exclusively for transition-metal complexes. In particular, very reactive representatives are considered to be promising candidates, which may become powerful and economical alternatives for catalytic applications in the future. Here, we present the isolation of an equilibrium mixture consisting of a tetrasilyldisilene and its isomeric bis­(silyl)­silylene, the first isolable silylene of this type. Preliminary investigations demonstrate the extreme inherent reactivity via facile small-molecule activation even under very mild conditions. Thus, the oxidative addition of challenging targets such as H2 and NH3 was achieved. In addition, by synthesizing donor-stabilized bis­(silyl)­silylenes we gained further insights into the disilene–silylene rearrangement by 1,2-silyl migrations. Thorough theoretical calculations support the observed experimental results