Multiple Silyl Exchange Reactions: A Way to Spirooligosilanes

Surefire generation of stannylpotassium: highly reactive stannyl anions and applications

Organometallic reagents such as organolithium and Grignard reagents have long been esteemed in chemical synthesis for their exceptional reactivity. In contrast, the application of their sodium and potassium counterparts has been comparatively sluggish, notwithstanding their augmented reactivity stemming from their heightened ionic character. This inertia persists due to the constrained accessibility of these heavy alkali metal reagents. In this study, our focus was directed towards devising a convenient and pragmatic approach for fabricating heavy alkali metal-based reagents, particularly those grounded in potassium. Herein, we present a novel, direct method for generating stannylpotassium (Sn-K) reagents through the simple combination of readily available silylstannanes and t-BuOK. Subsequently, the generated Sn-K reagents were effectively harnessed for stannylative substitution of aryl halides, furnishing an array of arylstannanes straightforwardly under transition metal-free conditions. This application distinctly underscores the potential utility of highly reactive Sn-K species, hitherto sparingly tapped into within the realm of synthetic organic chemistry. Furthermore, our investigation confirms that Sn-K reagents manifest notably superior reactivity compared with their well-established stannyllithium (Sn-Li) counterparts. This heightened reactivity can be ascribed to the increasing ionic character of Sn-K, which was supported by computational experiments.

Hydrogen-Bridged Oligosilanylsilyl Mono- and Oligosilanylsilyl Dications

Hydrogen‐bridged oligosilanylsilyl borates 8 [B(C₆F₅)₄], 9[B(C₆F₅)₄] and diborates 10 [B(C₆F₅)₄]₂ have been prepared by hydride transfer between α‐ω‐dihydrido‐ (11) and branched tetrahydrido‐oligosilanes (13) and trityl cation. The obtained cyclic intramolecularly stabilized silylium ions 8, 9 and bissilylium ion 10 were characterized by low temperature NMR spectroscopy supported by the results of density functional calculations. The branched Si−H−Si monocation 9 undergoes at low temperatures a fast degenerate rearrangement, which exchanges the Si−H groups with a barrier of 31 kJ mol⁻¹ via an antarafacial transition state. Reaction of the branched monocation 9 with a second equivalent of trityl cation or of the branched oligosilane 13 with two equivalents of trityl cation, gives at −80 °C the corresponding bissilylium ion 10, an example for a new class of highly reactive poly‐Lewis acids.

Novel diaminopropyl substituted organotin compounds

A novel synthetic pathway involving the desilylation of a tin trimethylsilyl species (Ph2Sn(SiMe3)2) towards nonprotected di(3-aminopropyl)tin dichloride ((H2N(CH2)3)2SnCl2) is described. Di(3-aminopropyl)tin dichloride is then converted to the respective dicarboxylates species (H2N(CH2)3)2Sn(OCOR)2 containing carboxylic acids of different lengths (R = –CH3, –(CH2)10CH3). Depending on the nature of R, discrete packing effects are observed in the solid state of di(3-aminopropyl)tin dicarboxylate derivatives. All the synthesized substances were characterized by 1H, 13C, and 119Sn nuclear magnetic resonance data and also single crystal X-ray analysis. These compounds are a promising class of substances for biological, pharmaceutical, and technical applications.

Recent Advances in Germanium-Based Photoinitiator Chemistry

Acylgermanes provide an outstanding photoinduced reactivity at very useful absorption wavelengths. This encouraged multidisciplinary research groups to utilize them as highly effective and non-toxic photoinitiators particularly for medical applications. In this Minireview, we present the most recent breakthroughs to synthesize acylgermanes. We also outline mechanistic aspects of photoinduced reactions of several acylgermane derivatives based on fundamental spectroscopic insights. These studies may aid future developments for tailor-made photoinitiators.

Tetraacylgermanes: Highly Efficient Photoinitiators for Visible-Light-Induced Free-Radical Polymerization

In this contribution a convenient synthetic method to obtain tetraacylgermanes Ge[C(O)R]₄ (R=mesityl (1 a), phenyl (1 b)), a previously unknown class of highly efficient Ge-based photoinitiators, is described. Tetraacylgermanes are easily accessible via a one-pot synthetic protocol in >85 % yield, as confirmed by NMR spectroscopy, mass spectrometry, and X-ray crystallography. The efficiency of 1 a,b as photoinitiators is demonstrated in photobleaching (UV/Vis), time-resolved EPR (CIDEP), and NMR/CIDNP investigations as well as by photo-DSC studies. Remarkably, the tetraacylgermanes exceed the performance of currently known long-wavelength visible-light photoinitiators for free-radical polymerization.