Radical Activation of SiH Bonds by Organozinc and Silylzinc Reagents: Synthesis of Geminal Dizinciosilanes and Zinciolithiosilanes

Synthesis and Characterization of New Counterion-Substituted Triacylgermenolates and Investigation of Selected Metal–Metal Exchange Reactions

The synthetic process to obtain triacylgermenolates with alternated counterions by single-electron-transfer reactions or by a direct approach is described. The formation of these derivatives was confirmed by NMR spectroscopy and UV–vis spectroscopy. Moreover, metal–metal exchange reactions of potassium-substituted triacylgermenolate 2a with MgBr₂, ZnCl₂, and HgCl₂ are presented. Additionally, 2a was reacted with nBu₄NBr, which led to the formation of ammonia-substituted triacylgermenolate 8. Furthermore, we reacted 2a with HCl/Et₂O to obtain triacylgermane 9. Subsequently, we investigated the reaction of 9 with tBu₂Zn and tBu₂Hg. NMR spectroscopy, single-crystal X-ray crystallography, and UV–vis spectroscopy are employed for analysis of structural properties.

Direct synthesis and applications of solid silylzinc reagents

The increased synthetic utility of organosilanes has motivated researchers to develop milder and more practical synthetic methods. Silylzinc reagents, which are typically the most functional group tolerant, are notoriously difficult to synthesize because they are obtained by a pyrophoric reaction of silyllithium, particularly Me3SiLi which is itself prepared by the reaction of MeLi and disilane. Furthermore, the dissolved LiCl in silylzinc may have a detrimental effect. A synthetic method that can avoid silyllithium and involves a direct synthesis of silylzinc reagents from silyl halides is arguably the simplest and most economical strategy. We describe, for the first time, the direct synthesis of PhMe2SiZnI and Me3SiZnI reagents by employing a coordinating TMEDA ligand, as well as single crystal XRD structures. Importantly, they can be obtained as solids and stored for longer periods at 4 °C. We also demonstrate their significance in cross-coupling of various free alkyl/aryl/alkenyl carboxylic acids with broader functional group tolerance and API derivatives. The general applicability and efficiency of solid Me3SiZnI are shown in a wide variety of reactions including alkylation, arylation, allylation, 1,4-addition, acylation and more.

A metal-free radical technique for cross-linking of polymethylhydrosiloxane or polymethylvinylsiloxane using AIBN

A new method was developed for the metal-free cross-linking of silicone rubbers. This process uses azobisisobutyronitrile (AIBN) to selectively react with Si-H and vinyl groups as a free-radical initiator for the thermal curing of polymethylhydrosiloxane (PMHS) and polymethylvinylsiloxane (PMVS). The AIBN-initiated curing reaction between the Si-H groups of PMHS generated Si-O-Si and Si-Si cross-links. In contrast, PMVS was cured via the formation of C-C bonds through "methyl-vinyl" and "vinyl-vinyl" mechanisms. Curing reactions were performed at 80-120 °C in air and confirmed by 13C and 29Si solid state NMR analyses and swelling trials.

Tuning the Si-N Interaction in Metalated Oligosilanylsilatranes

Most known silatrane chemistry is concerned with examples where the attached silatrane substituent atom is that of an element more electronegative than silicon. The current study features silylated silatranes with a range of electropositive elements attached to the silyl group. The resulting compounds show different degrees of electron density on the silatrane-substituted silicon atom. This directly affects the Si-N interaction of the silatrane which can be monitored either by 29Si NMR spectroscopy or directly by single crystal XRD analysis of the Si-N distance. Within the sample of study the Si-N distance is increased from 2.153 to 3.13 Å. Moreover, the bis(trimethylsilyl)silatranylsilyl unit was studied as a substituent for disilylated germylene adducts.

Activation of Homolytic Si-Zn and Si-Hg Bond Cleavage, Mediated by a Pt(0) Complex, via Novel Pt-Zn and Pt-Hg Compounds

The thermally stable [(tBuMe2 Si)2 M] (M=Zn, Hg) generate R3 Si(.) radicals in the presence of [(dmpe)Pt(PEt3 )2 ] at 60-80 °C. The reaction proceeds via hexacoordinate Pt complexes, (M=Zn (2 a and 2 b), M=Hg (3 a and 3 b)) which were isolated and characterized. Mild warming or photolysis of 2 or 3 lead to homolytic dissociation of the Pt-MSiR3 bond generating silyl radicals and novel unstable pentacoordinate platinum paramagnetic complexes (M=Zn (5), Hg (6)) whose structures were determined by EPR spectroscopy and DFT calculations.