Radical cations of phenyl silatrane

Electrooxidation of Hypercoordinated Derivatives of Silicon and Reactivity of Their Electrogenerated Cation Radicals: 1-Substituted Silatranes

Electrochemical oxidation of 1-R-substituted silatranes 1 (R = Me, vinyl, (CH₂)₂CN, CH₂Ph, CH₂(C₁₀H₇), Ph, C₆H₄Me, p-Cl-C₆H₄, Cl)-classical representatives of pentacoordinated silicon compounds-and the formation of their short living cation radicals upon reversible or quasi-reversible one-electron withdrawal were studied by means of cyclic and square-wave voltammetry, faradaic impedance spectroscopy and real-time temperature-dependent EPR spectroelectrochemistry supported by DFT B3PW91/6-311++G(d,p) (C-PCM, acetonitrile) calculations. The main reaction responsible for the decay of 1^+• is shown to be their deprotonation, and ways of increasing the stability of these species are proposed.

The hierarchy of ab initio and DFT methods for describing an intramolecular non-covalent SiN contact in the silicon compounds using electron diffraction geometries

In the series of silatranes XSi(OCH2CH2)3N, 1 (X = Me, 1a; H, 1b; F, 1c) with the known gas electron diffraction (GED) structures, the problematic geometry of 1-methylsilatrane 1a has been revised. In particular, the new value of the SiN distance (dSiN) in 1a turned out to be ∼0.06 Å longer than the generally accepted one. This dSiN resolves the long-standing contradiction between the data of the structural and spectral experiments regarding the sensitivity of 1 to the medium effect. We also performed the ab initio and DFT study of the combined series of silatranes 1a-c, silylalkylamines H3Si(CH2)3NMe2 (2a) and F3SiCH2NMe2 (2b), silylhydrazines F3SiN(Me)NMe2 (2c) and F3SiN(SiMe3)NMe2 (2d), and silyloxyamines ClH2SiONMe2 (2e,f), (F3C)F2SiONMe2 (2g,h) and F3SiONMe2 (2i), in which the GED dSiN values are in a wide range of 2-3 Å. None of the involved quantum chemical methods has succeeded in reproducing all the experimental gas-phase dSiN values in 1a-c, 2a-i with an acceptable accuracy (0.01-0.03 Å). The problems of the used methods, primarily CCSD with the Pople basis sets, are caused by four molecules with the geminal SiNN and SiON fragments (2d,f-i) and dSiN < 2.3 Å. A reasonable hierarchy of computationally accessible theory levels for studying the physicochemical manifestation of the non-covalent intramolecular SiN interactions can be constructed only at dSiN > 2.3 Å: MP2 < PBE0 ∼ B3PW91 ∼ SCS-MP2 < CCSD < CCSD(T).

Oligosilanylated Silocanes

A number of mono- and dioligosilanylated silocanes were prepared. Compounds included silocanes with 1-methyl-1-tris(trimethylsilyl)silyl, 1,1-bis[tris(trimethylsilyl)silyl], and 1,1-bis[tris(trimethylsilyl)germyl] substitution pattern as well as two examples where the silocane silicon atom is part of a cyclosilane or oxacyclosilane ring. The mono-tris(trimethylsilyl)silylated compound could be converted to the respective silocanylbis(trimethylsilyl)silanides by reaction with KOtBu and in similar reactions the cyclosilanes were transformed to oligosilane-1,3-diides. However, the reaction of the 1,1-bis[tris(trimethylsilyl)silylated] silocane with two equivalents of KOtBu leads to the replacement of one tris(trimethylsilyl)silyl unit with a tert-butoxy substituent followed by silanide formation via KOtBu attack at one of the SiMe3 units of remaining tris(trimethylsilyl)silyl group. For none of the silylated silocanes, signs of hypercoordinative interaction between the nitrogen and silicon silocane atoms were detected either in the solid state. by single crystal XRD analysis, nor in solution by 29Si-NMR spectroscopy. This was further confirmed by cyclic voltammetry and a DFT study, which demonstrated that the N-Si distance in silocanes is not only dependent on the energy of a potential N-Si interaction, but also on steric factors and through-space interactions of the neighboring groups at Si and N, imposing the orientation of the pz(N) orbital relative to the N-Si-X axis.

Zn-mediated decarboxylative carbagermatranation of aliphatic N-hydroxyphthalimide esters: evidence for an alkylzinc intermediate

Alkyl nucleophiles synthesized by decarboxylation of the corresponding N-hydroxyphthalimide esters (NHP esters) would inherit the complex structure of natural carboxylic acids and result in useful cross-coupling fragments. Herein, we report the synthesis of alkyl carbagermatranes via Zn-mediated decarboxylation of NHP esters without Ni catalysis or photocatalysis. Mechanistic studies indicate that an alkyl zinc intermediate was involved; however, the generation of alkyl zinc will be inhibited in the presence of Ni. Hence, this study provides valuable resolution to the perplexing problem about whether organozinc was involved in recently emerging catalytic systems of NHP ester-Zn. Meanwhile, alkyl zinc reagents from NHP esters are compatible with aryl/alkyl bromides and iodides; therefore the scope of carbagermatranation in this work precedes that of in situ-generated organozinc from alkyl halides.