Boris Tumanskii

The first isolated genuine germenyl lithiums (R₃Si)(1‐Ad)C=Ge(SiMetBu₂)(Li⋅2 L) (R₃Si=tBu₂MeSi, L=THF (1 a), or L=12‐crown‐4 (1 b) and R₃Si=tBuMe₂Si, L=THF (2 a), or L=12‐crown‐4 (2 b)), were synthesized by reaction of the corresponding acyl germanes 3 and 4, respectively, with tBu₂MeSiLi in THF at 70 °C. The novel 1 a and 2 b were characterized by NMR and UV/Vis spectroscopy, and also by X‐ray crystallography (r(C=Ge)=1.865 Å for 1 a and 1.877 Å for 2 b). Nucleophilic addition reaction of 1 a with MeI and a C−H insertion reactions to the C=Ge bond of 1 a, 2 a and 2 b, are reported. Oxidation of 1 a and 2 b (toluene, 230 K) produces the first persistent germenyl radicals (R₃Si)(1‐Ad)C=Ge⋅‐(SiMetBu₂) (R₃Si=tBu₂MeSi (13 a), R₃Si=tBuMe₂Si (13 b)), which were characterized by EPR spectroscopy (t_1/2≈30 min at 230 K, g=2.029, a_av(⁷³Ge) is 55.0G for 13 a and 60.2G for 13 b). The experimental EPR parameters and DFT calculations indicate that 13 a and 13 b have a strongly bent structure at Ge (calc. ∡(C=Ge−Si)=136.7° (13 a), 135.9° (13 b)), and that the unpaired electron has a substantial s‐character.

The first isolated genuine germenyl lithiums (R₃Si)(1‐Ad)C=Ge(SiMetBu₂)(Li⋅2 L) (R₃Si=tBu₂MeSi, L=THF (1 a), or L=12‐crown‐4 (1 b) and R₃Si=tBuMe₂Si, L=THF (2 a), or L=12‐crown‐4 (2 b)), were synthesized by reaction of the corresponding acyl germanes 3 and 4, respectively, with tBu₂MeSiLi in THF at 70 °C. The novel 1 a and 2 b were characterized by NMR and UV/Vis spectroscopy, and also by X‐ray crystallography (r(C=Ge)=1.865 Å for 1 a and 1.877 Å for 2 b). Nucleophilic addition reaction of 1 a with MeI and a C−H insertion reactions to the C=Ge bond of 1 a, 2 a and 2 b, are reported. Oxidation of 1 a and 2 b (toluene, 230 K) produces the first persistent germenyl radicals (R₃Si)(1‐Ad)C=Ge⋅‐(SiMetBu₂) (R₃Si=tBu₂MeSi (13 a), R₃Si=tBuMe₂Si (13 b)), which were characterized by EPR spectroscopy (t_1/2≈30 min at 230 K, g=2.029, a_av(⁷³Ge) is 55.0G for 13 a and 60.2G for 13 b). The experimental EPR parameters and DFT calculations indicate that 13 a and 13 b have a strongly bent structure at Ge (calc. ∡(C=Ge−Si)=136.7° (13 a), 135.9° (13 b)), and that the unpaired electron has a substantial s‐character.

Invited for the cover of this issue is the group of Thomas Müller at the University of Oldenburg. The image shows the calculated spin distribution of a persistent silacyclopentadienyl radical. Read the full text of the article at 10.1002/chem.202101415.

The synthesis of persistent sila‐ and germacyclopentadienyl (silolyl‐ and germolyl‐) radicals by careful stoichiometric reduction of the corresponding halides with potassium is reported. The radicals were characterized by EPR spectroscopy and trapping reactions. The reduction of tris(trimethylsilyl)silyl‐substituted halides was successful while smaller substituents (i. e., t‐Butyl, Ph) gave the corresponding dimers. The EPR spectroscopic parameter of the synthesized tetrolyl radicals indicate only small spin delocalization to the butadiene unit due to cross‐hyperconjugation. Silolyl‐ and germolyl anions are unavoidable byproducts and are isolated in the form of their potassium salts and characterized by X‐ray crystallography. The comparison of the molecular structures of two closely related potassium silolides provided an example for different coordination of the potassium cation to the silolyl anion (η¹ vs. η⁵ coordination) that triggers the switch between delocalized and localized states.

Phosphonyl radicals ([R₂PO]˙) and their adducts are proposed as intermediates in a number of important chemical and biological processes. Despite the great interest in these species, there are no examples of stable, isolated phosphonyl radicals or their adducts reported in the literature. Here we report the synthesis, EPR and theoretical study of stable, isolable cyclic (alkyl)(amino)carbene (cAAC)–phosphonyl radical adducts, [cAAC–P(O)R₂]˙ (R = OPrⁱ, Ph).

Reactions of carbon monoxide (CO) with tBu₂MeSiLi and (E)‐(tBu₂MeSi)(tBuMe₂Si)C=Si(SiMetBu₂)Li⋅2 THF (4) were studied both experimentally and computationally. Reaction of tBu₂MeSiLi with CO in hexane yields the first stable tetra‐silyl di‐ketyl biradical [(tBu₂MeSi)₂COLi]^.₂ (3). Reaction of 4 with CO yields selectively and quantitatively the first reported 1‐silaallenolate, (tBu₂MeSi)(tBuMe₂Si)C=C=Si(SiMetBu₂)OLi⋅THF (5). Both 3 and 5 were characterized by X‐ray crystallography and biradical 3 also by EPR spectroscopy. Silaallenolate 5 reacts with Me₃SiCl to produce siloxy substituted 1‐silaallene (tBu₂MeSi)(tBuMe₂Si)C=C=Si(SiMetBu₂)OSiMe₃. The reaction of 4 with CO provides a new route to 1‐silaallenes. The mechanisms of the reactions of tBuMe₂SiLi and of 4 with CO were studied by DFT calculations.

Herein is reported the first preparation of stable α-deuterium nitroxides of the IAPNO family.

CH-acids including o -carboranes add to C ₆₀ by a carbon atom via oxidative-ion-transfer reactions mediated by Mn(OAc) ₃ .

The first persistent platinum(I)‐centered radical was generated by homolytic cleavage of a Pt−HgSiR₃bond of a mercury‐substituted platinum(II) complex. The Pt^Iradical was characterized by EPR spectroscopy, chemical trapping experiments, and density functional theory (DFT) calculations.