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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 (t1/2≈30 min at 230 K, g=2.029, aav(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. [ABSTRACT FROM AUTHOR]

The first two persistent silenyl radicals (R2C=Si.−R), with a half‐life (t1/2) of about 30 min, were generated and characterized by electron paramagnetic resonance (EPR) spectroscopy. The large hyperfine coupling constants (hfccs) (a(29Siα)=137.5–148.0 G) indicate that the unpaired electron has substantial s character. DFT calculations, which are in good agreement with the experimentally observed hfccs, predict a strongly bent structure (∡C=Si−R=134.7–140.7°). In contrast, the analogous vinyl radical, R2C=C.−R (t1/2≈3 h), exhibits a small hfcc (a(13Cα)=26.6 G) and has a nearly linear geometry (∡C=C−R=168.7°). [ABSTRACT FROM AUTHOR]

Abstract: The first persistent platinum(I)‐centered radical was generated by homolytic cleavage of a Pt−HgSiR3 bond of a mercury‐substituted platinum(II) complex. The PtI radical was characterized by EPR spectroscopy, chemical trapping experiments, and density functional theory (DFT) calculations. [ABSTRACT FROM AUTHOR]

Tetrakis(trimethylsilyl)cyclobuta-1,3-diene ( 1) was subjected to a temperature-dependent EPR study to allow the first spectroscopic observation of a triplet diradical state of a cyclobutadiene ( 2). From the temperature dependent EPR absorption area we derive a singlet→triplet ( 1→ 2) energy gap, EST, of 13.9 kcal mol−1, in agreement with calculated values. The zero-field splitting parameters D=0.171 cm−1, E=0 cm−1 are accurately reproduced by DFT calculations. The triplet diradical 2 is thermally accessible at moderate temperatures. It is not an intermediate in the thermal cycloreversion of cyclobutadiene to two acetylene molecules. [ABSTRACT FROM AUTHOR]

We report the first direct spectroscopic observation by electron paramagnetic resonance (EPR) spectroscopy of a triplet diradical that is formed in a thermally induced rotation around a main-group π bond, that is, the SiSi double bond of tetrakis(di- tert-butylmethylsilyl)disilene ( 1). The highly twisted ground-state geometry of singlet 1 allows access to the perpendicular triplet diradical 2 at moderate temperatures of 350-410 K. DFT-calculated zero-field splitting (ZFS) parameters of 2 accurately reproduce the experimentally observed half-field transition. Experiment and theory suggest a thermal equilibrium between 1 and 2 with a very low singlet-triplet energy gap of only 7.3 kcal mol−1. [ABSTRACT FROM AUTHOR]