A One‐Step Germole to Silole Transformation and a Stable Isomer of a Disilabenzene

Abstract

An unusual germole-to-silole transformation is described. As key intermediates hetero-fulvenes are formed which rearrange to more stable bicyclic carbene analogues. The so-formed germylenes undergo a reductive elimination yielding elemental germanium and siloles. In contrast, the analogous silylenes are stable at ambient conditions and were identified by MS spectrometry and NMR spectroscopy supported by the results of quantum mechanical calculations. These bicyclic silylenes are stable derivatives of the global minimum of the C Si H potential energy surface.

Radicals and Anions of Siloles and Germoles

“…These results can be transferred to siloles, the tris(trimethylsilyl)silyl substituent allowed the synthesis of the corresponding silolyl radical by reduction of silolyl chloride 5 (Scheme 3). [24] The reduction of germolyl chloride 1 c and silolyl chloride 5 were performed at low temperature in THF and after changing to a non-polar solvent such as hexane intensive EPR signals of the neutral radicals 3 c and 6 were detected. In the absence of air and moisture, the germolyl radical 3 c is stable in solution for weeks.…”

“…Increasing the size of the substituent R at the germanium atom from the tert ‐butyl to the tris (trimethylsilyl)silyl group finally allowed the detection of the germolyl radical 3 c in high concentrations by EPR spectroscopy after reduction of germolyl chloride 1 c (Scheme 1 ). [24] The trapping reaction with cyclohexadiene gives 1H ‐germole 4 in high yield. The identity of germole 4 was verified by independent synthesis from germole chloride 1 c (Scheme 2 ).…”

Disila- and digermabenzenes

“…Against this theoretical background, it seems feasible to assume that the synthesis of dimetallabenzenes, in contrast to some isolated valence isomers, 11 remained unsuccessful for a long time due to the lack of appropriate synthetic routes and sufficient kinetic stability to avoid self-oligomerization. 12 The unexpected thermodynamic stability of dimetallabenzenes relative to the other valence isomers should most likely be interpreted in terms of their considerable aromatic stabilization energy and/or the severe ring strain in the valence isomers.…”

Designing the Backbone of Hexasilabenzene Derivatives with a High Unimolecular Kinetic Stability

“…It is known that Si−Si π bonds are not as stable as C−C π bonds. This makes it difficult to synthesize compounds having Si−Si multiple bonds, and hence, considerable efforts have been made to design and synthesize such compounds . One of the most challenging synthetic targets in this field would be hexasilabenzene.…”

“…This makes it difficult to synthesize compounds havingS i ÀSi multiple bonds, and hence,c onsiderable effortsh ave been made to design and synthesize such compounds. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Oneo ft he most challenging synthetic targets in this field would be hexasilabenzene. It was shown theoretically that the monocyclic (SiH) 6 takes an on-planar chair-type geometry at its local minimum (MIN) on the potential energy surface( PES).…”