Aromaticity of Group 14 Organometallics: Experimental Aspects

Abstract

The long story of aromatic compounds has extended over almost two centuries, since the discovery by Faraday of "bicarburet of hydrogen", or C(6)H(6), now called benzene. Since then, the chemistry of aromatic compounds has been developed extensively; this is reflected in the synthesis of novel classes of aromatic derivatives including charged species, nonclassical (Möbius, three-dimensional, homo-, metalla-) aromatics, and fullerenes. The theory of aromaticity has also undergone a spectacular evolution since the first definition of aromaticity by Hückel; the classification of aromaticity now requires the consideration of versatile criteria: energetic, structural, magnetic, among others. In this Review, we discuss the current state of affairs in the chemistry of aromatic compounds of the heavier Group 14 elements, the latest experimental achievements, as well as future prospects in the field.

The Versatile Chemistry of Disilenides: Disila Analogues of Vinyl Anions as Synthons in Low-valent Silicon Chemistry

“…36 Furthermore, this isomerization provided a further example of the unique role of lithium ion pairs for the stability of negatively charged aromatic species involving silicon and therefore their degree of aromaticity. 37 Only a preliminary X-ray structure of 18 was qualitatively discussed in the report mentioning a significantly more acute endocyclic bond angle at the central silicon atom compared to 17, which again was attributed to the high s character of the lone pair.…”

Structure and Reactions of an Isolable Ge=Si Doubly Bonded Compound, Tetra(t-butyldimethylsilyl)germasilene

“…Synthesis and structure of stable unsaturated compounds of heavy group-14 elements is one of the primary subjects of both experimental and theoretical main-group element chemistry; see reviews of experimental [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] and theoretical aspects [20][21][22][23][24]. Since the first synthesis of stable digermenes and distannenes by Lappert et al [25][26][27] and a stable disilene by West et al [28], a number of heavy alkenes (R 2 E=ER 2 , E, E' = Si, Ge, Sn, and Pb) have been synthesized and their unusual structures and properties have been revealed.…”

Diagnosis of the σ-, π- and (σ+π)-Aromaticity by the Shape of the NICSzz-Scan Curves and Symmetry-Based Selection Rules

“…The collection of recent reviews in the topic of aromaticity/antiaromaticity [1][2][3][4][5][6][7][8][9] shows a rather large consensus appear in the computation or experimental tests for the diagnosis of the aromaticity/antiaromaticity (structural, electronic, magnetic, thermodynamic and kinetic diagnostic tools) whereas the mechanisms themselves still remain open to the debate. Various criteria have been used to judge aromaticity/antiaromaticity, but no one is satisfactory, particularly in predicting the orbital type (s-, p-, d-, f-orbital) of aromaticity [10].…”