Some Silicon, Germanium, Tin, and Lead Analogues of Carbenes, Alkenes, and Dienes

Abstract

The isolation and characterization of thermally stable diaminocarbenes and diaminosilylenes has reawakened interest in the low‐coordinated compounds of group‐14 elements. The existence of these species is presumably due to interactions between the free electron pairs on the nitrogen atoms and the carbene carbon atom or the silicon atom. The present review is mainly concerned with the heavier analogues R2Ge:, R2Sn:, and R2Pb:, systems without intramolecular donor stabilization that owe their existence principally to steric shielding by the voluminous alkyl or aryl groups R. Dimerizations of these electron‐sextet molecules give rise to the double‐bond systems of the digermenes, distannenes, and diplumbenes; the latter species have for a long time been considered as being incapable of existence. The properties of these molecules are compared with the results of quantum chemical calculations. A separate section is devoted to the isomers of Si4R6, which include novel tetrasilacyclobutenes and the diene analogues, the tetrasilabuta‐1,3‐dienes.

What is the structure of Si3H5-?

“…So, what is the most stable structure of Si 3 H À 5 ? In general it is perceived that unsaturation is strongly disfavored for silicon species; however, many examples now exist (as do their Ge, Sn and Pb analogs) [18][19][20][21][22][23]. Furthermore, these examples of multiple bonded species illustrate a pervasive non-planarity in direct opposition to their carbon analogs.…”

Chemical manipulation of multifunctional hydrocarbons on silicon surfaces

“…In the views of chemists, Si=Si should obviously make a much better model of a silicon dimer on a Si(100)-2×1 surface than C=C. Although the comparison should definitely be treated with caution and although the number of chemical reactions studied with disilenes fades in comparison with the number of reactions investigated with alkenes, the predictions for -NO 2 , -NO, -N 3 , O 2 , and several other cycloaddition reactions with Si(100)-2×1 were accurate, based on the reactions with disilenes reported by Gillette et al in the late 1980s and in early 1990 s [37][38][39] and reactions of Si(100)-2×1 with alkenes and dienes were very similar to the chemistry reported by several groups [40][41][42][43][44] and reviewed by Weidenbruch [45][46][47][48]. Especially noteworthy is the fact that the processes following the initial attachment chemistry can also be compared quite reliably.…”

“…46. Schematic diagrams of plausible adsorption structures and thermal evolution products for (a) iso-dichloroethylene and (b) monochloroethylene exposed to Si(111)7 × 7 at room temperature.Figure reprintedwith permission from Ref [276]…”

Theoretical study on the addition reactions of MeOH, PhOH and PhSH to silastannenes

“…It belongs to the class of heteronuclear dimetallenes > E@E 0 < composed of different group 14 elements heavier than carbon [1,2]. In 1997, an intermediate compound with a Si@Sn double bond was proposed by Drost et al in the synthesis of the heteroleptic silylstannylenes [3].…”