The First Isolable 2‐Silenolate

Abstract

Eine umgepolte Si‐C‐Doppelbindung liegt in dem ersten isolierten 2‐Silenolat vor. [(TMS)2SiC(O)tBu]−K+, eine bei Raumtemperatur thermisch stabile und röntgenkristallographisch charakterisierte Verbindung, enthält eine C‐O‐Doppelbindung und eine Si‐C‐Einfachbindung. Diese Ergebnisse lassen zusammen mit NMR‐Daten und der Ladungsverteilung darauf schließen, dass die Resonanzstruktur II dominiert. TMS=Trimethylsilyl.

Zwitterionic Silenes: Interesting Goals for Synthesis?

“…In this regard, 2-silenolates [8,9] are also interesting, since these systems can have a negative charge localized to Si, and depending on the extent of charge localization they may be designated as Si dÀ C d polarized silenes. Indeed, our recent X-ray crystal structure of 1-tBu-2,2-bis(trimethylsilyl)-2-silenolate revealed that this 2-silenolate is SiÀC singly bonded, [9] proving that they are strongly affected by reversed polarization.…”

Donor–Acceptor Adducts of a 1,3‐Disila‐2‐oxyallyl Zwitterion

“…The chemical shift of the SiC unit reminiscent of cyclic silenes with donor substitution at the carbon atom 14. 21 With its pronounced zwitterionic character, 5 is best described as an silenolate‐type species, intermediate between the keto form prepared by Ottosson and co‐workers20 and the enol form reported more recently by the Apeloig and Zhivotovskii groups 29…”

Silylenes, Silenes, and Disilenes: Novel Silicon‐Based Reagents for Organic Synthesis?

“…[23] This leads to a lower release in energy upon dimerisation, [24] and slower reaction rates for addition of water and alcohols to the silenes. [30] Since Brooks first report of a stable silene, efforts have been made to extend this concept to conjugated and cumulated systems. [28,29] In particular, Ottosson has exemplified this concept in a recent report describing an isolable silenolate 10 a although, having a very long Si À C bond (1.926 ), this is probably better described by the alternative resonance structure 10 b.…”

“…Alkenes, alkynes and ketones/ imines undergo a [2 + 2] cycloaddition reaction whilst dienes and a,b-unsaturated carbonyl compounds normally follow a [4 + 2] pathway. (7)] [30,51] whilst the Brook-type siloxysilene 27 undergoes preferential [2 + 2] cycloaddition with the highly electron deficient diene, dimethylhexadienedioate [Eq. For example, highly reversed polarised silenes and silenolates undergo exclusive [4 + 2] cycloadditions [see Eq.…”

“…The most favourable orbital interaction between two singlet silylenes occurs at nonclassical bent structures, whereas the most favourable interaction between two triplet silylenes leads to a planar structure. [30] Therefore, silenolates are closely related to silyl anions, species with a markedly pyramidal and hence potentially chiral silicon centre. This ability of substituents to influence the structural features of the Si=Si bond has been probed through quantum chemical calculations and an excellent correlation between AEDE ST and pyramidalisation angles as well as Si=Si bond length was found.…”