Pentafluoroethylated Compounds of Silicon, Germanium and Tin

Abstract

In this contribution we present an account on pentafluoroethylated compounds of silicon, germanium and tin. The pronounced electron-withdrawing effect of the pentafluoroethyl group leads to a markedly increased Lewis acidity at the central atom which results in the stabilization of hypervalent complexes, anionic element(II) species as well as remarkable reactivities of element-element and element-hydrogen bonds. By addition to unsaturated C-C bonds or by reaction with organic halides as well as transition-metal complexes the molecules bearing a pentafluoroethyl-element group are readily accessible. Moreover, the utilization of pentafluoroethyl groups facilitates the formation of donor-stabilized germylenes and stannylenes. A series of such compounds serves as suitable pentafluoroethylation reagents. Conversely to the well-studied trifluoromethyl derivatives these compounds frequently exhibit a higher thermostability, which allows a more convenient handling.

Synthesis, Properties, and Application of Tetrakis(pentafluoroethyl)gallate, [Ga(C2F5)4]−

“…In contrast to [B(CF 3 ) 4 ] − , tetrakis(trifluoromethyl)gallate, [Ga(CF 3 ) 4 ] − , was previously synthesized by the direct reaction of gallium trichloride, GaCl 3 , with hazardous bis(trifluoromethyl)cadmium, Cd(CF 3 ) 2 . Although the trifluoromethyl and pentafluoroethyl groups exhibit similar electron‐withdrawing abilities, compounds with pentafluoroethyl substituents are usually thermally and chemically considerably more stable than their CF 3 analogues . Syntheses of pentafluoroethyl derivatives of main group elements are based on the treatment of the respective halides with pentafluoroethyllithium, LiC 2 F 5 .…”

“…Although the trifluoromethyl and pentafluoroethyl groups exhibit similar electron‐withdrawing abilities, compounds with pentafluoroethyl substituents are usually thermally and chemically considerably more stable than their CF 3 analogues . Syntheses of pentafluoroethyl derivatives of main group elements are based on the treatment of the respective halides with pentafluoroethyllithium, LiC 2 F 5 . Thereby LiC 2 F 5 is freshly generated by deprotonation of pentafluoroethane, HC 2 F 5 , with n ‐butyllithium at −80 °C .…”

Synthese, Eigenschaften und Anwendung von Tetrakis(pentafluorethyl)gallat, [Ga(C2F5)4]−

“…Im Gegensatz zu [B(CF 3 ) 4 ] − wurde Tetrakis(trifluormethyl)gallat, [Ga(CF 3 ) 4 ] − , durch direkte Reaktion von Galliumtrichlorid, GaCl 3 , mit dem gefährlichen Bis(trifluormethyl)cadmium, Cd(CF 3 ) 2 , synthetisiert . Obwohl die Trifluormethyl‐ und Pentafluorethyl‐Gruppen ähnliche elektronenziehende Eigenschaften aufweisen, sind Verbindungen mit Pentafluorethyl‐Substituenten in der Regel thermisch und chemisch stabiler als ihre CF 3 ‐Analoga . Hauptgruppenelement‐Verbindungen mit Pentafluorethyl‐Substituenten werden bevorzugt durch die Reaktion der jeweiligen Elementhalogenide mit Pentafluorethyllithium, LiC 2 F 5 , synthetisiert .…”

“…Obwohl die Trifluormethyl‐ und Pentafluorethyl‐Gruppen ähnliche elektronenziehende Eigenschaften aufweisen, sind Verbindungen mit Pentafluorethyl‐Substituenten in der Regel thermisch und chemisch stabiler als ihre CF 3 ‐Analoga . Hauptgruppenelement‐Verbindungen mit Pentafluorethyl‐Substituenten werden bevorzugt durch die Reaktion der jeweiligen Elementhalogenide mit Pentafluorethyllithium, LiC 2 F 5 , synthetisiert . Dabei wird LiC 2 F 5 durch Deprotonierung von Pentafluorethan, HC 2 F 5 , mit n ‐Butyllithium bei −80 °C generiert .…”

Phosphido‐Bridged Di‐ and Trinuclear Palladium Complexes from Electron‐Poor Phosphanes R2PH (R = C2F5, C6F5, (CF3)2C6H3)

“…decreased σ‐bonding) and an increased Lewis acidity (i.e. enhanced π‐back‐bonding) . One means to measure this effect is the Tolman electronic parameter.…”