A Neutral Germanium/Phosphorus Frustrated Lewis Pair and Its Contrasting Reactivity Compared to Its Silicon Analogue.

Chlorogermane (C2 F5 )3 GeCl with very electronegative pentafluoroethyl groups was converted with LiCH2 P(tBu)2 to obtain the intramolecular frustrated Lewis pair (FLP) (C2 F5 )3 GeCH2 P(tBu)2 , a neutral, germanium-based FLP. Its reactivity was compared to its silicon homologue (C2 F5 )3 SiCH2 P(tBu)2 . Both FLPs cleave NO but give cyclic (Si) and open-chain oxides (Ge). In reactions with HCl both FLPs gave the same adduct type in the solid state, while the proton seems more mobile in solution in the germanium case. Reactions with PhCNO and Me3 SiCHN2 result in ring-type adducts. The structures of (C2 F5 )3 GeCH2 P(tBu)2 and of five adducts with substrates were elucidated by X-ray diffraction. The study clearly showed the germanium compound to have a more moderate Lewis acidity compared to the silicon analogue.