Synthesis of Lewis Acid–Base Adducts between Trialkyltriels and Heavy Bis(trimethylsilyl)pnictogenides

Lewis acid–base adducts between potassium bis(trimethylsilyl)pnictogenides [KPn(SiMe3)2](Pn = Sb and Bi) and trimethyltriels (EMe3 (E = Al, Ga, In) were synthesized and crystallized using 18-crown-6 as ligand for the potassium ions. In the course of these investigations, we were able to fully characterize a row of compounds of the type [K(18c6)(thf)0–2][Pn(SiMe3)2(EMe3)n] (n = 1, 2) with a different amount of Lewis acids bonding to the group 15 element. Moreover, we investigated the influence of the steric demand of the Lewis acids through the use of GaEt3 and GatBu3. All isolated compounds were examined by NMR spectroscopy, IR spectroscopy, elemental analysis and X-ray structure analysis. The obtained adducts of negatively charged [Pn(SiMe3)2]− fragments with Lewis acids represent a new class of compounds, which illustrate the HSAB concept and show the different extents of the inert pair effect between antimony and bismuth. In particular, the dative bonds between the higher homologues of both main groups have so far been underdeveloped in research.