Study of Silyl Cations Bearing an Aryldiamine Pincer Ligand

In this paper, we describe two routes to prepare silyl cations with at least one Si−H bond by using the bis-chelating ligand C6H3(CH2NMe2)2-2,6. The first is the reaction between a pentacoordinate dihydrosilane ArRSiH2 [Ar = (C6H3(CH2NMe2)2-2,6] and an electrophile. The second is the reaction of the lithium derivative ArLi with a dichlorohydrosilane RSiHCl2. These cations are 5-coordinated owing to intramolecular chelation by the two NMe2 groups. By using the same bis-chelating ligand, the formation of silyl cations with Si−C bonds has also been investigated. We show that in an aprotic solvent with non-nucleophilic counteranions [(3,5-(CF3)2C6H3]4B-, BPh4-] there is also bis chelation of the two amino groups to the silicon atom giving 5-coordinated silyl cations while in the presence of nucleophilic anions (Cl-, Br-, I-, CF3SO3-) there is no bis chelation of the two NMe2 groups but rather a fluxional coordination of these groups occurring at silicon.