First experimental evidence for the elusive tetrahedral cations [EP(3)](+) (E = S, Se, Te) in the condensed phase

Condensed phase access to the unprecedented tetrahedral cations [EP(3)](+) (E = S, Se, Te) was achieved through the reaction of ECl(3)[WCA] with white phosphorus ([WCA](–) = [Al(OR(F))(4)](–) and [F(Al(OR(F))(3))(2)](–); –R(F) = –C(CF(3))(3)). Previously, [EP(3)](+) was only known from gas phase MS investigations. By contrast, the reaction of ECl(3)[A] with the known P(3)(3–) synthon Na[Nb(ODipp)(3)(P(3))] (enabling AsP(3) synthesis), led to formation of P(4). The cations [EP(3)](+) were characterized by multinuclear NMR spectroscopy in combination with high-level quantum chemical calculations. Their bonding situation is described with several approaches including Atoms in Molecules and Natural Bond Orbital analysis. The first series of well-soluble salts ECl(3)[WCA] was synthesized and fully characterized as starting materials for the studies on this elusive class of [EP(3)](+) cations. Yet, with high [ECl(3)](+) fluoride ion affinity values between 775 (S), 803 (Se) and 844 (Te) kJ mol(–1), well exceeding typical phosphenium ions, these well-soluble ECl(3)[WCA] salts could be relevant in view of the renewed interest in strong (also cationic) Lewis acids.