Heavy silylchalcogenido lanthanates synthesis Ph4P[Cp3La–ESiMe3] (E = S, Se, and Te) via fluoride-induced demethylation of dimethylcarbonate to Ph4P[OCO2Me] key intermediate

Abstract

We report a new high-yield synthesis of so far not accessible tetraphenylphosphonium methylcarbonate Ph₄P[OCO₂Me] via solvothermal fluoride-induced demethylation and MeF elimination at Me₂CO₃ (DMC) by Ph₄P–F, structurally characterized as λ⁵-fluorophosphoran by XRD. The synthetic value of Ph₄P[OCO₂Me] key compound for preparing nearly all kinds of other Ph₄P[anion] salts with perfectly crystallizing (not symmetry frustrated) cation is demonstrated by examples beyond ionic liquid research: a complete set of silylchalcogenide salts Ph₄P[ESiMe₃] (E = S, Se, and Te) including the first example of a structurally characterized non-coordinating, naked [Te–SiMe₃]⁻ anion is presented. With this set of soft Lewis bases and metal organic Lewis acids [Cp₃La] at hand, a comprehensive series of crystalline 1 : 1 lanthanate complexes Ph₄P[Cp₃La–ESiMe₃] has been prepared. Their structural features and trends such as complexation induced Si–E bond elongation and a pronounced trend in La–E–Si bond angle contraction with E = S < Se < Te are discussed. Heteronuclear ¹H, ¹³C, ²⁹Si, and ¹³⁹La NMR studies provide a set of ¹³⁹La NMR shifts for homologs of heavy chalcogen–lanthanum complexes.