Heavy silylchalcogenido lanthanates synthesis Ph 4 P[Cp 3 La-ESiMe 3 ] (E = S, Se, and Te) via fluoride-induced demethylation of dimethylcarbonate to Ph 4 P[OCO 2 Me] key intermediate.

We report a new high-yield synthesis of so far not accessible tetraphenylphosphonium methylcarbonate Ph ₄ P[OCO ₂ Me] via solvothermal fluoride-induced demethylation and MeF elimination at Me ₂ CO ₃ (DMC) by Ph ₄ P-F, structurally characterized as λ ⁵ -fluorophosphoran by XRD. The synthetic value of Ph ₄ P[OCO ₂ Me] key compound for preparing nearly all kinds of other Ph ₄ P[anion] salts with perfectly crystallizing (not symmetry frustrated) cation is demonstrated by examples beyond ionic liquid research: a complete set of silylchalcogenide salts Ph ₄ P[ESiMe ₃ ] (E = S, Se, and Te) including the first example of a structurally characterized non-coordinating, naked [Te-SiMe ₃ ] ^- anion is presented. With this set of soft Lewis bases and metal organic Lewis acids [Cp ₃ La] at hand, a comprehensive series of crystalline 1 : 1 lanthanate complexes Ph ₄ P[Cp ₃ La-ESiMe ₃ ] 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 ¹ H, ¹³ C, ²⁹ Si, and ¹³⁹ La NMR studies provide a set of ¹³⁹ La NMR shifts for homologs of heavy chalcogen-lanthanum complexes.