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

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.