Synthesis of Lewis acid-base adducts between trimesityltrieles and potassium cyanate and its heavier homologues

Abstract

Lewis acid-base adducts between trimesityltrieles (MMes3; Mes = 2,4,6-trimethylbenzene, M = Al-In) and potassium cyanate homologues (KNCE; E = O, S, Se) were synthesised in the presence of 18-crown-6 as an encapsulating agent. A series of compounds of the general composition [K(18c6)(thf)0-2ECN(MMes3)] was obtained and comprehensively characterised by multinuclear NMR spectroscopy, infrared spectroscopy, elemental analysis, and single-crystal X-ray diffraction. Structural analyses reveal systematic trends across both the triel and chalcogen series, while spectroscopic data provide insight into the electronic consequences of Lewis acid coordination. Complementary solubility studies demonstrate that adduct formation enhances the solubility of the otherwise poorly soluble potassium salts in selected solvents. The results highlight a class of Lewis acid-base adducts involving negatively charged cyanate and chalcogenocyanate fragments that has remained largely unexplored.