Cyclic silylated chalconium borates 13[B(C 6 F 5) 4 ] and 14[B(C 6 F 5) 4 ]w ith peri-acenaphthyl and peri-naphthyl skeletons were synthesized from unsymmetrically substituted silanes 3, 4, 6, 7, 9 and 10 using the standard Corey protocol (Chalcogen Ch = O, S, Se, Te). The configurationa tt he chalcogen atom is trigonal pyramidal for Ch = S, Se, Te ,l eading to the formation of cis-a nd trans-isomers in the case of phenylmethylsilyl cations.W ith the bulkier tert-butyl group at silicon, the configurationa tt he chalcogen atoms is predetermined to give almoste xclusively the trans-configurated cyclic silylchalconium ions. The barriers for the inversion of the configuration at the sulfur atomso fs ulfonium ions 13 c and 14 a are substantial (72-74 kJ mol À1)a ss hown by variable temperature NMR spectroscopy.T he neighboringg roup effecto ft he thiophenyl substituent is sufficiently strong to preservec hiral information at the silicon atom at low temperatures.