Oxidative chlorination of ArSbCl2 (1) with SO2Cl2 provided ArSbCl4 (2), the base hydrolysis of which gave rise to the arylstibonic acid (ArSb)4O6(OH)4 (3) having an adamantane type structure. The intramolecularly coordinating substituent Ar = 6-diphenylphosphinoacenaphth-5-yl- modulates the Lewis acidity of 1-3 and prevents extensive aggregation.