Organic–inorganic hybrid material as zwitterion: Synthesis and structure of terminal ammonium ions-containing organosilyl species supported on mono-lacunary Dawson polyoxometalate

The title compound 1 with a formula of (Bu4N)4[α2-P2W17O61{Me3N+(CH2)3Si}2O] · CH3CN was obtained in 77.1% (4.21 g scale) yield by a 1:2 molar-ratio reaction of the mono-lacunary Dawson polyoxometalate (POM) [P2W17O61]10− with N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride ([Me3N(CH2)3Si(OMe)3]Cl) in mixed water/acetonitrile solution under acidic conditions and unequivocally characterized with complete elemental analysis, thermogravimetric and differential thermal analyses (TG/DTA), FTIR, solution (31P, 1H, 13C and 29Si) NMR and X-ray crystallography. Compound 1 contained two types of the ammonium cations, i.e., the counterions Bu4N+ (free cations) and the terminal quaternary ammonium ions (bound cations) which are connected to the POM through the organosilyl groups.