Hydrogen Bonds as Essential Elements in the Crystal Structures of Three Piperidinium Thiotungstates

The crystal structures of [pipH]₂[WS₄] ( 1 ) and the new compounds [pipH]₃[WS₄](HS) ( 2 ) and [pipH]₄[WS₄][WOS₃] ( 3 ) (pip = piperidine) were determined. Hydrogen bonds between the piperidinium cations and the thiotungstate anions play a dominant structural role. Their strength and number correlates with the degree of distortion found for the tetrahedral anions. Unshared hydrogen bonds have a considerably stronger effect than bifurcated ones; the effect of trifurcated hydrogen bonds is extremely weak. HS^? and [WOS₃]^2? are considerably stronger H bond acceptors than the [WS₄]^2? anion.