Towards Polysulfuric Acids: The Hydrogentrisulfate Anion [HS O ] in A[HS O ] (A=Na, K, Rb).

The reaction of Na SO and K SO with fuming sulfuric acid (65 % SO ) yielded colorless extremely sensitive crystals of Na[HS O ] (monoclinic; P2 /n (No. 14); Z=4; a=707.36(2), b=1378.56(4), c=848.10(3) pm; β=94.817(1)°; V=824.09(4)⋅10  pm ) and K[HS O ] (orthorhombic; Pccn (No. 56); Z=4; a=1057.16(3), b=807.81(2), c=897.57(2) pm; V=766.51(3)⋅10  pm ). The analogous rubidium compound Rb[HS O ] (orthorhombic; Pnma (No. 62); Z=4; a=891.43(3), b=1095.34(4), c=839.37(3) pm; V=819.58(5)⋅10  pm ) originates from the reaction of Rb CO and SO . All of the different structures contain the hitherto unknown anion [HS O ] and are stamped by strong hydrogen bonds linking the anions either to dimers or chains. Theoretical investigations by DFT methods give further insight in the structural characteristics of [HS O ] . The preparation of the [HS O ] anion can be seen as an important milestone on our way to the still elusive polysulfuric acids.