Solid-State Models of Ion Solvation : Crystal Structures of Dimethyl Sulfoxide Solvates of Akaline Earth Cations

Structural studies of the dimethyl sulfoxide solvates of the perchlorates of Mg, Sr and Ba show the presence of a variety of complex ion species indicative of the forms possible in solution. While Mg(ClO4)2•6dmso contains the expected [Mg(dmso)6]2+ cation, the crystallised strontium species contains a mononuclear [Sr(dmso)6]2+ cation and two dinuclear species, the complex [(dmso-O)5Sr(μ-dmso-O)3Sr(OH2)(dmso-O)3]4+ containing both seven- and eight-coordinate Sr metal centres, and [{(dmso-O)5Sr(μ-dmso-O)}2]4+ containing seven-coordinate Sr metal centres. The barium complex, of empirical formula Ba(ClO4)2•5dmso, contains a centrosymmetric dimer, [Ba2(dmso-O)6(μ-dmso-O)4(O2ClO2)2]2+, involving an unsymmetrically chelating perchlorate and a nine-coordinate Ba metal centre.