2 CALCIUM SALTS OF O-TOLIDINE-6,6'-DISULFONATE

The dibasic and monobasic calcium salts of o-tolidine-6,6'-disulfonic acid, tetraaqua(4,4'-diamino-5,5'-dimethyl-1, 1'-biphenyl-2,2'-disulfo nalo-O:O')calcium, [Ca(C14H14N2O6S2)(H2O)(4)], (I), and hexaaqua onio- 5,5'-dimethyl-1,1'-biphenyl-2,2'-disulfonato- O)calcium 4-amino-4'-amm onio-5,5'- dimethyl-1,1'-biphenyl-2,2'-disulfonate hexahydrate, [Ca(C1 4H15N2O6S2)(H2O)(6)](C14H15N2O6S2).6H(2)O, (II), have structures built upon layers of anions, with the calcium cations and water molecules b etween these layers. The calcium ions are seven-coordinate. The coordi nation sphere in compound (I) contains three sulfonate O atoms and fou r water molecules, while that in (II) contains one sulfonate O atom an d six water molecules. Both structures are held together by a network of hydrogen bonds involving the amine, sulfonate and water groups. The biphenyl rings in the anions are approximately 75 degrees out of para llel and the ortho-sulfonate groups are in an anti conformation.