GROUP-15 COMPLEXES WITH CARBOXYLIC-ACIDS .5. THE PREPARATION AND CRYSTAL-STRUCTURES OF (AG5AS4(C4H2O6)4(H2O)5(X))N[(C4H2O6) = (+)-TARTRATE(4-) - X = NO3-, CLO4-]

The structures of two isomorphous silver(I) complexes with arsenic(III) (+)-tartrate [Ag5As4(C4H2O6)4(H2O)5(X)]n [X = NO3- (1), ClO4- (2)] have been determined by X-ray methods and refined to residuals R of 0.045 (1) and 0.028 (2) for 3822 and 3849 observed reflections respectively. Crystals are monoclinic, space group P2(1) with Z 2 in cells of dimensions a 12.057(3), b 10.651(1), c, 12.496(3) angstrom, beta 93.37(2)-degrees for (1), and a 12.170(5), b 10.570(1), c 12.634(4) angstrom, beta 92.74(2)-degrees for (2). The two complexes are isostructural, with polymer framework structures based upon two configurationally identical [As2(C4H2O6)2]2- dimer ions, analogous to these in the tartar emetic structure [As-O (hydroxyl): 1.790(7)-1.804(8) angstrom (1); 1.768(4)-1.818(4) angstrom (2). As-O (carboxyl): 1.966(9)-2.118(8) angstrom (1); 1.940(5)-2.127(5) angstrom (2)]. However, an arsenic of one of the dimers forms a short bond to a silver atom [As-Ag, 2.729(2) angstrom (1), and 2.723(1) angstrom (2)], completing a trigonal-bipyramidal coordination about arsenic. The arsenic dimers are in turn linked by a chain of five silver cation centres through both carboxyl and hydroxyl oxygens which also form intrachain links. All five water molecules are bonded to silver ions, with three of them bridging silver centres. The main difference between the two structures arises from the replacement of the nitrate group in (1) by a perchlorate in (2).