THE CONFORMATIONS OF THE HEXAAMMINERUTHENIUM(III) ION IN SIMPLE SALTS

Single-crystal X-my diffraction results are presented for six hexaammi neruthenium(III) salts, viz. [Ru(NH3)6]2 (SO4)3.5H2O, [Ru(NH3)6]CdCl5, [Ru(NH3)6]ZnCl5, [Ru(NH3)6]Cl2 SCN, [Ru(NH3)6]2(S2O6)3.H2O, and a sal t of approximate formula [Ru(NH3)6]2[POFs]3.4H2O. The 11 independent c ations in these and other published structures do not adopt a single c onformation in respect of hydrogen atom disposition. Analysis of the N -Ru-N-H dihedral angles and their correlations strongly suggests that the conformation is random, given the crystallographic site symmetry. The structure with torsional energy calculated at a minimum by ab init io methods is not observed. This suggests that there are only a limite d number of interionic geometries feasible in crystallization. Such a limitation suggests that computing crystal structures, with no assumpt ions as to space group or any other assumption; is not an open-ended p roblem with excessive alternatives.