structural characterization of both Ru(II) and Ru(III) compounds containing Ru(NH3)(5)(2+/3+) with pyridine or benzonitrile as the sixth ligand (L) is described. Crystal data for L = pyridine, [(NH3)(5)Ru(NC5H5)](SO3CF3)(2) (1) : orthorhombic space group Pbcn, Z = 4, a = 13.096(2) Angstrom, b = 11.541(2) Angstrom, c = 13.179(2) Angstrom. For [(NH3)(5)-Ru(NC5H5)]Cl-3 . 1.4H(2)O (2) : orthorhombic space group Pnma, Z = 4, a = 22.667(12) Angstrom, b = 7.095(2) Angstrom, c 10.097(8) Angstrom. For L = benzonitrile, [(NH3)(5)Ru(NCC6H5)](SO3CF3)(2) (3); monoclinic space group P2(1)/n, Z = 4, a 9.561(1) Angstrom, b = 18.424(4) Angstrom, c = 12.181(1) Angstrom, beta = 95.73(1)degrees. For [(NH3)(5)Ru(NCC6H5)](S2O6)(3/2). 2H(2)O (4) : triclinic space group Pi, Z = 2, a = 7.8947(6) Angstrom, b = 11.517(2) Angstrom, c = 11.630(1) Angstrom, alpha = 99.61(1)degrees, beta = 97.275(8)degrees, gamma = 102.25(1)degrees. The Ru-II-N(L) and Ru-III-N(L) distances are respectively 2.058(8) and 2.077(10) Angstrom for L pyridine and 1.945(5) and 2.025(4) Angstrom for L = benzonitrile. The new data yield a comprehensive set of structural parameters for modeling and interpreting electron transfer barriers and for investigating the dependence of metal-ligand coupling on d(M-N), for which the results of INDO calculations are also reported here.