The reaction of the dihydride [Ru-II(H)(2)(CO)(PPh3)(3)], 3, with excess azo-2,2'-bipyridine (abp) in boiling dry benzene has afforded the diradical bischelate [Ru-II(abp(.-))(2)(CO)(PPh3)], 4, and the hydridic monochelate monoradical [Ru-II(abp(.-))(H)(CO)(PPh3)(2)], 5. A Similar reaction between 3 and 2-(p-chlorophenylazo)pyridine (Clpap) did not yield a bischelate, but the hydridic monoradical [Ru-II(Clpap(.-))(H)(CO)(PPh3)(2)], 6, has been isolated. Upon treatment of 4-6 with NH4PF6 in a wet dichloromethane-acetonitrile medium, the one-electron-oxidized salts 4(+)PF(6)(-), 5(+)PF(6)(-), and 6(+)PF(6)(-) are isolated, H+ being the oxidizing agent. The X-ray structures of 4(+)PF(6)(-). CH2Cl2, 5(+)PF(6)(-). H2O, and 6(+)PF(6)(-) have been determined. In the monoradical 4(+) the azo N-N bond lengths in the two chelate rings are 1.284(6) and 1.336(6) Angstrom, showing that the radical electron is localized in the latter ring. The half-filled extended Huckel HOMO is indeed found to be so localized, and it has a large azo character. Complexes 4-6 display radical redox couples with E-1/2 in the range -0.5 to +0.10 V vs SCE. The E-1/2 values qualitatively correlate with corresponding nu(CO) values (1900-2000 cm(-1)). The monoradicals (S = 1/2) 4(+), 5, and 6 uniformly display a strong EPR signal near g = 2.00. Metal-mediated magnetic interaction makes the EPR-silent diradical 4 strongly antiferromagnetic with J = -299 cm(-1). Crystal data are as follows: (4(+)PF(6)(-). CH2Cl2, C40H33Cl2F6N8OP2Ru) monoclinic, space group P2(1)/c (no. 14), a = 14.174(6) Angstrom, b = 16.451(4) Angstrom, c = 18.381(4) Angstrom, beta = 98.00(3)degrees, Z = 4; (5(+)PF(6)(-). H2O, C47H41F6N4O2P3Ru) monoclinic, space group P2(1)/n (no, 14), a = 9.433(2) Angstrom, b = 38.914(17) Angstrom, c = 13.084(3) Angstrom, beta = 103.47(2)degrees, Z = 4; (6(+)PF(6)(-), C48H39ClF6N3OP3Ru) monoclinic, space group P2(1)/n (no. 14), a = 10.496(5) Angstrom, b = 22.389(8) Angstrom, c = 19.720(6) Angstrom, beta = 90.53(3)degrees, Z = 4.