The (pyridylazo)oxime ligand (C5H4N)N=NC(=NOH)C6H4R(p), HRL (R = H, Me), has been synthesized with the objective of promoting the very rare mononuclear oximato-O coordination. The synthesis involves hydrazone nitrosation. HRL reacts with M(ClO4)(2).6H(2)O, affording [M(RL)(2)](M = Mn, Fe), and X-ray structure determinations have indeed revealed the presence of the desired oximato-O coordination mode in the distorted octahedral MN4O2 sphere characterized by a a-fold axis of symmetry relating the two tridentate ligands, all chelate rings being five-membered. The M-N and M-O distances are relatively short(1.84-1.99 A), consistent with spin-pairing (M = Mn, S = 1/2; M = Fe, S = 0). The M-N bond length trend, Mn-II > Fe-II, is in accord with the larger radius of the low-spin Mn-II atom. The M-O length order is, however, Mn-II < Fe-II. This reversal occurs because of the rigidity of the ligand skeleton. Significant M-azo back-bonding is present (N=N length similar to 1.30 Angstrom). [Mn(RL)(2)] displays hyperfine-split axial EPR spectra (g(parallel to) similar to 1.98, g(perpendicular to) similar to 2.06, A(parallel to) similar to 170 G, A(perpendicular to) similar to 65 G) in frozen solution as well as in polycrystalline [Fe(RL)(2)] lattices. The quasireversible Fe(III)/Fe(II) couple of [Fe(RL)(2)] has E-1/2 similar to 0.7 V. The oxidized complex [Fe(RL)(2)]PF6 has been electrosynthesized. It is low-spin (S = (1/2)) and displays axial EPR spectra (g(parallel to) similar to 1.98, g(perpendicular to) similar to 2.14) in frozen solution. The Mn(II) --> Mn(III) oxidation (similar to 1.0 V) in [Mn(RL)(2)] is irreversible. Crystal data for [Mn(HL)(2)].CH2Cl2: crystal system monoclinic, space group 12/a, a = 14.142(7) Angstrom, b = 10.721(7) Angstrom, c = 16.933(10) Angstrom, beta = 93.01(4)degrees, Z = 4. Crystal data for [Fe(HL)(2)].CH2Cl2: crystal system monoclinic, space group 12/a, a =14.254 (6) Angstrom, b = 10.742(6) Angstrom, c 16.719(8) Angstrom, beta = 92.35(4)degrees, Z= 4.