A series of oxalato-bridged dinuclear copper(II) complexes of the general formula [Cu-2(Pz(2)CPh(2))(2)(X)(2)(mu-C2O4)] (X = Cl- (1), NO3- (2), ClO4- (3); Pz(2)CPh(2) = diphenyldipyrazolylmethane) or [Cu-2( Pz(2)(3m)CPh(2))(2)(H2O)(2)(mu-C2O4)]-(NO3)(2)-H2O (4) (Pz(2)(3m)CPh(2) = diphenylbis(3-methylpyrazolyl)methane) was synthesized where the axial ligand was systematically varied to study its effect on structure and magnetic coupling. The structures of compounds 1, 2, and 4 have been elucidated by single-crystal X-ray diffraction. [Cu-2(Pz(2)CPh(2))(2)(Cl)(2)(mu-C2O4)] and [Cu-2(Pz(2)CPh(2))(2)(Cl)(2)(mu-C2O4)] are isostructural and crystallize in the triclinic system, space group P1, Z = 2, with a = 8.6155(8) angstrom, b = 10.1435(g) angstrom, c = 11.3612(11) angstrom, alpha = 95.535(2)degrees, beta = 110.303(2)degrees, and gamma = 106.111(2)degrees for 1 and with a = 8.863(7) angstrom, b = 10.241(9) angstrom, c = 11.425(10) angstrom, alpha = 98.985(14)degrees, beta = 110.449(13)degrees, and gamma = 103.664(14)degrees for 2. [Cu-2(Pz(2)(3m)Cph(2))(2)(H2O)(2)(mu-C2O4)]-NO3-H2O crystallizes in the monoclinic system, space group C2/c, Z = 4, with a = 23.4588(14) angstrom, b = 8.8568(5) angstrom, c = 21.7818(13) angstrom, alpha = gamma = 90 degrees, and beta = 100.8890(10)degrees. Variable-temperature magnetic susceptibility studies indicate that all four compounds are strongly antiferromagnetically coupled (2J/k = -364, -344 cm(-1) (2), -424 cm(-1) (3), and -378 cm(-1) (4)). Magnetic and EPR results are discussed with respect to structural parameters to explore possible magneto-structural correlations.