Novel bis(mu-carboxylato)-bridged tetranuclear copper(II) complexes [Cu-2(NO3)(suc)(phen)(2)(MeOM)](2)(NO3)(2) (1), and [Cu-2(NO3)(glu)(phen)(2)(H2O)](2)(NO3)(2) (2), where suc = succinato, glu = glutarato, and phen = 1,10-phenanthroline were prepared and characterized by magnetic susceptibility and X-ray crystallography. Complexes 1 and 2 have a distorted square-pyramidal configuration around each copper(II) ion with end-to-end carboxylato-bridges of a syn-syn mode. The angular structural parameters (tau) for 1 and 2, which are applicable to five coordinate structueres as an index of degree of trigonality, are in the 0.11-0.25 range. The magnetic susceptibility data for 1 and 2 conform to the usual dimer equation with -2J values of 44 cm(-1) for 1 and 84 cm(-1) for 2, indicating an antiferromagnetic interaction is operative between copper(II) ions.