The reaction of 1,2,4-triazole and NaF with M(ox) (M = transition-metal dication; ox = oxalate dianion) under hydrothermal conditions has led to the isolation of a variety of hybrid organic-inorganic coordination polymers. Four structurally different 3D networks were obtained, depending on the transition metal, with stoichiometry [M-2(H2O)(mu(2)-ox)][M-2(mu(3)-trz)(6)] [M = Fe (1), Co (2), Ni (3)], [Zn-2(H2O),(mu(3)-trz)(2)(mu(2)-ox)] (4), [Mn-3(mu(3)-trz)(2)(mu(6)-ox)(mu(3)-F)(2)] (5),, and [Fe-3(mu(3)-trz)(2)(mu(6)-ox)(mu(2)-F)(2)] (6). In all cases, the magnetic Behavior is dominated by antiferromagnetic exchange interactions between paramagnetic centers. Remarkably, 5 and 6 present a novel magnetic connectivity around the oxalate anion: a mu(6)-bridging mode: This Magnetic geometry promotes multiple triangular arrangements among antiferromagnetically coupled spin carriers, resulting in a complex magnetic network because of the presence of competing interactions. These materials exhibit spontaneous magnetization below 9 and 66 K, respectively.