The hexaanion of mellitic acid, mel = (C-6(CO2)(6))(6-), links metal ions into extensively connected magnetic coordination polymers. Reaction of alkali metal mellitate salts, M-6(mel) (M = K, Rb), with M'Cl-2 precursors (M' = Mn, Co, Ni) under mild (473 K) hydrothermal conditions yields an extensive family of isostructural 3-dimensional mixed alkali metal/ transition metal polymers of general formula M-2[M'(2)(mel)(OH2)(2)] (M/M' = K/Mn (la); K/Co (lb); K/Ni (1c); Rb/Mn (2a); Rb/Co (2b); Rb/Ni (2c)). These materials incorporate distorted 2-dimensional magnetic hexagonal nets with a honeycomb topology that are exclusively based on metal-carboxylate-metal bridging interactions. A further isostructural alkali metal-free Co2+ material with NH4+ cations, (NH4)(2)[Co-2(mel)(OH2)(2)] (3), produced by reaction of H6mel with [Co(NH3)(6)]Cl-3 is also presented. The magnetic susceptibility data for I a c, 2a c, and 3 are presented. The susceptibility data for the Mn(II)- and Ni(II)-containing phases have been analyzed using a simple Mean Field Theory approach, and have been modeled using a high temperature series expansion. The comparative magnetism of the Co(II) phases is also presented, and is more complicated because of significant spin orbit coupling effects.