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Four complexes between thallium(I) and functionalized benzoate ligands, namely salicylate, p‐aminosalicylate, 3,4‐dimethoxybenzoate and 3,5‐dimethoxybenzoate have been prepared and their structures determined by X‐ray diffraction. They are all based on dimeric, centrosymmetric Tl2(RCOO)2 units with μ2‐bridging carboxylic groups resulting in Tl···Tl separations of 4.2−4.4 Å. These dimeric units are further linked to form infinite coordination polymers. In catena‐[bis(μ3‐salicylato)dithallium(I)] (1) and catena‐[bis(μ3‐4‐aminosalicylato)dithallium(I)] (2) are adjacent units are held together by secondary Tl−O(hydroxy) interactions resulting in a crystal organization which can be described as stair‐like, infinite one‐dimensional polymers. In catena‐[μ4‐(3,4‐dimethoxybenzoato)thallium(I)] (3) bridges each carboxylic group four thallium(I) cations resulting in infinite two‐dimensional, puckered sheets. Finally, in catena‐[μ3‐(3,5‐dimethoxybenzoato)thallium(I)] (4) each carboxylic unit acts as a μ3‐bridging ligand to give nearly planar, infinite double‐stranded arrays of Tl+ cations. Another characteristic structural motif is the tendency of the thallium ion to only use less than one hemisphere to coordinate ligands. This “half‐nakedness” is due to the stereochemically active inert pair (6s2), which thus plays a prominent role in controlling the structures of these compounds. The Tl+ cations are in approximate pyramidal geometries, with four or five oxygen donor atoms in the basal plane and the stereoactive lone pair occupying the apex position of the pyramid. There are, on the naked side of the metal ions, relatively large spaces in nonpolar environments provided by neighboring phenyl groups. The distances between the planes of the phenyl rings and the Tl+ cation are in the range 3.3−3.5 Å, indicating that Tl+−phenyl η6‐interactions are important in the crystal organization. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)