Two new cobalt 1,3,5-benzenetricarboxylate (trimesic acid, TMA) coordination polymers were synthesized and structurally characterized: [Co-3(H2O)(6)(TMA(3-))(TMA(2-))(TMA(1-))]. 2H(2)O (1) and K[Co-3(TMA(3-))(TMA(2-))(2)]. 5H(2)O (2). 1 crystallizes in the hexagonal system, space group P6(5)22 (no. 179), with a = 16.7265(2), c = 20.5822(4) Angstrom, V = 4986.9(2) Angstrom (3), and D-c = 1.889 g cm 3. 2 is monoclinic, space group P2/c (no. 13), with a = 9.6096(1), b = 12.5610(1), c = 13.9736(2) Angstrom, beta = 109.239(1)degrees, V = 1592.50(3) Angstrom (3), and D-c = 1.938 g cm(-3). 1 is two-dimensional and formed by a "dense" stacking of {Co-3(H2O)(6)(TMA(3-))(TMA(2-))(TMA(1-))} layers. In compound 2 the connection of sinusoidal chains of cobalt octahedra by two types of trimesate ions gives a three-dimensional network with pentahydrated channels.