Potassium o-nitrophenolate (1) was reacted with various lanthanide trichlorides under different reaction conditions. By using the smaller lanthanides and working under rigorous exclusion of air, infinite chains of composition [(THF)(4){K(o-O2N-C6H4-O)(4)Ln}(4)](n) (Ln = Y (2a), Er (2b), Lu (2c)) were obtained. Using the same conditions but performing the crystallization under air, tetradecanuclear clusters of composition H-18[Ln(14)(mu-eta(2)-o-O2N-C6H4-O)(8)(eta(2)-o-O2N-C6H4-O)(16)(mu(4)-O)(2)(mu(3)-O)(16)] (Ln = Dy (3a), Er (3b), Tm (3c), Yb (3d)) were isolated. Using larger center metals such as samarium, europium, and terbium and working under rigorous exclusion of air, infinite layers of composition [[K-2(o-O2N-C6H4-O)(5)Tb](n)] (4) and [[K-2(o-O2N-C6H4O)(5)Ln)](n)] (Ln = Sm (5a), Eu (5b)) were obtained. In 4 the layers have a closer packing than those in compound 5. The closer packing is a result of the increased coordination number of the lanthanide metal and the potassium atoms. In contrast, the more open structures of 5 results in channels which are rectangular through the layers. All compounds reported including 1 have been investigated by single-crystal X-ray diffraction.